I have translated from Japanese the specifications of the seduction freestyle wing airfoil.
i would really appreciate if some one could give me some explanations about wing airfoils, and in specific about this one.

''Main wing airfoil section originally symmetric . blade tip blade thickness 16% largest blade thickness position 20% , wing root blade thickness 13 5% largest blade thickness position 28. 5% Tail plane original symmetry , blade thickness 13% largest blade thickness position from 29% . center of gravity positioned 190mm of the main wing trailing edge ''

thank you

: )

Apparently they are using the word "blade" to mean "airfoil".

The "thickness" figures are just that...They mean for example that the main wing section is 13.5% thick (relative to it's length) at the root, and it is 16% thick (relative to it's length) at the tip. The tail plane is 13% thick, relative to it's length.

The other remarks about "largest blade thickness position" tells you where on the airfoil this maximum thickness occurs. On the wing, the maximum thickness appears to be at the 28.5% point on the wing root, and 20% at the tip.

It's a bit unusual for the CG position to be given as measured from the TRAILING edge of the wing. (although that's fine, if correct) Most American manufacturers list the CG measured from the LEADING edge.

Overall, it sounds like you have a rather typical "Pattern-style" wing, but with the maximum thickness point a bit further rearward than normal. I've attached an image of another typical Pattern airfoil, the Eppler 168, for your comparison.

Thank you mikejames0 for your excellent explanation.
now, for a model that should perform at low speed and hi speed as well (f3a\ 3d) what characteristics should I have in a wing airfoil? is it really possible to have such an airfoil that will satisfy them both?

: )

Well, I think tht depends on your skills and the power you have.

My "Extase" 3D airplane has a symmetrical airfoil about 17 or 18% thick, while most F3A planes have airfoils (like the Eppler 168) in the 13% range. I've seen Pattern flyers practicing for "Artistic Aerobatics" (some 3D) with normal (but somewhat overpowered) Pattern planes. They can hover, torque roll, etc., but would be hard pressed to do a harrier, for example.

So, if you want to attempt to have both qualities in one plane, which will be a tradeoff for both, I would try an airfoil in the 15% range at least. (Just a reasonable guess.) One major difference that comes to mind is that Pattern wings are generally designed to have a sharp stall, for clean snap rolls and spin entries, whereas 3D planes are designed to stall more gently at low speed. The physical attributes that cause crisper snaps are a sharper leading edge, and the thinner airfoil. Obvious too, is the fact that most 3D planes have huge control surfaces, and to have them on an F3A plane might make it "twitchy", unless you had great centering servos and lots of exponential.

On a side note... I love this concept, and have been thinking about it for a while...
I am working on a "Pattern-ish" design to allow me to do this test, via various plug-in wings, but I don't expect to have it finished until late summer or early fall. (I'm still working on the plugs.) It's called the "J-45", (image attached) and the article on my web site, with a lot of images, is at http://www.nextcraft.com/j45.html

Interesting translation...not to dispute Mike (he knows more about this than I do), but it reads like the wing airfoil is thicker at the tip than the root (13.5% root, 16% tip) with a more forward peak thickness. That seems odd...why would that be?

For that matter, I can't really find an airfoil that looks like the tip section (16% thickness, 20% position), although I've only poked around a few minutes on the UIUC site...

Well ncsmith it seems that way (that was my first impression), but if you read it again it is clear that the thickness is in relation of the length of of the wing section, this measn that the plane has a tappered wing (non-constant chord) like the extra. Also, it means that the thickens of the wing is more uniform form root to tip than the wing section.

Regards,
Patrick

You are correct about the tappered wing like the extra, going to the tip of the wing, the LE and TE both are tappered.

You can see here:

http://www20.tok2.com/home/rc/data2/...30/html/13.htm

I haven't decided if I am going to maiden mine today or tomorrow

I understand the wing is tapered...but normally a tapered wing keeps the same airfoil shape (just smaller chord) or has a thinner airfoil at the tip (to reduce drag and increase stall/snap performance for aerobatics). Increasing the airfoil thickness at the tip would seem counterproductive to an aerobatic ship, but I stipulate that I'm by no means an expert.

Right.

The tip is not physically thicker than the root, but RELATIVELY thicker for it's airfoil length. I'm guessing that since this was a "freestyle wing" (first post) that this was done to reduce the sharpness of the stall, unlike a typical Pattern ship.

...the symmetrical wing-equivalent of washout.

Perhaps Ollie or someone who is more expert in these matters can clarify it better, but that's my impression.

I'm not real sure I'm the one to explain here, but this is what I'm thinking as far as airfoil on tapered wing.

If you take the root foil, and the tip foil(I'm thinking of a wing of an Extra/Cap like plane), they are different. The percentages are different when it comes to chord vs. thickness. Just because it's tapered doesn't mean it tapers symetrically all the way around root to tip.

The thickness may taper 15%, whereas the chord could taper 25%. So in that, yes the airfoil has to change from root to tip. Take another example with the Edge wing, that has a straight leading edge, but drastically tapers root/tip trailing edge. I don't see how that airfoil remains the same.

If the thicknes/chord percentages remained the same the whole span of wing, that would not change airfoil.

But if you have a wing that has different percentages root to tip, that would have to change the foil.....wouldn't it??

I'm curious now....how about some other views?? We have some very educated users here, so how's about some education here.

Again, I'll restate I'm not an aerodynamics expert, just a mechanical engineer thumbing through his old turbomachinery books...

The airfoil shape doesn't have to change from root to tip...in fact, I would argue that many models don't. Since the airfoil thickness is specified as a percentage of chord, scaling down the tip airfoil uniformly will yield the same relative thickness, albeit thinner dimensionally. For example, NACA 0014 is 14% as thick as the chord, whether the chord is 10 inches or 10 feet.

Nonetheless, it's fairly trivial design-wise to change the section from root to tip...most of the airfoil packages I've played with do it. I imagine it is done mostly to alter the wing tip behavior (increase or decrease stall tendencies, for example as Mike suggested), but it might also be done to increase the wing strength for really thin wings for racing planes.

For what it's worth, in full scale aerobatic planes, some have the same thickness (by percentage, not physical dimension) and many are actually thinner (Extras, Sukhois and Yaks, for example). Didn't see any that were thicker at the tip in a cursory review. An interesting link of full scale aerofoils for those who are interested:

http://amber.aae.uiuc.edu/~m-selig/ads/aircraft.html

In looking at a picture of an airplane whether it be model or full size it would be difficult to see the difference in airfoils between root and tip. Some of the old pattern airplanes used the same airfoil for root and tip, but when people start looking for more performance out of an airplane the wing is one place to look. Using a variable airfoil is one way of fine tuning the airplane. I designed a sport Cap 10B once, and it had a very different airfoil at the tip as compared to the root to get the elliptical shape. The higher percentage of thickness of the tip will help with the slow high alpha type flying. Tom

I was about to start a thread about the same, the optimal freestyle wing, the variable airfoil tries to balance the tendence to tip stall because the taper (tip 60% of the root), all is about balance, for 3d you dont want the tip to stall, for pattern you need to do snaps that need tip stalling, so, the "ideal" wing can do snaps but only if you force it... best of both worlds.

Ps: With the data that you have post here I will try to reproduce that wing, thanks =)

I mentioned earlier that typical Pattern-type airfoils the past few years have been in the 13% thickness range. (i.e., the Eppler 168) This is fact, not guesses, gained from reviewing actual model data from several sources, and including measuring many of them myself. But...

Today at the flying field, I was able to take some measurements from a friend's "Angel's Shadow", which is an excellent pattern ship. That wing, at the root, is only about 10% thick, which I found surprising. Maybe "thinner" will be a trend. (for certain aerobatic types, but not for 3D)