We have a Beneteau 311 and it has a 2 blade prop. We get about 5 knots out of it while motoring. Would a 3 blade prop give us any more speed?
prop 2 or 3 blade, for speed?
- Thread starter pilots lady
- Start date
Problem is you usually can not "properly size" a two blade prop on a sailboat to be faster than a three...
I have converted many sailboats from two blade to three blade and the differences in motoring speed are noticeable and real, and power into wind or tidal current are excellent. The three blade does slow you down under sail though. On a coast with 10-24' tides, massive rivers with strong currents and many foggy windless days sometimes a three blade is the best compromise...
Most recently I went from three blades to two blades, then back to three blades. Both props were perfectly sized for our motor and both within 30-40 RPM of each other and spot on with what Westerbeke wanted to see. With the two blade FOF we lost top end speed, had considerably less power into wind and tidal current and had horrible vibration issues that could not be resolved.
Putting the three blade back on was like going from a Yugo to a Cadillac....
The two blade DID sail faster but did everything else worse..
Here are my observations of the Flex-O-Fold on our boat compared to our three blade Campbell Sailor.
Folding Prop Report
Folder is Gone
As for the OP he will want to check that his engine can attain max rated RPM in smooth current free water. Westerbeke / Universal demand this as part of warranty and Yanmar wants to be able to see 125 RPM over max rated RPM.. If you can't meet these requirements your speed will suffer with two or three blades. Also be sure the bottom is clean and the tach is accurate.
Maine,
You of course bring up some great points. Clearly a you have to factor in boat type and local conditions, and your individual sailing habits. On our First 36.7, which we race as much as cruise, we could not image not using the flex-o-fold 2 blader. But we weigh over 2 tons less in a similar length boat, and have to have minimal drag in light sailing conditions. Your heaver boat and tides make your choice wise.
Interestingly, Yachting Monthly did a comprehensive test on props on a boat very similar the OPs (Beneteau 323); I'm guessing you've seen it but I'll add the link for everyone else. The speed test is interesting. Sadly they did not test the Campbell Prop.
PS - Your right about the size; a two-blader would have to be slightly bigger in diameter to be faster than a three, but sticky details like hull proximity (or the runway on planes!) often make that impractical!
link to entire report.
http://www.flexofold.com/upload_dir/docs/Test_YachtingMonthly_low.pdf
You of course bring up some great points. Clearly a you have to factor in boat type and local conditions, and your individual sailing habits. On our First 36.7, which we race as much as cruise, we could not image not using the flex-o-fold 2 blader. But we weigh over 2 tons less in a similar length boat, and have to have minimal drag in light sailing conditions. Your heaver boat and tides make your choice wise.
Interestingly, Yachting Monthly did a comprehensive test on props on a boat very similar the OPs (Beneteau 323); I'm guessing you've seen it but I'll add the link for everyone else. The speed test is interesting. Sadly they did not test the Campbell Prop.
PS - Your right about the size; a two-blader would have to be slightly bigger in diameter to be faster than a three, but sticky details like hull proximity (or the runway on planes!) often make that impractical!
link to entire report.
http://www.flexofold.com/upload_dir/docs/Test_YachtingMonthly_low.pdf
Overall I really like that text but it leaves me with more questions than answers. My problem with that report is that I have never seen where they discuss that all props could turn the engine at the same identical max RPM or that the tach was calibrated...Maine,
You of course bring up some great points. Clearly a you have to factor in boat type and local conditions, and your individual sailing habits. On our First 36.7, which we race as much as cruise, we could not image not using the flex-o-fold 2 blader. But we weigh over 2 tons less in a similar length boat, and have to have minimal drag in light sailing conditions. Your heaver boat and tides make your choice wise.
Interestingly, Yachting Monthly did a comprehensive test on props on a boat very similar the OPs (Beneteau 323); I'm guessing you've seen it but I'll add the link for everyone else. The speed test is interesting. Sadly they did not test the Campbell Prop.
PS - Your right about the size; a two-blader would have to be slightly bigger in diameter to be faster than a three, but sticky details like hull proximity (or the runway on planes!) often make that impractical!
link to entire report.
http://www.flexofold.com/upload_dir/docs/Test_YachtingMonthly_low.pdf
Just because they took all props to max RPM does not mean all props were properly sized/pitched and some could still have been way off/under propped. This can cause discrepancies in the data.. Lot of area for fudge factor and while a good test it certainly lacked the scientific foundation/study design it needed to be truly accurate..
On my own boat both props were perfectly matched to what Westerbeke wanted which means size and pitch wise they were as perfect for the boat/engine as possibly could be. My tach is also spot on and I run two speed runs each direction and average them to rule out current or wind effects..