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Author Topic: Wing warp repair  (Read 797 times)

Offline redout

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Wing warp repair
« on: October 14, 2022, 11:40:18 PM »
I am in the final preparation stages prior to the first flight of my SIG Banshee. I checked for wing warp, by visually sighting the model from the back, the model having being placed in normal upright level flying position in a model stand. The inboard wing trailing edge tip appears to be about 1 cm ( almost 1/2 inch ) "down" from where it should be.

The model is covered with Solarfilm and I notice that I am able to twist the wing back to straight, with wrinkling of the film appearing.

Has anyone removed a wing warp of this magnitude on a shrink film covered plane by twisting the wing straight and then running over the film with a heat gun in the appropriate areas ?

I am also surprised to have found this warp as I could have sworn the wing was straight when I covered it several months ago and I even made sure to shrink one wing bay at a time alternating evenly between upper and lower surfaces, etc.




Offline Dan McEntee

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Re: Wing warp repair
« Reply #1 on: October 15, 2022, 07:52:32 AM »
   That is exactly what you should do to get the warp out. Solar Film is a lower temp covering material, so don't be too surprised if the warp creeps back after sitting in the sun. But then again it may not. Just be aware of the possibility. Also just be prepared for any funny stuff to happen on the first flight in case there is something you missed, but you are on the right track.

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Online Ken Culbertson

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Re: Wing warp repair
« Reply #2 on: October 15, 2022, 08:11:26 AM »
Let me double down on Dan.  You may have to take that warp out several times but balsa learns, even if it is slowly.  Make sure and check it after you have it out in the sun and take the warp out again before hanging it up.  I had a stubborn one in my last build and I had to uncover two rib sections (on the bottom!) and dampen the balsa inside the wing, weighted it in place and let it dry again.  Recovered the missing sections.  This is easy with film.  Warp is still out after a year.

Ken

One after thought.  Are you sure that the outboard is not 1/2" UP?  If you are going to be in this for the long term, get an incidence gauge, preferably two.  Sometimes this type of warp is a twist of the whole wing that entered in during building.  That 1/2" might be 1/4" on each side.  You will know what it really needs after flying it.  You just need to get it close enough that you get to fly it twice!
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Offline Tim Wescott

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Re: Wing warp repair
« Reply #3 on: October 15, 2022, 09:59:10 AM »
The Banshee wing lacks leading edge sheeting.  This is very nice from a crash perspective, because everything can flex when it hits, and it's exceedingly easy to repair.  If you have the right balance of wing and covering strength, when the plane hits the ground the covering will burst, and the wing will just break some glue joints.

The downside, such as it is, is that the wing framework is floppy in torsion.  This means that all of the torsional strength comes from the covering.

But this lack of torsional strength is yet another advantage -- it's dead easy to fix a wing warp.  This is especially nice if you're a helpful expert-ish pilot helping a beginner, because it's much easier to fix a horrible warp in one of these wings than in a D-tube wing.

Bend the wing in the direction to straighten it -- you probably want to overshoot by somewhere between half to the full amount of the warp.  For film covering, just reshrink the side that you can get at while holding in the "anti-warp".  Then check the amount of warp, and re-shrink the other side.  Don't be surprised if you have to take a couple of tries at getting it right -- you're learning.  As long as the severity of the warp is getting better each time, you're on the right track.

If you find your plane warping up every time you leave it in the sun at a contest, get a white sheet or a space blanket or something that'll fit over the plane and leave it covered.  I used to do this with a grubby old baby blanket with flowers and teddy bears on it because (A) it was in my trunk, (B) I'm lazy, and (C) any embarrassment from using such a blanket is less than the embarrassment of letting your plane get visibly warped up between the morning's flying and the afternoon's flying.
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Offline MikeyPratt

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Re: Wing warp repair
« Reply #4 on: October 15, 2022, 11:22:31 AM »
Redout,
Sorry but I don’t know your name lol.  To add to the others posts if it is warped 1/2” twist the the other direction the same amount, remove the winkles while holding until it cools.  Let in set for a few hours and check again, I’m sure it won’t be removed yet so twist it again the same amount of the remaining warp.  It should stay pretty close where you want it. Don’t be worried if you have to do it again.  Solar Film is good stuff and works well, but the warp needs to be gone to fly correctly,

Later,
Mikey

Offline redout

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Re: Wing warp repair
« Reply #5 on: October 15, 2022, 08:19:32 PM »
That's very promising with so much agreement on how this is done. I guess you guys have done it many times so your advice is invaluable to me.

Dan, thanks for confirming it will work.

Ken, I actually have just acquired an incidence gauge, and just in time for it's first use. I will attempt to see exactly where the twist is.

Tim, good explanation of why this particular wing may be a bit more prone to twisting due to lack of built-in torsional strength.

Mikey, the name is Richard. I will include it from now on  :).

Thanks everyone. Really looking forward to flying my first flapped stunt plane.

Offline Dan McEntee

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Re: Wing warp repair
« Reply #6 on: October 15, 2022, 08:39:20 PM »
Redout,
Sorry but I don’t know your name lol.  To add to the others posts if it is warped 1/2” twist the the other direction the same amount, remove the winkles while holding until it cools.  Let in set for a few hours and check again, I’m sure it won’t be removed yet so twist it again the same amount of the remaining warp.  It should stay pretty close where you want it. Don’t be worried if you have to do it again.  Solar Film is good stuff and works well, but the warp needs to be gone to fly correctly,

Later,
Mikey

      I now pronounce him as "Red", if he does not object!!??

     "That's very promising with so much agreement on how this is done. I guess you guys have done it many times so your advice is invaluable to me."

    This forum has been up around 20 years or so.  Unless it is something new that was just invented yesterday, some one on here has probably dealt with it, several times?? We all started out as beginners. There are some, like Mike Pratt, who have earned there living in the hobby industry and are a wealth of knowledge unto themselves. Add that to the rest of what the membership has under their hat and there isn't anything that can't be solved. A lot of us had to learn through the school of hard knocks, no internet back in the stone ages! Just magazines, books, and "on the job training"!! A lot of the fun is in the learning, and I hate to see some one struggle but enjoy the look on their faces when they find success!
 
Type at you later,
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