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Author Topic: Well crap.  (Read 2223 times)

Online Dwayne Donnelly

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Well crap.
« on: October 06, 2020, 08:17:07 AM »
I swear this wing came off the board dead straight, covering is off and I need ideas on how to straighten this, it's 3 degrees up in the middle, tip and root are zero.  HB~> HB~> HB~> HB~>
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Online Gerald Arana

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Re: Well crap.
« Reply #1 on: October 06, 2020, 09:09:26 AM »
Try a mono coat iron to heat it up. If that doesn't work well enough, us steam or hot water on it.

Good luck, Jerry

Online Ken Culbertson

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Re: Well crap.
« Reply #2 on: October 06, 2020, 10:20:59 AM »
I swear this wing came off the board dead straight, covering is off and I need ideas on how to straighten this, it's 3 degrees up in the middle, tip and root are zero.  HB~> HB~> HB~> HB~>
Looks like a case of **warped spar***.   Can you put a straight edge on the spar top and bottom and have no gaps.  In other words is the spar warped. TE's don't normally warp on their own without covering, but they will if the spar warps and the ribs push it down.  What is the construction?  If it is D-Tube and the front appears straight you are going to have to cut the ribs on one side to relieve the tension.  Probably have to remove the T/E sheeting on one side.  Do you cut your T/E planking from the same sheet so that it will have similar warp tendencies?  Do you add spacers or cross braces to keep the T/E from warping?  If not, now is the time.  Let's hope it is not a deformed D-Tube.  Is the LE straight?  It is possible that it is bowed as well.  Opposite if it is the spar, same if it is the LE planking.

If it is not D-Tube you have the joy of knowing that anything you do the TE will put pressure on the LE.

In either case you are going to have to relieve the pressure and replace anything that you have to bend to get into place.  Jigs can be your downfall if you allow them to force warped wood into place.
I hope others have a better solution for you, but I have never been successful in removing a warped TE without surgery.

You can use heat but that is a whole-lotta-warp and unless you find the cause it will come back.

Ken

PS - you said that the covering was removed.  Was it warped when you covered it?  Was moisture or heat involved?
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Online Ken Culbertson

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Re: Well crap.
« Reply #3 on: October 06, 2020, 11:16:33 AM »
Spray the frame with water and stake it out so it's straight. If you go too far or not far enough just do it again.


Motorman 8)
This may work but consider that it warped initially because either moisture or heat caused the wood to relax tension unheavenly.  I am guessing it was heat since the wing appears to have been monokoted.
If that is the case a good portion of the warp should lessen once the covering is removed and it sets for a while.  Balsa will mold quite easily and you can probably soak it and dry it out on a jig and get the warp out for now but if the cause is bad alignment (internal tension) or wood mismatch on the planking it is just going to come back (or maybe even worsen it down the road) and pulling it into place with the covering won't last the summer.

One thought on Monokote.  Different colors shrink differently.  I have monokoted a lot of planes and I have never had one that used different base colors on the top and bottom that didn't need a lot more maintenance that ones that used the same.   Mostly white and dark colors like red/blue.

Bottom line, the warp has to go.  Your flap hinges will never forgive you.

Ken

This just popped into my head.  I used to fly a lot of Nordic.  Both A-1 and A-2.  Warps are disaster in that event.  My flying buddy (who was a world team member) always cautioned me to dope the entire structure and let it set on the jig for several days before applying the Jap tissue.  I also did that to my stunt ships simply because (not just the planking, I did everything inside and out). Three A-2's and two stunters sat in my attic for over 10 years and none of them warped.   May have nothing to do with it.
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Online Dennis Toth

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Re: Well crap.
« Reply #4 on: October 06, 2020, 12:26:48 PM »
Dwayne,
Is just the trailing edge wrapped or the whole wing? If the whole wing it may not be a big problem just a little dihedral. If the trailing edge I would jig it so that it is 1/4 over sprung then use a heat gun to heat the wood area. You may need to apply the heat several times while it is in the jig to get it to take. When you heat it keep the gun moving but you will need to let it heat soak to get the heat into the inner part of the wood. I would heat top and bottom a total of about 20 minutes each side flipping which side you applied heat to. Let it sit in the jig at least a day then check. May need to repeat.

Best,    DennisT

Online Dwayne Donnelly

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Re: Well crap.
« Reply #5 on: October 06, 2020, 12:56:44 PM »
Thanks guys I took the covering off and after  2 hours it almost straight again so it's something I did, never had that happen with iron on before, I'll try again.
My purpose in life is to serve as a warning to others.

Online Ken Culbertson

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Re: Well crap.
« Reply #6 on: October 06, 2020, 01:12:22 PM »
Thanks guys I took the covering off and after  2 hours it almost straight again so it's something I did, never had that happen with iron on before, I'll try again.
Glad it was the Monokote.  What does the T/E look like?  Can you add some "X" bracing or webbing between the ribs before you cover it again?  You won't be sorry.

When I put monokote on I do it like I was torqueing an engine head or a tire.  Cover both sides but don't shrink them.  Then shrink each side a little at a time till it is snug then do the other side.  You can still get it drum tight but it will not warp that way.   Even more critical if the colors are different.

Ken
AMA 15382
If it is not broke you are not trying hard enough.
USAF 1968-1974 TAC

Offline john e. holliday

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Re: Well crap.
« Reply #7 on: October 06, 2020, 11:47:38 PM »
If you are using MonoKote. Cover both sides and shrink the covering.   The if there is a warp just get help or brace between your legs.  Twist the wing past what would be straight and hit it with the hot air gun and hold until the covering has cooled.  May take several tries doing both sides before it is straight.  When using the hot air gun don't hold it in one place either.  I also have had wings that checked to be straight and I still had to put a trim tab on them. D>K
John E. "DOC" Holliday
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Online Dennis Toth

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Re: Well crap.
« Reply #8 on: October 07, 2020, 09:28:55 AM »
One thing to watch for as you shrink the covering is a twist in the wing. The wing can be straight as an arrow but the root and tip twisted. I did this on my first full stunt ship, a Veco Smoothie I got for Christmas as a kid. I was so excited I started building that afternoon, checked that all the ribs were all perfectly aligned. All went well till it was time to fly, boy did it need a big trim tab. A twist can be worst then a wrap as both half's of the wing are involved.

Best,   DennisT 

Offline john e. holliday

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Re: Well crap.
« Reply #9 on: October 07, 2020, 12:22:19 PM »
Been there with the Sterling Skylark.  Kit showed building two panels and then joining.  Never again, but what did I know back then H^^
John E. "DOC" Holliday
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Shawnee, KANSAS  66203
AMA 23530  Have fun as I have and I am still breaking a record.

Online Ken Culbertson

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Re: Well crap.
« Reply #10 on: October 07, 2020, 01:44:38 PM »
Been there with the Sterling Skylark.  Kit showed building two panels and then joining.  Never again, but what did I know back then H^^
I have always had a limited area to work in and no way to build a perfectly flat bench big enough for a PA wing.  So I use a old fashioned floating jig patterned after the Great Planes Jig made from 32" target arrow shafts  I build the two halves separately then slide the arrow shafts to the center and join the wings. I cut one of the shafts to 24" and slid it back into the rear holes then glued it in.  It works.

Ken
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If it is not broke you are not trying hard enough.
USAF 1968-1974 TAC

Offline phil c

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Re: Well crap.
« Reply #11 on: December 08, 2020, 05:03:01 PM »
I swear this wing came off the board dead straight, covering is off and I need ideas on how to straighten this, it's 3 degrees up in the middle, tip and root are zero.  HB~> HB~> HB~> HB~>

Look on the bright side Dwayne- you're really living up to your motto!!
phil Cartier


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