Repairing Twisted Wing

Gentlemen:

Just acquired a very nice custom model that I would like to get flying again.

Problem is: The outboard wing is twisted down about 2.5 degrees. (5/16" in 8" chord.)

The structure is square LE top and bottom spars, 1" wide sheeted TE on 1/4" stick. Non-sheeted, non-capped.

Finish is clear dope over silkspan--and mirror smooth, polished!

I really dont know how to procede to un-twist this wing.

It is very stiff in torsion. Is there any way other than re-cover? I was thinking of a heavy wet coat of very thin dope with lots of retarder in it. Spray it on and then fixture the wing straight.

Anyone have a good method? Will heat do anyting? Steam?

Thanks,

I'm embarassed to say that I have done this a number of times.

First, fahgettabout it. I'm talking about your nice finish. Shoot it in the head, because you're going to move the wing frame. And your present covering will move along with it. Get the Xacto out, and cut the 'span out, and say a few appropiate words about your now-departed wing surface. It truly has gone to a Better Place, where all the finishes are 20 points, all the loops are 5 feet and...never mind...

Now: go the the stove. Get a big pot of water boiling. And grab some oven mitts, because, if this procedure is going to work, you're going to need them. The water will get hot.

Get the offending warp overtop the now bubbling H2O, and start twisting that warp in the opposite direction. You don't need to baptize the ribs, but get them pretty close to the water. Kind of brace the wing with your hands and elbow when twisting. You'll get the hang of it; it's hard to explain the exact grip you use. In fact, go a bit past neutral, and in the opposite direction. The wing will start to "give" after a minute or so of twisting, maybe earlier. It'll start to feel rubbery. The wing may make some funny, prootesting sounds. Ignore them.

Let it sit for a while. Hey, turn the oven off. Sometimes, you go too far, twist wise, or not far enough. Repeat above as required.

I recently did a horribly contorted Super Ringmaster this way, plus a cute little Kimura .15 stunter, and even solid wing Scientifics, which are 15" no brainers.

This procedure works. Come on over to Shelby Twp. sometimes, and I'll show you the Ringmaster.

Try this first. Don't strip the covering. Heat the wing up, just over a burner, and twist it. Dope is thermolabile and will reconfigure with heat. It is probably not the fault of the structure that wing is twisted, but rather the fault of the covering. If that doesn't work, then try Currell's method.

TIME OUT OREGON.......TRIM TAB!!!!!!!!!!
make a TRIM TAB and adjustable one. PLEASE

Scott

>Gentlemen:
>
>Just acquired a very nice custom
>model that I would like
>to get flying again.
>
>Problem is: The outboard wing is
>twisted down about 2.5 degrees.
>(5/16" in 8" chord.)
>
>The structure is square LE top
>and bottom spars, 1" wide
>sheeted TE on 1/4" stick.
> Non-sheeted, non-capped.
>
>Finish is clear dope over silkspan--and
>mirror smooth, polished!
>
>I really dont know how to
>procede to un-twist this wing.
>
>
>It is very stiff in torsion.
> Is there any way
>other than re-cover? I
>was thinking of a heavy
>wet coat of very thin
>dope with lots of retarder
>in it. Spray it
>on and then fixture the
>wing straight.
>
>Anyone have a good method?
> Will heat do anyting?
> Steam?

YIKES! You guys are overreacting! Steam as conventionally applied will not fix it. Heat may or may not (but be careful over a gas burner) but it probably won't stay. A trim tab will sort of work but not really solve it completely.

I got this out of an old AAM R/C column, and GMA told me that Sal Taibi was the one to come up with it.

Take a bath towel and wrap it around the wing. Boil a lot of water. Have someone brave hold the wing twisted straight. Pour the boiling water over the towel on both sides. Hold the wing twisted for about a minute until it cools off a bit, then take off the towel and let the wing cool off. Let relax for an hour, then see if it's really straight. Repeat if necessary.

The wing should stay for a while. Depending on the type of dope and how old it is, it may or may not go back towards the original shape.

>
>
> I got this
>out of an old AAM
>R/C column, and GMA told
>me that Sal Taibi was
>the one to come up
>with it.
>
> Take a bath
>towel and wrap it around
>the wing. Boil a lot
>of water. Have someone brave
>hold the wing twisted straight.
>Pour the boiling water over
>the towel on both sides.
>Hold the wing twisted for
>about a minute until it
>cools off a bit, then
>take off the towel and
>let the wing cool off.
>Let relax for an hour,
>then see if it's really
>straight. Repeat if necessary.
>
> The wing should
>stay for a while. Depending
>on the type of dope
>and how old it is,
>it may or may not
>go back towards the original
>shape.
>
Brett: I remember this suggestion well, since none other than GMA himself passed it along.

I tried it. Once.

Trouble was, it worked too well. The entire wing fell apart. It is very hard to control the boiling water, for one thing.

Have you ever actually tried this method? Tip of the EZ Just if you got it to work. (I guess it will, but you must be very careful. (Not so with the steam route).

After I tried it, I went to another of GMA's suggestions, which was steam.

And that works well. It doesn't attack the wing, industrial strength-wise, as did the hot towel method.

At least, that's what happened to me. Currell

>I tried it. Once.
>
>
>Trouble was, it worked too well.
>The entire wing fell apart.
>It is very hard to
>control the boiling water, for
>one thing.
>
>Have you ever actually tried this
>method? Tip of the EZ
>Just if you got it
>to work. (I guess it
>will, but you must be
>very careful. (Not so with
>the steam route).
>

I've done it several times, and it always worked like a charm for me. The best thing about it that the finish wasn;'t damaged.

I can't imagine it falling apart.

Pouring hot water on the wing works fine, and it works in just a few seconds. Please don't put the wing over a burner-- even an electric one. You will be lucky if the model is the only thing burned.

I've used dry heat (electric stove) to remove warps for years. It does take alot of care, but the results hve been much better for me then wet or moist heat. I overwarp the panel, wait and hour or two and recheck. With experience you can get it near perfect every time. I use the method with tissue, silk, silkspan, everything. It works.

Randy

Pouring boiling water over the wing works! If you twist the wing right after pouring the water on it, you will feel it move easily when you twist it into the new position. In a very short period of time the wing will set. You may need to leave it twisted a little past where you want it for overnight. ( or longer; it depends on the airplane)

The only time I have seen glue joints come apart was on a Barnstormer which was built in the 1950's with ambroid glue. Ambroid over a long period of time seems to dry out so much that it breaks like glass if it is flexed.

De