- Fixed.
Simple and cheap, but causes drag while sailing and performs badly in reverse.
Some suppliers: Michigan Wheel - Flexing-blade: blades flex to flatten at higher speeds.
Some suppliers: PerfectPitch (certain sizes only). - Folding: when stopped, blades fold back to lie along the shaft.
Least drag while sailing.
May require more clearance aft of end of shaft.
Helps minimize snagging of crab traps ?
Expensive.
Some suppliers: Flex-O-Fold, Gori, Martec, Tristream, VariFold
"Very poor reverse power and doesn't always unfold evenly, which can be noisy and hard on the cutless bearing and shaft coupling."
Can be a "lag" between when it's put in gear and when it grips the water.
These comments may apply to older models; newer models are better.
- Feathering: when stopped, blades turn to lie parallel to water direction,
perpendicular to the shaft.
Less drag while sailing, especially good in reverse (because they flip to present same leading edge in forward and reverse).
May require large aperture.
Very expensive.
May have factory-adjustable pitch.
Can be a "lag" between when it's put in gear and when it grips the water.
Some suppliers: P. E. Luke (requires custom shaft taper), Brunton Autoprop, Hydralign, Kiwi, Martec, Max-Prop, VariProp, Bomon Jprop
Some folding or feathering props are also: - Variable-pitch / Controllable-pitch.
Could be automatic pitch adjustment by propeller, adjustment by replacing gears, manual adjustment from outside boat, manual adjustment from inside boat.
Some suppliers:
auto adjustment: Brunton Autoprop;
replacing gears: Max-Prop (Classic model);
manual outside boat: Kiwi, Max-Prop (V.P. model), Bomon Jprop, Hundested;
manual inside boat ("controlled-pitch"; generally for larger boats): Hundested, VPF Propellers;
SailNet - Mark Matthews' "First Look: AVP Autoprop"
fixed $275, folding $600, feathering $1200.
Another idea of prices, 3-blade for 40-foot heavy boat, from "Propellers and prop choices" article by Jim Wolstenholme in Jan 2002 issue of Blue Water Sailing magazine:
fixed $375, folding $1400, feathering $2600.
Specs:
- Type (listed above).
- Diameter.
- Pitch (distance boat travels in one propeller revolution).
- Blade area.
- Material (aluminum, bronze, stainless steel, composite).
- Number of blades (more == more thrust when motoring, less vibration, but more drag when sailing).
- Rotation direction (left-handed or right-handed).
- Shaft diameter and taper.
BoatU.S.'s "Propellers"
SailNet - Sue and Larry's "Choosing the Right Propeller"
"Propellers and prop choices" article by Jim Wolstenholme in Jan 2002 issue of Blue Water Sailing magazine
Nautica's "The Perfect Pitch"
Propeller protection/failure article by Chuck Husick in Mar/Apr 2001 issue of Ocean Navigator magazine
BoatDiesel - Tony Athens' "Propeller installation / Big Nut vs. Little Nut"
BoatDiesel - Roberto Ritossa's "Adjusting Propeller Pitch for Sailboats"
The Marine Doctor's "Propellers" (mainly for outboards)
Jesse Brett's "Drive System Maintenance and Repair"
General Propeller (props, shafts, couplings)
Terminology: "pitch", and "pitch angle" / "blade angle" are not the same. Most fixed props have constant pitch from blade base to tip. But because the tip travels further through the water than the base during each revolution, the angle of the blade decreases from base to tip (if it doesn't, that is "twist" or "cup" ?). "Pitch angle" is the angle of the pressure face of the blade at some particular point.
From "Offshore Cruising Encyclopedia" (1989) by Steve and Linda Dashew:
- The typical sailboat prop will be lucky if it gets 30 percent of the power actually into the water, and efficiency levels below 20 percent are not uncommon. ... it becomes quickly apparent that one of the best ways to improve powering performance is not by increasing engine power, but by making the prop better.
- For displacement speed, large, slow-turning props are much more efficient than smaller, fast-turning props. But large props take more space underwater and exert unbelievable amounts of drag when you're sailing.
- [Feathering propellers are the best compromise between sailing and powering performance. And you can change pitch while hauled out, and you get as much thrust in reverse as in forward.]
- [Tip clearance between hull and tips of blade: minimum is 30 percent of diameter for flat or very round-bottomed hull, 25 percent for sharper hull shape.]
- Diesel engines burn about 0.4 pounds of fuel per HP per hour.
From an Alberg 22 page:
...
The propeller has several parameters to be considered, but two in particular: its diameter and its pitch. The pitch is the distance that a propeller with no slippage would advance in one full turn. These two parameters are usually expressed in inches and as "(diameter) x (pitch)". Thus, an "8 x 7" propeller would have a diameter of 8 inches and a pitch of 7 inches.
The diameter is determined by the HP of the motor and the need to minimize drag particularly in sailboats when operating on sail.
The pitch, on the other hand, is a function of the maximum hull speed of the boat and the recommended operating RPM of the engine at maximum throttle. A pitch below optimal will cause the motor to deliver less than its maximum power at maximum throttle while a pitch above optimal will cause the motor to operate below its intended RPM which [in an outboard] will foul spark-plugs and fail to charge the batteries. It will also cause the boat to accelerate to maximum speed even at low throttle. This makes difficult the maneuvering of the boat at low speeds, which can only be attained by bursts of power at low throttle interspersed between intervals in neutral.
Ideally, at maximum throttle the boat should reach maximum speed and the pitch * RPM (prop) should be covering the same distance as the hull speed - or a fraction above it due to slippage of the propeller.
...
The propeller has several parameters to be considered, but two in particular: its diameter and its pitch. The pitch is the distance that a propeller with no slippage would advance in one full turn. These two parameters are usually expressed in inches and as "(diameter) x (pitch)". Thus, an "8 x 7" propeller would have a diameter of 8 inches and a pitch of 7 inches.
The diameter is determined by the HP of the motor and the need to minimize drag particularly in sailboats when operating on sail.
The pitch, on the other hand, is a function of the maximum hull speed of the boat and the recommended operating RPM of the engine at maximum throttle. A pitch below optimal will cause the motor to deliver less than its maximum power at maximum throttle while a pitch above optimal will cause the motor to operate below its intended RPM which [in an outboard] will foul spark-plugs and fail to charge the batteries. It will also cause the boat to accelerate to maximum speed even at low throttle. This makes difficult the maneuvering of the boat at low speeds, which can only be attained by bursts of power at low throttle interspersed between intervals in neutral.
Ideally, at maximum throttle the boat should reach maximum speed and the pitch * RPM (prop) should be covering the same distance as the hull speed - or a fraction above it due to slippage of the propeller.
...
From Nigel Calder in 9/2005 issue of Sail magazine:
"... most sailboat propellers do not have enough blade surface area, so the propeller will cavitate at higher revolutions. The more surface area there is - which basically means more blades - the better top-end performance will be. But there is a tradeoff, and that is more friction, or drag, when the boat is under sail. ..."
Folding and Feathering Props:
Terrific article by Greg Jones in Feb 2004 issue of Blue Water Sailing magazine
Seahawk's "Feathering, Folding or Fixed ?"
Max-Prop
Folding or feathering prop can get jammed in an odd position if a line gets tangled into it (or barnacles grow in the wrong places). Unlike a tangle in a fixed prop, you could end up with no forward and/or no reverse.
Folding or feathering props require lubrication at some interval, from every 6 months to every 2 years. Usually requires a haul-out, but some can be lubricated in the water.
From Alan Lewis on The Live-Aboard List:
From Justin on Cruising World message board:
From John / Truelove on IRBS live-aboard mailing list:
From Jon Eisberg on Cruising World message board:
From Dan Blanchard on the WorldCruising mailing list:
From Doug Sterrett on the WorldCruising mailing list:
From JeanneP on Cruiser Log Forums:
From Richard on SailNet's Gulfstar mailing list:
From James Moran on the Yacht-L mailing list:
From Jane McKelvie on The Live-Aboard List:
From Steven Dubnoff on The Live-Aboard List:
From Ron Rogers on The Live-Aboard List:
From Luke Curtis on SailNet's Gulfstar mailing list:
From natanzon on SFSailing:
From Alan Lewis on SailNet's Gulfstar mailing list:
From Don / Allied Mistress 39 on Latitudes and Attitudes Cruisers Forum:
From Philip Lange on World-Cruising mailing list:
From Grandma Rosalie on World-Cruising mailing list:
From Lynn Ogden on World-Cruising mailing list:
From Philip Lange on World-Cruising mailing list:
From Gregg O'Malley on SailNet's Gulfstar mailing list:
From Fred Fraim on The Live-Aboard List:
From Nick on Cruising World message board:
From Charlie Stillman on Cruising World message board:
From Gary Elder:
From tsenator on Cruising World message board:
From Andy Anderson on The Live-Aboard List:
From Bob Perry on Cruising World message board:
From bernie on Cruising World message board:
From Jeff H on cruisersforum.com:
From haffiman37 on the Sailing mailing list:
From Jerry on Cruising World message board:
From Ivars on SailNet's Gulfstar mailing list:
From Bad Matt on Latitudes and Attitudes Cruisers Forum:
From Paco PWD on Latitudes and Attitudes Cruisers Forum:
From The Barnacle on Latitudes and Attitudes Cruisers Forum:
From 5/1/2000 issue of Practical Sailor:
Max-Prop: flat blades so less efficient in forward, better in reverse.
Autoprop: requires less RPM than Max-Prop, but longer to get traction when starting, more drag and vibration.
From Bruce Clark on Latitudes and Attitudes Cruisers Forum:
From Senator on Latitudes and Attitudes Cruisers Forum:
From PhantomSailor on Latitudes and Attitudes Cruisers Forum:
From article by Greg Jones in Feb 2004 issue of Blue Water Sailing magazine:
From Steve Rust on cruisersforum.com:
From delmarrey on cruisersforum.com:
From Roy Brown on the Morgan mailing list:
Seahawk's "Feathering, Folding or Fixed ?"
Max-Prop
Folding or feathering prop can get jammed in an odd position if a line gets tangled into it (or barnacles grow in the wrong places). Unlike a tangle in a fixed prop, you could end up with no forward and/or no reverse.
Folding or feathering props require lubrication at some interval, from every 6 months to every 2 years. Usually requires a haul-out, but some can be lubricated in the water.
From Alan Lewis on The Live-Aboard List:
In spite of all the positive reasons for choosing a feathering prop (vs.
folding) -- including more speed under sail and better performance in
reverse -- I just encountered a serious drawback. A few weeks ago I picked
up a 20' length of nylon rope on my Maxprop which, unlike pot warp which
usually stops the engine, shredded and lodged between the blades. The prop
continued to spin and stripped the gears in the propellor, rendering the MaxProp
useless. Fortunately I was able to sail to my home port and get hauled. It
appears that the prop may be unrepairable and will need to be replaced. I
am seriously reconsidering getting another MaxProp in favor of a return to a
conventional fixed blade. It is nearly impossible to replace a MaxProp in
the water, making emergency repairs unlikely. Furthermore, I had to shorten
the shaft to accommodation the end cap on the MaxProp which leaves room for
only a single shaft nut to hold on a conventional prop (which means I should
also replace the [two year old] shaft).
From Justin on Cruising World message board:
Some boats with an aperture don't have the space for a feathering
or folding propeller. With a traditional feathering propeller you
have to be careful that the extra length of the hub doesn't cause
the blades (or hub) to hit the rudder, and with an Autoprop you have
to make sure your shaft is long enough that the blades don't hit
your keel (or whatever is supporting your shaft) when you are
powering in reverse. Twouldn't be fun to spend all that dough and
then find out a fixed-blade is the only thing that will fit on your boat.
From John / Truelove on IRBS live-aboard mailing list:
I installed a 20" 3-blade Martec Autostream S stainless feathering wheel last
spring. Some advantages over the Max-prop (which I also considered): 2/3 the
price; greasing and pitch adjustment for ahead and astern can be done without
hauling; reasonably-priced replacement zinc is retained by one fitting. I
asked Martec to ship the wheel with the pitch set to equal my 20" x 14"
3-blade, and they were "spot-on."
There is a huge difference with the new prop vs the old fixed 3-blade. Despite the fact that the astern pitch is much less (on purpose) than the ahead, the stopping power is much greater and the prop "walk" reduced to almost nil. ...
There is a huge difference with the new prop vs the old fixed 3-blade. Despite the fact that the astern pitch is much less (on purpose) than the ahead, the stopping power is much greater and the prop "walk" reduced to almost nil. ...
From Jon Eisberg on Cruising World message board:
I just installed an Autoprop [6 months ago], and am very pleased with its performance ...
I had come from a conventional two-blade, and the reduction in vibration was
considerable - not to mention the achievement of hull speed at a reduced RPM ...
The mechanical complexity of these things is, of course, a concern ... I made a couple of very minor modifications to my installation - for example, I didn't care for the original setscrew arrangement which locked that shaft nut in place, so I added a large lock washer under the lock nut itself, and changed to a longer setscrew with lock washers which would put a positive pressure on the lock nut itself ... And I didn't like the nylon bolts for attaching the zinc, so I switched off to stainless ones ...
The only thing I find takes a bit of getting used to with an Autoprop is the initially disconcerting "clunk" you notice when first engaging a gear, and the blades "snap" into position ... There's a bit of a learning curve with close maneuvering with a feathering prop - I find you have to occasionally give a slight burst of RPM to really "set" the blades in their proper orientation, but none of this is any big deal ... And, the Autoprop - at least on my boat - has reduced the initial degree of prop walk in reverse significantly ...
Of course, as with any piece of gear this complex - you'd be a fool not to keep a simple fixed-blade backup tucked away somewhere aboard. And, by the way, most conventional prop pullers are unlikely to fit an Autoprop properly - mine required just a bit of modification, easily done.
The mechanical complexity of these things is, of course, a concern ... I made a couple of very minor modifications to my installation - for example, I didn't care for the original setscrew arrangement which locked that shaft nut in place, so I added a large lock washer under the lock nut itself, and changed to a longer setscrew with lock washers which would put a positive pressure on the lock nut itself ... And I didn't like the nylon bolts for attaching the zinc, so I switched off to stainless ones ...
The only thing I find takes a bit of getting used to with an Autoprop is the initially disconcerting "clunk" you notice when first engaging a gear, and the blades "snap" into position ... There's a bit of a learning curve with close maneuvering with a feathering prop - I find you have to occasionally give a slight burst of RPM to really "set" the blades in their proper orientation, but none of this is any big deal ... And, the Autoprop - at least on my boat - has reduced the initial degree of prop walk in reverse significantly ...
Of course, as with any piece of gear this complex - you'd be a fool not to keep a simple fixed-blade backup tucked away somewhere aboard. And, by the way, most conventional prop pullers are unlikely to fit an Autoprop properly - mine required just a bit of modification, easily done.
From Dan Blanchard on the WorldCruising mailing list:
I installed a three-blade Autoprop on our 40' Brewer sloop "Augusta" two
years ago. The power train includes a 46 HP Westerbeke diesel with a Hurth
V-drive, the auto-prop has a 19" diameter. The performance figures below
were taken with much of our heavy cruising supplies off the boat, around
23,000 lbs. I have noted the following improvements in performance under
power:
New max. 2600 RPM, 7.9 knots
Old max. 2600 RPM, 7.1 knots
Old cruise speed at 2450 RPM 6.5 knots
New cruise speed at 2250 RPM 6.5 knots
I have seen no real change backing our boat down, she never pulled hard to port with the old fixed three-blade either so I guess there was not a lot of room for improvement here. I have noticed a considerable increase in emergency backing power, I can stop the boat in half the distance of our old fixed three-blade.
I am very pleased with the performance of this prop. I wish I had installed one prior to our Seattle-Sydney cruise a few years ago. I could have saved a lot of fuel and wear and tear on the engine given the lower cruise RPM. It is surprising how this prop performs at lower RPMs on flat water. At 1500 RPM we can poke along at 5 knots as long as there is no head sea. I can't help but think how nice this would have been on one leg of our last cruise that had us becalmed north of the Cook's for three days.
As I recall, the prop was expensive, around $2,800 for the whole thing.
New max. 2600 RPM, 7.9 knots
Old max. 2600 RPM, 7.1 knots
Old cruise speed at 2450 RPM 6.5 knots
New cruise speed at 2250 RPM 6.5 knots
I have seen no real change backing our boat down, she never pulled hard to port with the old fixed three-blade either so I guess there was not a lot of room for improvement here. I have noticed a considerable increase in emergency backing power, I can stop the boat in half the distance of our old fixed three-blade.
I am very pleased with the performance of this prop. I wish I had installed one prior to our Seattle-Sydney cruise a few years ago. I could have saved a lot of fuel and wear and tear on the engine given the lower cruise RPM. It is surprising how this prop performs at lower RPMs on flat water. At 1500 RPM we can poke along at 5 knots as long as there is no head sea. I can't help but think how nice this would have been on one leg of our last cruise that had us becalmed north of the Cook's for three days.
As I recall, the prop was expensive, around $2,800 for the whole thing.
From Doug Sterrett on the WorldCruising mailing list:
I got a tip from
Downwind Marine in San Diego about the zincs for my Autoprop: Drill a hole
(3/8" - 1/2") in the center of the zinc. This will allow the zinc to
corrode more evenly and will extend the life of the zinc without
sacrificing functionality. Also paint the inside of the bolt holes where
the shafts of the bolts would contact the zinc metal. This will prevent
the zinc from prematurely corroding where it is attached and falling
off. So says Downwind Marine and they sell a lot of these.
Use conductive grease between zinc and shaft to make better contact.From JeanneP on Cruiser Log Forums:
We put an Autoprop feathering prop on SV Watermelon to reduce the vibration and pressure
on the transmission more than to increase speed.
Although we had slightly less prop walk with the feathering prop, we lost almost a knot of motoring speed in forward, and reversing required a bit more initial power to get the blades to reverse.
I did not notice any improvement in weather helm with our changing to the feathering prop. As we got better at trimming our sails, most importantly reefing earlier, the weather helm eased significantly.
When we sold Watermelon in Singapore, we agreed to take the new owner out for several days to help him become accustomed to the boat. Because we felt the feathering prop required more skill than this owner possessed (he was a complete sailing novice when he bought the 'Melon), we put the original fixed prop back on the boat.
Peter and I were both surprised at the faster motoring speed with the fixed prop, and the quicker response when the boat was put into reverse. I had forgotten what we gave up to get that little bit of extra sailing speed and reduced vibration.
We had one frightening episode that I think was due to the feathering prop. Rather than relate it here, it's in our log for Papua New Guinea, the 2nd and 3rd paragraphs.
...
It was an Autoprop, made in Australia, that was installed in St Martin by the Aussie riggers there (absolutely fantastic sailors, those guys!). Peter says he doesn't think he'd install another of that make, though changes to the design were made several times while we owned ours and it was a better prop by the time we removed it than when we first installed it.
I should also add that since the winds in the Caribbean are so strong and reliable, we did not use our engine very much at all in the four and a half years that we sailed there (we probably used about 50 gallons of diesel per year). The feathering prop was far more useful there, and in our long passages in the S. Pacific, than once we arrived in SE Asia where there wasn't much wind at all and motoring was more important.
Although we had slightly less prop walk with the feathering prop, we lost almost a knot of motoring speed in forward, and reversing required a bit more initial power to get the blades to reverse.
I did not notice any improvement in weather helm with our changing to the feathering prop. As we got better at trimming our sails, most importantly reefing earlier, the weather helm eased significantly.
When we sold Watermelon in Singapore, we agreed to take the new owner out for several days to help him become accustomed to the boat. Because we felt the feathering prop required more skill than this owner possessed (he was a complete sailing novice when he bought the 'Melon), we put the original fixed prop back on the boat.
Peter and I were both surprised at the faster motoring speed with the fixed prop, and the quicker response when the boat was put into reverse. I had forgotten what we gave up to get that little bit of extra sailing speed and reduced vibration.
We had one frightening episode that I think was due to the feathering prop. Rather than relate it here, it's in our log for Papua New Guinea, the 2nd and 3rd paragraphs.
...
It was an Autoprop, made in Australia, that was installed in St Martin by the Aussie riggers there (absolutely fantastic sailors, those guys!). Peter says he doesn't think he'd install another of that make, though changes to the design were made several times while we owned ours and it was a better prop by the time we removed it than when we first installed it.
I should also add that since the winds in the Caribbean are so strong and reliable, we did not use our engine very much at all in the four and a half years that we sailed there (we probably used about 50 gallons of diesel per year). The feathering prop was far more useful there, and in our long passages in the S. Pacific, than once we arrived in SE Asia where there wasn't much wind at all and motoring was more important.
From Richard on SailNet's Gulfstar mailing list:
Re: MaxiProp
Folding prop ... forget it. We were heading into our slip and guess what ... It never engaged in reverse and we crashed into the dock. Need I say more?
Folding prop ... forget it. We were heading into our slip and guess what ... It never engaged in reverse and we crashed into the dock. Need I say more?
From James Moran on the Yacht-L mailing list:
We recently had a customer install an Autoprop on his yacht. Based on his
experience, we probably won't be recommending them again. Maneuvering with
them can be pretty difficult. It takes a fair amount of RPM to get the
blades to pitch, especially if you want reverse when the boat is moving
forward or vice-versa. At low engine speeds, it doesn't develop much
thrust.
It has the feeling of an automatic transmission with a slipping torque converter. The engine revs for a while, then the boat starts to respond.
We like Max-Props. They develop excellent thrust in forward and reverse. The VIP models allow one to adjust the pitch with the boat in the water, but we do a pretty good job of getting the pitch settings correct before the boat is launched so the Classics are what usually get installed on our designs.
It has the feeling of an automatic transmission with a slipping torque converter. The engine revs for a while, then the boat starts to respond.
We like Max-Props. They develop excellent thrust in forward and reverse. The VIP models allow one to adjust the pitch with the boat in the water, but we do a pretty good job of getting the pitch settings correct before the boat is launched so the Classics are what usually get installed on our designs.
From Jane McKelvie on The Live-Aboard List:
We have two Max Props on our 50' catamaran that are powered by two Volvo
Penta MD40 engines. We are very happy with the performance of the props but
there are a few things you should take into account:
1) Max Props (ours anyway) have to be removed from the shaft with a special tool (one-off purchase).
2) Max Props come off in several pieces which then have to be replaced very precisely to get the correct pitch.
3) After six years of working with the props we are now able to remove one, clean it up, grease it, and replace it in two hours.
4) Check out the anodes that you need for the props - we have to buy special anodes and unfortunately the one between the s-drive and the prop is a cone which can only be replaced by removing the prop.
5) As a result of all the fiddling about we feel we would not happily/easily be able to remove/replace the props under water. There are too many pieces to lose. We also have rope cutters to add to the pieces!
Despite this we have never changed our minds and returned to fixed-blade props.
1) Max Props (ours anyway) have to be removed from the shaft with a special tool (one-off purchase).
2) Max Props come off in several pieces which then have to be replaced very precisely to get the correct pitch.
3) After six years of working with the props we are now able to remove one, clean it up, grease it, and replace it in two hours.
4) Check out the anodes that you need for the props - we have to buy special anodes and unfortunately the one between the s-drive and the prop is a cone which can only be replaced by removing the prop.
5) As a result of all the fiddling about we feel we would not happily/easily be able to remove/replace the props under water. There are too many pieces to lose. We also have rope cutters to add to the pieces!
Despite this we have never changed our minds and returned to fixed-blade props.
From Steven Dubnoff on The Live-Aboard List:
I just went though the same choice this year. Everyone I talked to (my
mechanic, and those with similar boats) advised me to get the
Maxprop. I bought one and have been very happy.
Recently another Nauticat owner made the other choice and bought an Autoprop which he says vibrates like mad. They have been also known to drop blades.
The Maxprop is expensive and you really have to watch the zincs. I had mine put on by a yard where they knew what they were doing. It did not look easy.
Pyacht.com has them at 10% off list all the time. They will get a recommendation from PYI for you (PYI will support you anyway).
Recently another Nauticat owner made the other choice and bought an Autoprop which he says vibrates like mad. They have been also known to drop blades.
The Maxprop is expensive and you really have to watch the zincs. I had mine put on by a yard where they knew what they were doing. It did not look easy.
Pyacht.com has them at 10% off list all the time. They will get a recommendation from PYI for you (PYI will support you anyway).
From Ron Rogers on The Live-Aboard List:
I've owned a Maxprop and was very satisfied. It improved reverse
tremendously, and reduced prop walk. However, there was a small loss in
top-end speed. Be sure to pay attention to zincs and try to get the one that
allows you to adjust pitch underwater and grease underwater. You may find
that you can improve on the factory recommended pitch setting by trial and
error.
A friend of mine purchased the Autoprop and noted improved performance in all aspects, HOWEVER, the blades became loose. In consultation with Autoprop, they advised him that their propeller requires a haul every six months to repack it! They fixed it anyway, but he did not purchase an Autoprop for his new boat.
A friend of mine purchased the Autoprop and noted improved performance in all aspects, HOWEVER, the blades became loose. In consultation with Autoprop, they advised him that their propeller requires a haul every six months to repack it! They fixed it anyway, but he did not purchase an Autoprop for his new boat.
From Luke Curtis on SailNet's Gulfstar mailing list:
We have a three-blade Max Prop on our Gulfstar Sailmaster 39. Great performance under sail
compared with our old fixed Michigan (+ 1/3 to 1/2 knot) plus much better
backing ability under power.
Like many other Max Prop owners, we have been plagued with short zinc life. In addition to the 63M zinc on the prop, we carry a shaft zinc as well. We need to replace the 63M every three months.
Part of the issue with the Max Prop zinc life is the design as the three attachment points are at the bottom of the cone and wear through quickly, tossing off the balance of the zinc. Also, we have a hot marina which doesn't help!
At the Seattle boat Show, the PYI folks gave us the following tips to prolong zinc life:
Like many other Max Prop owners, we have been plagued with short zinc life. In addition to the 63M zinc on the prop, we carry a shaft zinc as well. We need to replace the 63M every three months.
Part of the issue with the Max Prop zinc life is the design as the three attachment points are at the bottom of the cone and wear through quickly, tossing off the balance of the zinc. Also, we have a hot marina which doesn't help!
At the Seattle boat Show, the PYI folks gave us the following tips to prolong zinc life:
- Clean and rough up both the zinc and prop surfaces prior to replacement
(suggest same on shaft zincs as well).
- Put conductive grease around base of zinc.
- Apply bottom paint to zinc around the screw hole areas.
- Use an O-ring on the screws to reduce conductivity between the
dissimilar metals.
- Use locktite on the screws to keep them in position.
From natanzon on SFSailing:
I am using a 3-blade Max-Prop. It is set for 18" X 13" for a Volvo 50 HP Sail Drive.
I like the use of the prop. I had it set at first for 18" X 12" and
after a year when pulling the boat changed the pitch.
One real problem with the Max-Prop is parts and grease that you need for it. If you need to replace the zinc every year or other year and you need to pump the prop full of a special liquidy grease you may be finding it hard to get. The factory is willing to mail it, but will not accept credit cards use for payments, only bank transfers, so that easily it can cost over $120.
One real problem with the Max-Prop is parts and grease that you need for it. If you need to replace the zinc every year or other year and you need to pump the prop full of a special liquidy grease you may be finding it hard to get. The factory is willing to mail it, but will not accept credit cards use for payments, only bank transfers, so that easily it can cost over $120.
From Alan Lewis on SailNet's Gulfstar mailing list:
I installed a three-blade Max-Prop on my Gulfstar 41 this spring, and it
has performed flawlessly. It was easy to install myself; I was a little
intimidated by the need to cut off an inch from my shaft, but it worked
out well. I gained at least 0.5 knots under power, and about the same
under sail. I especially noticed an improvement in light-air conditions
(always nice for a '41 which isn't known for its light-air abilities).
From Don / Allied Mistress 39 on Latitudes and Attitudes Cruisers Forum:
I have a Maxprop on my full-keel boat, with wide "deadwood" ahead
of the prop aperture, very similar to the Morgan OI.
It works very well; adds 1/2 to 3/4 knot under sail and
provides good handling in reverse.
From Philip Lange on World-Cruising mailing list:
We had a Max Prop on our Searunner 37. Twelve years of 'on the
move' cruising and the only problem I had was after I backed into a rock
with it. (Got it straightened out in VZ and it worked just fine.) Sent it
off after ten years to have it tightened up. Found the guys there to be
fast and reasonable. When I got the prop back it was like new.
Boat always backed well.
Boat always backed well.
From Grandma Rosalie on World-Cruising mailing list:
We have replaced our fixed prop (3 blade) with a MaxProp, and I think
it has been money well spent. The shaft no longer sounds like a
freeway at full speed when we are under sail. Other CSY owners have
also put MaxProps onto their boats and they've been happy with them.
We did a short test sailing with the engine on but in neutral (to run
the refrigeration) and the prop free-wheeling, and then with the
engine off and the prop feathered and figure that we gained about a
half knot in speed.
It does take a little bit of time to learn to make the prop feather.
Other people in the group have put on the AutoProp which I think is a folding prop, and they also were happy with it. They also did test runs with the old prop first, and then with the AutoProp. We got the MaxProp because it was less expensive.
It does take a little bit of time to learn to make the prop feather.
Other people in the group have put on the AutoProp which I think is a folding prop, and they also were happy with it. They also did test runs with the old prop first, and then with the AutoProp. We got the MaxProp because it was less expensive.
From Lynn Ogden on World-Cruising mailing list:
None are as efficient as a fixed two- or three-blade prop. They cost a lot of money. They require
more maintenance than a fixed prop, and some expensive replacement components. For me, I think
they are a waste of money - unless you race a lot. Further, having a component with a lot of moving
parts that can foul or break under the boat, under water, that you can't see or repair without a
diver or a haulout or extra spare parts isn't for me.
From Bryan Genez on World-Cruising mailing list:
Simple is always good (KISS), but every so often, simple can be improved.
Feathering props are one of those improvements. They *are* more efficient than fixed props in reverse. They *are* robustly made, and rarely, if ever, fail. Maintenance might involve five minutes per year to add grease ... not exactly a back-breaker. The winches on your sailboat are more fragile and require more maintenance than the feathering prop. Further, they can be adjusted by the owner to most efficient pitch, depending upon your cruising RPM. Some - like the Autostream - can be adjusted while the boat is in the water.
A feathering prop will probably add one-half knot of speed over a fixed and locked prop. That's 12 miles/day or two hours/day of cruising time. A fixed-blade prop will be more efficient when you're moving forward under power. Definitely a benefit if you prefer motoring to sailing.
I've had a three-blade Max-Prop for 18+ years. I never race. I'd cheerfully "waste" my money on another, if I were to purchase a new cruising boat.
From Lynn Ogden on World-Cruising mailing list:Feathering props are one of those improvements. They *are* more efficient than fixed props in reverse. They *are* robustly made, and rarely, if ever, fail. Maintenance might involve five minutes per year to add grease ... not exactly a back-breaker. The winches on your sailboat are more fragile and require more maintenance than the feathering prop. Further, they can be adjusted by the owner to most efficient pitch, depending upon your cruising RPM. Some - like the Autostream - can be adjusted while the boat is in the water.
A feathering prop will probably add one-half knot of speed over a fixed and locked prop. That's 12 miles/day or two hours/day of cruising time. A fixed-blade prop will be more efficient when you're moving forward under power. Definitely a benefit if you prefer motoring to sailing.
I've had a three-blade Max-Prop for 18+ years. I never race. I'd cheerfully "waste" my money on another, if I were to purchase a new cruising boat.
I don't know about you, but I spend very
little time in reverse to warrant a +/- $2000 prop that "backs up" well. Likewise, 12 miles a day
aren't worth $2000 to me either.
In Annapolis many years ago I went sailing with a friend who had to dive over the side to scrape the growth off his folding prop before he could get out of the marina. To me that would be a back-breaker. ... one barnacle in the wrong place can render a feathering/folding prop inoperable and unusable; a fixed prop would have its efficiency reduced, but would still work.
From Bryan Genez on World-Cruising mailing list:In Annapolis many years ago I went sailing with a friend who had to dive over the side to scrape the growth off his folding prop before he could get out of the marina. To me that would be a back-breaker. ... one barnacle in the wrong place can render a feathering/folding prop inoperable and unusable; a fixed prop would have its efficiency reduced, but would still work.
I haven't experienced anything close to this. While barnacles are quite
strong, the forces against a feathering prop are stronger (in my
experience). A barnacle that interfered with the action of a feathering
prop would be broken off.
As recently as last year, I had fouling so severe on my prop that I had a diver clean it. I hadn't used the boat until the end of the year, and the Chesapeake barnacles had free rein to grow at will. But prior to the cleaning, the blades rotated properly; the problem was that the water flow across the blades was so turbulent that the prop lost about half its efficiency. It was exactly comparable to the losses experienced by a fixed-blade prop with barnacle growth.
As recently as last year, I had fouling so severe on my prop that I had a diver clean it. I hadn't used the boat until the end of the year, and the Chesapeake barnacles had free rein to grow at will. But prior to the cleaning, the blades rotated properly; the problem was that the water flow across the blades was so turbulent that the prop lost about half its efficiency. It was exactly comparable to the losses experienced by a fixed-blade prop with barnacle growth.
From Philip Lange on World-Cruising mailing list:
Sometimes that extra half knot gets you into the harbor before dark. A
half knot on a five-knot boat is a 10% increase in speed. If your boat is
faster, you will most likely have a proportional increase in
speed. Twelve miles a day on a thirty-day passage is 360 miles. You get
where you are going three days sooner.
On a faster boat it is a safety feature. Turbulence from a fixed wheel causes the rudder to loose its "bite".
I had my three-blade Max Prop for 12 years and did not have any problem with it that was related to its being a feathering prop.
There is a world of difference between a folding and a feathering prop. No one should talk about them as if they are interchangeable. I have experience with both and don't have much good to say about the two-blade folder I had. Folders are usually much less expensive and can be easily found secondhand for very little. I would not consider any that did not have the blades geared together. The Gori propeller is one that does. They make a three-blade folder. They are not cheap. No folder backs as well as a feathering prop.
Feathering props are rare on the used market. I remember seeing a well-used Max Prop at the BAM in Annapolis. It went for over half the new price.
On a faster boat it is a safety feature. Turbulence from a fixed wheel causes the rudder to loose its "bite".
I had my three-blade Max Prop for 12 years and did not have any problem with it that was related to its being a feathering prop.
There is a world of difference between a folding and a feathering prop. No one should talk about them as if they are interchangeable. I have experience with both and don't have much good to say about the two-blade folder I had. Folders are usually much less expensive and can be easily found secondhand for very little. I would not consider any that did not have the blades geared together. The Gori propeller is one that does. They make a three-blade folder. They are not cheap. No folder backs as well as a feathering prop.
Feathering props are rare on the used market. I remember seeing a well-used Max Prop at the BAM in Annapolis. It went for over half the new price.
From Gregg O'Malley on SailNet's Gulfstar mailing list:
I had a Martec on my Catalina; not in the same league with Max Prop.
From Fred Fraim on The Live-Aboard List:
I would not give up my Martec
folder. With the Martec I can steer just as well in reverse as in forward. ...
From Nick on Cruising World message board:
Two or three years ago we put a Martec Autostream feathering prop on our Catalina 42.
The Martec and Max are similar design - I took the Martec because it was $400
less. It replaced the 18" 3-blade.
Regarding speed increase, there was a slight improvement. Bob and Rick have an identical boat and in the past we could sail a long time with almost identical speeds. With the new prop we gained about 0.1 kt at 6-7 kts to weather. Without a head to head match race we'd never notice the speed increase. They've since put on an Autoprop so we no longer have the upper hand. Back to luck and skill in that order.
The most noticeable improvement is in helm response and rudder effectiveness. The feathered prop doesn't disrupt the water flow over the rudder nearly as much as the fixed prop so we have noticeably less weather helm. The improvement was pretty dramatic. Keep in mind our boat has the stubby square rudder the Catalina put on the 42's in the earlier years. This may not have been as important with the new, deeper rudder.
Under power it isn't as smooth as the fixed prop. I think this is due to the compromised blade shape. I noticed this the first couple of times out but have since gotten used to the slight vibration and don't think about it anymore. You can't set the pitch the same as for a fixed prop. The fixed pitch was 13". Translating that to the degree setting would have resulted in way too little pitch. Martec gave us an initial recommendation which turned out to be too little pitch. When summer came I spent an afternoon diving/adjusting and testing. After about 3 tries I finally got it where I wanted. The Martec is very easy to adjust in the water. Performance in reverse is very good with almost no prop-walk. Sometimes this isn't a totally good thing since the prop walk can be used to help pivot the boat in a tight spot. Sometimes, though, you want to swing the other way so the lack of prop walk is a good thing.
I can't compare performance of the Max v.s. the Martec since we haven't done a head to head. The Max does have greater blade area which may be a benefit. Same for durability and resistance to damage. The Max is bronze, the Martec stainless steel. There are arguments for and against each.
I'd do it again. Might consider the Max the next time because of the larger blades.
Regarding speed increase, there was a slight improvement. Bob and Rick have an identical boat and in the past we could sail a long time with almost identical speeds. With the new prop we gained about 0.1 kt at 6-7 kts to weather. Without a head to head match race we'd never notice the speed increase. They've since put on an Autoprop so we no longer have the upper hand. Back to luck and skill in that order.
The most noticeable improvement is in helm response and rudder effectiveness. The feathered prop doesn't disrupt the water flow over the rudder nearly as much as the fixed prop so we have noticeably less weather helm. The improvement was pretty dramatic. Keep in mind our boat has the stubby square rudder the Catalina put on the 42's in the earlier years. This may not have been as important with the new, deeper rudder.
Under power it isn't as smooth as the fixed prop. I think this is due to the compromised blade shape. I noticed this the first couple of times out but have since gotten used to the slight vibration and don't think about it anymore. You can't set the pitch the same as for a fixed prop. The fixed pitch was 13". Translating that to the degree setting would have resulted in way too little pitch. Martec gave us an initial recommendation which turned out to be too little pitch. When summer came I spent an afternoon diving/adjusting and testing. After about 3 tries I finally got it where I wanted. The Martec is very easy to adjust in the water. Performance in reverse is very good with almost no prop-walk. Sometimes this isn't a totally good thing since the prop walk can be used to help pivot the boat in a tight spot. Sometimes, though, you want to swing the other way so the lack of prop walk is a good thing.
I can't compare performance of the Max v.s. the Martec since we haven't done a head to head. The Max does have greater blade area which may be a benefit. Same for durability and resistance to damage. The Max is bronze, the Martec stainless steel. There are arguments for and against each.
I'd do it again. Might consider the Max the next time because of the larger blades.
From Charlie Stillman on Cruising World message board:
I had a three-blade maxprop on a previous boat and it was fantastic
compared with the old two-blade Martec prop. By jingo, the
Maxprop worked great EVERY time in reverse!
Here's the problem I have with Maxprops. Look at the blade shape. They are shaped like paddles. Now look at most fixed three-blade props. They have more of a foil shape. They are optimized for moving a boat through the water. The Maxprop is a compromise between feathered profile and engaged profile. They are mechanically complex and require regular maintenance.
The Flexofold prop folks have test data claiming greater efficiency *and* tied for lowest drag compared with the competition. (Such data could be cooked of course, and tank tests may not be same as real world. BTW, Maxprop claims 96% efficiency compared with a regular prop. Evidence?) Flexofold blades look more like those of a regular fixed prop to me than Maxprop blades. That would fit with claims by Flexofold for greater efficiency and less likelihood to cavitate.
One Maxprop advantage is you can change the pitch.
There are many satisfied Maxprop users. I just think there are better cheaper alternatives. We were skeptical when we heard about Flexofold props, based on our experience with Martecs. But we found that Flexofold props have awesome stopping power.
I ran into an HR43 friend at Armchair Sailor yesterday. He had had problems with his Gori and was replacing it with a Flexofold.
Flexofold zincs cost $30 apiece. THAT is a problem. I have no room for a shaft zinc. Gotta get a zinc fish to help at the dock!
Propellors are a case of: there may be more than one right answer. Getting size and pitch right is critical.
Here's the problem I have with Maxprops. Look at the blade shape. They are shaped like paddles. Now look at most fixed three-blade props. They have more of a foil shape. They are optimized for moving a boat through the water. The Maxprop is a compromise between feathered profile and engaged profile. They are mechanically complex and require regular maintenance.
The Flexofold prop folks have test data claiming greater efficiency *and* tied for lowest drag compared with the competition. (Such data could be cooked of course, and tank tests may not be same as real world. BTW, Maxprop claims 96% efficiency compared with a regular prop. Evidence?) Flexofold blades look more like those of a regular fixed prop to me than Maxprop blades. That would fit with claims by Flexofold for greater efficiency and less likelihood to cavitate.
One Maxprop advantage is you can change the pitch.
There are many satisfied Maxprop users. I just think there are better cheaper alternatives. We were skeptical when we heard about Flexofold props, based on our experience with Martecs. But we found that Flexofold props have awesome stopping power.
I ran into an HR43 friend at Armchair Sailor yesterday. He had had problems with his Gori and was replacing it with a Flexofold.
Flexofold zincs cost $30 apiece. THAT is a problem. I have no room for a shaft zinc. Gotta get a zinc fish to help at the dock!
Propellors are a case of: there may be more than one right answer. Getting size and pitch right is critical.
From Gary Elder:
Considering the design of your boat [beamy shoal-draft full-keel motor-sailer]
and its intended use [liveaboard cruising], I would not do
it. Many times, I've had to try to help West Marine customers sort out various
problems with folding and feathering props. One of the better feathering
props has a major problem with electrolysis, but the manufacturer won't
admit it - always blames it on the boat owner, but it's always the prop that
causes it. I don't think you will see much improvement in performance - with your boat - by
changing to a folding or feathering prop.
...
... MaxProp. Today I was able to talk to one of the 'unfortunates' who purchased one of these things. He is really pissed. He paid about $2K for it, spent about that much again trying to troubleshoot the electrolysis problems, and the only performance improvement he can notice is that it will stop a little quicker when he puts it in reverse.
The boat is a Pacific Seacraft 34, which like your boat doesn't go to weather very well (but better than yours), and like yours, doesn't have a bottom that will let it perform really well. It is, however, a very seaworthy boat.
His performance improvement under sail alone is so unremarkable that he can't tell any difference between the MaxProp and his old three-blade prop. He has been able to get the MaxProp folks to admit that the speed increase using their prop is usually measured in tenths of a knot. If you are a racer one tenth of a knot is important; if you are a cruiser it's nothing. His advice? Spend it on a new 150 jib and some rig improvements. My perception of that is that you will still have a MOTORsailor; the basic design of the hull and rig will never let it be a motorSAILOR.
[Another guy,] who used to work for Morgan and Gulfstar, said there are "a hundred other things to spend $2K on that will help you more than a MaxProp".
...
... MaxProp. Today I was able to talk to one of the 'unfortunates' who purchased one of these things. He is really pissed. He paid about $2K for it, spent about that much again trying to troubleshoot the electrolysis problems, and the only performance improvement he can notice is that it will stop a little quicker when he puts it in reverse.
The boat is a Pacific Seacraft 34, which like your boat doesn't go to weather very well (but better than yours), and like yours, doesn't have a bottom that will let it perform really well. It is, however, a very seaworthy boat.
His performance improvement under sail alone is so unremarkable that he can't tell any difference between the MaxProp and his old three-blade prop. He has been able to get the MaxProp folks to admit that the speed increase using their prop is usually measured in tenths of a knot. If you are a racer one tenth of a knot is important; if you are a cruiser it's nothing. His advice? Spend it on a new 150 jib and some rig improvements. My perception of that is that you will still have a MOTORsailor; the basic design of the hull and rig will never let it be a motorSAILOR.
[Another guy,] who used to work for Morgan and Gulfstar, said there are "a hundred other things to spend $2K on that will help you more than a MaxProp".
From tsenator on Cruising World message board:
I've had the Autoprop for 2 years now and I am very happy with it,
but I agree it might not be for
everyone. I suspect that most Autoprop or Maxprop
users will say theirs is best. Who will admit
that they made a $2000 bad choice?
My take on it:
Autoprop - a lot more efficient under power and especially motor-sailing since the prop always finds it's own best pitch. Sort of like an automatic transmission. Good speed gain under sail with the feathering. Some early users might have had an issue with the right size Autoprop, I think with years of experince they have gotten really good with specing the sizes. You probably won't go wrong with their recommendation if you have a popular boat, as they've already gone through the trial and error to find the right size. Some owners also might have an issue with clearance from the strut or other geometry depending on your boat, this is because the blades will swing all the way forward and cover a wider area to swing into reverse. Also remember these props are really not as good for smaller boats as the hub size needs to be a certain size no matter what, and if your blades are small then naturally the blade size to the hub size is a smaller ratio. The other thing is that these are very heavy props and you should go to stainless steel shaft as bronze doesn't have the stiffness needed. (Trust me on this; I know.)
Maxprop - slightly less drag under sail because the blades are flat rather than cupped like the Autoprop. Good motoring power compared to standard prop, but not quite as good as Autoprop except perhaps at full power. Since the pitch can only be adjusted for max efficiency at full power, the efficiency at part-throttle or motorsailing will be less. Because you have to adjust the pitch yourself, some owners report having a diver make several dives and adjustments before they are happy with the pitch. This seems to be trying the recommended setting and then trial and error to get it perfect. Probably not that great a deal unless you are a perfectionist and it is only done once.
If I was a racer, I would absolutely lean towards the Maxprop, especially nice is that they have a 2-blade option not available on the Autoprop.
For some cruisers, I think the Autoprop has some real benefits. Especially the efficiency of motorsailing, it's amazing, when I have the engine running at just idle, and I am motorsailing it feels like the boat goes into turbo mode. I always pick up a few knots of speed and much more than I ever did with my 3-blade at the same RPM's. Also I have noticed a drastic increase in fuel economy, where I used to get about .8 Gal/hour, I now am rarely above about .6 Gal/hour. So the fuel economy alone with limited fuel on a long distance cruiser might really help. BUT if I was a full time cruiser and cruised with an Autoprop, I would definitely carry a spare fixed-blade prop and an autoprop prop-puller, because, you never know, it "is" a mechanical device and there "is" a small chance of a problem. But the service from the Autoprop people have been very good and I have heard mostly good things about them. They will make things right for you.
So why did I finally decide on the Autoprop? I will not argue about sailing drag -- especially when racing a boat. The other folding props will be much better for drag, no question about it (especially is very light air) -- But I just cruise and go gunkholing and besides it is WAY better with drag than my previous 3-blade prop. (Autoprop has 85% less drag than a 3-blade fixed -- Folding Prop has 95% less drag than a 3-blade fixed.)
Cruisers tend to motorsail when the winds are light. They don't want to pull the sails down completely but want to get where they are going. Reaching hull speed at low RPM's while motorsailing can be done with the Autoprop due to the automatic variable-pitched prop. The blades will increase their pitch due to the assist from sailing and create thrust over all RPM's. This will increase your speed and cut hours off a voyage.
But one of the main reasons I got the Autoprop is the amount of power in reverse. Most of the props and, yes, especially the fixed ones are very inefficient in reverse. There is NOTHING better (nothing less than putting on a reverse-turned fixed propeller) than the Autoprop in reverse. The Autoprop is designed to produce the same lift and thrust in forward and reverse.
You might ask why I care so much about power in reverse, well, like I said above, I like to go cruising and gunkholing. And, well, the places I like tend to go into shoal a bit and have *very* thin water under my keel. So if I touch bottom, the Autoprop is by far the most powerful propeller your boat can have to "un-ground" itself ... I look at it as part of my "Tow Insurance" ...
My take on it:
Autoprop - a lot more efficient under power and especially motor-sailing since the prop always finds it's own best pitch. Sort of like an automatic transmission. Good speed gain under sail with the feathering. Some early users might have had an issue with the right size Autoprop, I think with years of experince they have gotten really good with specing the sizes. You probably won't go wrong with their recommendation if you have a popular boat, as they've already gone through the trial and error to find the right size. Some owners also might have an issue with clearance from the strut or other geometry depending on your boat, this is because the blades will swing all the way forward and cover a wider area to swing into reverse. Also remember these props are really not as good for smaller boats as the hub size needs to be a certain size no matter what, and if your blades are small then naturally the blade size to the hub size is a smaller ratio. The other thing is that these are very heavy props and you should go to stainless steel shaft as bronze doesn't have the stiffness needed. (Trust me on this; I know.)
Maxprop - slightly less drag under sail because the blades are flat rather than cupped like the Autoprop. Good motoring power compared to standard prop, but not quite as good as Autoprop except perhaps at full power. Since the pitch can only be adjusted for max efficiency at full power, the efficiency at part-throttle or motorsailing will be less. Because you have to adjust the pitch yourself, some owners report having a diver make several dives and adjustments before they are happy with the pitch. This seems to be trying the recommended setting and then trial and error to get it perfect. Probably not that great a deal unless you are a perfectionist and it is only done once.
If I was a racer, I would absolutely lean towards the Maxprop, especially nice is that they have a 2-blade option not available on the Autoprop.
For some cruisers, I think the Autoprop has some real benefits. Especially the efficiency of motorsailing, it's amazing, when I have the engine running at just idle, and I am motorsailing it feels like the boat goes into turbo mode. I always pick up a few knots of speed and much more than I ever did with my 3-blade at the same RPM's. Also I have noticed a drastic increase in fuel economy, where I used to get about .8 Gal/hour, I now am rarely above about .6 Gal/hour. So the fuel economy alone with limited fuel on a long distance cruiser might really help. BUT if I was a full time cruiser and cruised with an Autoprop, I would definitely carry a spare fixed-blade prop and an autoprop prop-puller, because, you never know, it "is" a mechanical device and there "is" a small chance of a problem. But the service from the Autoprop people have been very good and I have heard mostly good things about them. They will make things right for you.
So why did I finally decide on the Autoprop? I will not argue about sailing drag -- especially when racing a boat. The other folding props will be much better for drag, no question about it (especially is very light air) -- But I just cruise and go gunkholing and besides it is WAY better with drag than my previous 3-blade prop. (Autoprop has 85% less drag than a 3-blade fixed -- Folding Prop has 95% less drag than a 3-blade fixed.)
Cruisers tend to motorsail when the winds are light. They don't want to pull the sails down completely but want to get where they are going. Reaching hull speed at low RPM's while motorsailing can be done with the Autoprop due to the automatic variable-pitched prop. The blades will increase their pitch due to the assist from sailing and create thrust over all RPM's. This will increase your speed and cut hours off a voyage.
But one of the main reasons I got the Autoprop is the amount of power in reverse. Most of the props and, yes, especially the fixed ones are very inefficient in reverse. There is NOTHING better (nothing less than putting on a reverse-turned fixed propeller) than the Autoprop in reverse. The Autoprop is designed to produce the same lift and thrust in forward and reverse.
You might ask why I care so much about power in reverse, well, like I said above, I like to go cruising and gunkholing. And, well, the places I like tend to go into shoal a bit and have *very* thin water under my keel. So if I touch bottom, the Autoprop is by far the most powerful propeller your boat can have to "un-ground" itself ... I look at it as part of my "Tow Insurance" ...
From Andy Anderson on The Live-Aboard List:
Re: Autoprop variable pitch propeller:
We have owned a 1977 P365 for about 8 years now. When we first bought her the previous owner had installed a folding prop, I don't know why but presume for more boat speed. We used it for the first season and found that the boat would not back up! Thus, we took the folding prop off at winter haul out and put the original 17X10 fixed 3-blade back on.
We have owned a 1977 P365 for about 8 years now. When we first bought her the previous owner had installed a folding prop, I don't know why but presume for more boat speed. We used it for the first season and found that the boat would not back up! Thus, we took the folding prop off at winter haul out and put the original 17X10 fixed 3-blade back on.
From Bob Perry on Cruising World message board:
I have a Gori on my own boat and I like it a lot.
I have had it for eight years without a problem.
From bernie on Cruising World message board:
Have a Gori on my HR. I like the two-speed option ... but
still think that the Max-Prop is better.
From Jeff H on cruisersforum.com:
I had a Gori prop on my last boat. The props were not terribly reliable
(the polyurethane connection between the hub and the shaft socket failed
several times, and a hinge pin failed once as well) and the factory support
was far worse than awful. I would never buy a Gori prop again and would
consider it a deal-breaker on a larger boat if it required one.
Getting back to the original question, my boat made a very distinct 'thunk thunk' at speed. I had been concerned that it was a problem with the Martec prop and had it rebuilt and the noise did not go away. This spring I replaced the cutless bearing and it is amazing how much quieter the engine and drive train became. The thunk thunk is gone.
Also, it turns out not all props are made the same. Many folding props are actually made so that they are more efficient in motoring in the forward direction than a fixed prop because they do not have to have the compromised shape to reduce drag when sailing. Like many things in sailing, the improved efficiency in forward sometimes results in a reduced efficiency in reverse. Autoprop claims a higher efficiency than other props because the pitch changes with load. That said, I have come across some negative comments on the Autoprop when used in rough conditions.
Getting back to the original question, my boat made a very distinct 'thunk thunk' at speed. I had been concerned that it was a problem with the Martec prop and had it rebuilt and the noise did not go away. This spring I replaced the cutless bearing and it is amazing how much quieter the engine and drive train became. The thunk thunk is gone.
Also, it turns out not all props are made the same. Many folding props are actually made so that they are more efficient in motoring in the forward direction than a fixed prop because they do not have to have the compromised shape to reduce drag when sailing. Like many things in sailing, the improved efficiency in forward sometimes results in a reduced efficiency in reverse. Autoprop claims a higher efficiency than other props because the pitch changes with load. That said, I have come across some negative comments on the Autoprop when used in rough conditions.
From haffiman37 on the Sailing mailing list:
A year ago I replaced my original Radice 2-blade prop with a Gori
16,5 x 12 x 3 on my Janneau SO37 2002 model. The main attraction was
the advantage of the "overdrive" function that would, if worked, give
me an extra range of approx 20%. Quite interesting as I am going for
quite a trip later this year: Norway to Malaysia through the Panama
Canal and Pacific.
The propeller was calculated by Gori who was given all info on the boat. However approx 150 RPM was missing when testing on "empty" boat. Next shock came when I lifted the boat after one year at sea: severe galvanic corrosion, beyond repair as stated by Gori. The original factory-mounted anode was of course gone. The original Radice had no signs of corrosion after 14 months and exactly the same conditions. No shorepower hookup etc. The boat is always moored with battery-switches off.
However Gori denied any responsibility whatsoever both for corrosion and even for the wrong prop calculation. Instead they claimed 150 RPM below required RPM was "bulls eye", and corrosion a result of neglected maintenance, (change of anode). My opinion is of course quite different, as I claim that a service-interval of 12 months has to be expected and calculated when designing the propeller and anode dimension. Not to forget that the service department of Gori threatened me with a lawsuit if I went public with this case, giving Gori a bad reputation. No need to say that buying a Gori 3-blade is not what I recommend if you are looking for lasting quality and good service!
The propeller was calculated by Gori who was given all info on the boat. However approx 150 RPM was missing when testing on "empty" boat. Next shock came when I lifted the boat after one year at sea: severe galvanic corrosion, beyond repair as stated by Gori. The original factory-mounted anode was of course gone. The original Radice had no signs of corrosion after 14 months and exactly the same conditions. No shorepower hookup etc. The boat is always moored with battery-switches off.
However Gori denied any responsibility whatsoever both for corrosion and even for the wrong prop calculation. Instead they claimed 150 RPM below required RPM was "bulls eye", and corrosion a result of neglected maintenance, (change of anode). My opinion is of course quite different, as I claim that a service-interval of 12 months has to be expected and calculated when designing the propeller and anode dimension. Not to forget that the service department of Gori threatened me with a lawsuit if I went public with this case, giving Gori a bad reputation. No need to say that buying a Gori 3-blade is not what I recommend if you are looking for lasting quality and good service!
From Jerry on Cruising World message board:
I have had severe problems with Gori prop (3-blade folding). I have for the second time lost a
blade placing myself, guests, and boat in danger. Both incidents happened with less than 10 hours
on the prop. I returned the prop with their authorization two months ago and have not heard from
them since. I am preparing to take further action.
From Ivars on SailNet's Gulfstar mailing list:
Re: folding prop on GS 41 ketch
You need to check the amount of clearance behind the prop to determine whether a folding prop or a feathering prop will be better suited. Most prop manufacturers should have data as to which prop will be better suited. A folding prop needs more space (to fold), whereas with a feathering prop the blades just rotate into a feathering position. Either one will enhance the entire sailing experience and is the best bang-for-your-buck performance enhancement. Typical speed gains under sail are close to 1 knot. At 5 knots that is a 20% speed gain. Performance under power is not affected vs a fixed prop.
You need to check the amount of clearance behind the prop to determine whether a folding prop or a feathering prop will be better suited. Most prop manufacturers should have data as to which prop will be better suited. A folding prop needs more space (to fold), whereas with a feathering prop the blades just rotate into a feathering position. Either one will enhance the entire sailing experience and is the best bang-for-your-buck performance enhancement. Typical speed gains under sail are close to 1 knot. At 5 knots that is a 20% speed gain. Performance under power is not affected vs a fixed prop.
From Bad Matt on Latitudes and Attitudes Cruisers Forum:
A fixed prop is designed to spin forward. Its blades are not properly curved to spin in reverse.
It will work in reverse, just not well, which is why fixed-prop boats usually are
somewhere between bad and useless in reverse (lots of prop-walk usually).
The feathering prop allows the prop blades to be properly aligned when
spinning in reverse, thus making the boat handle better in reverse.
Almost like if you were to take the prop off and put it back on backwards
when going in reverse (at least for the Gori).
Re: which prop:
The Beneteau list has a semi-annual prop war, which usually deteriorates into the kind of name-calling and childishness one would expect on the Ford vs. Chevy forum. I think this happens because those who have upgraded (myself included) to a Gori-Auto-Flex-o-Max-a-Vari-who-the-hell-cares-what prop have found it to be some of the best money you can possibly spend on a boat (unless it's sinking). I have a Gori and I absolutely love it and would recommend it again without hesitation. That said, some portion of that euphoria is simply the handling under power and substantial increase in speed under sail (like, a knot's worth) that I've observed. Now, I can't say that any other, or all, of the competitors' products would or would not provide the same enjoyment. I think I can say this: you will NOT regret getting a high-tech prop. I don't know that the Gori is necessarily so superior to the others. In theory, it's curved blades allow it to power better in reverse than the Max (I buy that, I guess). I've made several people nearly commit suicide when they saw how easily I get into my slip.
From Jeffrey Kay on Latitudes and Attitudes Cruisers Forum:
Re: which prop:
The Beneteau list has a semi-annual prop war, which usually deteriorates into the kind of name-calling and childishness one would expect on the Ford vs. Chevy forum. I think this happens because those who have upgraded (myself included) to a Gori-Auto-Flex-o-Max-a-Vari-who-the-hell-cares-what prop have found it to be some of the best money you can possibly spend on a boat (unless it's sinking). I have a Gori and I absolutely love it and would recommend it again without hesitation. That said, some portion of that euphoria is simply the handling under power and substantial increase in speed under sail (like, a knot's worth) that I've observed. Now, I can't say that any other, or all, of the competitors' products would or would not provide the same enjoyment. I think I can say this: you will NOT regret getting a high-tech prop. I don't know that the Gori is necessarily so superior to the others. In theory, it's curved blades allow it to power better in reverse than the Max (I buy that, I guess). I've made several people nearly commit suicide when they saw how easily I get into my slip.
I have learned that one of the major differences with the Gori is that it has an "overdrive" feature.
From their web site: The "overdrive" is used when motorsailing in fair weather or when
using the engine under sail. The "overdrive" gives the same speed at lower RPMs.
The result is less engine noise, less vibration and better fuel economy.
The function is simple. E.g. when changing from "overdrive" to normal ahead the
shift and throttle control is set in neutral, which allows the propeller to fold.
Then the shift and throttle control is set in forward again.
It sounds a little confusing -- like how do you know if your in overdrive or not -- but I'd imagine you'd get used to it.
From Bad Matt on Latitudes and Attitudes Cruisers Forum:
It sounds a little confusing -- like how do you know if your in overdrive or not -- but I'd imagine you'd get used to it.
You know, I forgot about the overdrive part (boat's on the hard - go figger).
I've used that a couple of times. It's nice. You gotta be serious about it though,
because to get into overdrive, you gotta go backwards, then pop the throttle into
neutral, then forward and you're in overdrive. It is nice when motorsailing though.
I've never had a problem accidentally winding up in OD. It's pretty easy to tell
when you're in OD inadvertently (i.e. no sails helping out) because the engine
will be laboring and won't wind up like normal when throttle is applied.
If you think about it (and this is one of the reasons I don't use OD all THAT much),
putting the prop in OD without the sails helping to move the boat is basically
like having an over-pitched prop, which is overloading the engine.
From Paco PWD on Latitudes and Attitudes Cruisers Forum:
I had all the same issues with the original 18x13 fixed 3 blade prop on my Corbin 39.
Since we got a "J Prop" variable pitch / feathering prop, it's like a different boat,
sailing and motoring. I very highly recommend it.
The blades have the same profile in Forward and Rev.
and the pitch is externally adjustable (even in the water) by indexing a marked dial on the hub.
In case of the J Prop, you can go with the largest diameter that can fit, as you can easily pitch down if need be.
From Jeffrey Kay on Latitudes and Attitudes Cruisers Forum:
In case of the J Prop, you can go with the largest diameter that can fit, as you can easily pitch down if need be.
> how much speed under sail does your feathering prop gain you over a fixed?
All things being equal, about a knot.
[1980 Gulfstar 44 CC Sloop]
From Bad Matt on Latitudes and Attitudes Cruisers Forum:
All things being equal, about a knot.
[1980 Gulfstar 44 CC Sloop]
> how much speed under sail does your feathering prop gain you over a fixed?
So, another way to think about it would be that it's about a 15-20% increase in speed. It is extremely noticeable.
So, another way to think about it would be that it's about a 15-20% increase in speed. It is extremely noticeable.
From The Barnacle on Latitudes and Attitudes Cruisers Forum:
One comment about gaining 3/4 to 1 knot sailing speed by using a feathering prop
or 2-blade vs 3-blade [2-blade turned to "hide" behind the keel].
Those are VERY optimistic numbers. I've towed buckets,
people, anchors and all types of draggy items while sailing different boats
just to check drag/speed. It takes a lot more area than a prop to slow a 30-40'
sailboat boat down 3/4 to 1 knot. If it does there isn't enough sail out and
you are in ghosting wind conditions.
From John Dunsmoor:
Would not completely agree, the personality of vessels is many times unique.
I can attest that the difference between fixed prop left free to rotate and
not rotate while sailing is negligible. One of the reasons that we always lock
the prop when sailing on our boats. But having sailed with fully feathering
props the difference can be dramatic. We were on a 78 foot Cheoy Lee motorsailer
with huge propellers, they must have been around 30" and the boat would not
tack without cranking up the outboard engine and helping the boat out.
The boat had a lot of sail and really powered along in anything approaching twenty knots.
But between the twenty foot beam and a massive amount of windage it just would not
come through the eye of the wind. The boat was modified to use a set of Max Props,
which feather, and the boat would tack without cranking an engine.
On Ciboney, 400 Beneteau, this is a modern clean underwater design and one time we lost the prop and had to sail back from the Bahamas without a prop, you could feel the difference. Everything about the handling of the boat was different, not spectacularly different but you could tell.
On our little Columbia with or without the motor in the water, large difference in both handling and speed.
Now the fellow is right about maximum speed potential, if the hull speed of the vessel is eight knots and you can reach this with a locked three bladed prop in twenty knots of wind, then the installation of a very expensive feathering prop (and the Max Props set the Choey Lee owners back a fortune) is not going to change the formula much. Your hull speed is still going to be eight knots, with a feathering prop you might be able to achieve hull speed in 15 knots of wind, instead of twenty, who knows.
But the fact is most of our sailing is done in less than twenty knots, and do you want to be sailing in ten knots of wind at four knots, or five and a half knots. Twenty four hours the difference is 36 miles, going across the Gulf Stream the difference would be hours. Four knots is barely enough to beat the current; the difference between four and six knots is dramatic.
On Magnolia [Gulfstar 44 motor-sailer]: I would think that the change would be dramatic. You could experiment by pulling your prop and sailing without it for a bit, an awful lot of work. The personality of the boat would change. At the same time the boat is a bit of a barge with lots of sail area so maybe the difference would not be so dramatic, especially once you had some wind. On the other hand a three-bladed Max prop is going to set you back thousands of dollars. Is half a year's cruising fund worth it ? One element is how much time you are actually spending moving, which would make a boat that is sailing only a few days a month less worth the investment than a cruising vessel that is continually on the move.
Another problem is growth, a fouled prop is a pain, and a fouled feathering prop is more of a pain.
I was on a 65-foot Lancer with Max Props, and one thing that I did not like was the bang that emanated from changing from forward to reverse. I was sure that we would eventually shear something, but it never happened. And also there was a time lag when docking between forward and reverse, which was another queer element that one needed to get used to. It was only a delivery so I never got used to the idiosyncrasies of the power train on this vessel.
On Ciboney, 400 Beneteau, this is a modern clean underwater design and one time we lost the prop and had to sail back from the Bahamas without a prop, you could feel the difference. Everything about the handling of the boat was different, not spectacularly different but you could tell.
On our little Columbia with or without the motor in the water, large difference in both handling and speed.
Now the fellow is right about maximum speed potential, if the hull speed of the vessel is eight knots and you can reach this with a locked three bladed prop in twenty knots of wind, then the installation of a very expensive feathering prop (and the Max Props set the Choey Lee owners back a fortune) is not going to change the formula much. Your hull speed is still going to be eight knots, with a feathering prop you might be able to achieve hull speed in 15 knots of wind, instead of twenty, who knows.
But the fact is most of our sailing is done in less than twenty knots, and do you want to be sailing in ten knots of wind at four knots, or five and a half knots. Twenty four hours the difference is 36 miles, going across the Gulf Stream the difference would be hours. Four knots is barely enough to beat the current; the difference between four and six knots is dramatic.
On Magnolia [Gulfstar 44 motor-sailer]: I would think that the change would be dramatic. You could experiment by pulling your prop and sailing without it for a bit, an awful lot of work. The personality of the boat would change. At the same time the boat is a bit of a barge with lots of sail area so maybe the difference would not be so dramatic, especially once you had some wind. On the other hand a three-bladed Max prop is going to set you back thousands of dollars. Is half a year's cruising fund worth it ? One element is how much time you are actually spending moving, which would make a boat that is sailing only a few days a month less worth the investment than a cruising vessel that is continually on the move.
Another problem is growth, a fouled prop is a pain, and a fouled feathering prop is more of a pain.
I was on a 65-foot Lancer with Max Props, and one thing that I did not like was the bang that emanated from changing from forward to reverse. I was sure that we would eventually shear something, but it never happened. And also there was a time lag when docking between forward and reverse, which was another queer element that one needed to get used to. It was only a delivery so I never got used to the idiosyncrasies of the power train on this vessel.
From 5/1/2000 issue of Practical Sailor:
Max-Prop: flat blades so less efficient in forward, better in reverse.
Autoprop: requires less RPM than Max-Prop, but longer to get traction when starting, more drag and vibration.
From Bruce Clark on Latitudes and Attitudes Cruisers Forum:
I have a Maxprop and am very pleased with it. I have one friend who removed
an Autoprop after one year because he was not pleased with the performance
for some reason. I have heard of a few boats having motor-mount problems
because the Autoprop is so effective in acceleration and reversing.
This would not be a problem with the prop - more of an endorsement.
From Senator on Latitudes and Attitudes Cruisers Forum:
My take on each is this:
Autoprop - probably more efficient under power and especially motor-sailing, since the prop always finds it's own best pitch. Just as good in forward as reverse. Sort of like an automatic transmission. Also one of the few/only props that swivel 180 degrees and can make this claim. If I was a bluewater cruiser where I might have to get as much efficiency as possible and put as many miles per gallon while motoring ---- I don't think there is anything better than the Autoprop at efficiency under varying loads, which happens often when the motor is needed to cruise. (Autoprop is 25% more efficient than fixed 3 blades and 30% more than folding.) Good speed gain under sail only with the feathering, but not as much as with folding props or the Maxprop. A few users report a little more vibration under power. (I don't notice it.) Some people also report they have to maneuver at speeds above slow idle to get the blades to start to grab. Some people choose to add a little length to the prop shaft with a "drivesaver" to give more clearance from the strut depending on your boat. So I say the nod goes to the Autoprop for cruisers.
Maxprop - slightly less drag under sail because the blades are flat rather than cupped like the Autoprop. Good motoring power compared to standard prop, but not quite as good as Autoprop except perhaps at full power. Since the pitch can only be adjusted for max efficiency at full power, the efficiency at part throttle or motor sailing will be less. Because you have to adjust the pitch yourself, some owners report having a diver make several dives and adjustments before they are happy with the pitch. This seems to be trying the recommended setting and then trial and error to get it perfect. Probably not that great a deal unless you are a perfectionist, and it is only done once. So I say the nod goes to the Maxprop for racers.
Basically the Autoprop is great for getting the most out of your engine and at different speeds and ideal for motorsailing. Debatable, but more generated thrust in forward and reverse. The Maxiprop gets the upper hand in reducing drag especially in lighter air. (I think when the wind picks up you won't notice the difference.) I have heard a few times that fuel consumption is poor with the Maxprop in heavy and hard conditions
With any of these props works with the dealer/factory to make sure the size and pitch is correct for your boat, engine and transmission type. In these cases one size does not fit all.
Autoprop - probably more efficient under power and especially motor-sailing, since the prop always finds it's own best pitch. Just as good in forward as reverse. Sort of like an automatic transmission. Also one of the few/only props that swivel 180 degrees and can make this claim. If I was a bluewater cruiser where I might have to get as much efficiency as possible and put as many miles per gallon while motoring ---- I don't think there is anything better than the Autoprop at efficiency under varying loads, which happens often when the motor is needed to cruise. (Autoprop is 25% more efficient than fixed 3 blades and 30% more than folding.) Good speed gain under sail only with the feathering, but not as much as with folding props or the Maxprop. A few users report a little more vibration under power. (I don't notice it.) Some people also report they have to maneuver at speeds above slow idle to get the blades to start to grab. Some people choose to add a little length to the prop shaft with a "drivesaver" to give more clearance from the strut depending on your boat. So I say the nod goes to the Autoprop for cruisers.
Maxprop - slightly less drag under sail because the blades are flat rather than cupped like the Autoprop. Good motoring power compared to standard prop, but not quite as good as Autoprop except perhaps at full power. Since the pitch can only be adjusted for max efficiency at full power, the efficiency at part throttle or motor sailing will be less. Because you have to adjust the pitch yourself, some owners report having a diver make several dives and adjustments before they are happy with the pitch. This seems to be trying the recommended setting and then trial and error to get it perfect. Probably not that great a deal unless you are a perfectionist, and it is only done once. So I say the nod goes to the Maxprop for racers.
Basically the Autoprop is great for getting the most out of your engine and at different speeds and ideal for motorsailing. Debatable, but more generated thrust in forward and reverse. The Maxiprop gets the upper hand in reducing drag especially in lighter air. (I think when the wind picks up you won't notice the difference.) I have heard a few times that fuel consumption is poor with the Maxprop in heavy and hard conditions
With any of these props works with the dealer/factory to make sure the size and pitch is correct for your boat, engine and transmission type. In these cases one size does not fit all.
From PhantomSailor on Latitudes and Attitudes Cruisers Forum:
I have an Auto Prop on my 1997 Catalina 42. I just love the propeller.
Moves the boat a 7.2 knots at 2500 RPM with fuel consumption at .73 - .76 GPH.
The engine is a Yanmar 50hp 4JH2E. Stops on a dime and very little prop walk in reverse.
Sailing performance is about the same as my friend's Flexofold 3 blade feathering prop
on an identical boat.
FYI, Autoprop recommends that you put the transmission into forward gear while sailing to fully feather the blades and to stop rotation. The common practise of putting the gear shift into reverse will not work with an Autoprop as the blades will rotate to the reverse position which causes the prop and shaft to rotate in the reverse direction. Most trannies will allow rotation in the same direction as the gear shift indicates. I.E. if you have a right hand prop, the prop and shaft rotates clockwise (looking at the prop from the stern)in forward gear. With engine shut off, the gear shift in reverse, and sailing forward, the Autoprop will go to the reverse blade position and the prop will want to freewheel CCW. The trannie in reverse will allow this because that is the direction the trannie rotates the shaft in reverse. If you place the gear shift in forward, the prop still tries to rotate the shaft CCW but the trannie will not freewheel since CCW is the opposite direction the trannie drives the shaft with the engine running. Once the prop is fully feathered, you can return the gear shift to neutral but I seldom bother. BTW, it takes 3 or 4 knots of boatspeed to fully feather the blades. However, once feathered, they will stay feathered even if the boat speed drops again.
FYI, Autoprop recommends that you put the transmission into forward gear while sailing to fully feather the blades and to stop rotation. The common practise of putting the gear shift into reverse will not work with an Autoprop as the blades will rotate to the reverse position which causes the prop and shaft to rotate in the reverse direction. Most trannies will allow rotation in the same direction as the gear shift indicates. I.E. if you have a right hand prop, the prop and shaft rotates clockwise (looking at the prop from the stern)in forward gear. With engine shut off, the gear shift in reverse, and sailing forward, the Autoprop will go to the reverse blade position and the prop will want to freewheel CCW. The trannie in reverse will allow this because that is the direction the trannie rotates the shaft in reverse. If you place the gear shift in forward, the prop still tries to rotate the shaft CCW but the trannie will not freewheel since CCW is the opposite direction the trannie drives the shaft with the engine running. Once the prop is fully feathered, you can return the gear shift to neutral but I seldom bother. BTW, it takes 3 or 4 knots of boatspeed to fully feather the blades. However, once feathered, they will stay feathered even if the boat speed drops again.
From article by Greg Jones in Feb 2004 issue of Blue Water Sailing magazine:
- Taking spare blades with you is not practical,
as the blades are a carefully matched and balanced set.
Better to carry a fixed prop as a spare.
- Feathering props (and Autoprop) have larger hubs than
the others, and often larger blades to compensate.
- Feathering props (and Autoprop) need annual
greasing (some can be lubricated in the water); folding props
need less maintenance.
- Saildrives have a splined, non-tapered shaft.
USA-built boats have one standard shaft taper.
European-built boats have one of at least four different shaft tapers.
- Feathering props are slightly better for motoring or motor-sailing; folding props are slightly better for sailing.
From Steve Rust on cruisersforum.com:
A couple of additional points from the article in Feb 04 edition of Blue Water Sailing:
Feathering props will generally provide more power in reverse than folding props because they present the same leading edge whether in forward or reverse. And as stated before, folding props will generally provide more power in forward due to the more efficient blade shape.
Folding props are superior if reduced drag under sail is your goal with one exception. If your prop shaft is at a considerable angle from horizontal, then a feathering prop with independently rotating blades will deliver less drag as each blade can weathercock to the water flow. Folding or ganged feathering blades will be pulled through the water at the same angle as the prop shaft. Kiwi Props and Autoprop were two listed as having independent blades.
Feathering props will generally provide more power in reverse than folding props because they present the same leading edge whether in forward or reverse. And as stated before, folding props will generally provide more power in forward due to the more efficient blade shape.
Folding props are superior if reduced drag under sail is your goal with one exception. If your prop shaft is at a considerable angle from horizontal, then a feathering prop with independently rotating blades will deliver less drag as each blade can weathercock to the water flow. Folding or ganged feathering blades will be pulled through the water at the same angle as the prop shaft. Kiwi Props and Autoprop were two listed as having independent blades.
From delmarrey on cruisersforum.com:
I vote for the feathering prop.
I've run both, and the feathering prop really makes a difference.
Once you learn the personality of the feathering prop you'll forget all about the fixed.
They do need to be kept in good shape or they'll vibrate.
From Roy Brown on the Morgan mailing list:
I went with the 4-blade Variprop which is probably the most expensive. Once
I installed it I experienced significant shaft vibration as the prop is very
heavy so now my additional expenses are:
1) Haulout to remove variprop and re-install original prop.
2) Install a new shaft - SS to replace the bronze shaft.
3) Install an extra strut mid-shaft since the distance between engine and prop is extremely long (this is the recommendation of both the marina and prop manufacturer once I explained the vibration problem).
...
Re-installing the old prop solved all the problems so I am confident the shaft and alignment are OK.
The old prop is a LH 18" diameter 20" pitch - the new Variprop is 23" diameter and 19" pitch. This is the size recommended by the manufacturer for the engine (Perkins M65) and there is more than enough clearance from the tip of the blades to hull.
I measured the shaft length and there is 46" inside the boat and 63" outside and so the additional strut is going outside where the shaft exits the hull.
From Ed Merta on the Morgan mailing list:1) Haulout to remove variprop and re-install original prop.
2) Install a new shaft - SS to replace the bronze shaft.
3) Install an extra strut mid-shaft since the distance between engine and prop is extremely long (this is the recommendation of both the marina and prop manufacturer once I explained the vibration problem).
...
Re-installing the old prop solved all the problems so I am confident the shaft and alignment are OK.
The old prop is a LH 18" diameter 20" pitch - the new Variprop is 23" diameter and 19" pitch. This is the size recommended by the manufacturer for the engine (Perkins M65) and there is more than enough clearance from the tip of the blades to hull.
I measured the shaft length and there is 46" inside the boat and 63" outside and so the additional strut is going outside where the shaft exits the hull.
... you might be getting some vibration from the skeg shadow, which will
change the pressure on the prop blades, as they go behind it. You can also
have this problem with a two-bladed prop.
That is one of the advantages to the three-bladed prop, you always have two blades loaded.
That is one of the advantages to the three-bladed prop, you always have two blades loaded.
From Maine Sail on SailNet forum 11/2009:
Re: Campbell Sailor:
Here's a review I posted on another forum earlier this fall:
After much research and consternation I decided on a new prop this past winter. [Boat: CS-36T.]
Mechanical vs. Fixed:
As much as I would have liked a feathering prop (Max-Prop was my choice), I decided against it after speaking at length with my local prop shop and a few friends at boatyards. With the tides in Maine we get lots of floating debris, floating line and lobster pots. As was stated to me by more than one prop shop, and more than one boatyard employee, the mechanical props are just not as reliable when you hit something. This happens in Maine. This is not to say they are not durable, but when I was staring at a four year old mechanical prop overhaul, on the bench at my local shop, for "$900-$1000", it made my decision that much easier.
The minimal drag of a feathering prop would be awesome, but I don't race my own boat, so 3-6 seconds per mile lost out to durability, simplicity and reliability. Folders were not even considered this time around, and because I have already owned them in the past it was easy to rule them out this time.
Two blades vs. three:
For me this one is easy. Over the years I have had numerous two-blade props and have never found one I liked. When I want to use my motor I want a real motor, not the feel of an electric trolling motor. With the tidal currents in Maine and the lack of summer winds we often see, having a smooth well-balanced three-blade prop is a must for us.
I am not one who is afraid to fire up the Japanese genny when the wind dips below 5 knots, especially with an antsy toddler who's ready for some island exploring etc ... We also like to venture up some of our many rivers which can have massive currents. Two-blade props have never given me a feeling of total confidence, with a small aux motor, in battling head on with these currents.
Which Fixed Prop?:
After lots of research I decided on a Campbell Sailor Prop ("CS" from here forth). I had read many, many, many prop reviews and discussions using the search tool on about 20+ sailing forums, from SBO to SCCA to SailNet, and every one in-between. One thing I noticed was that I had not read much if any negative comments about the CS. So the Campbell Sailor three-blade it was.
Ordering:
After consulting with Norm at West By North, the makers of the Campbell Sailor, I ordered a 16"X10X1" RH prop. The prop took about three to four weeks for delivery which was fine due to my off-season planning.
Sizing:
Contrary to popular beliefs and misconceptions, prop sizing is NOT an exact science. In order to hit max RPM and size the prop to do that without going over or under by much is not easy and often takes two or more attempts to get it spot on. I can remember working with my old friend Brian, a marine surveyor, who always checked the prop sizing against max rated RPM. We found that close to half the boats had the wrong size prop.
The CS prop is EXTREMELY efficient. Norm spec'd mine at 16" diameter X a 10 pitch. I was skeptical at first because my three-blade Michigan Wheel was a 16" X 12 pitch which is a lot more aggressive. I could not understand how, with losing so much surface area, I could also reduce pitch ? Norm used the Michigan Wheel prop size calculator, which he tweaks for the CS prop design, and decided on the 16X10. Unfortunately when I got the 16X10 it was still over-propped and I was under max rated RPM by about 300 RPM. Not good. Over-propping your engine is never a good idea so I wanted to fix this as soon as possible.
Once I discovered the 16X10 was still too aggressive, despite the blade surface area being MUCH smaller than the Michigan Wheel, I called Norm. Norm decided to drop the pitch to a 9 and remove some of the cupping on the trailing edge of the CS prop's blade.
The customer service Norm provides is stellar! He actually sent me a brand new replacement prop ahead of time so I could literally change out my prop, with the boat still in the slings, and then send the used 16X10 prop back. The 16X9 prop worked flawlessly and I am now within 30 RPM of max rated with a clean bottom and prop.
If you've been paying attention the Campbell Sailor is a full 3 increments of pitch smaller than the Michigan Wheel prop and has far less surface area for less drag through the water. Efficient does not even begin to describe this prop's unique design. Pitch is basically the theoretical travel a prop makes in one revolution. For example a 10 pitch will theoretically travel 10" in one full revolution provided there is no "slip", but there is almost always slip.
Vibration / Smoothness:
This prop has proven to be the smoothest prop I have ever used or owned on a sailboat. The drive train exhibits no vibration throughout the entire RPM range even at WOT. My Michigan Wheel was tuned and balanced less than one year ago and still could not compete with the smoothness of the CS even on a brand new shaft.
Prop Walk:
Despite the aggressive design of the CS blades the prop displays considerably less prop walk than did the Michigan Wheel. I can not say it has none, but it is about 70% better than the fixed three-blade Michigan was.
Drag:
As some of you may know I conducted my own little prop drag study. The results were rather eye-opening. The CS prop has about 13 pounds real of drag at about 4.2-4.4 knots while the three-blade Michigan Wheel had about 39 pounds of drag at only 4-4.2 knots. For those of you doing the math that is roughly a 200% increase of drag for the Michigan 16X12 than for the CS 16X10. Yes, this is still more drag than a Max-Prop but nowhere near the drag of the Michigan Wheel..
Speed:
I have always run my boat to put the stern wave right at point where my the hull sides and transom meet but without the water climbing up the transom. This puts me at about 6.6-6.8 knots. I used to be at 2400 RPM to do this with the 16X12 Michigan Wheel and am now consistently at about 2250 to do the exact same thing with the CS 16X9. Both props would hit a WOT max rated throttle of 3000 RPM within +/- 30 RPM.
Fuel Use:
I could not decipher any real measurable difference in fuel consumption, perhaps because we also have engine-driven refrigeration which tends wreck the mathematics of measuring fuel consumption for moving the vessel through the water.
Conclusion:
If you are looking for a rugged, reliable, smooth and efficient fixed three-blade prop with less drag than the typical Michigan Wheels, that come standard on most boats, then the Campbell Sailor certainly fits the bill.
While slightly more expensive than a Michigan Wheel it is certainly considerably less than any of the feathering or folders. I think I paid about $540 delivered but I'll need to find my credit card statement to be sure.
I waited until I had nearly a full season of use to post this so it could be more accurate and less impulsive. I find if I write something shortly after I buy it I can be admittedly little more biased, in a pro fashion, towards it, then if I wait and use it more. After nearly a full season of use I find I like it even more now than when I initially bought it, perhaps due to the sizing mishap.
From TractorJohn on SailNet forum 11/2009:Here's a review I posted on another forum earlier this fall:
After much research and consternation I decided on a new prop this past winter. [Boat: CS-36T.]
Mechanical vs. Fixed:
As much as I would have liked a feathering prop (Max-Prop was my choice), I decided against it after speaking at length with my local prop shop and a few friends at boatyards. With the tides in Maine we get lots of floating debris, floating line and lobster pots. As was stated to me by more than one prop shop, and more than one boatyard employee, the mechanical props are just not as reliable when you hit something. This happens in Maine. This is not to say they are not durable, but when I was staring at a four year old mechanical prop overhaul, on the bench at my local shop, for "$900-$1000", it made my decision that much easier.
The minimal drag of a feathering prop would be awesome, but I don't race my own boat, so 3-6 seconds per mile lost out to durability, simplicity and reliability. Folders were not even considered this time around, and because I have already owned them in the past it was easy to rule them out this time.
Two blades vs. three:
For me this one is easy. Over the years I have had numerous two-blade props and have never found one I liked. When I want to use my motor I want a real motor, not the feel of an electric trolling motor. With the tidal currents in Maine and the lack of summer winds we often see, having a smooth well-balanced three-blade prop is a must for us.
I am not one who is afraid to fire up the Japanese genny when the wind dips below 5 knots, especially with an antsy toddler who's ready for some island exploring etc ... We also like to venture up some of our many rivers which can have massive currents. Two-blade props have never given me a feeling of total confidence, with a small aux motor, in battling head on with these currents.
Which Fixed Prop?:
After lots of research I decided on a Campbell Sailor Prop ("CS" from here forth). I had read many, many, many prop reviews and discussions using the search tool on about 20+ sailing forums, from SBO to SCCA to SailNet, and every one in-between. One thing I noticed was that I had not read much if any negative comments about the CS. So the Campbell Sailor three-blade it was.
Ordering:
After consulting with Norm at West By North, the makers of the Campbell Sailor, I ordered a 16"X10X1" RH prop. The prop took about three to four weeks for delivery which was fine due to my off-season planning.
Sizing:
Contrary to popular beliefs and misconceptions, prop sizing is NOT an exact science. In order to hit max RPM and size the prop to do that without going over or under by much is not easy and often takes two or more attempts to get it spot on. I can remember working with my old friend Brian, a marine surveyor, who always checked the prop sizing against max rated RPM. We found that close to half the boats had the wrong size prop.
The CS prop is EXTREMELY efficient. Norm spec'd mine at 16" diameter X a 10 pitch. I was skeptical at first because my three-blade Michigan Wheel was a 16" X 12 pitch which is a lot more aggressive. I could not understand how, with losing so much surface area, I could also reduce pitch ? Norm used the Michigan Wheel prop size calculator, which he tweaks for the CS prop design, and decided on the 16X10. Unfortunately when I got the 16X10 it was still over-propped and I was under max rated RPM by about 300 RPM. Not good. Over-propping your engine is never a good idea so I wanted to fix this as soon as possible.
Once I discovered the 16X10 was still too aggressive, despite the blade surface area being MUCH smaller than the Michigan Wheel, I called Norm. Norm decided to drop the pitch to a 9 and remove some of the cupping on the trailing edge of the CS prop's blade.
The customer service Norm provides is stellar! He actually sent me a brand new replacement prop ahead of time so I could literally change out my prop, with the boat still in the slings, and then send the used 16X10 prop back. The 16X9 prop worked flawlessly and I am now within 30 RPM of max rated with a clean bottom and prop.
If you've been paying attention the Campbell Sailor is a full 3 increments of pitch smaller than the Michigan Wheel prop and has far less surface area for less drag through the water. Efficient does not even begin to describe this prop's unique design. Pitch is basically the theoretical travel a prop makes in one revolution. For example a 10 pitch will theoretically travel 10" in one full revolution provided there is no "slip", but there is almost always slip.
Vibration / Smoothness:
This prop has proven to be the smoothest prop I have ever used or owned on a sailboat. The drive train exhibits no vibration throughout the entire RPM range even at WOT. My Michigan Wheel was tuned and balanced less than one year ago and still could not compete with the smoothness of the CS even on a brand new shaft.
Prop Walk:
Despite the aggressive design of the CS blades the prop displays considerably less prop walk than did the Michigan Wheel. I can not say it has none, but it is about 70% better than the fixed three-blade Michigan was.
Drag:
As some of you may know I conducted my own little prop drag study. The results were rather eye-opening. The CS prop has about 13 pounds real of drag at about 4.2-4.4 knots while the three-blade Michigan Wheel had about 39 pounds of drag at only 4-4.2 knots. For those of you doing the math that is roughly a 200% increase of drag for the Michigan 16X12 than for the CS 16X10. Yes, this is still more drag than a Max-Prop but nowhere near the drag of the Michigan Wheel..
Speed:
I have always run my boat to put the stern wave right at point where my the hull sides and transom meet but without the water climbing up the transom. This puts me at about 6.6-6.8 knots. I used to be at 2400 RPM to do this with the 16X12 Michigan Wheel and am now consistently at about 2250 to do the exact same thing with the CS 16X9. Both props would hit a WOT max rated throttle of 3000 RPM within +/- 30 RPM.
Fuel Use:
I could not decipher any real measurable difference in fuel consumption, perhaps because we also have engine-driven refrigeration which tends wreck the mathematics of measuring fuel consumption for moving the vessel through the water.
Conclusion:
If you are looking for a rugged, reliable, smooth and efficient fixed three-blade prop with less drag than the typical Michigan Wheels, that come standard on most boats, then the Campbell Sailor certainly fits the bill.
While slightly more expensive than a Michigan Wheel it is certainly considerably less than any of the feathering or folders. I think I paid about $540 delivered but I'll need to find my credit card statement to be sure.
I waited until I had nearly a full season of use to post this so it could be more accurate and less impulsive. I find if I write something shortly after I buy it I can be admittedly little more biased, in a pro fashion, towards it, then if I wait and use it more. After nearly a full season of use I find I like it even more now than when I initially bought it, perhaps due to the sizing mishap.
Having purchased a Campbell Sailer myself, I second everything that has been said
and will buy another when I need to. But I was not told that I would be charged for repitching,
and ultimately paid several hundred more to get it right.
Now if they had used my requested pitch (based on Catalina factory recomendation),
rather than their own ideas initially I would expect it to pay for changes, but they (CS)
told me they knew best from experience. The final pitch was exactly what I had asked
for originally (Catalina did know best).
So I would get it in writing who is paying for repitching and the associated costs. Two repitch's meant pulling the boat three times. Ouch.
So I would get it in writing who is paying for repitching and the associated costs. Two repitch's meant pulling the boat three times. Ouch.
Keeping lines out of the propeller:
From Bryan Genez on WorldCruising mailing list:
I was tempted to install a strut from the bottom-aft point of my keel to the bottom-forward point of my rudder skeg, to keep trap lines out of my propeller. But then I worried that a hard grounding might break the strut and let it bend up to hit the propeller. So I didn't install one.
From Robin Roberts on The Live-Aboard List:
To dive and cut a line off the shaft and prop, use a hacksaw blade, not a knife.
[For crab pot protection, instead of a line-cutting "spur":]
I have a system that I prefer for two reasons, cheaper and "kinder". It's a simple stainless vane that bolts to the bottom of the shaft strut and is angled backwards to a point beyond the prop. Any line crossing my shaft will drag down the vane, then pop up on the hull at a point where it cannot foul in the screw.
It was on the boat when I bought her. Since I've never seen one advertised, I presume it's custom made. But I'll bet the whole thing didn't cost $100. In twelve years, sailing in the crab-pot enriched waters of the Chesapeake, I've never fouled my prop. I did once manage to foul it in Maine by backing over a mooring toggle, though.
The vane doesn't cut lines. The watermen still have a trap they can locate and harvest.
I have a system that I prefer for two reasons, cheaper and "kinder". It's a simple stainless vane that bolts to the bottom of the shaft strut and is angled backwards to a point beyond the prop. Any line crossing my shaft will drag down the vane, then pop up on the hull at a point where it cannot foul in the screw.
It was on the boat when I bought her. Since I've never seen one advertised, I presume it's custom made. But I'll bet the whole thing didn't cost $100. In twelve years, sailing in the crab-pot enriched waters of the Chesapeake, I've never fouled my prop. I did once manage to foul it in Maine by backing over a mooring toggle, though.
The vane doesn't cut lines. The watermen still have a trap they can locate and harvest.
I was tempted to install a strut from the bottom-aft point of my keel to the bottom-forward point of my rudder skeg, to keep trap lines out of my propeller. But then I worried that a hard grounding might break the strut and let it bend up to hit the propeller. So I didn't install one.
From Robin Roberts on The Live-Aboard List:
We have SPURS, and are very happy with them. They're easy to maintain - there's a little zinc and
some noise-reducing inserts that get replaced every year or so - takes no time at all.
From Lee Haefele on The Live-Aboard List:
I have tested the Spurs brand, it does work. (Check out my spliced
dockline!) It does require about 1"+ space between prop and strut. Buy from
P-yacht at about 20% off.
To dive and cut a line off the shaft and prop, use a hacksaw blade, not a knife.
Trying to keep barnacles off propeller (none of these work well; best first):
- Scrub propeller often.
- Wrap plastic garbage bag over propeller if not going anywhere for a while.
- Polish propeller to very shiny state.
- Zinc oxide cream.
- Teflon grease.
- Bottom paint (primer first).
Sizing a propeller:
- Propeller diameter too small == cavitation at less than max RPM.
Propeller diameter too big == big aperture needed, lots of power and torque needed, stern squats at high RPM. - Aperture between propeller and hull should be 15% or more of
propeller diameter.
- Increasing a propeller's pitch by 1 inch will
reduce the RPM by 50 to 200, depending on who you believe.
Maybe 50-100 for bigger slower props, 100-200 for smaller faster props ?
- "get Dave Gere's 'Propellor Handbook' - it's the bible."
- With normal load and clean bottom, your boat/engine/propeller
combination should allow engine to just barely reach listed max RPM.
If not, something is wrong.
Engines should be capable of driving the boat at hull speed in flat water at
no more than 85% of full rated RPM in flat water. The wheel [propeller] should be
selected to absorb the engine's full rated HP under maximum head sea and wind
conditions. Doing otherwise means that under conditions such as sailing
(motoring) out of a lee shore anchorage, the engine cannot attain full RPM
(and HP). This may make the difference between motoring away from a lee shore
successfully, or not.
From Gordon Endler:
... you will not explode your engine by giving it full power even out of gear.
The injector pumps are set to a top rev limit, so you can not over-rev the engine; so
long as you have good oil pressure your engine is safe. But diesels like to be
under load; it makes them run cleaner and a lot smoother. The modern diesels
don't like to be revved, as a lot of them have cam belts and if these belts
are not changed they will let go then you say goodbye to your valves.
It is part of the MOT over here on road-going vehicles: once a year they
just flat out the engines to check the exhaust. They do it for 2 min's;
doesn't sound long but it makes me cringe when I have to do it.
Still, if your engine has the right prop it should not reach top RPM;
it should fall just short. If it gets to the top it is not loading
the engine and not running clean; if it does not get anywhere near
the top you are over-propped and will be using loads of fuel for nothing.
...
[Later:]
It is better to be over-propped than under; the engine likes to work, they don't like idle, plus you will use less fuel.
...
[Later:]
It is better to be over-propped than under; the engine likes to work, they don't like idle, plus you will use less fuel.
- Paraphrase of Bill Crealock:
"Regarding the hull drag produced by the prop, aperture, shaft, etc, in the lower wind ranges, a 3-blade fixed prop will generate 40% of the total drag ... a 2-blade prop 28%." - Surface pitting on forward side of propeller
probably means cavitation is occurring.
- Propeller shaft zinc:
- If installing when boat is in water, put polysulfide caulk on the screw threads to lock them.
- If zinc has copper buttons that contact the shaft, you're supposed to tighten the zinc, hammer on it to flatten the buttons, and tighten again.
- Having a Max-Prop refurbished:
From Justin/PYI on Cruising World message board:
If you've had a lot electrolysis, nicks, or play then yes refurbishing is a good idea. ...From Rick Farman on Cruising World message board:
A prop really needs refurbishing if electrolysis causes a loss of blade material which in turn unbalances the blades.
Sent my 3-blade to PYI in January. The blades were getting a little sloppy and had a few nicks. Couldn't believe what they sent back. Looked brand new. You could have shaved in the reflection off the high-polished blades. All the power boat owners in the marina were green with envy. About $300 including shipping. - Never hammer on a propeller or its shaft to get them off;
you'll damage the shaft bearings or transmission bearings.
- To make it easy to pull propeller next time, thread
a nut onto the shaft in front of the propeller before putting
it back on. Use the nut as a puller next time.
- From "Bill Gardella Jr. On Marine Motors":
"If you have a stainless-steel prop, there is more chance of damage to the shaft when you run aground because stainless steel is tough and transmits stress to the shaft."
- Brake horsepower is output of engine.
Shaft horsepower is about 96% of that, but can be less if engine also drives high-output alternator, compressor, pump, etc.
Propeller output is 50% to 20% of that. - A practical motoring speed for most cruising sailboats is about 75% of hull speed.
- Maximum ratio between propeller diameter and shaft diameter: 14:1 for bronze, 17.5:1 for Aquamet or Monel.
Letting a fixed prop free-wheel versus locking the drive-shaft while sailing:
From Andrew Rooney:
> I've heard huge arguments about whether you get
> more drag by free-wheeling or by stopping the prop.
> Have you tried it both ways and seen the difference ?
Short answer - yes. For my boat, it makes about 0.4+ knots difference, as noted on the log.
Longer answer: if the prop is still, area of prop producing resistance being dragged through the water is just the area of the blades when viewed from the front. If it is spinning, "effective area" producing resistance becomes a disc with a diam = the diam of the prop. As my boat has a 2-bladed prop, this increase in "area" is considerable, probably something of the order of 6x more. Secondly, the lever that stops the prop on my boat ensures that it is held vertical behind the keel (and hence partly shielded) where there is already turbulence. It may be that the more and wider the blades (and hence actual area), the less the effect would be.
> more drag by free-wheeling or by stopping the prop.
> Have you tried it both ways and seen the difference ?
Short answer - yes. For my boat, it makes about 0.4+ knots difference, as noted on the log.
Longer answer: if the prop is still, area of prop producing resistance being dragged through the water is just the area of the blades when viewed from the front. If it is spinning, "effective area" producing resistance becomes a disc with a diam = the diam of the prop. As my boat has a 2-bladed prop, this increase in "area" is considerable, probably something of the order of 6x more. Secondly, the lever that stops the prop on my boat ensures that it is held vertical behind the keel (and hence partly shielded) where there is already turbulence. It may be that the more and wider the blades (and hence actual area), the less the effect would be.