Thorp Air Command - T18.net

Supporting Owners, Builders and Pilots of the Thorp T-18 and its variants.
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fytrplt
 Post subject: Wing Tips
PostPosted: Sun May 31, 2020 9:08 am 
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This is off a Grumman Cheetah/Tiger. Might have some clues as to Hoerner profile.

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Bob Highley
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Ryan Allen
 Post subject: Re: Wing Tips
PostPosted: Sun May 31, 2020 2:10 pm 
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Ah, I see the difference now in what I have. Thanks for posting


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hjubm2
 Post subject: Re: Wing Tips
PostPosted: Sun Jun 14, 2020 11:43 pm 
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Location: Barossa Valley, South Australia
Has anyone built the Hoerner tips out of fiberglass? And if so how hard is the process? My tips are 40+ years old and the fiberglass is going bad so it might be time to replace the original tips with a new style.


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dickwolff
 Post subject: Re: Wing Tips
PostPosted: Mon Jun 15, 2020 8:04 am 
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Paul McMicheal in Seattle built a pair quite recently and he raved about the performance improvement.

There is a good article in one of the newsletters describing how to build them. It may have been written by John Evans, but I’m not sure.


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Ryan Allen
 Post subject: Re: Wing Tips
PostPosted: Mon Jun 15, 2020 9:15 am 
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I would be all over buying a set of Hoerner wing tips if anyone has a set. As far as me building them, that's too much for my current fiberglass skill level.


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leewwalton
 Post subject: Re: Wing Tips
PostPosted: Mon Jun 15, 2020 10:17 am 
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Cubes sells them .. there's also a great 'how to' out there ... I can probably track down the exact newsletter. If I had to guess it's in the '90s era.

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Ryan Allen
 Post subject: Re: Wing Tips
PostPosted: Mon Jun 15, 2020 11:46 am 
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Didn't, think of Thorp Central. Well, I guess they will get some more of my money.


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dickwolff
 Post subject: Re: Wing Tips
PostPosted: Mon Jun 15, 2020 4:29 pm 
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Don’t hesitate to spend money at Thorp Central!!!! We need TC to stay in business.


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James Grahn
 Post subject: Re: Wing Tips
PostPosted: Mon Jun 15, 2020 11:30 pm 
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Our Hoerner tips are in the S18 profile. They would make a great start for someone who wanted them on a T18. All you would have to do is cut the splice about 1/3 of the way back, pull them down to the T18 profile, and reglass them.
For the T18, we stock the original profile tips.
Cubes


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Doug S
 Post subject: Re: Wing Tips
PostPosted: Tue Jun 16, 2020 6:16 pm 
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Tried to upload John Evens article but failed (maybe too big)
Author date was Sept. 2003 if it helps.


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Doug S
 Post subject: Re: Wing Tips
PostPosted: Tue Jun 16, 2020 6:39 pm 
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Here's a drop box link
https://www.dropbox.com/sh/o403ydna8v66 ... r6_Za?dl=0


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pmandel
 Post subject: Re: Wing Tips
PostPosted: Wed Jun 17, 2020 8:15 am 
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Forgive my ignorance, but advantages of Hoerner on the T-18 are...?? According to https://www.aircraftspruce.com/catalog/ ... ngtips.php which is for C-150/172/etc:

Typical Improvements are:
• Increase cruise 3-6 mph
• Increase rate of climb 75-100 ft./min.
• Increase stability with more positive aileron control
• Decrease stall speed 4-5 mph
• Decrease distance for take-off
• Gives a modern, more aerodynamic profile

And according to https://www.eaa.org/eaa/news-and-public ... troduction --

"The result is a 5 percent improvement in cruise speed." (at least on a Sonerai, obviously much slower than our birds)

Does anyone have actual numbers/advantages -- meaning measured, real world, not theory -- for the T-18? Please convince me that I want them. Very intriguing!
(PS: My A&P would do all the modifying ("cut the splice about 1/3 of the way back, pull them down to the T18 profile, and reglass them"), fitting, painting, etc. I have zero ability in that regard, but he does.)

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jrevens
 Post subject: Re: Wing Tips
PostPosted: Wed Jun 17, 2020 11:55 am 
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FWIW - here is a portion of an email I recently sent to a couple of other Thorp owners...

"There was no particular subjectivity in my testing of their performance. As I reported at the time I actually flew with one of the new and one of the original tips, with the new one on the left wing - the wing that normally was "heavy" with just me onboard, requiring a bit of the original roll trim (slightly lowering the position of that flap). Not only did I not need the trim, but I had to hold a considerable amount of left aileron pressure to compensate for what was obviously greater lift. It was surprising, right from lift-off, but increased as speed increased. Then I installed the other one and it was nicely balanced again. It's a little surprising and I have no explanation for it, but I saw no discernible difference in my full-throttle top speed - approximately 204 mph TAS at 7500' MSL. The biggest difference in handling was then during landing & especially when getting into ground effect... that extra lift was very obvious and I grew to like it a lot. I ended up lowering my approach/landing speeds quite a bit... seriously, about 10 mph.

Richard Eklund had a friend who was quite a good metal-worker - I don't recall his name, but you probably know who I'm talking about. He & Richard carefully studied and took careful measurements of my tips one year at OSH. He then proceeded to build a set out of metal. They were very well done and matched the fiberglass ones pretty closely, except for a more rounded outer edge. He sold that first set to my best friend and hangar-mate, Dean Cochran. Dean put just one on at first, and performed the same test that I had. He actually took a spring scale up with him and measured the force needed to hold that wing down & level. I don't recall what it was but it was considerable, and he documented it in the newsletters I believe. Richard's friend later built a second set for Richard's airplane, and he confirmed similar results."

I had enough Thorp time with the original design tips at the time to be able to make a good comparison of the new ones with my airplane. I can't attribute all of the decreased landing speed to the new tips, but they definitely made a very noticeable difference for me, making the landings more comfortable at those speeds. The level WOT speed referenced may have varied a couple of MPH one way or the other, but 204 is very close, with or without the "new" tips. 160 hp O-320-D2A and Aymar-Demuth prop.

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John Evens
Arvada, Colorado

T-18 N71JE (sold)
Kitfox 7 SS N27JE


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pmandel
 Post subject: Re: Wing Tips
PostPosted: Fri Jun 19, 2020 10:35 am 
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That is seriously cool info, John. Thank you.

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Philip Mandel
N118BC
S/N 957
Beaverton OR


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dickwolff
 Post subject: Re: Wing Tips
PostPosted: Fri Jun 19, 2020 8:06 pm 
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There is a series of videos on YouTube showing how to build Hoerner tips.... similar methods as what is described in the Newsletter article.

https://m.youtube.com/watch?v=sDHynvw9Ozo
https://m.youtube.com/watch?v=RoOh-fgI8oU
https://m.youtube.com/watch?v=ULhZchv7ito

D


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