I was looking at a P-40 (model) and the aileron 'ribs' (fabric covered) are perpendicular to the its leading edge and are not parallel to the 'airflow' or rib pattern of the wing....surely there is a real solid reason for this...I just don't know it Can someone explain it to me?

thanks,

Jerry

shortest distance between 2 points = less weight

http://upload.wikimedia.org/wikipedi...e_AAF_1943.jpg

Quite a number of WWII aircraft had fabric covered surfaces. One thing that happened to many of them was an upgrade from fabric to "solid covering". Their surface response and overall speed increased when that happened. Those two improvements suggest the skin texture and shape caused problems.

That suggestion suggests the ribs sticking into the boundary layer was not done on purpose.

The last suggestion suggests the orientation of the surface ribs was not based on aerodynamic considerations.

Needless to say, fabric covering had been around before WWII, and rib orientation probably had not ever been considered as significant aerodynamically until then.

Actually the reason most control surfaces were "metalized" was not for aerodynamic efficiency as much as practicality. The fabric would blow off at 400+ mph! The Corsair was was of the early designs to have a real problem with this. The whole outer wing panels were fabric covered as well. As fighters got faster and were sneaking up on ompressibility, this became a very real issue.

The rib design of the ailerons wasn't an aero problem either oer se, it was simply easier to mass produce right angles. It's really that simple.

Not just a matter of "blowing off" at high speed, the pressure differentials on a fabric-covered airfoil distort its shape with a corresponding effect on the aerodynamics.

And the direction of airflow over a wing, in general, is NOT in straight lines parallel to the direction of flight, especially near the tips, so aligning the aileron ribs in that direction doesn't accomplish much.

The most significant thing I noticed from building and flying home built full scales is from the time of completion and first flight of the aircraft with cloth covered wings and ailerons I could see just how much the wings and ailerons would puff up in flight, and what my best level cruise speed was. Now after the airplane spent 8 to 10 months the hanger in the heat of the Mojave Desert the covering would draw tighter and I could easily see the effects during flight, not to mention the aircraft cruise speed when up. So solid covered wings and control surfaces are much better for obtaining higher top speeds due to the lower drag coefficient of a thinner/stable airfoil during flight.

Bob