Richard Lamb wrote:

But then the topic is resonance, isn't it.
And?
With the exception of combinations which are known to have
engine/prop/AIRFRAME
resonance issues (hint, hint, hint), certified engines avoid that trap
entirely
(well, mostly?).


I'm 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 can't 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.


--
This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."