I have a 2001 Beneteau 331 with the Westerbeke 30B Three, and am looking for a new propeller. The current prop is a fixed 2 blade, and besides not having a lot of push, its also not particularly smooth at higher engine speeds because of the turbulence behind the skeg and keel. I'm considering a Flexofold prop, and have been told that a 16"dia x 11"pitch 3 blade would be the one recommended for my boat and engine. It would be great to hear from anyone else who has the same type of boat and propeller combination, as I'd like to get the prop sized right the first time. Any other experience - good or bad - would also be appreciated.
Folding Prop Size for Beneteau 331
- Thread starter Ben 331
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Go with a Max-prop. Folding prop is a PITA for reverse because it won't fully open when you want to brake. The forward water flow prevent it from fully opening. It depends on centrifugal force to act against water flow to open. Thus a delay when you needed trust the most.
A feathering prop, like Max-prop, align itself to the water flow thus reduce drag. The trust is the same for forward or reverse.
Either prop will give you 1/2kt sailing speed gain. Reverse is the deciding factor for me. BTW the pitch on the Max-prop is adjustable so you can experiment it yourself.
IMHO 11 inch is too little pitch. Pitch means it goes 11 inches for every turn of the prop shaft. Just do the math. At 2500-2600 engine speed, the boat should reach just below hull speed. You keep a few hundred RPM in reserve in case you need it.
Someone in this forum already posted the way to calculate prop.
A feathering prop, like Max-prop, align itself to the water flow thus reduce drag. The trust is the same for forward or reverse.
Either prop will give you 1/2kt sailing speed gain. Reverse is the deciding factor for me. BTW the pitch on the Max-prop is adjustable so you can experiment it yourself.
IMHO 11 inch is too little pitch. Pitch means it goes 11 inches for every turn of the prop shaft. Just do the math. At 2500-2600 engine speed, the boat should reach just below hull speed. You keep a few hundred RPM in reserve in case you need it.
Someone in this forum already posted the way to calculate prop.
Backing With A Folder
You'll hear that backing is a problem with folders. I fully expected that when I purchased my Slipstream 2 blade geared folding prop eight years ago. What I found surprised me, backing as good with less prop walk than the fixed two blade it replaced. It does require a delay to let RPM fall shifting between forward and reverse which I would think is a good idea with a feathering prop too, and it does require more throttle (RPM), but we're talking degrees, not a big blast.
So, at least in my case, I gave up really nothing in reverse and was pleasantly surprised as I was ready to. BTW, I do a lot of maneuvering in reverse.
You'll hear that backing is a problem with folders. I fully expected that when I purchased my Slipstream 2 blade geared folding prop eight years ago. What I found surprised me, backing as good with less prop walk than the fixed two blade it replaced. It does require a delay to let RPM fall shifting between forward and reverse which I would think is a good idea with a feathering prop too, and it does require more throttle (RPM), but we're talking degrees, not a big blast.
So, at least in my case, I gave up really nothing in reverse and was pleasantly surprised as I was ready to. BTW, I do a lot of maneuvering in reverse.
I had a 2-blade Flexofold on my H340, and it took a little getting used to the extra throttle needed in reverse, but once used to it, I had no problems even with the wind off the stern. Just had to get over the mental hump of running the revs up when needed. I investigated going to a 2- or 3-blade fixed, mostly for improved reverse thrust, but I learned how to drive the folder better and never looked back. Much cheaper than more sophisticated props, too, though it was on the boat when I got it, so that wasn't an issue for me. The two blades were geared to each other, by the way, so no chance of one blade getting stuck folded with the other one open and working.
http://www.flexofold.com/2-blade-folding-propeller/
http://www.flexofold.com/2-blade-folding-propeller/
Alexco, thanks for the post. I was also wary of the astern performance of folding props, although a test of several folding and feathering props in Yachting Monthly in 2009 showed that there are significant performance differences between props of the same type... and not all folders are poor in reverse. This test is particularly relevant to me, as their test boat was a Beneteau 321, quite similar to my 331. I'll check out the prop sizing formal you referenced to see what that comes up with.
Thanks Ron, even though the two props are different makes, it
sounds like 16 x 11 would not be far off of the mark. The gear ratio of my transmission is 2.47:1, I expect your ratio may be a bit higher, which could allow a 16 x 11 prop to work for both boats despite differences in size and engine HP.
Thanks for the post. I would go for a 2 bladed folder as well, but my boat's prop is skeg mounted and as a result any 2 bladed prop (fixed or folding) tends to cause some vibration at higher speeds. The 3 bladed design also has the blades geared to each other so they move in unison.
Folding Prop in reverse
agrees with your findings - not all folding props are necessarily poor in reverse.
Rick, thanks for the feedback. Flexofold references a propeller test that Yachting Monthly carried out in 2009 (http://www.flexofold.com/upload_dir/docs/Test_YachtingMonthly_low.pdf), that
agrees with your findings - not all folding props are necessarily poor in reverse.
Ben331 did you ever buy that 3-blade Flexofold? If yes I would really like to hear your findings. Do you still get vibrations? How does it perform in comparison to the 2-blade fixed? Any feedback will be appreciated.
Thanks
Thanks
Flex o Flod
I have a 3 blade flex o fold on my 2007 Hunter 36 and love it,flex o fold will help pick the right prop for you with your boat info.
Motoring and sailing and reverse is much better with my three blade than my old fixed three that was really the right pitch for my boat,I can stop on a dime in reverse either backing into my slip or going forward and than slowing down in reverse.
It is geared so 3 blades always open and close together no worry,just keep barnecals off it,if I leave it for 2 or 3 months here in Florida it will need ccleaning.
Nick
I have a 3 blade flex o fold on my 2007 Hunter 36 and love it,flex o fold will help pick the right prop for you with your boat info.
Motoring and sailing and reverse is much better with my three blade than my old fixed three that was really the right pitch for my boat,I can stop on a dime in reverse either backing into my slip or going forward and than slowing down in reverse.
It is geared so 3 blades always open and close together no worry,just keep barnecals off it,if I leave it for 2 or 3 months here in Florida it will need ccleaning.
Nick
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