Feathering or folding prop recommendations?

Aug 2, 2010
502
J-Boat J/88 Cobourg
Wanting to increase our racing results next year and working on the best elements to address. B323 with two blade fixed prop which sings so I have a perfect justification to get it off the boat! Cost is not an issue if it is better.
Sailing in fresh water with little risk of snagging lines, but weeds can be a significant issue in some years in some harbors. I want to be able to cruise under power when needed but most of the time the prop is just to get me out into Lake Ontario and back to the dock. For me, prop walk is not an issue though less would not be a problem when I have the rare southerly across my slip causing me to need to back to port out of the slip and down the fairway which can be a challenge.
The most important issue for me is the risk of no reverse when I need it and this seems to be a risk with the folding props....is it?
In summary, decent motoring and solid reliability is all I need but I really want to increase performance under sail, particularly in light winds.
Advice?
 
May 17, 2004
5,032
Beneteau Oceanis 37 Havre de Grace
We switched from our OEM 3 blade fixed to a 3 blade flex-o-fold a couple seasons ago and love it. The PHRF hit for changing the 3 blade is 9 seconds, but the speed improvement in light winds is minutes not seconds. Prop walk is about 50% of the fixed, just enough so that I can still use it to my advantage when needed, without being overpowering. Speed under engine is basically the same as the fixed prop, maybe 0.1 knots more at cruising RPM. Thrust in reverse is noticably less than the fixed prop, so when I'm coming into the dock and need to slow down I rev to 1200 or 1500 RPMs instead of idle. Never had a problem with it not unfolding. No required periodic maintenance or lubrication; I just polish it quickly each winter.

I've read some reports that the 2 blade FOF is more susceptible to vibration issues, so you may want to consider that, but that aside I have nothing bad to say about it.
 
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Nov 26, 2012
1,653
Hunter 34 Berkeley
My understanding is that a folding prop will be faster sailing and a feathering prop is a better prop especially in reverse. I have a folding and it has been a big improvement. Motoring is fine.
 
Aug 1, 2011
3,972
Catalina 270 255 Wabamun. Welcome to the marina
Went to a FlexOFold two years ago. Marked improvement in acceleration, and overall boat speed.
 
Apr 12, 2007
175
Hunter 420 Herrington Harbor South
I have had Goris on two boats and am very satisficed with the performance. Equal thrust in forward or reverse, very little prop walk, folds to almost no resistance. Can increase speed from .5 -1.25kts sailing. Another advantage, OVERDRIVE, excellent for motoring if necessary. Will pick up 1kt to 1.5kts boat speed at same RPM.
 
Jul 12, 2011
1,165
Leopard 40 Jupiter, Florida
Putting together a speed improvement for your boat is a combination of factors, but here are some points that we can discuss:
  • Under sail, prop drag is only a factor for lighter air, where you have insufficient power to overcome friction. In 20 knots, you can drag a bucket behind and it won't slow you below hull-speed.
  • In lighter air, you can expect a significant improvement from a folder, and slightly less from a feathering prop, e.g. moving you from 4.5 to 5 kts in a drifting race for a 30 foot boat. How often are you racing in winds under 10 kts in your area?
  • If you cruise the boat, what is your decision point for motoring? If I am moving less than 4 kts and I have someplace to go, I'll motor-sail the rest of the way. Usually, I set this number for each passage.
  • Based on the studies I've read, folding props are 80% of fixed props for forward, but really lack efficiency in reverse. Feathering props are 90% efficient in both directions, which is even slightly better than a fixed for reverse.
  • At slow / docking speeds, a great deal of inefficiency and prop walk can be overcome by changing how you handle the throttle. Expect to learn to handle the boat differently when you get the new prop, but do not let the few minutes of docking determine which prop to buy.
  • Most prop manufacturers recommend mounting on stainless steel shafts. If you have bronze, figure in the additional cost of the shaft and labor to replace. Might as well do your cutlass bearing and think about a dripless seal at the same time. $hit adds up!
BTW: I went through this decision model for a club racer, but mainly cruiser, and it said "Maxprop" and $5,000. How important is that extra knot to you?
 
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May 17, 2004
5,032
Beneteau Oceanis 37 Havre de Grace
Under sail, prop drag is only a factor for lighter air, where you have insufficient power to overcome friction. In 20 knots, you can drag a bucket behind and it won't slow you below hull-speed.
Generally true, although our Beneteau suffered at high wind speeds with the fixed prop due to the turbulence caused by the spinning blades in front of the rudder. As wind speed increased, especially in gusty conditions, the boat would round up or need excessive (slow) rudder angles to keep down. Switching to the FOF fixed the turbulence and we've picked up speed both at low wind speeds and high (but not much difference in moderate winds).

Based on the studies I've read, folding props are 80% of fixed props for forward, but really lack efficiency in reverse. Feathering props are 90% efficient in both directions, which is even slightly better than a fixed for reverse.
I've read different things than that. This test, in particular, from Yachting Monthly, Folding and feathering propeller test puts several folding/feathering props ahead of fixed in many categories. I'm sure the fixed prop benchmark wasn't anything special like a Campbell Sailor, but still, fixed is not always best for motoring. In case you're not sure about the impartiality of the article, Practical Sailor also has a write-up at Folding vs. Feathering Props - Practical Sailor Print Edition Article which is less scientific and quantitative, but not inconsistent with the Yachting Monthly conclusions.
 
Aug 2, 2010
502
J-Boat J/88 Cobourg
Putting together a speed improvement for your boat is a combination of factors, but here are some points that we can discuss:
  • Under sail, prop drag is only a factor for lighter air, where you have insufficient power to overcome friction. In 20 knots, you can drag a bucket behind and it won't slow you below hull-speed.
  • In lighter air, you can expect a significant improvement from a folder, and slightly less from a feathering prop, e.g. moving you from 4.5 to 5 kts in a drifting race for a 30 foot boat. How often are you racing in winds under 10 kts in your area?
  • If you cruise the boat, what is your decision point for motoring? If I am moving less than 4 kts and I have someplace to go, I'll motor-sail the rest of the way. Usually, I set this number for each passage.
  • Based on the studies I've read, folding props are 80% of fixed props for forward, but really lack efficiency in reverse. Feathering props are 90% efficient in both directions, which is even slightly better than a fixed for reverse.
  • At slow / docking speeds, a great deal of inefficiency and prop walk can be overcome by changing how you handle the throttle. Expect to learn to handle the boat differently when you get the new prop, but do not let the few minutes of docking determine which prop to buy.
  • Most prop manufacturers recommend mounting on stainless steel shafts. If you have bronze, figure in the additional cost of the shaft and labor to replace. Might as well do your cutlass bearing and think about a dripless seal at the same time. $hit adds up!
BTW: I went through this decision model for a club racer, but mainly cruiser, and it said "Maxprop" and $5,000. How important is that extra knot to you?
Parsons, thanks for putting so much time and energy into your response, it is helpful. Our races are held on what has been dubbed Windless Wednesdays and all too often we are fighting our way around the course in 5 knots or even less of breeze. We struggle to compete with some of the smaller boats in our fleet on these nights especially downwind. As for cruising, it seems like every cruise has a batch of motoring in it and therefore I want something that is going to be good in this mode too but it seems like they all are decent in that regard from what I have read. Though I have seen lots of folks refer to folders not opening, I have not seen any where that has happened so I think I will set that aside for the time being though some of the weedy spots in Lake Ontario will bear watching for sure.
In the final analysis, an extra knot would be worth $ 5k to me but I am not at all sure I will see that much coming from a two bladed prop!