15.75-xx 3 Blade

[RUDDERCABL at aol.com]

In a message dated 8/16/2005 12:51:26 AM Eastern Standard Time,  
DaveL322 at comcast.net writes:

With the 2 failures on 2Cs (both well used props from the  original mold), 
I'm personally going to limit the number of flights I put on a  given prop and 
retire some of my old ones.  Perhaps my thinking is  flawed or too aggressive, 
but I don't think it unreasonable that a high  performance prop in a high 
performance application has a limited life  expectancy.  

Regards,

Dave  Lockhart
 
I agree with that. The prop that I had fail was an old prop with many  
flights. It was used as a test prop and flown on many different setups before  and 
after Dave repitched it. I really liked the prop and want another. Dave, you  
got one handy?
 
I want to take this opertunity to say that I don't blame APC or Dave for  the 
failure. 
 
My memory may not be as good as I want it to be, but I think it was Brian  
Hebert and Todd Blose that I was telling about the failure while at the Nats.  
They told me they had seen a couple of failures on some 2 blades also. The  
common thread was that they were old props. Todd and Brian had already made  the 
decision to replace their props on an annual basis.
 
After much thought, I am now of the opinion that many of us (including  
myself ) have a tendency to tighten the props too much when we put them on our  
engines. In the past, I have seen people tighten them so much that it was a real  
bear to remove the propnut. Over tightening them has got to have a crushing  
effect on the hub. Over the life of the plane the prop is on, it can be 
removed  and replaced many times for maintenance or engine changes. It is not  
unreasonable to believe that each time the hub is tightened down and then later  
removed, a cycle has occured where the fibers and resin of the prop have been  
squeezed and relaxed. Over time this could lead to small cracks that may not be 
 visible that are inside the hub. At this point, failure is only a matter of  
time. 
 
Robert Gainey 
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