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Author Topic: Covering undercambered wings is it easy?  (Read 712 times)
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USch
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« Reply #25 on: June 15, 2019, 04:32:25 PM »

Just to bring the argument out of the corner US vs. Brit. I started building and therefor covering models in the beginning of the '60. The first Wake wing was done with dope and acetone, with acceptable result. The second, a Bill Hartill design, with PVA. As there where some wrinkles I decided to recover the PVA wing. Trying to remove the jap tissue I discovered that there was no way to do so. Actually the wing remained 5 days in the bath tube without anything coming politely away. The most remarkable result was the amazement of my mother, fortunately a very quite person  Cheesy

So I adopted covering wings, fuselages and all the rest with dope and thinner as the solution for me during all these years! And being in good company with J O'D, whom I met in '65, fells comfortably.

An added advantage to me is that in the first place I cover the whole wood structure with a 50/50% dope thinner mixture. Moisture is high in Italy in the morning air and this helps excessive adsorption of moisture in the wood, changing the weight of a wing by a few grams. And it raises the free wood fibres, sanded away with 400 grit paper. And then 2 coats of full strength dope on the ribs, spars, TE and LE.

That's my way....

Urs
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bbdave
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« Reply #26 on: June 15, 2019, 04:48:37 PM »

Thanks folks sorry I didn't mean to start anything. I have only built a couple of stick and tissue models and just use dope and thinners etc. and seem to get on ok with it I was only curious if undercamber would be a problem.

Dave
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Pete Fardell
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« Reply #27 on: June 15, 2019, 05:42:38 PM »

Not much to add as I've only done three or four undercambered wings, all on quite small scale models, and having used thinned PVA on all of these I'm not really qualified to comment on the comparative merits of other techniques. But I did sometimes have the tissue ping away from the ribs in a few places as it tautened and found I was able to save the situation by making a few pin pricks along the rib line, running in a little thin CA and then pressing the tissue back up against the rib. Preferably use something metallic or non-sticky to hold it till the CA grips, rather than a finger (unless you really like the pretty effect of small pink pieces of your skin forever glued to the rib in question).
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billdennis747
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« Reply #28 on: June 15, 2019, 05:54:53 PM »

I used tissue paste till they stopped making it, then dope ever since. It's a big advantage to be able to put a model in a bin bag, chuck in some thinners, give it a shake and have all the tissue fall off.
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danmellor
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« Reply #29 on: June 15, 2019, 07:10:26 PM »

I know dope is supposed to be THE method, but I've never got on with it at all. Probably just me rather than anything to do with the technique. Try it with silver Esaki and I reckon you'd be in a straitjacket within an hour...

Dan.
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Mike Thomas
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« Reply #30 on: June 15, 2019, 07:15:43 PM »

I know dope is supposed to be THE method, but I've never got on with it at all. Probably just me rather than anything to do with the technique. Try it with silver Esaki and I reckon you'd be in a straitjacket within an hour...

Dan.
Silver Esaki is a bit of a special case though.
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Big G
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« Reply #31 on: June 16, 2019, 06:49:49 AM »

OK, I did get a bit excited, but I'm not on my own in that respect, as far as different aeromodelling techniques are concerned. Perhaps, like Queen Elizabeth I, 'must' is not a word for princes or aeromodellers.....

When I was flying and pranging FF models, I was told my the late great Stafford Screen to use MEK (methyl ethyl ketone) for stripping tissue from a wing. Works better and faster than acetone. It sure does. The first time I tried it was on a 1/2A wing that I'd built using balsa cement, and of course the MEK soon reduced the wing back to a kit! (and yes, I re-built it!). After that, I took to using PVA for wing construction, with a dab of cyano here and there. The MEK didn't affect either.

G
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Bargle
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« Reply #32 on: June 22, 2019, 12:27:53 PM »

gluestick works well but let it dry properly before shrinking.

Seconded. I always use gluestick. I make sure I've got a thorough layer of glue on the rib, no thin spots, then let it set for at least 5 hours and usually overnight, before shrinking and doping.
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Don McLellan
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« Reply #33 on: June 22, 2019, 01:19:05 PM »

Agree with Bargle and ZK-AUD, glue stick works just fine.  And as Bargle said, let the glue fully cure on the underside of the wing before shrinking.  Also, when I shrink tissue on undercambered wings, I 'thin' the water with at least 50% isopropanol (rubbing alcohol).  It's the water that shrinks the tissue not the alcohol.
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