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John Minchell

Old School wing repair

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John Minchell

Spent a few happy hours looking here for a "how to" on repairing creases in an 80's wing, mouldies I can now do.

The construction is white foam with veneer and glasscloth finish.

The creases are where the veneer has indented the foam.  So do I need to cut slots and insert a full depth ply "spar" across the creases?

Or is there a better way? 

I assume I'll have to fill, sand and paint afterwards to bring up the hollow to the true aerofoil surface anyway.

Any advice appreciated.

John M

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isoaritfirst

If it’s a big crease you could remove a veneer patch bit bigger than the crease and melt out the damaged bit of white foam to allow a new piece to be dropped in. Gorilla foaming pu works well to stick in the new foam. 

Sand it flush when it’s dry and re veneer the patch. 

If the patch is bigger than the repaired foam it should be plenty strong enough. 

You could  also put a layer of glass cloth under the veneer adding more strength and use it to stick the veneer down. 

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Skip

Silly as this sounds, you can iron/steam them out. Then massage thin laminating resin through pin holes to reattach glass to balsa and foam.

If that doesn't work, cut the crease and try to steam out the foam to the correct level. If the repair is more stubborn. Remove the offending parts with a knife. Shape and replace foam, leaving room to add glass with feathered or bevelled edge to original. 

 

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isoaritfirst

I have reformed ellapor with heat 

applied with hot air gun or just a hot strip of metal. 

I think it does loose some of texture and possibly strength. 

But with repairs the fun is ripping up the rule book and finding ways that please you or suit your skill set or the materials you have to hand

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oipigface

Gorilla glue works better with foam than almost anything else I know. Just make sure not to let it escape. A little bit of liquid GG makes an awful lot of foam.

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Kyri

Mixing some water with gorilla glue  can make it fill a bigger area with a lower density foam. 

 

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John Minchell

Thanks for the suggestions guys.

Will try the Profilm iron first, as the other methods seemed more extreme.

Was hoping to get an easy method, other than stripping off the veneer and glass cloth which just leaves a bigger job for finishing.

Spar is ok - creases are shown in attached pics outlined in pencil.

P1010044.JPG

P1010045.JPG

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isoaritfirst

You might be able to remove and reuse the veneer. 

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isoaritfirst

Or dependent on how “posh” the model is insert a small vertical soar to strengthen the break then fill the dent with lightweight filler. 

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paulj

If the spar is OK, could you not just fill the crease with epoxy / microballoons and sand flat? Depending on the wingspan of the model and the position of the crease, you might not need much effort to return the structural integrity. The picture below shows the repair I did to my Eliminator wing some years back. The wing broke all the way through , down to the carbon reinforced leading edge. There isn't a spar in the wing - it is blue foam with veneer. I glued the two parts back together, then let in carbon tows across the break. Although not evident from the picture, the number of tows reduces as you move away from the break, to reduce the potential for a stress raiser at the end of the repair. It's flown (and continues to fly) for years since without issue. If you have a spar in the wing already, maybe no need for this type of repair. Epoxy and microballoons will return the structural integrity of the skin without adding much weight.

PS: I know the repair is very visible in my Eliminator - the wing is skinned in glass/epoxy, and I didn't want to add any more weight than necessary by painting it!

Eliminator.JPG

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