View Single Post
  #3  
Old April 22nd 09, 02:52 AM posted to rec.aviation.homebuilt
Charlie[_2_]
external usenet poster
 
Posts: 56
Default "Lippsing" a Q-tip propeller

Joe Brophy wrote:
On Thu, 16 Apr 2009 21:14:38 -0400, "Capt. Geoffrey Thorpe"
The Sea Hawk @See My Sig.com wrote:

"MP" wrote in message
...
Thought I'd ask for comments before doing something stupid and
irreparable
to our propeller.

...
It's a homebuilt, so I'm deep into "experimental" mode on this one.
Anyone
want to warn me about how I might kill myself doing this? Has anyone done
this before?

Sure, I'd be happy to warn you.

Has anyone killed themselves after cutting down a prop?

Yup.

Cut down props were popular on the early T-18's - at least until the first
few fatal accidents. When the blade broke due to resonance / fatigue the
engine would part company with the aircraft and the result was typically a
dead pilot / passenger.

Changing the length of the prop changes the resonant frequencies with
unpredictable results.

http://www.t18.net/technical_info.htm#Cutdown



That is why, after you finish with the sawzall, then smooth
it off with a harbor freight angle grinder, make sure the
prop gets a heavy coat of 3m rubberized undercoating. It
dampens out those nasty vibs before they have a chance to
rattle their way through the prop and cause a catastrophic
failure. Good luck, make sure you wear eye protection using
those power tools....regards, Joe.

Are we making a test club with no thrust requirements, or are you just
trolling?