gregory_west2001 wrote:
>
>
>
> After reading your posts on this and other sites, I bought a number of
> the airplane props (9" and 10" with 6", 7" and 8" pitches), but I
> wonder if the blade area will be too small for the boat if we need to
> move through some tide or wind. I am also considering the new Torqeedo
> two-blade kayak prop (8" x 8"). The Torqeedo kayak prop is designed
> for the Torqeedo motor turning at 1200 rpm, which is the rpm that I am
> hoping to get at just under 30 amps. I would appreciate any thoughts
> you or anyone else might have on whether we should worry about not
> having enough blade area with those airplane props for this little
> boat. The airplane props just don't look like boat props.
>
> Greg
>
Hey Greg,
A shrink once told my late wife that worrying was the act of discomfort
over something that hasn't happened.
Largest Diameter that will fit, slow RPM, lowest number of blades is the
formula for best efficiency. Square prop diamensions i.e. 12"x12" have
been cited as best, but that is why you are messing with airplane props.
Surface area of the airfoil creates drag thus the need for more power,
but bite is important as well, so we live with drag.
Fluid dynamics are calculated the same in water or air based on density
of the fluid. The hardest part to deal with is the slower the blade
turns the stronger it must be to handle the torque it is expected to
handle, making a thicker blade thus wider foil, and more drag.
What you will be able to do:
Test different pitches to find optimum pitch.
Find optimum RPM.
Test different Diameters. (/Larger Diameter more bite)
/The cost to you for such great data is very low, so no worries mate.
Kevin Pemberton
P.S. Keep an eye on motor temps, the major reason trolling motor
manufactures don't talk pitch of their blades to the customers.
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