15.75-xx 3 Blade

[Bill Glaze]

A couple of years ago, I was running an engine with my stepson looking 
on.  He noticed a fine spiderweb appearing area near the prop hub, and 
asked about it.  I hadn't noticed it, but later wondered if it was the 
beginning of a fracture.  I replaced the prop immediately, haven't given 
it any thought until this shread started.
(APC 16-10)
Bill Glaze

RUDDERCABL at aol.com wrote:

> 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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