Filling a hole

[cranky]

I've got a hole in my bumper about 4"x1" what would be the best way to go about filling this?

My initial idea is to fibreglass a strip of fine mesh behind the hole then use the isopon bumper filler to cover but I have worries that this will flex/sag too much then crack.

My other thought was to but out a section of plastic that could fill most of the hole above the mesh, glass fibre the whole of the back and fill the remaining cracks on the front side :confused:

Any help appreciated :thumbs:

[sxbaz]

you'll get away with meshing the hole, and using some fibreglass over the back of it, ull need to build it up a fair bit on the back and spread it out for some strength, the stuff with the glass already mixed in would b good enough rather than seperate resin. then use usual filler for the front, it should hold up. when it comes to painting watch for filler shrinkage tho, thats where u might get a few problems.

[cranky]

I thought seeing as it was quite a large expanse and the bumper is pretty flexable regular filler would crack?

[sxbaz]

i see your point, iv never used bumper filler but i assume it flexes with the plastic, i feel u may have to strengthen the surrounding area a fair bit, iv only ever filled small plasic trims and metal bodywork.. let us know what u decide and if it looks like it'll work!

[tallpaul]

I thought seeing as it was quite a large expanse and the bumper is pretty flexable regular filler would crack?

Yes, both filler and fibreglass will crack. If its only a track car, and you're not fussy, use fibreglass matting or even metal mesh to reinforce the repair. Then use filler to smooth it. If you can get hold of a damaged section of another bumper, take it to a bodyshop, and they should be able to weld in the new plastic.
If its a road car, and you want it to look decent, buy a second hand bumper. However you try to repair it, I very much doubt the results will stay invisible for long.