Don Dunbar wrote:

Hello ACRE,

Hi Paul,
I have come across a new product that I think would make a good prop
blade as it has other properties that Carbon fibre does not.
The product is fibre glass reinforced polypropylene. It does not have
the tensile of carbon fibre but does not chip and fracture like other
resins. The most popular use for this product is for under body
protection for Rally cars and high impact and abrasion components.
The tensile of this material is 350 mpa with good flexibility.
It comes as glass impregnated and is vacuumed into moulds and place in
the oven for curing. Steel or alloy moulds work best as they transfer
the heat better.
What are your comments

--
Best regards,
 Don                            mailto:ddunbar@echidna.id.au

Worth a test on the ground. The U.S. FAA required it spun up to twice
redline as a test as I recall. I don't know how one could
do that with out a zillion HP. Perhaps if you just used a static
pull on the end of the blade with a calculated load of
twice the expected blade mass centrifugal force.

Another question is heat generated in the hub either by conductance
from the engine heat or slip friction because the prop bolts are not
torque down properly. What is the max temp of polypropylene?

A third issue is blade torsional stiffness. Glass has a much lower modulas of 
elasticity than carbon fiber so it could untwist at high thrust levels.
Tracy Saylor thinks he ran into that problem with the MT wood and glass 
composite propeller. It was untwisting compared to his aluminum 
constant speed prop he usually uses to go 240 MPH in his RV6. Slowed 
the top speed down about ten MPH.

BTW how is your 13B powered Mustang II coming? You should be close to flying.

Paul Lamar
 
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