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J.L. Frusha

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So, just having found this thread today, is there a summary choice for the highest lift and lowest drag airfoil for ultralight aircraft?



What is optimization of wing lift and drag distribution?

Do you believe airfoil selection has a hand in the drag?

Do you believe drag should be zero? That would be fairly optimum.

Should airplanes fly at slow speeds for safe take off and landing, or takeoff, cruise, and land at the same speed?

Are runways required? What length? No runways seem to be optimum.


As always, there are many ways that compromise leads to function.

For an ultralight, we (in the U.S.A.) have parameters and limitations...
Must weigh less than 254 pounds with fuel and engine
Carry only 1 person (not counting training designs for training purposes only)
Power-Off stall of 24 mph or less
Max Air Speed 54 knots indicated
Etc., etc.

I didn't think it was that difficult a question, but, rather, a simple request for information based on the stated purpose of this thread, to gather information on airfoils. Not sure why the contrariness seems so abundant. Nevertheless, I shall proceed with my own ideas and heed the sage advice that I do find freely given, to the best of my ability. Eventually, the results will speak for themselves.
 

BJC

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The only NACA that I would consider in an LSA aircraft would be the 747 series.
I know a successful multi-time designer / builder named Dick who appears to have a contrary opinion.
There is a lot of Dicks here but no Richards
That’s not nice. Fewer than ten posts, and you start applying unflattering innuendo to people here?

Richard “Dick” VanGrunsven, aka Van, uses a NACA 23013.5 airfoil on several of his E-AB designs, with some success. Yes, that very same airfoil that many have advertised as dangerous.


BJC
 
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BJC

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I checked the University of Illinois-Urbana airfoil useage page.
The airfoil became a "Fad" that a few designers were tricked into using, eg Glasairs, Lancairs, Cirrus Vk-30, Express, Heintz 100, Prescott Pusher, Sweringen SX-300, Seawind 2500/3000, Piper Tomahawk, LoPresti Sharkfire, Giertz Probe, Nemisis NXT, Vulcanair VA-600w, Varieze main wing, etc.
Airfoils evolve into “families” with variations. The “NLF” descriptor can be applied to dozens of airfoils. The Glasair uses the NASA/LANGLEY LS(1)-0413MOD. How was Tom Hamilton tricked into using it?

Lancairs have several airfoils, some designed by highly accomplished aerodynamicist, including Greg Cole. How was Greg tricked?

Ted Sweringen has a solid track record. How was he tricked?

NXT was designed by some guys at Lockheed. Tricked?

Please share the justification for your claims.

Please also specify the airfoils that the Glasair, Lancair, SX-300 and NXT should have used.

Thanks.


BJC
 

bhooper360

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I didn't think it was that difficult a question, but, rather, a simple request for information based on the stated purpose of this thread, to gather information on airfoils.

Ok. Just for you:

"Gone Fishing"

Main wing: Clark Y
Horizontal stabilizer: FX 71-L-150 MOD 50[% elevator chord]
Vertical stabilizer: Flat plate, or NACA 0012

These recommendations are suitable for the Watson Windwagon, contingent on a) closed canopy, b) CG at max thickness and c) wing loading not exceeding 6-7 lbs/ ft^2 as flown.

The short-coupled / flying wing designs are not suitable for you. The slats are not appropriate.

Do you see that cusp on the bottom of the NLF airfoil you posted? It contributes to the drag bucket by restricting the separation of the boundary layer when the wing is at a very low angle of attack. You won't see this feature on airfoils optimized for lower Reynolds numbers, because there is no, uhm, hysteresis in the way the flow separates. (I'm not quite fluent in this language, yet.)

For legal ultralights, laminar runs are extremely niche optimization. You end up with a very high fuel efficiency and almost lethally poor climb performance. As in, you're very likely to hit a tree or something, ten minutes after takeoff.

You've got so many innovative ideas that, aerodynamically-speaking at least, I recommend something mind-numbingly boring. Long tail boom, traditional proportions, and optimized for high lift and high drag. If you decide to innovate, start with an airfoil with a big leading edge radius, and then go nuts.

Good luck!
 
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J.L. Frusha

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@bhooper360

Thank you. I will take it under advisement. Not trying to be aggrivating, just asked a question that got a snarky response, so I tried to rephrase it.

By the way. Found this a couple of days ago. Just finished reading what I can understand of it...

"Multi-Element Airfoil Design, Analysis and Wind-Tunnel Test for a S.T.O.L. Ultra-Light Aircraft"

1641107712127.png
 

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TFF

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The term Ultra Light in that paper is the more international definition, which in the USA is called LSA. The aerodynamics work the same, application might not be for reasons not associated like weight of mechanism or other components. Slat leading edge works great, but for a plane that weights 254 lbs. it has the weight of two leading edges which in tight constants can be one too many. Hinges, handles. Same with a flap, multiple fuel tanks, doors; anything that can be redundant. Doesn’t sound like much, but USA ULs it is. If it’s not there it doesn’t weigh anything.
 

J.L. Frusha

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@TFF

I understand the Italy has a different set of standards than the U.S. I am not throwing random pieces together, rather, I am trying to use proven STOL wings to achieve STOL performance in a lighter aircraft to meet my needs. The greater the low-speed angle of attack for both take-off and landing, the better, for the field I own, vs the inconvenience of hauling. partial assembly/disassembly and paying fees at a local airport, as well as having a semi-permanent Scooter-Tow type installation vs needing a tow where there may not be one and paying for that, as well.

Sure, Hershey-Bar wings might be sufficient to get somewhat satisfactory performance, but, by having forward swept wings, I should be able to increase the angle of incidence without stalling. That 24 mph power-off stall is important, but at what angle of incidence? The harder it is to stall, the better.

Will it work? If nobody builds it, no one will ever know.
 

bhooper360

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Yay, science!

Okay, first of all, the CH 701 is a big boy. It takes off at over 1,000 lbs. gross, and it's powered by a Rotax 912. These guys claim to be waist-deep in the process of making one which is the same, except also faster. It's understood that the biggest problem with this approach is that they won't be able to spend the profits quickly enough, and they'll end up tripping over bags of money everywhere.

The goals of the ADAG Research Group is to secure research grants, get their Masters and PhD students some valuable design experience, and then get the researchers jobs once they graduate. The EASY-FLY exists on hard drives and in wind tunnels, and while the underlying concepts may find their way onto a pair of winglets, the EASY-FLY itself doesn't exist out in the wild. That's probably why they put three exclamation marks after all the lift coefficients, but they don't mention the monstrous gearbox assembly they invented to actuate the control surfaces in lieu of Cheetos-encrusted postdoc hands.

The rest of the paper involves coming up with a favorable pressure distribution using as many interacting surfaces as possible. Nice.

How does this research apply to you? It mostly doesn't. Since you're not allowed to exceed a set cruise speed, if you make your airplane too efficient at cruise, you have to compensate by using a smaller engine. Generally not what you want.

Why do you care about high-lift devices in the first place? Given the constraints, you'd be hard-pressed to make an ultralight that doesn't exhibit good short-field performance. And, if you are operating with space constraints, the main issue isn't lift generation, it's risk management.

The authors of that paper didn't put a lot of effort into defining the mission, because they'll end up working for a big company where somebody else will do it for them. Since you're a homebuilder, you're also the boss man. You have to figure out what satisfactory performance is and what the purpose of the flight is.
 
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WINGITIS

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A comparison and ANALYSIS between the G1F airfoil in the "MULTI COMPONENT" paper above and the WINGITIS WG-2022:

COMPARISON BETWEEN G1F 299 POINTS AND WINGITIS WG-2022.png
 

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WonderousMountain

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So I thought to inflate the Grant-X derived airfoil
From (Notes:SnS) to .1C across the Spar position, easy right? Not really, As you can tell, splines don't take kindly to changes.

Screenshot_20220311-142953_kindlephoto-4695962.png
Need help if found around. Nose circle taken up to 2.5%, doesn't look big, Flap tube 2X original at 1&1/2" Faux spar
thinned to 5/8", same as wing rib blocking. Camber went up, 4.05° guestimate.

I'm looking to seal the flap gap with polycarbonate um maybe.
Idea is to keep the first 5%, negotiate points till 30%, and keep
A general line until 75% Rib end. Flaps are 15cm across straights, with 2mm HM Carbon Closeout.

Sincerely,
C.K. LouPai

Original issue - no clearance through spar rib cap crossover.
 
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MACOWA

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@TFF

I understand the Italy has a different set of standards than the U.S. I am not throwing random pieces together, rather, I am trying to use proven STOL wings to achieve STOL performance in a lighter aircraft to meet my needs. The greater the low-speed angle of attack for both take-off and landing, the better, for the field I own, vs the inconvenience of hauling. partial assembly/disassembly and paying fees at a local airport, as well as having a semi-permanent Scooter-Tow type installation vs needing a tow where there may not be one and paying for that, as well.

Sure, Hershey-Bar wings might be sufficient to get somewhat satisfactory performance, but, by having forward swept wings, I should be able to increase the angle of incidence without stalling. That 24 mph power-off stall is important, but at what angle of incidence? The harder it is to sta ll, the better.

Will it work? If nobody builds it, no one will ever know.
Get the book GA Airfoils by Harry Riblett. I believe ACS still has it. Very straightforward catalog by a brilliant designer. I am using the GA 30-613.5 foil on my Ultra cruiser. Best one out there for this application. Will it Work? If YOU build it its YOUR butt in that seat then you will know
 

J.L. Frusha

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Get the book GA Airfoils by Harry Riblett. I believe ACS still has it. Very straightforward catalog by a brilliant designer. I am using the GA 30-613.5 foil on my Ultra cruiser. Best one out there for this application. Will it Work? If YOU build it its YOUR butt in that seat then you will know

Yet you aren't building what I am planning, much less configuring for the needs I am planning around, or designing a complete aircraft around the decision-making process.

You are building a totally different aircraft, merely trying to improve its performance based on your understanding.

I'm certain the Wright brothers faced the same dire warnings that you are projecting on my designs, without using the reasoning that led the Wright brothers, myself, or any aircraft designer making our decisions.
 

MACOWA

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1) You have no Idea what I am building or what I have actually built and flown. 2) Your planing configuring and needs are not on my agenda. 3) I would venture to guess that you have never had your best friend crippled in an aircraft of your own construction. 4) Contempt prior to investigation can only result in everlasting ignorance.
 

J.L. Frusha

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