I think the best way is to use thick carbon fiber skins laid up in female
molds  and bond them together at leading and trailing edges. Clamp them back
in the mold and inject them under pressure with syntactic
foam. Syntactic foam

Paul, Far and away better is to wrap the prepreg around a rubber form, (hollow)
place it in a female mold with clearance to trail the fiber out the trailing edge.
Then close the mold pressurize the rubber form and heat the whole mess. The resultant
blade has a "single sheet" strength the trailing edge is trimmed and you are done.
The layers of the trailing edge are clamped togeather and the leading edge is continous.
My $.02. If I'm making the molds that is how I'll do it.
Bill Jepson

That sounds like a less labor intensive way of doing it.
What do you use for the rubber bladder Bill? How closely must it be shaped
to the final planform of the prop blade? Can a section of bicycle inner tube
be used?

Send me some sketches on this process. Would it help if a flat wood insert
was placed in the rubber bladder the shape of the prop blade plan form?

Paul Lamar

Sounds like an interesting process if the blade is thick and hollow,
like the LAEV prototype blades. However, I think that blade was made too
thick. The beauty of carbon fiber is the blade can be made very thin
like a metal blade. Thinner blades give better performance, and it shows
in my computer prop simulations. My fan blades are also very thin, and
almost solid carbon fiber.

--
Perry Mick
Custom Composite Props
mick@bridgingworlds.com
http://www.ductedfan.com

I agree thinner is better. Are you using a female mold Perry?

Paul Lamar

 
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