Warbird Information Exchange

Hello Guys:

Since this is an aviation issue, I'm working with the EAA/IA on it. With that said, here's the question just out of curiosity:

Does anyone know about putting a flush patch out near the wingtip? Has anyone tried it? Did your airplane have different stall/spin characteristics? I'm putting a patch out near a wingtip in accordance with the T-6 repair manual, and noticed a slight impression of less than 1/32 inch out there (The flush patch works out a material thickness of bulge).

Chris

1. Might improve the stall characteristics...(just kidding here)
2. Use Bondo.
3. Upper surface of the leading edge is the most critical.
4. In a perfect world you might have to add a little trim, but there aren't ANY perfect T-6s out there.

Hi BDK,

Um.....use "bondo" ??? Not real sure that is entirely legal as far as signing off maintenance in ANY logbook. And I agree...there are far too few "perfect" Warbirds out there. But then again anything made by the hand of man is never perfect.

Paul

Hello Paul,

Apparently you've never seen a Learjet after stripping the paint off of it!

To enhance the laminar flow characteristics a Mustang wing is supposed to have all of the seams and fasteners filled back to the main spar before painting, although unfortunately very few are done this way any more. If done correctly it adds about 5 to mph at cruise speed.

Glenn

Oops! Pardon me, I meant "aerodynamic filler." Part of the topcoat process to obtain the required aerodynamic smoothness.

T-6's and bondo, once apon a time a long time ago a buddy and I were going to visit some friends in casper Wy. there we were at 10,000 ft. over douglas Wy. when we heard Fights On ! as I looked back here came Wildcatter there racing T-6 from out of the sun, several turns later we had enough and headed for casper, when we got on the ground we noticed all the bondo pulled off the racer OOPS !!! by the way it is quite a sight to have a Corsair surprise you by coming head on thru your formation ! Great Fun !

i dont know if I understood the thing completely but...
A "patch" on a metal surface is invisible once painted if done properly.
I dont know how to explain it technically in english, but I've seen it being done and it's usually piece of cake, with any extruding layer or rivet. As per Bondo... Any good metal worker would take it back to the original shine without it. We took the fairing that go from the fuselage to the wing to an aeronautical workshop which makes aeroplane overhauls for the air force. The fairings were full with little bumps (pilot and chiefies boots I guess..), some of them really thin.. Well they took it for a good 20 mins and we got them back as new!!! I'd leave bondo for cars and boats

Alex

BDK,

No sweat on the bondo thing. But as one other perspn put it, about the Learjet, I am sure it has been used...although the term "Areodynamic Dent filler" is more appropriate. And basically that is only an interim fix at best. And on fairings....it is WIDELY used. But primary structure dents ....no way ! Just my two cents though...

Paul

I know that u could well apply a small patch even on the wing skin.. If it's big then u "just" change the whole panel..

Alex

We're talking a T-6 here, not a fracture critical wing skin. Also there is virtually no structural load at the tip, only a small air load.

Most structural repair manuals for military aircraft include allowable limits for dents including depth and spacing between dents.

bdk:

Your response to Paul, results in another question:

You said the air loads are minimal at the wing tip, of course, this is true.

However, you've got to consider the torsional reaction load on the wing from a deflected aileron.

Also, my other question along these lines is in regards to the lift differential caused be a minor flush patch out near the wingtip. Would this low differential be enough to result in a tendency for a wing to drop during a stall?

The question above relates to my friend who won the Reno races 3 yrs in a row. He had ballast in the tail of his plane to contribute some extra speed. Anyway he plane was spin prohibited, and a passenger decided to spin it, and they nearly bought the farm. Well, the reason why they didn't is that the PIC opened the canopy to bail out, and the pressure differential from the opened canopy recovered the aircraft!

"Would this low differential be enough to result in a tendency for a wing to drop during a stall?


How many T-6's have you flown that don't drop a wing when stalled?

You are saying that it should recover straight and level with no use of rudder?

If you are that concerned just fixture the wings, reskin them, and replace all of the attach angles and get it over with!


Glenn

Hi Glenn:

Not concerned, curious, and since we have aero engineers who frequent this board, why not ask? There are good resources available on this board..

Your patch does not change the torsional forces from the aileron. They are the same with or without the patch. Also, torsional load is primarily reacted by shear in the wing skins. Your patch with a doubler ring is stiffer than the original skin, so torsional deflection should be reduced- although this should not be significant enough to be noticable.



If the patch is truly flush the airfoil will not know it is there. The leading edge shape contributes the most to lift at the stall. Any disturbance there has a large effect. As you go aft, the T-6 airfoil sees turbulent flow so roughness or deviations from loft have a lesser effect. I have been told by someone who did it that his well Bondoed T-6 wing exhibited much gentler stall characteristics because the flow stayed attached to the wing much further aft.



Well, maybe. Either the plane was on the verge of recovering and the time it took to open the canopy was enough to finally gain control, or the opening of the canopy changed the airflow over the tail enough to regain control.