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"Lippsing" a Q-tip propeller



 
 
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  #1  
Old April 16th 09, 07:38 AM posted to rec.aviation.homebuilt
MP[_2_]
external usenet poster
 
Posts: 5
Default "Lippsing" a Q-tip propeller

Thought I'd ask for comments before doing something stupid and irreparable
to our propeller.

We have a Hartzell Q-tip prop on our Glasair. That's the fancy bent over tip
that gets all the jokes about the FAA Inspector who grounded a Cheyenne when
the propellor first came out. (Looks like the prop had a ground strike.)
When we got it, the Q-tip was a hot thing, and we were coming off a Prince
P-tip, which also had a turned under "winglet."

Then Paul Lipps came along and wrote that putting a big hunk of metal out
there on the prop tip is about the stupidest thing one could do, since the
prop tip is where velocity - and therefore, drag - is highest. He wrote
about cutting the tips off a Prince wood prop and getting a phenomenal
improvement in propeller efficiency.

I'm not going to cut off the Q-tip entirely. But I thought I would try a
compromise solution, and cut part of it off. I should link a photo to show
you my markups on the tip, but the plan is to cut the front of the winglet
to put a 60 degree shear on the front, like you see on the Katana wingtips
and on Paul Lipps' Lancair. I will be careful, will sand out the stress
risers, etc. I have a good gram scale to weigh the cutoffs to match, and a
dynamic prop balancer to rebalance after the operation.

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?

Thanks,

Mike Palmer


  #2  
Old April 17th 09, 02:14 AM posted to rec.aviation.homebuilt
Capt. Geoffrey Thorpe
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Posts: 790
Default "Lippsing" a Q-tip propeller

"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

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.

  #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?
  #4  
Old October 20th 17, 11:17 PM posted to rec.aviation.homebuilt
[email protected]
external usenet poster
 
Posts: 1
Default "Lippsing" a Q-tip propeller

On Thursday, April 16, 2009 at 6:38:17 AM UTC, MP wrote:
Thought I'd ask for comments before doing something stupid and irreparable
to our propeller.

We have a Hartzell Q-tip prop on our Glasair. That's the fancy bent over tip
that gets all the jokes about the FAA Inspector who grounded a Cheyenne when
the propellor first came out. (Looks like the prop had a ground strike.)
When we got it, the Q-tip was a hot thing, and we were coming off a Prince
P-tip, which also had a turned under "winglet."

Then Paul Lipps came along and wrote that putting a big hunk of metal out
there on the prop tip is about the stupidest thing one could do, since the
prop tip is where velocity - and therefore, drag - is highest. He wrote
about cutting the tips off a Prince wood prop and getting a phenomenal
improvement in propeller efficiency.

I'm not going to cut off the Q-tip entirely. But I thought I would try a
compromise solution, and cut part of it off. I should link a photo to show
you my markups on the tip, but the plan is to cut the front of the winglet
to put a 60 degree shear on the front, like you see on the Katana wingtips
and on Paul Lipps' Lancair. I will be careful, will sand out the stress
risers, etc. I have a good gram scale to weigh the cutoffs to match, and a
dynamic prop balancer to rebalance after the operation.

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?

Thanks,

Mike Palmer





so how did it work?

 




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