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Veneer lifting problems

Renovation of old veneered foam wing

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Phil B14/10/2019 19:03:25
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157 forum posts
150 photos

My old Acrowot bought as it was in a state is now looking much better as the complete restoration continues. The main problem left:veneer lifting on the wing. Has anyone successfully dealt with this? If so please advise.

My intention is, after curing the veneer lift, to cover the wing with epoxy/glass cloth, or possibly silk and dope. (I am a bit worried that dope seepage might attack the polystyrene foam and would have to test this firstl

So far my ideas to correct the veneer lift are:

1 cut a new veneer boat shaped patch as per the old cabinet mzkers' approach

2 just glass over and hope to press the veneer down

3 drill small holes and inject thin Epoxy, possibly pin down veneer with cocktail sticks whilst curing then sand smooth and glass

4 cut patches of veneer out and lay in glass cloth, then sand smooth and glass over

Any comments more than welcome, especially if anyone has found a good method!

Thanks in advance...

Bob Cotsford14/10/2019 23:20:41
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8029 forum posts
444 photos

I've just slit the lifting veneer along the grain, brushed in thin PVA, masking tape over the split then weighed it down for a day or so. It worked for me!

This one needed a lot of work both on the skin and the inset aileron linings.

kfc side view.jpg

Edited By Bob Cotsford on 14/10/2019 23:22:31

Martin Harris14/10/2019 23:27:59
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8872 forum posts
221 photos

It's also worth running a covering iron over the veneer - some adhesives used are heat activated and can reactivate with heat and pressure - it worked with an old part built Priory Models Super Nova that I rescued from Death Row before the club executioner/pyromaniac put it onto the bonfire.

Edited By Martin Harris on 14/10/2019 23:29:27

Nightflyer15/10/2019 13:03:55
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187 forum posts

I have found that where the veneer has split or lifted that using copydex gives a stronger bond than PVA. This was advice I was given back in the early 80's when making and repairing foam wings, and has worked for me all these years when necessary. I always use dome weights to help hold the veneer down for a day or so to ensure a strong reliable bond.

With regard to finishing the wing I would opt for using glass cloth and epoxy resin rather than dope and nylon as if the wood is old it is likely to have more open pores allowing dope through to attack the foam.

Doc Marten15/10/2019 16:37:23
378 forum posts
4 photos

I've used new veneer cut in to match large areas and reglued lifting veneer cracks as a means of repair, with both I've used Copydex and an iron when it's dry to finish.

It works well.

Doc Marten15/10/2019 16:40:26
378 forum posts
4 photos
Posted by Nightflyer on 15/10/2019 13:03:55:

I have found that where the veneer has split or lifted that using copydex gives a stronger bond than PVA. This was advice I was given back in the early 80's when making and repairing foam wings, and has worked for me all these years when necessary. I always use dome weights to help hold the veneer down for a day or so to ensure a strong reliable bond.

With regard to finishing the wing I would opt for using glass cloth and epoxy resin rather than dope and nylon as if the wood is old it is likely to have more open pores allowing dope through to attack the foam.

I use masking tape in the absence of weights and a water based wood treatment with talc to seal the wing if I intend to dope over foam.

Peter Christy15/10/2019 16:43:40
1582 forum posts

Like Martin, I used a covering iron (turned up high!) on an old wing. This worked on 90% of the wrinkles. Only the worst ones resisted and needed more extreme measures!

Back in the day when foam cores came as just that - cores with no covering - I always used Copydex as the adhesive, and those cores NEVER wrinkled! It is heavier than watered PVA, though.

--

Pete

Andrew Calcutt15/10/2019 16:49:13
14 forum posts

I wouldn't be tempted to use poly c on veneer,I have tried it and it made the veneer ripple up.I think there must be to much water in poly c.

Philip Baker15/10/2019 16:54:03
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52 forum posts
48 photos

Thanks all. I shall try the copydex trick first and heat. Patches if necessary. If my Acrowot comes out half as nice as your model Bob I shall be well pleased!

Bob Cotsford15/10/2019 17:51:05
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8029 forum posts
444 photos

That was an old (80s-90s?) airframe from a job lot, all the veneer edges were lifting and there were significant bubbles in the middle. When I completed the model in 2013 I tried heat but in this case it did nothing, probably because not much glue had been used in the first place. I suspect it had originally been veneered using copydex but as I didn't have any I used thin PVA. I sold the stilll airworthy model last year and it shows no further signs of lifting veneer. If you can get Copydex in then you would expect it to give a better bond if it was used to bond the veneer in the first place.

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