Most of this argument dovetails with the prop article in the latest Contact
magazine.  It also is very similar to the new blade profiles that Whirlwind
Props are selling for the RVs.  All the logic for the blade planform stacks
up.  It is an unusual looking prop.

It amounts to a very large cord at the root with an extreme taper out to
the very small tip.  Large diameter spinners not required.  Paul
Lipps,  the guy writing the article, has some pretty impressive comparisons
with other props and his incremental performance improvements to his
Lancair 235.  It sounds like he is working with Craig Catto to carve and
layup his design.  He also worked with Klaus Savier on various
projects.  He's a retired engineer/rocket scientist, Vance probably knows
him.   P-)

You can do a lot worse than Catto for a prop maker based on comments I've
gotten from those running his props.  http://www.cattoprops.com/  He has
several running at Reno every year.

It would be really interesting to take the pitch numbers from Tracy's prop
and have one of Lipps' props cut in a three blade version for a 200 hp rotary.

Lipps also seems to know what he's doing in regards to efficient cooling
ducts.  Look how small these are on the nose of his Lancair.  Granted he's
only cooling 123 hp but he's only using 12 sq inches of opening.  That's
another Contact article entirely.

An article in the RVator (Van's Aircraft factory newsletter) a few months
back talked about the philosophy behind the new Whirlwind prop blade
shape.  These props don't look quite as radical as Lipps' profile, but,
they're still unusual looking.  We have a few RVs here in the Portland area
that are running Whirlwind 200RV props. http://www.rv-8.com/Prop.htm  The
new Whirlwind 151 blade profile follows this same cord distribution.

Perry- have you seen these two articles?  I can scan them for you if you
want to read them.  I don't want to publish them to the group without
permission from the publishers first.  The scans would be pretty big to
read all the pages anyway.

If you guys aren't subscribed to Contact magazine I highly recommend it.
http://www.contactmagazine.com/

Well, that got long winded...

Mike McGee, RV-4 N996RV, O320-E2G, Hillsboro, OR
13B in gestation mode, RD-1C, EC-2

Hi Mike, yes I get Contact magazine. I've already read the articles and
they are very interesting. He uses the same propeller analysis program I
do, he modified and improved the program, as I also have done. I might
try to contact him directly.

Perry

 
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