Please excuse the fact its not a locost i'm building. Feel free to choose between the long and short versions!

Short version:

Is there a significant difference in the shrinkage you might expect between gelcoat and the fibreglass underneath?


Long version:

I'm building an XE powered phoenix, but the XE being a rather tall engine doesn't quite fit under the bonnet. So I am currently in the process of lifting the bulge about 3/4" - 1". The plan is to fill in the gap and sculpt the join with clay, make a local mould over the join, remove clay, glass in from the inside, remove mould. Hopefully this should remove the need to have large chuncks of filler which will crack and fall out.

So 2 weekends ago i cut out the bulge out and on saturday/sunday I made props to hold the bulge at the right height. Backed the gap with wire to hold the clay in a filled in the gap. Tonight I carried on with a bit more clay, filling in where it had cracked as it dried out. then I noticed that the top of the bulge had gone rather concave! So we checked Marc's (ST) bonnet and although it is VERY slightly concave its nothing like mine is now. (see the photos i just added to my album)

So I undid all the rigid connections between the bonnet and bulge leaving only the wire mesh and clay hoping it would pop back out - needless to say it didn't. I'm not convinced that if it could it wouldn't force its way back if it needed to...

Which leaves the only explaination i can think of for it to have gone that shape when I cut it out - perhaps from difference in shrinkage between the gel coat and glassfibre? But i can't believe i wouldn't have noticed before now.

The only way to find out for sure is to dig out all the clay I've put on and see what happens which I don't want to do if I don't have to. From photos i can't tell if this might be the case but it wasn't like it before i took the knife to it.

Anyone know if my shrinkage hypothesis could be plausible? Or am I clutching at straws?

Thanks,
Chris

anyone?

still a problem shared is a problem 273rd-ed!

Just looks like it's sagged with it being unsupported, will it push back up and reinforce it from behind with something bonded to the back.

Bet you a quid it was made and pulled from the mould in the same day.. ..even cycle wings will spread if pulled from mould too early.

Turns out it did change shape when I cut it out.

So to plan B: push and hold bulge convex again and take a mould off the complet enlarged bulge. lay up new bulge and graft into bonnet - sounds easy!?

On the plus side when I stuff it into the scenery i'll have a mould to make modifying bonnet no2 easier

Make your mods then take mould of the whole thing......so any new ones made will be tickety boo.....easyish but certainly nice and messy and smells great.....float for ages afterwards

Well I finally sorted my bonnet out with its bigger bulge

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