>From the Kolb list:

snip

I wish I could post pictures for you, but as I stated earlier I
don't have a scanner and I'm using an old windows 95 computer as
of now.  Have taken a couple of pictures, but still have the film
in the camera.  If you want a good close up of what I did, just
visit your nearest model airplane shop and look at the new Top
Flight wood props for RC's.  That's where I got my idea from and
the dimensions!  I did try my best to describe what I did on an
earlier post.

I'm experiencing the 4 mph gain at cruise, which for me is at
5,000 to 5,200 rpm.  The fuel burn is still the same at
approximately 2 gph.  This is not the reason I made the change.
My intent was to eliminate prop noise, which it has done and the
reason the RC boys are using this design.  It worked better than
expected on my full size prop!!!  The gain in performance is just
a side benefit.  Hope this answers some of your questions!

snip

-"Schemmel, Grant" wrote:

Greetings All,

I have a question for the propellor experts on the list.  Found this

posting on the Matronics (www.matronics.com) Kolb list while searching for
something else.  The guy making the post took his wood prop and modified it
to match the profile of a prop he found in an RC model
shop(http://www.top-flite.com/accys/topq5000.html), and is now claiming it
got him a 4 mph gain in cruise and a higher static rpm along with much
quieter operation.

Another person on the same list did the same mod to an IVO prop, and

claims about a 1.5 mph speed gain. He documented the mod at:
http://www.thirdshift.com/jack/firefly/firefly100.html

Anyway, I'm thinking of doing the same to my Warp Drive (since I've not

been very impressed with the performance), and was wondering what the
overall opinion might be since my tapered Warp Drive is only about 1.5" at
the tip and maybe 3/16" thick.

Thanks

Grant Schemmel
(Rotary BD-4 someday)

Since the tip is going near supersonic at top speed  anything you do to

add

or reduce drag to the tip is critical. Making the prop shorter or the tips

thinner

including adding sweep back helps.

Paul Lamar

The reshaping shown is very similar to a current trend in wing tip shaping
in which the trailing edge is longer than the leading edge. The approach
is to reduce tip vortice losses, and is probably equally applicable to
props. The reduction in noise would seem to be an indicator of some
improvement. As an interesting aside, the Sensenich metal prop for RV's
for the O-360 is a reverse of this - tho the prototype was the long
trailing edge - they maintain there is no difference? (tooling
mistake?) - Vance

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