Fibreglass panels.

[boxbush]

I'm guessing that among you kit car guys there's probably someone who can answer this:

I have fitted Sebring style fibreglass wheel arches to my MGB but I now need to find an extra 10mm width. There is enough flex in the arches to bend them out to the required width but of course when I stop pulling they spring back. Would it work if I were to heat the fibreglass and then pull them out or am I going to damage the fibres?

Thanks in anticipation.

[Aprisa]

boxbush
I'm afraid it wont work, fiberglass cures with a non-reversable chemical reaction and is not like some forms of plastic that can be re-formed.

you could however make new arches or extend your current ones but you will need to make a new mould to do a proper job that does not look crappy!

HTH Nick

[chris_n]

Don't think it will work. Think the resin used in GRP is thermoset not thermoform if I remember the terminology right i.e. once it has set it heat won't allow it to regain its plastic properties.

HTH

Chris

[spartan_andy]

Agree with aprisa.

That's why, to quote cheryl crow "everybody get high" when your using it it's all the chemicals

[boxbush]

Thanks guys,

I had a nasty feeling you were going to say something like that

PS: Anyone want to buy some 11" wide Minilites?

[Purple AK]

Hi Boxbush
Is it possible to find an extra 10mm on the inside?
If so, it may be possible to machine 10mm off the inner mounting face of the wheel, and get over the problem that way. It depends how much meat there is on the wheel centre of course!
Cheers Chris

[boxbush]

Good thought Chris but the wheels are splined so can't really be machined down. I have however been told that narrower rear axles are available so I will be investigating that option.

Thanks for the suggestion.

[chris_n]

As you're only talking about 10mm it should be easy to cut and shut the fibreglass arches without it looking like an abomination.

GRP is nice and easy to work with. Only complication would be if they are already painted?

Chris

[mattstead]

Now, I might be getting the wrong end of the stick, but couldn't you insert a steel brace bar(bars) inside the wheel arch back to the inner wheel arch, and fibre glass them in place inside the arch, thus giving you the encouragement the arches need?

Just make sure that the GRP has a hint of flex left in it and you'll be fine. This is actually the technique I used on a Tiger Cat to even up the slightly different width of rear wings (Tiger reccommended it).

[Avocet]

Heating definitely won't work. They'll just go brown and smell horrible. With a bit of work you would be able to extend them (fibreglass kit from Halfords or similar, a tin of filler and a load of work).

[cinqster]

mattstead said:

Now, I might be getting the wrong end of the stick, but couldn't you insert a steel brace bar(bars) inside the wheel arch back to the inner wheel arch, and fibre glass them in place inside the arch, thus giving you the encouragement the arches need?

This would also be my approach.

However, if you're a real sucker for punishment you could thin the panel by grinding back a lamination or two to help bend it, jig it into shape with wood/metal formers and then reglass new laminations on the back.

John S.

[boxbush]

Mattstead / Cinqster.
The reason that I need to modify the wing is in order to fit the wheel inside the arch. I'll do my best to explain: If you can imagine looking at the wing from the rear of the car, it actually curves in slightly at the top of the wheel aperture and therefore when the suspension is compressed will foul the wheel, for that reason I can't brace it as you suggest because the wheel is between the outer and inner arch.

I'm not sufficiently competent at bodywork to extend the arch I'm sure I would really screw up if I tried, also I quite like the existing shape of the wing. I'm going to try the narrower axle option, if not I will give up and get some smaller wheels.

Thanks to you all for your knowledgable replies.

Pete.

[cinqster]

Pete,

I probably didn't explain it very well.

The formers would be temporary so that once the new GRP laminations had fully cured the formers would be removed. If the glasscloth layup is thicker than the remainder of the original old moulding the new shape would be set. How you'd design the formers to be removable is the problem.

Off the top of my head you could pull the wing out to shape by drilling a hole in the arch top and using wire/rope tied to an imovable object (garage wall) Once the GRP has cured you'd have to grind out the remains of the rope and glass over the hole of course!

[cinqster]

chris_n said:

Don't think it will work. Think the resin used in GRP is thermoset not thermoform if I remember the terminology right i.e. once it has set it heat won't allow it to regain its plastic properties. HTH Chris

True to a degree. Large GRP structures can be gently coaxed into shape with careful heat application though - was the done thing for certain manufacturers twisted beachbuggy shells to help them seat down on VW chassis!

[boxbush]

Cinqster you're a bloody star . Now that I understand what you were saying I reckon it would work, I'll give it a try this weekend.
Thanks.