Cool picture.
We switched to a Flexofold 3 blade at the start of this season. I had been meaning to write a post about our experiences, but hadn't gotten around to it. Anyway, I'll give my input here. Bottom line is that it's been completely positive for us.
We replaced our OEM 3 blade fixed prop (17x12) with a Flexofold 3 blade (16x12). The Flexofold staff recommended the size given our engine model, HP, max RPM, transmission gearing, and boat size. I initially took the transmission gearing from the service manual and got a very strange recommendation from them. It turns out the service manual was unclear, and when I gave the actual gearing from the placard on the engine they recommended the 16x12.
We had our yard pull the old prop off, but I did the Flexofold installation myself. Very straightforward and simple.
Under power the boat speed is about the same as before, cruising at about 7.1 kts @ 2800 RPMs with a clean bottom. Some others on forums have reported a slight increase in motoring speed, but I didn't see that myself. There is no additional vibration - just as smooth as the fixed prop was. Maine Sail once reported unacceptable vibration with a FoF 2 blade but I don't think the 3 blade has that issue.
In reverse the Flexofold does generate a bit less power than a fixed prop, but it's not a significant problem. I need to bring the RPMs up to about 1500 to get the same amount of power as idle was before, but 1500 still leaves plenty of headroom. I rarely need more than that moving around a dock. There is still a bit of prop walk, probably about half as much as the fixed prop. It's enough to be able to use to maneuver without interfering.
Under sail it's a huge improvement, especially at low wind speeds. I have the data from my chartplotter and I've compared it from my races this season vs. previous years. In light winds the boat's a solid 0.25 kts faster with the Flexofold. As wind speed increases (above 8kts or so) it's less of an advantage, but then it's a big help again at high wind speeds (over about 15kts). The fixed prop was causing a lot of turbulence in front of the rudder, so in high winds with high weather helm I would need to use lots of rudder angle to keep the boat going straight. With the Flexofold there is no turbulence, so the rudder angles are less and the boat can go about 0.25kts faster again. There were also less times this year when I felt at risk of rounding up, with the added rudder efficiency. The advantage far outweighs the 9 seconds/mile PHRF adjustment, especially in a light wind area like the Chesapeake.
