Remodelling a fibreglass body

[RazMan]

I need to remodel an existing fibre glass wing, raising a body line by about 20mm and smoothing out some sharp corners in the process. I could just start dolloping on loads of filler and carving out the shape but I am sure there must be a better way - it would weigh a ton!

Can I pad out the wing with a plywood former (attached with rivets) to increase stiffness, then apply filler over the top?

[gary_tholl]

The great thing about fibreglass - if you get it wrong the first time, you can just cut it out and start again.

I wouldn't bother with filler, fix it right. Sand right down to the gelcoat, then just start fibreglassing. Use wax paper to stop the 'glass from sticking to anything you don't want it on. Then break out the sander.

It's not tough, but it is a messy, time-consuming job.

Gary

[RazMan]

My main worry is that the 'prosthetic' (sp) part will be very heavy - not to mention expensive on filler. At the thickest point it will be about 100mm and roughly a metre long!!

I was thinking to pad it out first with wood or another material (screwed to the existing bodywork) to get the rough shape and finish it off with a layer of matting, and finally filler.

[Fatboy]

RazMan said:

My main worry is that the 'prosthetic' (sp) part will be very heavy - not to mention expensive on filler. At the thickest point it will be about 100mm and roughly a metre long!! I was thinking to pad it out first with wood or another material (screwed to the existing bodywork) to get the rough shape and finish it off with a layer of matting, and finally filler.

No need to make it solid - just knock up a mould for the basic shape, make a fibrglass piece on the mold, then bong it to the appropriate section with more fibreglass...

[RazMan]

Leaving a hollow void? Won't this create problems?
Also, what is the easiest way to make a mould? I would need to make two 'handed' ones for left and right wings.

[Fatboy]

RazMan said:

Leaving a hollow void? Won't this create problems? Also, what is the easiest way to make a mould? I would need to make two 'handed' ones for left and right wings.

Hollow is not a problem - remember we're advocating using proper firbreglass (matting and resin) not the glass fibre reinforced filler.

I would knock up a basic mold out of scrap wood, cover it in wood filler, then sand to the right shape, cover it in clingfilm, apply the release agent and lay the fibreglass on top of it - remember if you're making a male mold that it needs to be slightly smaller (though the same shape) than the desired final piece - femal molds are harder to make, but give you exactly the shape you're looking for. You could make on by7 making the desired shape out of wood+filler as above, then using that to make a cast female mold out of plaster....

[RazMan]

Thanks Fatboy, when the time comes I will give it a try

[Fatboy]

Quick tip - stick to the chopped strand mat (CSM), not the woven stuff, CSM is much easier to lay (absolute piece of piss).

[RazMan]

The big boys use clay don't they? How about carving the shape 'in situ' using clay applied directly to the bodywork, then covering with cling film, release agent - then CSM to create a female mould. Then more release agent and apply CSM to make the prosthetic .... then attach and fill.

Does that sound like a plan?

[Fatboy]

RazMan said:

The big boys use clay don't they? How about carving the shape 'in situ' using clay applied directly to the bodywork, then covering with cling film, release agent - then CSM to create a female mould. Then more release agent and apply CSM to make the prosthetic .... then attach and fill. Does that sound like a plan?

Sounds like a bloody good plan IMHO. Better than my arseing around with wood and filler then plaster idea.
No idea where you get clay from though, can't be hard to locate.

[RazMan]

Fatboy said:

No idea where you get clay from though, can't be hard to locate.

My missus is a potter and won't miss a 25kg bag or two! I'll just go into stealth mode and see what I can find