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Folding Prop Is Gone

Feb 6, 1998
11,454
Canadian Sailcraft 36T Casco Bay, ME
So this afternoon I got short hauled and removed the new Flex-O-fold two blade prop. The vibration was at a level that was 100% unacceptable to my wife and I. I re-installed our Campbell Sailor three blade and the minute she was dropped back into the water the vibration issues were 100% gone. She is as smooth as a Lexus now...

It was rather funny because as I was getting ready to yank the prop off the US Flex-O-Fold distributor walked into the yard. He went through the whole litany of questions. In the end he admitted that everything was spot on and correct, which I already knew, but he wanted to be sure. He admitted they just went through a similar issue on another boat that also had a long shaft.

With the two blade Flex-O-fold I had entire RPM ranges that were literally unusable and were likely due to shaft whip. I had two "usable" ranges of 900-1300 then 1900-2200 that were somewhat tolerable. All other RPM settings were AWFUL. The prop was pitched correctly so FOF got that spot on.

The difernce in vibration between the two blade FOF and the three blade Campbell is about as drastic as it gets, night & day not even close.

With the Campbell back on I now have 100% of my RPM range from 800-3000 RPM fully usable and silk smooth. Not one bad spot or any hint of a vibration. Out of frustration I used every alignment trick in the book when the FOF was on and she's now aligned to .001" which makes the Campbell even smoother than it was last year. .001" is NOT easy to do and is extremely tedious and time consuming.

So if you still have vibrations when all else is SPOT ON consider that a two blade prop, especially one that moves the blades further away from the cutlass bearing, could be the root cause..

Here's where I feel the problem of shaft whip gets greatly compounded. This is the difference between the fixed prop blade centers, beyond the bearing, and the folding prop.. The difference in overhang between the fixed prop and folding, beyond the cutlass bearing, is a full 3 3/4" ! :eek:

This is the Flex-O-Fold hub. Sorry, but I was hanging in the slings and did not want to tie up the yards lift for long. This was literally a ten minute swap out. Unfortunately before I remembered to snap the shot I had taken the blades off the FOF. Does not really matter though the "pin hole" is where the blades are centered. This is about 6 3/8" beyond the cutlass bearing.


This is the Campbell Sailor which is about 2 5/8" from the bearing to blade centers...:


Having been using the FOF since mid April re-installing the Campbell Sailor was a very happy day except for the lost $$..:cussing: Depsite the very minimal increased drag of the CS three blade, I would much rather have SMOOOOOTH when the engine is on vs. that extra .1-.2 knots (about what I saw).. Vibrations eventually cause damage and that was also a concern that weighed heavily on my decision to yank the FOF..... I will happily give up that 0.1 - 0.2 knots for a prop that won't damage my gear box or vibrate my boat until things start falling off.

Interestingly enough I found it very, very enlightening that this two blade Flex-O-Fold would NOT fold when the engine was shut off and the gear was left in neutral. The split second it was locked into reverse you could hear if "slap" shut.

So, which causes more drag free spinning or locked...:D The free spinning did not even create enough drag to fold this prop.... But yeah a locked prop causes less drag... Right.......;)

My wife can now take the rags out of the oven, no more rattles....:D

This was an expensive lesson I won't repeat, though I actually did, because my last Martec two blade was even worse....Doh', when will I learn...:doh:

All I can say is the Campbell Sailor is an exceptionally smooth and powerful prop, oh and it actually has reverse...;);) While I dislike the drag I have not yet been willing to bite the bullet for a three blade feathering prop. Maybe someday...
 
Nov 23, 2009
437
Beneteau Oceanis 361 Clipper --
What if you were buying a 3-blade FOF instead of the 2-blader (no don't pay extra $$$$ to try it!!!!)? Would you think it would have been as smooth as the CS?
 
Feb 6, 1998
11,454
Canadian Sailcraft 36T Casco Bay, ME
What if you were buying a 3-blade FOF instead of the 2-blader (no don't pay extra $$$$ to try it!!!!)? Would you think it would have been as smooth as the CS?
It would have been smoother but still not as smooth. I could not justify the extra 1k per blade for the speed gain under sail, we're not racing...

The hub of a folder moves the blades aft. This aft placement, beyond the cutlass, can cause shaft whip. Fixed props keep the blade centers closer to the cutlass bearing. Some feathering props and all folders move them considerably further aft which can lead to vibration problems especially on longer shafts...

With the CS prop the blade centers are about 2.75" from the cutlass with the FOF the blade centers were closer to 7" from the cutlass..That is a huge difference.
 
Dec 19, 2006
5,738
Hunter 36 Punta Gorda
So Smooth

I have the 3blade Flex O Fold on my 2007 Hunter 36 and so smooth and the engine is pretty quiet and performance sailing,motor and reverse is excellant.
Nick
 

njsail

.
Feb 18, 2010
216
Bavaria Ocean 40 CC Forked River
sorry to hear of your prop troubles. I was a little anxious since I just put a 3 blade Kiwi prop on in place of a 3 blade fixed prop. It was set at the factory and all I kept thinking is what if it doesn't work how I expect. That would be an expensive ....doh! + a short haul out to fix it. I have to say it was incredibly smooth,, didn't sing or vibrate through the entire range. I hit hull speed at ~2k RPM. Reverse really bit into the water and stopped the boat quicker than the fixed blade. The real noticeable difference was the smoothness. So far I'm a fan but it's early in the season. I haven't put the sails on yet so I can't comment on any gains while sailing. Good luck with the prop change.
 

BobM

.
Jun 10, 2004
3,269
S2 9.2A Winthrop, MA
Don't keep us in suspense!

Maine, what sort of improvement did you see under sail compared to the CS? I think every sailor flirts with the idea of a folding or feathering prop. Stories of a half knot improvement seem unlikely to me. What's the real scoop? Was the CS the stock prop or did you add that too? I have a stock Michigan Wheel prop on my boat. I have thought about the CS prop as an upgrade, but still pricey.
 
Feb 6, 1998
11,454
Canadian Sailcraft 36T Casco Bay, ME
Maine, what sort of improvement did you see under sail compared to the CS? I think every sailor flirts with the idea of a folding or feathering prop. Stories of a half knot improvement seem unlikely to me. What's the real scoop? Was the CS the stock prop or did you add that too? I have a stock Michigan Wheel prop on my boat. I have thought about the CS prop as an upgrade, but still pricey.
Hard to say accurately but roughly .1-.2 knots when below hull speed compared to a locked Campbell.. When at hull speed no noticeable difference. I thought I would feel it in the rudder, as I have on other boats, but our rudder is pretty far from the prop so I felt no real change there. I have some pretty good data on out boat at certain wind speeds, locked vs. free etc. and tried to compare that to the FOF. Definitely less drag on the FOF when the CS was locked but hard to discern when I allow the CS to freewheel.

There's no doubt it was slightly faster, most noticeable when ghosting along though..

Interestingly enough I found it very, very enlightening that a two blade FOF would NOT fold when the engine was shut off and the gear was left in neutral. The split second it was locked you could hear if slap shut.

Just one more bit of evidence that a free spinning prop causes considerably less drag than a locked one. Heck on dry land this prop would gravity close both blades yet it will continue to free spin when left in neutral...
 
Sep 25, 2008
1,096
CS 30 Toronto
Maine Sail,

May be it's the nature of the folding prop, as you said, shaft whip. I have a 15" 2 blades Max-prop feathering prop on a CS30. It is a lot smoother (less turbulence bubbles) than the fixed 2 blades Mertec I had before.

My friend has the same prop on a Niagara 35, which is heavier but closer to a CS36. Again, very smooth.

IMO, the folding prop uses centrifugal force to open. The centrifugal force and water resistance are not even (top and bottom) on a slanted down shaft in relation to water flow. The prop is essentially out of balance caused by the slanted shaft and flowing water. Since you have a longer overhang, the out of balance is amplified.

In theory, there should be 2 harmonic frequencies that the prop will run smooth through the RPM range.

On a feathering prop, the blade is locked in place by the internal gear. Unless there is excessive wear with the gears, it isn't going to move due to un-even water flow.

I race so the extra speed and pointing ability helps. I also like that fact that I can arrive earlier (by a beer) when cruising. It's about 10%.
 
Oct 2, 2006
1,517
Jboat J24 commack
At this point i am more pleased with Flex-o-Fold than i was as i have tweaked things and gotten back to having enough power to submerge the stern :)


In my case the old two blade 12 X 8 whatever sailor prop pretty much had ZERO reverse ability compared to the flex-o-fold which will pick the stern up out of the water in reverse
 

zeehag

.
Mar 26, 2009
3,197
1976 formosa 41 yankee clipper santa barbara. ca.(not there)
seems like a lot of expense for only a .1-.2 kt difference.
 

RobG

.
Jun 2, 2004
333
Ericson 28 Noank, Ct
Maine, another Michigan vs CS prop comparison question. I consider my E28 under powered with just a 10hp Universal M12 (as do other owners by their reviews). I have a two blade Michigan prop now. Would a two blade CS help the effectiveness of the motor? Three blade CS? I remember (your?) posts about its efficiency compared to a Michigan. Thanks.
 
Sep 5, 2007
689
MacGregor 26X Rochester
That's interesting. My H340 had a 2-blade Flexofold, and I too had several rpm bands that were annoying at best, unusable at worst. I was going to try a 3-blade CS, but sold the boat before I got around to it. Alignment was very good, so I had written it off as an engine issue, but I'm not so sure about that now.​

Mine would also keep turning if I had a head of steam when putting it in neutral, but if I was just creeping along, there wasn't enough centrifugal force to keep it open, and it would close right away. Obviously, plopping it into reverse would allow it to close, and it didn't try to spin once put back into neutral.​

Interesting stuff. Thanks for the update. :)
 

Rick D

.
Jun 14, 2008
7,013
Hunter Legend 40.5 Shoreline Marina Long Beach CA
seems like a lot of expense for only a .1-.2 kt difference.
I saw about .3 -.4 knot average difference in moderate wind, but a very big difference in light air and none at all in heavy air. However, the pointing was much better and I could tell the turbulence around the rudder was vastly reduced.

My prop will likewise free wheel when I shut the engine off. I close it by going into reverse to fold it and then into neutral.
 
Oct 2, 2006
1,517
Jboat J24 commack
My prop folds so WELL when i cleaned the bottom for the first time this year it was CLOSED sitting on the mooring after motoring in and making no effort to close it :)
 
Nov 23, 2009
437
Beneteau Oceanis 361 Clipper --
I like the campell sailer but living on the other side of the Atlantic will cost me including delivery and import duties around 1000 dollars. This is still half than a 3 blade FOF but I also worry if I don't get the correct size. Returning back is simply not an option. Any experience with these guys getting it wrong the first time (I know Maine sail did)?
Now Maine Sail's experience with FOF made me thinking because vibrations is something I really would like to get rid of. I have plenty with the current 2 blade fixed and would prefer a propeller causing as little vibrations as possible. The drag of the current prop if indeed same as the CS is fine for me but definitely would't like to have more.
 
Dec 30, 2009
679
jeanneau 38 gin fizz sloop Summer- Keyport Yacht Club, Raritan Bay, NJ, Winter Viking Marina Verplanck, NY
Maine, reading your impressions of these props has me interested,I repowered 2 years ago, and everything new, shaft , with a 2 blade sailor. I have been running this boat for a long time and it always had a 2 blade prop. the prop is center 1" overhang, spade rudder, always sucked backing up, and I was thinking of changing to a three blade fixed. I am not worried about losing speed with drag, however will it help the performance in your opinion. Its not bad with the 2 blade, and its sized correctly, what do u think??thanks Red
 

Gunni

.
Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
Like many Beneteau owners, have a 3-blade maxprop feathering prop, it will not feather in neutral. And on a kanzaki tranny you don't want a freewheeling shaft. However, drop it into reverse and she feathers out, the shaft quits freewheeling. The noise below from that freewheeling prop shaft made the aft cabin a noisy place.

Alexco points out some important differences about how the FOF folding prop works v. a geared feathering prop.
 
Feb 6, 1998
11,454
Canadian Sailcraft 36T Casco Bay, ME
Like many Beneteau owners, have a 3-blade maxprop feathering prop, it will not feather in neutral. And on a kanzaki tranny you don't want a freewheeling shaft. However, drop it into reverse and she feathers out, the shaft quits freewheeling. The noise below from that freewheeling prop shaft made the aft cabin a noisy place.

Alexco points out some important differences about how the FOF folding prop works v. a geared feathering prop.
Actually on a Kanzaki you do want a freewheeling shaft, per Yanmar, or to use a shaft brake. With a fixed prop a Kanzaki should not be locked in reverse unless a shaft brake is employed. With a feathering prop this is a non-issue as you're only locking it to stop the freewheeling and the cones won't be loaded up constantly..
 
Nov 28, 2009
495
Catalina 30 St. Croix
A friend and I had two identical Idylle 15.5's. He kept the 3 blade fixed and I installed the Variable pitch Max prop. Both boats have Perkins 4-236. We sailed against each other with same sail plan and mine was on the average one knot faster. It also backed better and stopped better. Under power I was .5 knots faster at the same RPM's. Both boats had just been launched after a new bottom job. The fact that I could dive and change the pitch was worth the extra $'s. I could go from Trinidad to St. Croix averaging 7-8 knots under sail. The slowest 24 hr period was 145 nautical miles and the fastest was 190 miles. Sailing as much as we did in the 12 years that we owned Cayenne III, we never once regretted having spent the money on the folding prop. We could motor at 7-8 knots without going over 2500 RPM's. No vibrations because of a CV joint. Alignment is not an issue and the thrust bearing mounted on a bulkhead takes the load instead of the transmission.
 
Nov 28, 2009
495
Catalina 30 St. Croix
Meant to say feathering prop. my J-36 has a folding prop. Sold both boats and now I have a power boat. Can't go up the mast or crank winches anymore. First time in 44 years without a sailboat.