Nerd alert! Airfoil Comparison: Modified NASA 65018 vs Clark Y, and NACA 23000 series

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Topaz

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Re: Nerd alert! Airfoil Comparison: Modified NASA 65018 vs Clark Y, and NACA 23000 se

My main consideration is getting the best lift from a given area. Having dealt with aircraft for many years, I find it difficult to believe that a light plane using the TLAR airfoil, such as is used on the Quad City Challenger series, could not positively benefit from a better airfoil section.
Very likely it could, provided the section chosen is well-suited to the wing of the airplane and its particular design goals.

Just a word of caution about trying to get the "best" (most?) lift from a given wing area. Climb rate is strongly influenced by wing loading, so it's quite possible to go "too far" in using very large flaps, extremely high-lift airfoils, etc. in an effort to get wing area down. Keep an eye on climb rate in hot-and-high conditions when you're putting your wing/airfoil combination together. Sacrificing too much climb rate in the name of a small wing can make for a dangerously poor-performing airplane when getting out of small airports, or airports with obstacles in the area.
 

challenger_II

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Re: Nerd alert! Airfoil Comparison: Modified NASA 65018 vs Clark Y, and NACA 23000 se

Your points are valid. High density altitude conditions are one of my main considerations. The joys of dealing with low horsepower! :)
 

pictsidhe

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Re: Nerd alert! Airfoil Comparison: Modified NASA 65018 vs Clark Y, and NACA 23000 se

Climb rate is also heavily influenced by span loading. A thicker airfoil can be built into a longer wing of the same weight as a thin airfoil wing. Another pro of high lift airfoils is, as Billski loves to point out "weight is the enemy" On a 103, keeping the weight under 254lb is not an easy job, less wing area will help, as will less spar due to a thicker wing.
 

TFF

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Re: Nerd alert! Airfoil Comparison: Modified NASA 65018 vs Clark Y, and NACA 23000 se

How much R&D went into the TLR? Just because there is no name for an airfoil does not mean it was not tested and modified to work best for them. It is a very specialized aircraft.
 

challenger_II

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Re: Nerd alert! Airfoil Comparison: Modified NASA 65018 vs Clark Y, and NACA 23000 se

I am beginning to see a pattern, here: Folks are under the impression I am designing a Part 103-Legal ultralight. Such is not the case.
What I am attempting is to build a single-place light plane, utilizing a 31hp engine weighing 150 lbs.
I have real-world knowledge that this engine will carry me in the air. One aircraft used was a Quad City Challenger II, which weighed 426# empty with
the specified engine mounted. With its 170 sq ft wing, and the TLAR airfoil, a loaded weight of 680#, an ambient air temperature of 85 degrees F, and a field elevation of 2,000ft, the plane would get off the ground in 500ft, climb at 500ft per minute, and wasn't sluggish in the air. Other than being a tad slow (65 mph, as opposed to the 77 mph max speed, with the original Rotax 503 DCDI engine, 2.2:1 reduction drive and 54x37 prop) , it was quite fun.
The second aircraft I flew with this engine was a TEAM Minimax, empty weight of 368#, and a wing area of 112 sq/ft. With the same load (220# pilot, and
30# of gasoline), the plane would climb at 400-500fpm, and cruise at 70 mph indicated. The plane would, and did, fly around comfortably.

I am attempting to design an aircraft, with this engine, that will duplicate the stated parameters. My intention is to build it with aluminum, and, most likely, a bit of doped fabric.

According to the "published" numbers, a TEAM Tandem Airbike weighs 400# empty, 900# max load, has 138 sq/ft wing area, and flies with a 52hp Rotax 503. The Box Stock Challenger II Long Wing that I owned weighed 396# empty, had a max recommended weight of 800#, and flew quite nicely, at max weight, on the same engine. I can't help but believe the Tandem Airbike, with way less wing area, derived its performance on a better airfoil section.

Again, the floor is open.
 

challenger_II

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Re: Nerd alert! Airfoil Comparison: Modified NASA 65018 vs Clark Y, and NACA 23000 se

I believe the nomenclature you are refering to is "TLAR". That stands for "That Looks About Right". It is a description of the polywog airfoils used on a bunch of ultralight designs, such as the Quad Cities Challenger, and the Kolbs. The basic airfoil planform dates to the old Beaujon manual. As far as I know, there is NO wind tunnel-derived data on said airfoil sections. However, as there are a ton of old ultralight designs flying with adaptations to this section, it does fly.



How much R&D went into the TLR? Just because there is no name for an airfoil does not mean it was not tested and modified to work best for them. It is a very specialized aircraft.
 

TFF

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Re: Nerd alert! Airfoil Comparison: Modified NASA 65018 vs Clark Y, and NACA 23000 se

Yes that's my point. It works.
 

challenger_II

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Re: Nerd alert! Airfoil Comparison: Modified NASA 65018 vs Clark Y, and NACA 23000 se

Agreed: it works. However, a flat plate will laso work, with enough power. My question is whether a particular aircraft, originally designed with a TLAR airfoil, would not have better performance with a different airfoil.

The TLAR airfoil is used because it is easy to fabricate, and easy to use with sailcloth sails, as used on some wings. It is a compromise.
 

BJC

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Re: Nerd alert! Airfoil Comparison: Modified NASA 65018 vs Clark Y, and NACA 23000 se

Agreed: it works. However, a flat plate will laso work, with enough power. My question is whether a particular aircraft, originally designed with a TLAR airfoil, would not have better performance with a different airfoil.

The TLAR airfoil is used because it is easy to fabricate, and easy to use with sailcloth sails, as used on some wings. It is a compromise.
That depends on the TLAR airfoil and wing. You would need to know its characteristics to determine if a different airfoil and wing would perform better.


BJC
 

Aesquire

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Re: Nerd alert! Airfoil Comparison: Modified NASA 65018 vs Clark Y, and NACA 23000 se

Ah! The old 225-75-15. Or 235-70-15.

That's the inflated tire size used to bend the front of the ribs over. Straight from there.

Has the advantage of a front loaded camber and mild pitching moment. May or may not have a lower surface. Lower surface often given just enough negative camber to ease flutter of the sail cloth. That's the speed wing.

The above is not a joke. Might be the third most copied airfoil since the Clark Y & US35b.

Yep, you can do a bit better.

I do caution against being overly enthusiastic about reducing area. Aircraft gain weight. Wing loading affects climb and speed on a curve. Aspect ratio as calculated as span ratio is important. There's a formula I forgot.

Thick airfoils cost little at sub 200 mph speeds.
 

challenger_II

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Re: Nerd alert! Airfoil Comparison: Modified NASA 65018 vs Clark Y, and NACA 23000 se

I would never take it as a joke! You just described the method Homer Kolb used to make the airfoil on the Flyer, and the Ultrastar. Said so, himself, and
is listed in the Flyer plans (yes: they do exist!) as the method of bending the rib tubes.

I follow you, on the "aircraft gain weight". That is a factor for the operator to never loose sight of. I have had 3 Challengers: the first was an absolute "Plain Jane", with only electric start as a mod: weighed 396, empty. The second had all the speed mods, door kit, plus electric start. Weighed 500#, empty. While it flew faster than the Plain Jane, it stalled at a much higher speed, and was never as much fun to fly.

Referencing my initial post, the Minimax, with the engine I am using, had a higher wing loading that the Challenger, with the same engine. It still would get off quicker, and climb as well, as the Challenger. I may be kidding myself, but I can't help but believe the airfoil was the major contributor. This is why I have come, seeking "adult supervision" regarding airfoil performance for a very light plane, with limited power.




Ah! The old 225-75-15. Or 235-70-15.

That's the inflated tire size used to bend the front of the ribs over. Straight from there.

Has the advantage of a front loaded camber and mild pitching moment. May or may not have a lower surface. Lower surface often given just enough negative camber to ease flutter of the sail cloth. That's the speed wing.

The above is not a joke. Might be the third most copied airfoil since the Clark Y & US35b.

Yep, you can do a bit better.

I do caution against being overly enthusiastic about reducing area. Aircraft gain weight. Wing loading affects climb and speed on a curve. Aspect ratio as calculated as span ratio is important. There's a formula I forgot.

Thick airfoils cost little at sub 200 mph speeds.
 

Aesquire

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Re: Nerd alert! Airfoil Comparison: Modified NASA 65018 vs Clark Y, and NACA 23000 se

You just described the method Homer Kolb used to make the airfoil on the Flyer, and the Ultrastar. Said so, himself, and
is listed in the Flyer plans (yes: they do exist!) as the method of bending the rib tubes.

I follow you, on the "aircraft gain weight". That is a factor for the operator to never loose sight of. I have had 3 Challengers: the first was an absolute "Plain Jane", with only electric start as a mod: weighed 396, empty. The second had all the speed mods, door kit, plus electric start. Weighed 500#, empty. While it flew faster than the Plain Jane, it stalled at a much higher speed, and was never as much fun to fly.

.
Also the Original Quicksilver plans. I've seen it used on a lot of the Quicksilver clones, and it works. I wan't kidding on the "third most copied airfoil".

The worst weight gain I've seen was a lovely Lancair 235, with a 360, full leather interior, Full IFR cockpit, wet bar, soundproofing, stereo. ( I might be wrong about the wet bar ) Weighed so much that the pilot didn't dare land at less than 100. It was comfy. It was fast. It was sexy. It was also dangerously obese.
 

Arkan

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Okay i need some help, I have been studying different airfoil types for my design, I have just about settled on the Clark Y or a variation there of like the YH which i believe is a flat bottomed version of the Y. but i come across theses comparison graphs regularly, and honestly have no clue as to what they mean, i am basing my choices on performance from other planes that have used the wing and my experience with the Clark Y in RC plane builds. (When in doupt go with what you know.) I am trying to balance between Low drag and Low stall speeds. my airframe plans are based on Piper, i am rounding edges, widening the cab and slightly extending the cab for comfort. ( i am 6 foot and dont like to be cramped. My plans for this plane are to design it build it, and fly to camping and fishing destinations like some i have found and seen in Utah and Idaho, maybe some back country bush flying, but limited on that.

So can someone explain the graphs, just what i am looking at in the graphs so i can make a better informed choice on airfoils?
 

llemon

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Okay i need some help, I have been studying different airfoil types for my design, I have just about settled on the Clark Y or a variation there of like the YH which i believe is a flat bottomed version of the Y. but i come across theses comparison graphs regularly, and honestly have no clue as to what they mean, i am basing my choices on performance from other planes that have used the wing and my experience with the Clark Y in RC plane builds. (When in doupt go with what you know.) I am trying to balance between Low drag and Low stall speeds. my airframe plans are based on Piper, i am rounding edges, widening the cab and slightly extending the cab for comfort. ( i am 6 foot and dont like to be cramped. My plans for this plane are to design it build it, and fly to camping and fishing destinations like some i have found and seen in Utah and Idaho, maybe some back country bush flying, but limited on that.

So can someone explain the graphs, just what i am looking at in the graphs so i can make a better informed choice on airfoils?
The best thing you can do is read through the Roncz EAA series, you can find them all here; Downloads

Then perhaps get Raymer or Stintons books.
 

challenger_II

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Oddly enough, the answer to your question was answered in 1930, by Ivan Driggs. His dissertation on airfoils is published in the Flying and Glider Manual, reprinted by the EAA.
In his article, he compares several airfoils, based on the graphs, and demonstrates the USA 35A airfoil is superior to the Clark Y. Thousands of rag-wing Pipers demonstrate the USA 35A's capabilities.
As to your model airplane comparison, (a) the airfoils that have been labeled as "Clark Y" generally are not. There are a LOT of people that claim anything with a relatively flat bottom, and a humped curve on top is a "Clark Y". (b) Model airplanes do not accurately represent the performance of an airfoil, as would be observed on a full-scale aircraft.

If you are looking for STOL performance, yet do not worry about flat-out speed, look at the airfoil used on the Savana.

As regards the "CYH" airfoil, look at the root airfoil on the Seversky P-35, and there you are.


Okay i need some help, I have been studying different airfoil types for my design, I have just about settled on the Clark Y or a variation there of like the YH which i believe is a flat bottomed version of the Y. but i come across theses comparison graphs regularly, and honestly have no clue as to what they mean, i am basing my choices on performance from other planes that have used the wing and my experience with the Clark Y in RC plane builds. (When in doupt go with what you know.) I am trying to balance between Low drag and Low stall speeds. my airframe plans are based on Piper, i am rounding edges, widening the cab and slightly extending the cab for comfort. ( i am 6 foot and dont like to be cramped. My plans for this plane are to design it build it, and fly to camping and fishing destinations like some i have found and seen in Utah and Idaho, maybe some back country bush flying, but limited on that.

So can someone explain the graphs, just what i am looking at in the graphs so i can make a better informed choice on airfoils?
 

Victor Bravo

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Arkan, also you should very very strongly consider the other benefit of the 701/Savannah airfoil. Being very thick, it allows you to have a significantly lighter main spar. So you might save enough weight - and gain enough strength - that this airfoil "paid for itself" on that alone, regardless of the aerodynamic performance. But then the aerodynamic performance of that airfoil is also very good in the STOL department.

So I would bet dollars to donuts that OVERALL, all things considered, you will have a hard time doing any better than the 65018. I would also forget about the slats, slots, etc. and leave it as the standard 65018 wing. But the Junkers flaperons work very well, and might simplify some of the construction.
 

challenger_II

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One thing never mentioned, when discussing Junkers flaps: if designed, and set up correctly, the airfoil of the Junkers flap creates a vacuum on the airflow over the main plain. At higher angles of attack, this helps reduce the onset of the airflow over the main plane becoming turbulent, i.e: reducing the stall speed/increasing the full-stall angle of attack. At full deflection, this effect goes away, as the flap is nearing its own stall condition.
Also, the Junkers flap is considered a portion of the total wing chord, ergo, with a given chord design, the main plane can be of a shorter chord.
Example: Basic TEAM Mini Max wing is 54". If you had, say, an 8" chord flap, with 2" tucked under the main plane, you would have 6" aft the trailing edge of the main plane. That would mean your new main plan chord would be 48". As One would prefer to keep the original main plane thickness, the new 48" main plane's thickness would be increased, which would make for a higher-lift plane, of slightly less weight. Of course, the weight saved in the main plane would be offset by the weight of the flap, and its corresponding mounting attachments. However, if carefully designed, One could get a lighter over-all wing cell.

(Flame-retardant suit is being worn)
 

Norman

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That's the main element of a slotted STOL airfoil. Cruise performance will be crap! Junkers flaps produce more force than plain control surfaces of the same dimensions with a fairly small drag penalty in cruise so can be a good choice but there's also a structural weight cost so the design tradeoffs can get complicated. If you just want to widen the performance envelope of the J-3 a bit look at NACA 44xx between 13 and 15% thick.
 
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