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"Ernest Christley" <echristley@nc.rr.com> wrote in message
news:hKkYf.56420$915.53670@southeast.rr.com...
<...>
> I am glad to add the "(well, mostly?)", because I could read that as "not
> at all". What you do have with a certified engine is a situation where
> the prop manufacturer has tested their prop with that engine. It's a well
> studied combination that everyone knows how to work with.
>
> For instance, you cannot cut a metal prop down but so far. Why? Because
> everyone knows where that resonant point is, and cutting the prop down to
> 70" will land you smack-dab in the middle of patooky when one of the
> blades comes off.
>
> But build a new prop of your own design, sufficiently different from the
> typical prop...then it doesn't matter if you put it on a certified
> powerplant or the front of your Oldsmobile. Unless you have the
> facilities to test it, its longevity is just guesswork.
That was a problem on some of the early T-18's that were using cut down
propellers - resonance was fatiguing the propeller which would then shed a
blade, which would then encourage the engine to attempt to part company with
the airframe...
--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
Spell checking is left as an excercise for the reader.
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Re: PSRU design advantages
