"Lippsing" a Q-tip propeller

[MP[_2_]]

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 <><

[Capt. Geoffrey Thorpe]

"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.

[Charlie[_2_]]

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?

[[email protected]]

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?