Small folding/feathering prop

[freddyj]

My small sailboat has a saildrive and the fixed prop is really slowing me down. But there is only space for a 9 inch prop and no one seems to make a folder that small. Any ideas?

 

[KeithO]

Sailing in Neutral ? Have you removed the prop to verify the effect ? If that test verifies that the mechanical drag in Neutral is an issue you may want to overhaul the lower unit and validate that there are no bad bearings or gears and that the right viscosity oil is being used.

 

[gonzo]

What model saildrive do you have? They usually fit at least a 12" propeller.

 

[freddyj]

My saildrive is a homebuilt electric, using a 10hp outboard bottom end.

 

[gonzo]

You should be able to cut off the anti-ventilation plate and fit a larger propeller.

 

[philSweet]

What gonzo said, but be aware that folders aren't all that great except for lowering drag. They need a good bit of rpm and power, are typically used only for basic maneuvering around a marina, and basically suck at reverse and crash stops. You'll need a geared type such as Martec Slipstream because I doubt your electric will have the oomph to spin an ungeared Martec Eliptec (meaning the blades are geared together and not simply hung on a pin and free to move independently.

And you will need a minimum of a rebuilt 40hp leg in order to carry the torque and vibration of a 14" geartec/slipstream. Or a 25hp high trust leg. Better just to find an old sail drive since the props are available for them.

 

[JSL]

what is the size & displacement (weight) of your 'small sailboat'? Is the prop 'free wheeling' (auto-rotation) or locked.? How many blades?
Years ago we did some experiments on a 40' racing cutter fitted with a 16" 2 blade fixed prop. Under sail in very light winds we made 4.5 knots with the prop 'locked'. Free-wheeling we made 4.0 knots.