[hpv-boats] Propeller Slip

[2scott]

The term or concept may be a convienent and maybe even an effective
approach to understanding propeller behavior but it is far from
the truth... even though the results may be usefully accurate.
Props are foils that have an angle of attack that represents
the best Lift/Drag ratio and anything more or less ( which
I guess can be quantified in slip terms ) is less efficient.
Learn what the angle of attack is of your prop blades at
various stations from 30 percent to 90 percent of the length
to the tip and see if at a certain prop rpm and forward
speed the angle of attacks are to see if you need to be
using either a larger slower ( or faster turning smaller 
prop with more or less pitch to match that magic angle
of attack.  remember a prop blade  is like a sailplane
wing and the sailplane pilots know exactly what speeds
produce the best lift and least drag for their planes.
( all based on angle of attack for the foil )

--- On Fri, 9/17/10, dennis <flareking at talktalk.net> wrote:

> From: dennis <flareking at talktalk.net>
> Subject: [hpv-boats] Propeller Slip
> To: "Human Powered Vehicles -- Boats" <hpv-boats at bikelist.org>
> Date: Friday, September 17, 2010, 9:35 AM
> Rick
> Your prop slip figures are similar to those given by the
> PropSim program.
> I will test one of  my non-folding props to see if it
> is the hinge zone that is causing the problem.
> My simple GPS is a Holux 245 which gives Max and current
> speed, distance and time.Speed/time or distance can be
> plotted onto my computer.
> 
> Dennis
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