Dale Smith wrote:

Hi Paul (and all),

Found some free programs available for determining the correct
prop for a given airplane and engine combination if you know
the cruise speed, and cruise horsepower and RPM available from
the engine.

EAA member Ed Dokus  <dokus@attglobal.net>  has put the
programs in the public domain & no claims are made as to
applicability to different situations, .... but ... the price
is right!  Check out:

http://www.nicon.org/chapter328/PropDesign/

Originally written by Ed Dokus, and then made into a Windows
version by Joe Dubner.  In his words:

"PropDesign is a Windows port of Ed Dokus' DOS/BASIC propeller
design program.  It calculates propeller pitch, diameter,
chord, thrust and efficiency when given a propeller type
(planform, airfoil, number of blades, etc.) and cruise
conditions airspeed, altitude, etc.).  Output is in graphical
or tabular form, allowing an experimental aircraft designer to
ask "what if?" without having to carve/bolt on/fly each new
design."

The version on this site is always the current (latest
version) and it's about a 600 kB download. The site also has a
spread sheet available to calculate propeller blade load
stresses, and links to sites on propeller construction.

Another site worth looking at is on propeller design:

http://members.tripod.de/MartinHepperle/Airfoils/

This  second web site is the product of the German
Aerodynamics Consultant  Dr. Martin Hepperle.

All his pages can be reached through his main business site:

http://www.MH-AeroTools.de/

or go straight to the prop page at:

http://members.tripod.de/MartinHepperle/Airfoils/javaprop.htm

Dr. Hepperle gives  a wealth of information here, on
aerodynamics, airfoil design, propellor design, and tuned pipe
design.

There are free programs to download in all these areas.  Most
of this information is aimed at model aircraft, but as you
know, the principles are the same (though of course with
different Reynolds numbers), and I don't think that the
physics of tuned pipes differ from large engines to small ...
do they?

Since it is designed for model aircraft, high RPMs (such as
our engines turn) is not likely to be a problem.

This site definitely deserves a look.

Getting in line for a LAEV prop .... keep up the good work,
guys.

Dale Smith

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