vjaqua wrote:

Pine - The center 20 percent radius portion of the propeller has almost

no impact

on performance, and in many cases is almost, if not completely,

encompassed by

the spinner. My programs essentially ignore this area, especially since

true

helical pitch would usually result in very steep angles for these points.

I can

give you a starting point prop configuration with data on engine shaft
horsepower, prop shaft rpm at that power,and a realistic value for

airplane top

speed at that power. If you have some diameter limitations based on gear
clearance, that can be considered also. in most cases optimum performance

is

realized with the maximum diameter allowed by tip speed and clearance.
Vance

Pine Pienaar wrote:

Hi Vance

This prop is for my Weight shift trike, powered by a Rotax 503 and B box.
The current wood prop is a 64X32 and at 6400 engin 2480 prop rpm I'm seeing
64.5 Mph this is top speed for this prop. Max engin rpm is 6800. With 5200
rpm (cruise) 2015 prop rpm I;m getting 46 Mph

This engine is rated at 52 Hp max with 39 Hp calculated in the cruise.

Although the airframe can and do take a 72" prop its not used with this
engine and B box 2.58:1 ratio. For some reason they only use it with a C or
E box that has a 3.47:1 ratio.

I would like to use a Naca 16 series or the ARA D series airfoil as I'm
planning a solid Carbon blade, and can use CNC machines to cut the moulds.

Many many Thanks

Pine

Man am I jealous. :-)

Paul Lamar

 
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