Your article is loads better than the current one on prop effective pitch.
Vance

I just read that Effective Pitch article in EAA Sport Av and it is not
all that bad of an idea. Course it is a bit redundant with just specifying
the top speed achieved with a given prop.

It would be better if the prop building guys used a cord pitch instead
of the bottom of the blade. Also a speed specification for optimum twist.

If that seems impractical then specify the angle of the blade every
0.1 blade radii. Too many props out there with the wrong twist, improperly
twisted or no twist at all.

Perhaps the EAA could apply some pressure for standardization.

Why don't you write an article on props Vance? Send it to me first and
I will critique it :-)

Paul Lamar

Paul/Vance,
It looks like your the expert on props Vance.
I've been doing some research and I just can't seem to get anywhere
too much maths and not enough info - for me.
It would also seem Paul is correct with his statement about the Props out
there.
There seems to be a lot of guessing on the part of the prop makers and much
of it is incorrect.
I for one would like it if you did an article on Props Vance.
I know it is and can be a complex issue. I initially sought simple
solutions,
I believe many Prop makers use these, however the more you read the more
you wonder if anyone could ever get it right.
Perhaps there is a good book - perhaps a computer program ???
So Vance if your up on it - please, help!!
George (down under)

This is why I wrote the prop sim program and ran about 500 iterations
before I felt like I had a decent blade design.   I have studied nearly all
the old
NACA papers, understanding most except Theodorsen's.  I tried to use
his methods (separate paper basically"interpreting" his earlier papers) and
got gibberish at the end.  It relies highly on pulling info off of graphs
and the
props we need are always at the extreme end of their plots, since they were
interested in props at 1000-3000 hp and 300+ mph.   Most of the theoretical
basis for my sim program came from Von Mises "Theory of Flight" which I
recommend.  Perry is reading it now, a good book.

Bill Freeman
Long EZ builder & pilot
BSME, MSME
EAA Technical Counselor

 
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