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Eppler Airfoils

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plncraze

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I have looked on this this site for some "real world" experience with some of Eppler's airfoil from his book and have not found any. Are there any folks out there using them?
The reason I am asking is that Eppler has both tail less and prop air foils. I am curious about both.
 
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Topaz

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I've done a lot of XFoil investigation with a slightly-increased-camber variant of the Eppler 361 helicopter airfoil. That's not "real world," but it's reasonable results and information. I started exploring this as a low-Cm laminar 'foil for a small motorglider with a low-Reynold's Number requirement, and it's very nice for that.

What is it you're trying to determine? Are his airfoils any good? Quite a few have been used on sailplanes (Eppler 662, for example), with quite good success.
 

fly2kads

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In addition to sailplanes, I think some of the experimental canard aircraft have used Eppler airfoils. I also remember reading an article about someone who used Eppler's prop airfoils for a custom propeller, and it turned out well.

I have experimented with Eppler airfoils in Xfoil, as well. They tend to require a little bit of cleanup as the point distribution isn't that great. Once that's out of the way, they seem to work as advertised.

Other people have used Eppler's airfoil code for the development of their own successful airfoils, as well. For example, at least some of the NASA NLF sections....
 

plncraze

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I was interested in whether his airfoil were close to their promises or if they were just a design exercise. I was thinking about using them on a real aircraft.
 

Grimace

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Is there a rhyme or reason to Eppler's naming conventions? I'm hoping to find a 10% thickness version of his E472 for an ultralight glider tail. I want that one for the reason of simplicity of construction (relatively straight aft of max thickness) and having a rather "forward" max thickness to reduce the size of the d-box.
 

fly2kads

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If there is, I don't know what it is. I don't remember anything of his that meets that exact definition, but it wouldn't be too hard to tweak the E472 down to 10% thickness with XFOIL or XFLR5.
 

Lendo

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Grimace,
I had to read your message a couple of times, I thinking you mean in terms of Vertical tail?, max thickness is usually from 25% to 30% cord of any Airfoil. The max a Rudder is 40% of chord many are 30 to 35% chord.
A Vertical tail like the RV is a good performer (least drag dues to reasons of Sweep). I would look at seep at 25% being no more than 20° and if you want a vertical trailing edge rudder, design it from there.
Otherwise I'm confused about what your saying.
George
 

Retiree

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Eppler numbers his airfoils in series. So a type of airfoil might start at E600. Then the next airfoil in the series would be E601, he might be changing thickness or pitching moment.
He wrote a book with all his airfoils, up to that point. He even put in the parameters he used for the designs. The title of the book is Airfoil Design and Data.
Doug
 

Retiree

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If there is, I don't know what it is. I don't remember anything of his that meets that exact definition, but it wouldn't be too hard to tweak the E472 down to 10% thickness with XFOIL or XFLR5.
You can't be sure that after you "tweak " it, the airfoil will have the same characteristics you want. It will not be an Eppler airfoil anymore.
If you do tweak it, please don't post the airfoil coordinates as an Eppler airfoil.
Doug
 

Grimace

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Grimace,
I had to read your message a couple of times, I thinking you mean in terms of Vertical tail?, max thickness is usually from 25% to 30% cord of any Airfoil. The max a Rudder is 40% of chord many are 30 to 35% chord.
A Vertical tail like the RV is a good performer (least drag dues to reasons of Sweep). I would look at seep at 25% being no more than 20° and if you want a vertical trailing edge rudder, design it from there.
Otherwise I'm confused about what your saying.
George
The E472 has max thickness at 17.5% of chord. Max thickness is 12.1%. It is a rather unusual airfoil that's designed for aerobatic aircraft, but I am considering repurposing it for an ultralight, due to the aforementioned benefits... Because, realistically, a flat slab of plywood with some stiffeners would be good enough for part 103. A little more refinement and a little less drag is just gravy. And structurally it could make sense.


I was just wondering if Eppler had a thinner version because the materials I'm using wouldn't require such a thick tail (Horizontal or vertical).
 
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davidjgall

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I was interested in whether his airfoil were close to their promises or if they were just a design exercise. I was thinking about using them on a real aircraft.
There appear to be about 70 known real world aircraft types using Eppler airfoils. Follow the link below and press Ctrl-F to bring up a search box, then type in the word "Eppler" and click the down-arrow in the search box.

 

Retiree

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I was just wondering if Eppler had a thinner version because the materials I'm using wouldn't require such a thick tail (Horizontal or vertical).
As a point of information, why do you want to use an aerobatic airfoil for a horizontal or vertical tail?
 

Grimace

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As a point of information, why do you want to use an aerobatic airfoil for a horizontal or vertical tail?
Great question. And I could be very well proven mistaken, but here is my thinking.

1. At ultralight speeds (even with there being no speed limit for Part 103 gliders) there may not be a huge aerodynamic advantage to using any airfoil at all as opposed to even a flat plane.
2. Weight is a very big factor on an ultralight and structurally, an airfoil with a forward max thickness could offer a weight advantage by allowing for a smaller d-box.
3. A thicker selection than just a flat plate could allow for lighter weight by taking advantage of thickness for mechanical efficiency (thicker airfoils are more efficient mechanically).
4. The difference between the ideal and a mediocre airfoil seems to be less than an average airfoil and a flat plane (as is common in many ultralights).
5. The straight run aft of max thickness may allow for VERY simple rib construction (simplicity is a major focus with this design).

So my logic is that an airfoil would be better than no airfoil and that this "aerobatic airfoil" offers a more efficient structure and simpler construction than others that probably offer only marginal improvements at best.

But... As a counterpoint: that's an awful lot of thinking when you could just glue a few flat sticks together.
 
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