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Author Topic: Pinning wings flat solution  (Read 1372 times)
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faif2d
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« on: June 20, 2016, 09:27:52 AM »

Over the years I had tried a number of methods to space the structure off the building surface and had not found anything that worked well.  When water shrinking almost anything will work but after doping I could not get anything that would not stick to the structure while pinned up.  About 4 weeks ago I finally broke down and ordered a foot of Teflon 1/8" thick and 1/2" wide.  I got it from McMaster Carr and the shipping was more than the cost of the Teflon but I bought it anyway because I thought this would end my problem once and for all!  I have just built and covered a Hotbox P-30 and the Teflon worked super well!!!  I cut the strip into pieces about 3/8-1/2" wide and drilled a small hole #60 drill for a pin.  Even smaller would be better but the #60 worked.  I have since learned that Amazon has started to branch out into industrial materials so I may have been able to save the shipping charges by adding other stuff with the Teflon to get to the minimum for free shipping.
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I used to like painting with dope but now I can't remember why!    Steve Fauble
Andrew Darby
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« Reply #1 on: June 20, 2016, 11:02:26 AM »

I use aluminium blocks as spacers, these are just 3/8" square stock cut into lengths.  The once the dope thinners has flashed off the surface it doesn't seem to stick to the Aluminium very much at all (it does a little)...

Andrew
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« Reply #2 on: June 20, 2016, 11:40:22 AM »

Typically I have used a set of blocks from scrap every few inches.

 But reading this it occurred to me how about the plastic grid for florescent overhead lights pinned to the board?  Full support, and room for circulation.  I'm trying it on my next build.
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PB_guy
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« Reply #3 on: June 20, 2016, 11:43:34 AM »

Teflon tape/Plumber's tape (PTFE) used for sealing threaded joints could be laid between the spacer blocks and the doped surface.
ian
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Andrew Darby
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« Reply #4 on: June 20, 2016, 12:27:16 PM »

Selotape doesn't stick either.....

Andrew
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« Reply #5 on: June 20, 2016, 01:12:39 PM »

I use a magnet board that I built with a sheet of steel glued to 3/4" plywood.  When I dope the wings I use 4 magnets in each corner of the wing which spaces the wing off the board.  Then I use a magnet on top to hold everything down.  If I want to build in wash out I put a 1/16 to 1/8 spacer in the outside aft corner to get wash out.  I make sure the magnets just barely catch the edge of  the wing so they don't stick.  This method has worked well for me even with stabilizers I end up flat....no potato chips.  The teflon tape idea would really work well on the magnets....gonna try that on my next wing.
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faif2d
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« Reply #6 on: June 20, 2016, 01:28:51 PM »

I had thought about using Teflon plumbing tape.  I in fact use that material over corrugated cardboard for laminating outlines, Thanks Bob for that tip, and it works very well in that application.  I felt that it would have a problem staying in place on a small block and discarded that idea.  I did try cello tape and that stuck to the structure.  I may have been pinning the structure down while the dope was still too wet however.
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I used to like painting with dope but now I can't remember why!    Steve Fauble
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« Reply #7 on: June 21, 2016, 06:55:30 AM »

I've used regular "TESA" brand tape (NOT the "magic"/frosted type!) to protect the working areas on plans, and also to make "no-stick" spacers from scrap whatever.  The process has worked best with a magnet board, but I never had any problem with my cork/pins boards.  No problems even with CA.

Definitely cheaper than nylon or Teflon, but lacks the "cool" factor Wink.
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RalphS
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« Reply #8 on: June 29, 2016, 04:56:48 AM »

Covering with mylar completely gets rid of the problem  Grin
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« Reply #9 on: October 31, 2018, 02:40:09 AM »

I'm about to start covering again.
Maybe I'll try the magnets on the magnetic board.
I have a bunch of strong rare earth types for the top clamp.
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mick66
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« Reply #10 on: January 23, 2019, 02:05:50 AM »

Hi

If doping, just dope the tissue and allow to dry until touch dry (it's the days and weeks after where the real shrinking takes place). Then just lightly weight panel down on a flat building board with appropriate packing for wanted warps.  I typically water shrink, then apply 2 coats of 30% shrinking, then maybe 3 coats of 50% non shrinking followed by a couple of coats of Banana oil ... all over a period of a couple of weeks.  If you definitely want to keep it 'off the board' then just use packing pieces here and there to lift it up.  The panel should never be wet enough to risk the packing pieces actually adhering to it.  Rub some wax or sellotape the packing pieces for belt and braces approach.  But weighting down is the way to go, not pinning.  Then I always store my wings in the rafters on their LEs.  I also always build warps in rather than relying on the covering.

I think that one of the worst pieces of mantra that's often repeated in mainly 'old school' modelling books is to 'pin down panels whilst dope is wet' ... it's total tosh ... and I never quite got over gluing my first set of Tomboy wings to my building board aged 8.

I do make sure that the tissue is stuck down to every rib, spar etc top and bottom .... rather than just the panel outline.  That's asking for warps.  Tissue over Mylar gives great and more durable results and is way easier than it sounds!





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