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Hello all,

Like Walter Guinon, I believe prop walk has to do with shaft angle. George
Huxtable has convincingly refuted Walter's explanation based on reactive
torque. But what about this one:

Imagine looking from behind at a 4-blade right hand prop on a horizontal shaft.
All trailing edges of the blades are angled towards you. Now lift the forward
end of the shaft, or lower the aft end, exactly the way most shafts come out of
boats. The blade on the starboard side, going downwards, will tilt even more
towards you, increasing pitch as measured in the horizontal plane. The blade on
the port side, turning upwards, will be tilted less. Indeed, it could be
exactly vertical for a moment, producing no pitch at all. Thus the increased
forward thrust on the starboard side of the prop.

Why then would a prop on a horizontal shaft generate prop walk, if it does at
all? Such a prop cannot be submersed too deeply, and paddle-wheel effect could
take over. It certainly will, as soon as even the tiniest part of the screw
protrudes from the surface of the water.

Herbert Prinz

   

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