Foling Propellers

[Chris_Stannard]

I am thinking of fitting a folding three bladed propellor to my 37 foot, 9 ton boat. I like to sail well but need good astern power when coming into my marina berth because of the weith of my boat. I am considering the Gori or the Flex-o-Fold propellers and wonder if anyone has any experience of thses units or comments to offer

 

[Chris_Stannard]

Oh dear, as usual my spelling is up the creek. Should have been Folding Propellers.

 

[HaraldS]

There is a similar post on the other forum here.
I'll copy the answer again below. Before doing so let me say some more about power in reverse: I was very sceptical about that, since one would expect a folding prop to collapse when reversed, at least partially. At that time the yard was fitting a MaxProp feathering prop as the standard, but I was concerned about the poor efficency with the flat profile, which gets worse with larger diameter props. Given those two concerns, I planned for an Autoprop. I didn't know the flex-o-fold then, but the yard very prositive about it and I finally agreed to go with the flex-o-fold.

It turns out it is quite cleverly designed so that the torque adds force to the centrifugal force and nicely opens the prop going backwards. If any drawback is noticeable it is that it might need some reving up in reverse before it bites when you still make substantial forwards progress. Once it's opened up in reverse it works like a fixed one.

I anchor a lot and usually slowly pull in the anchor and then increase power until I feel true confidence. If I really power it up in reverse, the pull is huge. I know it is well over a ton, because that's what the windlass is specified for and I can stall the windlass long before I'm at full power reverse.


The answer I have given previously follows here:

I have a 3-bladed flex-o-fold on my boat. No complaints.
In more detail:
Boat is a 49 ft Najad with close to 20 tons and a 100HP Yanmar engine.
Full throttle ahead she does 9.1 knots on the GPS and engine revs are 3500, which is slightly below the spec.
I usually run it at 2200RPM and get abot 7 knots.
When sailing it folds nicely as soon as put it in gear.
Manuvering is no problem either.
From standing still into reverse I can go with quite low power and after a moment of slight walk to port she starts to take off nicely.
The only negative thing I have noticed is, that when to go reverse while making good progress forward, you need to rev it up quite a bit before it bites.
Still I can stop the boat in a length and a half from 7 knots forward.
One other little snag is that when motorsailing, you need to give the engine enough power for the prop to start pushing, otherwise it oscilates undecided about folding or opening.

I'd take it again. But I have no comparison to another prop on this boat.

 

[seahorse]

Chris, I've been re-engining my "Centaur" & thinking about a folding orop. Try the "Seven Seas Cruising Association" site
for more info.