[hpv-boats] Single person easily driven displacement hull drive systems

[dennis]

Hi Rick

As you are aware I have suffered several design failures on my manufactured props caused by excessive slipping of up to 30%.
This stalling was virtually throughout the operational range and predicted by Theo Schmidt in his 1999 paper on Propsim.
He advises slender type blades with high pitch /dia ratios are subject to stalling.
My APC 16 x16 only slipped a maximum of  2 to 3 % but when I made a new version with a pitch of 24" the problem started.
Your design for the constant cord prop suffered slightly worse, but the problem was over come by widening the cord which I did to the extreme ( this I believe created increased drag due to the larger surface area).
The slipping is created by the greater resistance of my boat compared to your V14 boat
What this really shows is that there can be no hard and fast rules as the prop must be tuned to the application ie the boat.
I like you feel that a 4 to 1 gear ratio is about right, bur like Bob Stuart I also feel that  if the pitch and dia are equal the prop is more flexible 
and even though the revs would be higher the efficiency might be better.  To sum it up regardless of the prop design programmes, prop design it still very trial and error

Dennis a