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Author Topic: GRP Panels  (Read 1238 times)

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ferretjuggler

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GRP Panels
« on: January 25, 2010, 03:29:15 AM »

Anyone on here ever had any experience of moulding replacement panels from GRP?
I'm seriously (honest) considering making new roof top panels for two of my FSJ's from GRP but I have very little idea of resources and costs involved.
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Dave69

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Re: GRP Panels
« Reply #1 on: January 25, 2010, 08:29:44 AM »

as with anything preperation is the main point when making grp moulds. waxing the surface of the panel ensures a clean removal of the mould. but before removal reasonable strengthening should be included to stop the mould from twisting. Use large weave matting over the flat areas and fine strand where there are tight corners. Plenty of websites that can detail the methods
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Nosebolt

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Re: GRP Panels
« Reply #2 on: January 25, 2010, 10:02:08 AM »

er I done a bit, first question is do you have a good panel to copy? second question is how many panels do you want to pull? this will help decide the quality of mould needed, and cost of mould.

next is release agent options, there are 2 obvious options I see for this application, PVA will be cheaper and easier to use but will not last as long and will need more finishing after after its pulled, WAX is normally a multi stage process (sealer, filler, release) this will give a much better surface finish but will take a lot longer to prep the mould and will be much more expensive.

next is construction, heat cured epoxy is not viable so a poly is really your only option, for auto applications you will need a minimum of class 2 fire retardant (if you want to be official) and would suggest you use a low-voc just for your own compfort. if your going to fill and paint, gel coat is optional, personally for this I would not use gel coat, long term this will reduce crazing. For cost reasons I would use matt rather than weave for this, prob looking for about 5-6mm thickness so start with a tissue, then a 200gram followed by 3 layers of 600gram, then some foam inserts for rigidity, 2-3 more 600's and finish with 200 or tissue.

for a panel this size I would normally put half a dozen holes in the mould and fill with putty to use as blow holes, you can then use an air line to force a layer of air into the mould to release.
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ferretjuggler

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Re: GRP Panels
« Reply #3 on: January 25, 2010, 03:59:01 PM »

Cheers Guys
The more I look into this the more viable it seems.
I have a good 4 door cherokee with a perfect roof panel (the vinyl cover will have to be ripped off but it traps moisture against the metal anyway)
The J series has a substantial perimeter subframe of steel pressings inside the roof skin (which is what causes rot around the roof edge)
I plan to keep that or fabricate a new tube substructure to replace it.
My 2 door was picked up on 2  legged chains through the door window openings.
OK it distorted enough to crack the windscreen but that was it, nice to know the roof wont collapse if you roll the jeep, I intend to keep it that strong
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