Frenchy wrote:John, I noticed you're planning on a folding two-blade propeller, so thought I'd share my experience
which is probably an outlier. The propeller was put on a Cal 27, which previously had a fixed two-blade.
I sensed greater noise and vibration, so I sent the prop back to the manufacturer for balancing. It didn't help.
Later, underwater, I noticed that if the blades aren't aligned horizontally, one blade would flop down-into the
water stream.
The blades weren't geared together, as on some folding props.
I put the fixed prop back on and had less noise and vibration. The difference in sailing speed was
barely detectable. I hope someday to put a three blade feathering prop on "Grace".
Your modification to "Far Reach" looks fantastic - Jean
Hi Jean
My plan is to go with a geared flex o fold two blade. It’s supposed to reliably close shut. Lots of reviews say that is the case. Sounds like you had an old Martec or similar ungeared prop.
I don’t think one can compare a fin keel boat with prop and a full keel boat with aperture and prop. Two different animals. Not having an aperture on my boat has made a huge sailing performance difference in every measurable way. To be truthful, it’s a stunning difference. And not just in light air. There is no turbulence on the rudder in windier conditions...the rudder is dead smooth while the boat is underway regardless if we are making 2 kts or 8 kts. The boat never fails to tack regardless how light the wind. She accelerates coming out of a tack far better without the aperture. And with no desire to go back to an aperture the challenge is how to maintain the boat’s wonderful sailing characteristics after installing an engine.
I agree underway performance motoring will be better with a fixed prop. Everything I have read and all I have talked with about feathering props suggest they perform well in forward but offer the greatest advantage in reverse. If I had an aperture, I’d go with a feathering prop...probably a J prop.
But fixed blade props (including feathering props) while sailing, especially one exposed, as will be the case on my boat, are prone to snagging all kinds of things in the water....from crab pots to sargasso.
I agree there will be vibration with a two blade. My research indicates that is partly due to shaft whip which can be caused by long prop shafts. Ours will be relatively short. Also, we have no aperture so the prop is not beating through the dead space. Without an aperture my expectation is the prop will be turning in relatively clean water. Maybe that will reduce vibration a little.
Unless the vibration is rattling our fillings out I think it’ll be fine. After all, performance under power is far down the priority list for us. As far as reverse, my view is based on how much time we spend going backward under power as opposed to going forward under sail.
I admit, some of this is theoretical. My opinion is informed by as much research as I could do and some personal experience with our family boat when I was a youngster (full keel Allied) which we converted from a three to two blade prop.
I also admit, for those for whom performance under power is more important than performance under sail they would probably not be happy with our choices. I absolutely respect that view. I hope I have never come off suggesting that our way is better than everyone else’s way...only that our way is best for us given our priorities.
While I’m not convinced I’ll be delighted with an inboard engine in the Far Reach (considering what we give up) it seems like the best choice given the things I’d like to do with her. Time will tell if I chose wisely.
I’m interested to see how it works out.
