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Building Tips and technical articles. => Building techniques => Topic started by: Craig Beswick on November 28, 2016, 08:02:49 PM
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Hi guys,
I am back to control line after about a 40 year lay off.
I chose a Jr. Lightning Streak as my first model back because on Brodaks site it said it was a trainer and on special and I thought I wouldn't be too heart broken when I put it in the dirt.
The build has gone very smoothly so far. I am using Silkspan and applied as per Brodaks instructions. The wing tips, on the trailing edge, are about 2 inches wide. I was very precise when installing them that they were square and true.
After applying the second coat of dope, onto the Silkspan, to the wing frame only, I have thinned it 50/50, I have noticed the trailing edge on the outboard wing tip is warped upwards and the inboard warped downwards. I have applied a couple of coats of dope in the opposite side of the warp and the outboard seems to be straightening up but no movement on the inboard!
I also covered the Stabilizer and it was perfectly true to the wing and fuselage prior to covering but is now about a half inch higher on the outboard side! It is perfectly straight so I wonder if the fuselage has twisted near the rear rather than the stabilizer actually being warped. I have not tried to fix this yet.
I do not want to waste anyone's time so I have spent about an hour searching for warp fixes and reading through threads but not found one that actually explains a fix. They suggest steaming but not how you do it.
Is there a fix?
Many thanks in advance.
Craig
Ps. I did sand and dope the airframe, as per Brodaks instructions, prior to applying the Silkspan.
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Is the final coats of dope on the plane? If so, let it gas off for a while and see what happens. If the warps are still there that means steaming or hot water. You should have an extra set of hands when you do or blocks of something to warp the surfaces the other way and hold until the plane dries out again. I have used a hot air gun on one plane that was badly warped, but being with no help it took me several sessions to get it straight. Also don't want it hot enough to blister the dope.
Now the deal on steaming is to get an old fashioned tea kettle that will give off a lot of steam. Have help and good gloves. Don't want to scald your self. Wish I was there to look at your plane in person.
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Hello Doc,
It looks like the outboard is coming good.
It is not ready for paint yet. I am going to put another coat on the frame of the wings then coat the open bays in the wings and sand her off. Then a coat on the fuse then sanding for paint.
Thanks for the, "How To" on the steaming and the reply I appreciate it.
Craig
Also the Fuse isn't warped so not sure what I am going to do there. May cut a wedge in the fuse and just re glue it straight.
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Also the Fuse isn't warped so not sure what I am going to do there. May cut a wedge in the fuse and just re glue it straight.
You can nudge a stabilizer into alignment by cutting a slit in the fuselage and jamming a sliver of 1/32 plywood into the slit. Check alignment and use thicker/thinner ply as needed. Once it's right sand flush and apply CA.
I've used the same technique on fixed flaps to trim for roll.
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Hello Jim,
thanks for that. I was thinking of something similar but cutting a V on the other side and folding the stabilizer into it.
But, there must be a warp I just can't see it! It is out horizontally and also a quarter of an inch out of parallel with the wing.
The wing tips are nearly right so that is something. I just need to twist and straighten the last 2 inches of the fuselage!
Thanks for the input much appreciated.
Craig
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Craig,
If you Epoxied the stab, just use a heat gun to soften the Epoxy then reset the stab.
Charles
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Hello Charles,
thank you for the reply.
I think that is what it is going to come down to. It now needs to move in 2 directions! I drowned the inboard side of the fuse with dope this morning and gave it a nudge, trying to encourage it to move, it seemed to work with the wing tips! I want to give it the day to settle and see where it ends up.
Thanks once again.
Craig
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You can also try slicing the wood, and making it straight , then fill with thick CA and balsa dust /make sure it is in a stable enviroment, being out in a garage, hat and cold can make the move a lot
Randy
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Hello Randy,
that seems the easiest fix. I am letting it sit today, if there is no change tomorrow I think I will do that.
Thanks for the reply.
Craig