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Filling a Hole?

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Roger Dyke15/10/2019 18:59:21
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229 forum posts
10 photos

Hi All,

Recently, I encountered two large dings in the leading edge of my aircraft's wing each side of the fuselage about half way between the fuselage and the wing tip. The wing is foam with 4" of balsa sheeting on the front edge (top & bottom) where it is glued to the leading edge. The dings pushed the leading edge back about a inch or so and crushed the foam and balsa sheet. The dings are about 3-4" wide. I am making up a new piece of leading edge for each, but before I repair the sheeting I need to fill the hole left by the expired foam.

What is the best way of doing this? I do have a large block of foam at my disposal so I was thinking to shred some of this into the hole probably mixed with a little PVA glue. What do you reckon?

Your thoughts would be very much appreciated.

Roger

Don Fry15/10/2019 19:26:59
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4038 forum posts
45 photos

One way forward is use gorilla (expandeded polyurethane) glue. Wet the foam. Put some gorilla on the wet foam, put masking tape on the wing, to follow the final outline, and the foaming glue tends to fill the hole. And repeat if you were parsimonious. Final fill with micro light filler.

Don Fry15/10/2019 19:47:33
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4038 forum posts
45 photos

You could also shred some foam, and mix it with Gorilla glue. Keep it light. Weight is the enemy of repaired aircraft.

Roger Dyke15/10/2019 20:27:44
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229 forum posts
10 photos

Thanks for that. Do they have that sort of Gorilla glue in the local DIY?

conrad taggart15/10/2019 20:31:18
96 forum posts
5 photos

B&Q sell it - the clear one is the best - most versatile in terms of matching / not showing. They also do a brownish one

john davidson 115/10/2019 21:38:18
19 forum posts

the clear gorilla glue does not foam up to expand into spaces like the brown one, both excellent glues

Roger Dyke15/10/2019 21:47:38
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229 forum posts
10 photos

Thanks for the replies and the info.

Old Geezer15/10/2019 23:51:33
630 forum posts

The way I've repaired similar damage in the past is: cut out the entire damaged section using a razor saw, a nice fresh and very sharp #22 blade and a straight edge, cut a piece of soft balsa ( grain running laterally, obviously ) to exactly fit your now tidy hole in the leading edge. My own preference is to cut out the damage obliquely at each end and the ends of the balsa replacing the deficit at a similar angle - thus ensuring a snug fit without lots of trimming, logical when you think about it. Now all you have to do when the white glue is dry is plane and sand the balsa to section and re-cover.

The balsa was usually found in those cheap packs of off cuts at your LMS - used to be too cheap not to always have a pack or two in the shed, kept in the 'might come in useful' box.

DDH16/10/2019 06:58:51
35 forum posts
2 photos

Helpful info here re repairs to foamies:

https://www.modelflying.co.uk/forums/postings.asp?th=126936

http://www.crashtesthobby.com/how-to-repair-a-damaged-plane.html

https://www.modelairplanenews.com/easy-foam-repair-tips/

DDH16/10/2019 07:03:25
35 forum posts
2 photos

I'm told by those who know about these things that 'Copydex' adhesive is superior to PVA:

**LINK**

Edited By - on 16/10/2019 07:04:22

Roger Dyke16/10/2019 07:25:29
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229 forum posts
10 photos

Old Geezer: I never really thought of filling it with soft balsa. That's a good idea, thanks for that.

- : Thanks for the links, I'll have a look at them.

Old Geezer16/10/2019 08:16:39
630 forum posts

Roger - my first skinned foam wing repair was a build-it-yourself Fuji40 powered Wot4 that I had flown into a Leylandii at full chat on one of my rare off duty Sunday afternoons - the wing was repaired, solartexed, fuel proofed and ready to go by the middle of the week, as usual, the limiting factor was the drying time of the aliphatic glue and curing time of the fuel proofer.

By the by - varnished or fuel proofed Antique Solartex looks really nice on one of C.F.'s b.i.y. Wotties, it shows up the grain of the balsa and adds some strength to the airframe - ok, not as much as glassing, but so so much less of a faff.

Roger Dyke16/10/2019 08:33:05
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229 forum posts
10 photos

Old Geezer: That sounds very encouraging. Thanks for that.

Stuart Z16/10/2019 15:36:04
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381 forum posts

Depending on size of “hole” I’ve used Polyfilla Advanced, pick up a tub and you’ll see it is very light.

S

Roger Dyke16/10/2019 17:05:05
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229 forum posts
10 photos

Hi Stuart,

I haven't seen that one. I'll have a look at it. Thanks.

Roger

Rich too16/10/2019 17:44:36
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3052 forum posts
1070 photos
Posted by Old Geezer on 15/10/2019 23:51:33:

The way I've repaired similar damage in the past is: cut out the entire damaged section using a razor saw, a nice fresh and very sharp #22 blade and a straight edge, cut a piece of soft balsa ( grain running laterally, obviously ) to exactly fit your now tidy hole in the leading edge. My own preference is to cut out the damage obliquely at each end and the ends of the balsa replacing the deficit at a similar angle - thus ensuring a snug fit without lots of trimming, logical when you think about it. Now all you have to do when the white glue is dry is plane and sand the balsa to section and re-cover.

The balsa was usually found in those cheap packs of off cuts at your LMS - used to be too cheap not to always have a pack or two in the shed, kept in the 'might come in useful' box.

You could use soft balsa block, or make a few “ribs” to fill the hole and give the sheet some support.

Roger Dyke16/10/2019 18:04:40
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229 forum posts
10 photos

Yes, that's true.

I now have more than enough ideas from your good selves to have a look at.

My thanks to you all for you very valued replies.

Roger

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