Can anybody make a prop recommendation for the French heavy cruiser Suffren class? It is dual rudder and has three props. I am planning on only driving the centre prop, probably with a 550 motor connected to an ESC. Any help is much appreciated. Thank-you.
We've got one local running a 550 motor, geared, to a 1.5" 4 blade, shallow pitch prop. About 4600rpm at the prop if I remember right.
Why would you only want to drive the center shaft? Wouldn't the stern constantly be walking in the direction of the prop rotation sorta like the Perry Class frigate?
Well the conventional wisdom is that it makes the boat turn better I believe. I haven't noticed any p-factor effect on other centre shaft powered boats, other than the fact that it obviously turns better one way than the other.
Power the center, get to use the outboards as drag props which lets you run the center faster and shove more water over the rudder surface. Ran our local Suffren for a year or two and didn't notice any significant walking issues. We don't sail in straight lines for long anyways.
I get stern walk on Scharnie. Frankly, I use it to help aim when going backwards. I plan for it and the other guy doesn't
As big a propeller as you can fit, 4+ blades. Stern walk is pretty negligible in fwd as it is easily corrected through proper rudder setup, in reverse it is harder to do anything about but most people set up their ships to take advantage of it and then try to use it to their advantage as much as possible. The performance gain you get from only driving the center shaft is generally worth not being able to back up straight. Though if you're building to IRCWCC rules I'm pretty sure you can still run the center prop in fwd but then run the outers in reverse so you can backup straight, you'd probably give up a little turning/acceleration since you would be using real props for drag disks but with a proper choice there I bet you wouldn't lose much at all.
