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F-15 Wing-Thickness

flateric

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The thickness ratio varies from 5.9% at the
exposed root to 3% at the tip.


The F-15 wing development program
NIEDLING, L. G. (McDonnell Aircraft Co., St. Louis, Mo.)
AIAA-1980-3044
In: The evolution of aircraft wing design; Proceedings of the Symposium, Dayton, Ohio, March 18, 19, 1980. (A80-31001 12-05) New York American Institute of Aeronautics and Astronautics, Inc., 1980, p. 125-129.
 

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r16

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ı was about to write it was 6.6 at wingroot , thinning to 3 at the wingtip area . The source was a Klaus Huenecke book from 80s , but I guess the post by Flateric is the right one .
 

flateric

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I've seen number 6% at wingroot, and *exposed* wingroot is not the same, of course. Again, here we have original MacAir sourced paper...
 

flateric

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BTW, this is painful story of F-15 wing planform evolution
 

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weirc

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Hi this site http://www.ae.uiuc.edu/m-selig/ads/aircraft.html gives the root airfoil as NACA 64A 006.6 and the tip airfoil as NACA 64A 203 I have always found this to be a reliable site. With NACA 64 series airfoils the last 2 whole digits give the T/C ratio. On the drawing posted by Flateric the most inboard profle given is not the actual root airfoil but the one at the inboard end of the flap, so this could be the source of any confusion here.
 

KJ_Lesnick

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I take it the unexposed wingroot is the front of the wing-body fairing back to the tip of the booms on the back?

BTW: Just out of curiousity:
-What is that line down the airfoil (I think it looks like a conical camber thing or something, but I'm not sure)?
-The reason they deleted leading-edge devices from the design was because they were not necessary correct?


Kendra Lesnick
 

r16

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flateric , I am not doubting your source , it is just my typing . For all ı know we might be both right as ı understand wing areas are calculated to include parts what everybody would accept as the fuselage

what follows is an attempt to show how ı understand it and not an attempt to teach anything ; ı try to avoid to give such an impression even when I actually know anything about the subject ...

black lines are fuselage sides , wing area includes the yellow part inside the fuselage and my 6.6 would be at the blue line .

and the post by Weirc tells this might be the case . We are not disagreeing , just looking at the same thing from different perspectives .

about the book ; I don't understand at least %80 percent of it ...
 

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weirc

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Hi, I think everybody is correct on this one. The line labled BL 0.0 on Flateric's post is the center line of the aircraft, and, if the wing were continued to this point would be 6.6 percent thick. However the wing on the F-15 is only exposed to the airflow outboard of the inner end of the flap, so the most inboard part of the wing to be exposed to the airflow does have a thickness of 5.9 percent.

The line drawn along the airfoil in this case just shows the position on the wing of where the given airfoil section was taken from. If you were to see a straight line drawn from the leading edge radius to the tip of the trailing edge this would be the cord line, if you were to see a line drawn equally distant from the top surface and bottom surface of the airfoil that would be the camber line.

Hope it's getting clearer...........
 

KJ_Lesnick

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I have two more questions (I'm pretty sure I can't find an answer to these anywhere else and you guys know your stuff).

1.) What is the thickness of the F-15's wings at the thickest point and/or the unexposed root [/i](where it's at 6.6%)[/i], the exposed root, and around the area where the wing reaches 3% T/C?
2.) What is the chordwise length of the F-15's wings at the thickest point and/or the unexposed root (where it's at 6.6%), the exposed root and around the area where the wing reaches 3% T/C?


Also, if anybody knows these ones... (I'm not even sure you guys will know this one, but I might as well ask)

1.) What is the T/C ratio of the F-15U's (The F-15E derivative with the enlarged wings) wings?
2.) Does anybody know the chordwise thickness of the F-15U's wings at the exposed root, the unexposed root (if possible), and at the tips?
3.) Does anybody know the chordwise length of the F-15U's wings at the exposed root, at the unexposed root (if possible), and at the tips?


Kendra Lesnick
BTW: I have a good reason for why I'm asking all these extra questions... I'm actually working on a WHIF-design that is essentially an F-14/F-15 hybrid -- an "Eagle-ization of the F-14" if you will: The airplane basically is to look like a twin-seat F-15 style-design with the F-14's radome-size, the F-15U's larger wing area, the F-15A/C's wing-thickness, with droops and multiple-position flaps. Other ideas included a single all-moving vertical fin.
(I'm not trying to go off topic here... I just want people to know why I'm asking all these highly-detailed questions about the F-15 and it's wings!)
 

weirc

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Hi, if you want to know the thickness of an airfoil for a given cord and you have the t/c ratio of the airfoil, it's easy to work out. Measure the cord length of were ever you want on the wing, then, divide the answer by 100, then multiply that answer by the t/c ratio and that will give the size of the thickest point on the airfoil.

Sizes on airfoils, thickness, camber etc are often expressed as %'s of the cord so are usually straitforward to work out once you have the cord length for modeling purposes measuring form a decent scale drawing, to get the cord length, should be fine.
 

KJ_Lesnick

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weirc,

Not exactly as easy as you'd think. I can't find any really detailed 3-view drawings of the F-15U...


Kendra
 

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