Pine Pienaar wrote:

My program seems to favor a 70 inch diameter with roughly 34 inch pitch.

Pitch is

based on flat bottom measurements with foils similar to Clark Y and RAF

sections

frequently used for props. I could find no info on the 16 series in

Abbott and Von

-- , and I am not familiar with the ARA D you referenced. Propellors are

much more

forgiving of airfoils than wings. Dowty, I believe, uses undercambered

foils on

some of their props, but really fast planes use sections with very littls

camber,

and thin sections. With your gear ratio 70 in dia is pushing the limits

for wood

blades, but with the carbon you can use metal  thickness practice. With

thin

carbon sections I would use some Bi-directional for torsion, you will not

need UNI

for the centrifugal, the stresses usually are less than you first think.

The

program uses true helical pitch, and the angles and suggested blade

widths (2

blade use 2/3 for 3 blade) are 0.9R 2.8in 9.8deg. 0,7R 3.7in 12.6deg

0.5R 5.0in

17.4deg  0.3R 6.0in 27.5deg.  I do not know what your power curve for

that engine

looks like, so I cannot estimate static rpm and thrust.

Your application is a natural for props like the ground adjustible Warp

drive, but

I can certainly identify with your desire to do your own design.

Your spread between cruise and top speed seems too wide, you are probably

cruising

well below 70 percent power.Vance

Just to avoid misunderstanding the blade widths you gave are for a 2 blade
and I must use a 66% of that for a 3 blader. Also how does profile thickness
affect the performance??? Can I just make it as thin as possible considering
the bending forces or does your software give an staring point. (What is the
practice for metal blades) ???

Many Thanks

Pine

 
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