Old foam wings, obechi sheeting delaminating. Repair/replacement options?

[Jon H]

Be careful with glues like that as the water in them makes the wood swell and it can be hard to get it flat. On my delaminating Hurricane i drilled 3 holes in each crack, one in the middle and one at each end. I then used a syringe full of epoxy to inject glue into the middle hole. When it came out of the ends i would flatten it down, wipe off the excess and leave it to cure with appropriate weights/clamps etc

[Outrunner]

Is gluing down delaminating veneer like whack-a-mole, push it down in one place and it pops up in another?

[Andy Stephenson]

On 10/06/2023 at 23:47, Roy Thompson said:

Hi Nick, thats where i saw the popular veneer originally. My question is, is it a good alternative for obechi. The website give no information on that, so I assuming it’s maybe but what’s different is it better or worse.

According to Wikipedia, obeche has been harvested in a non-sustainable way, which is why alternatives have to be found. Has anyone tried poplar veneer from Balsa Cabin, if so, what is their conclusion.

[Jon H]

As previously mentioned i recently picked up a Spitfire with wings that look like an onion. The veneer is done, thats a given, but i do not fancy fitting new veneer as the chance of warping the cores is high and the wing has washout cut into it so i have to keep it straight. My plan is to just glasscloth the foam but cant decide on what grade of cloth to use. I usually use 24g or lighter but that has no strength and is only good for surface finish. Its hard to work out how robust a cloth is just from the gsm number, so has anyone got any ideas which cloth would be best to use? 

[Roy Thompson]

Love to know how this goes for you Jon, as it was one of the idea’s I thought about for mine and it maybe the way to go on the second wing. Like you, only ever used light cloth on the finish.

[Martin Gay]

I have known modelers that laminated fiberglass onto a sheet of glass, or mirror, under pressure and used the cured sheet as a wing skin. Kind of like a home made "pro-skin".

 

Lovely surface finish from the mirror!

[Eric Robson]

It had to be a mirror finish 🙂

[stu knowles]

For larger (70" plus) 50 gsm cloth would be the norm.  I have glassed foam cores with 80 gsm cloth over a brown paper/pva covered foam core and no veneer.  It worked on a simple wing without wheel wells and would have doubed up as a cricket bat on days when it was too windy to fly.

 

You don't have to cover the whole wing in the same cloth.  Perhaps 50 gsm overal with heavier or doubled up over the centre section and wheel wells.

 

I have also experimented with a carbon tow laid under the glass, top and bottom in lieu of spars and that seemed to work very well for no weight at all

[Jon H]

Very helpful Stu thanks. 

 

Given the fact that its an 88 inch span Spitfire I am not worried about saving every last bit of weight on the wing. I was thinking about using 80gsm cloth already and would rather deal with a slightly overweight wing i can use as a cricket bat than a nice light one that breaks. 

 

As i am worried about warping the cores i may strip the bottom veneer, glass with 80, and then see where that leaves me with weight and strength. If it really is like a rock, but heavy, then i can cover the top with 50 or something to save the weight. If its not mega heavy then i wont worry. Even at 80gsm i only expect to use about 300g of cloth given the area. Its just the resin i need to watch.