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Author Topic: USA-5 airfoil  (Read 575 times)
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Tapio Linkosalo
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« on: October 01, 2020, 01:09:45 AM »


Decades ago I ran into USA-5 airfoil and chose to use it in my P-30. Have been a happy camper with that airfoil. But now I have no recollection where I spotted the airfoil. Who has designed it, and in what model was it originally used? Thx.
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PB_guy
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« Reply #1 on: October 01, 2020, 01:59:13 AM »

See: http://airfoiltools.com/airfoil/details?airfoil=usa5-il
ian
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lincoln
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« Reply #2 on: October 01, 2020, 02:14:19 AM »

NACA technical report 18 has information on the origin of the USA-5. I don't know who's used it in a model. According to the Incomplete Guide to Airfoil Usage, a couple of full scale aircraft have used it. Search engines can find these faster than I can figure out how to copy and paste the URL's with my Stoopidfone (R).
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Tapio Linkosalo
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« Reply #3 on: October 01, 2020, 02:59:54 AM »

Thanks.

I tried to google but was not able to find any info on the airfoil. I chose to use that on my P-30 in 1986 (I think), so there was no internet to mention back then. Thus I just wonder where did I pick the airfoil up. Must have been a model, for sure I would not have chosen an airfoil from a full-sized airplane.
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lincoln
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« Reply #4 on: October 01, 2020, 03:49:08 AM »

I seem to recall that in the report, they had been testing the airfoils with small wind tunnel models of three inch chord. That might explain why they thought the USA-5 was a good airfoil, and why you had success with it. I think a bunch of models have been built with full scale airfoils, appropriate or not. I doubt the NACA 6409 or anything else in the four digit series was intended for models, but it has been widely used. The RAF 32 was popular for Wakefields and the like for years, though I'm sure it cost many seconds of flight time on all but the largest models. The only full scale use I'm aware of was in the Hjordis sailplane. We're all familiar with the Clark Y. I don't know if anyone's used the RAF 15, but they should have. Especially in scale models whose subjects also used it. It was quite popular in full scale use, though I should think it gave the structural engineers the heebie jeebies. No matter, they were probably more easily subdued in those days.  Maybe a stroke or two with a cricket bat....  I imagine deHavilland employed a number of powerful batsmen in the early days.


A number of model magazines used to publish airfoils, so maybe that's where you got it from. Some of the magazine's even printed them out in different sizes, in addition to providing coordinates.
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Tapio Linkosalo
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« Reply #5 on: October 01, 2020, 04:10:23 AM »

Good point. I was subscribing to Aeromodeller back then, so maybe that was the source. Have to check!

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billdennis747
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« Reply #6 on: October 01, 2020, 04:16:09 AM »

A number of model magazines used to publish airfoils, so maybe that's where you got it from. Some of the magazine's even printed them out in different sizes, in addition to providing coordinates.
I often think that my brain needs wiping and reinstalling to get rid of all the redundant knowledge therein . I've no idea what a USA 5 looks like but do remember reading in Aeromodeller a humourous reference to this aerofoil in French as 'Yousasank'.
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Soc
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« Reply #7 on: October 01, 2020, 04:27:53 AM »

Tapio
Many French Coupes use airfoils based on USA 5 so you probably saw it mentioned on a drawing.
I've been very happy with the airfoil from Matherat's Trumeaux on the P-30s I've built.
I believe it is one of those derived from USA 5.
The top side is the same, or very close, and the bottom side is modified.

Sean
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billdennis747
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« Reply #8 on: October 01, 2020, 06:47:23 AM »

Tapio
Many French Coupes use airfoils based on USA 5 so you probably saw it mentioned on a drawing.
I've been very happy with the airfoil from Matherat's Trumeaux on the P-30s I've built.
I believe it is one of those derived from USA 5.
The top side is the same, or very close, and the bottom side is modified.

Sean
Well there you go - I just built a Trumeaux with a 'yousasank' without knowing it
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Indoorflyer
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« Reply #9 on: October 01, 2020, 10:12:27 AM »

https://ntrs.nasa.gov/search.jsp?R=19930091301

http://airfoiltools.com/airfoil/details?airfoil=usa5-il
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RobinB
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« Reply #10 on: October 01, 2020, 01:09:10 PM »

Didn't Hank Cole use it?
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Tapio Linkosalo
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« Reply #11 on: October 02, 2020, 02:21:49 AM »


Thank you, my dear Sherlocks - you were quite on the money recalling that French Coupe fliers used the USA-5 airfoil. I did manage to find my most likely source of the airfoil, Aeromodeller that is. In June 1985 issue, on "Free Flight Scene" -column, Dave Hipperson describes Bryan Spooners Coupe from 1978. Desription says that "The model climbs positively throughtout the run [... and] glides well on the USA-5 wing section." The 3-view has a picture of the airfoil, on which I have drawn horizontal pencil line for reference. So obviously I have been interested on the airfoil, and most likely copied it for my P-30 model. Jolly good!

My P-30 dates back to 1986, and I recently built a new version of the same design, so the model is still going strong!
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bentodd
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« Reply #12 on: January 08, 2021, 02:57:32 PM »

One more source, Free Flight Quarterly Coupe d'Hiver Survey 2009 pt2, pg 67, The USA 5 airfoil  by Sergio Montes  He notes that it was a popular airfoil for French Coupes in the '40's and '50's.

The flat trailing edge makes it easier to build however flapping it will add some improvement.
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