Fiberglass materials for a box build

icetraxx · Apr 5, 2017

What is everyone using as far a fiberglass to create their custom boxes? I cannot determine from the pictures I am seeing as to what is going down on top of the carpet that the fiberglass would not stick to. Also, I am assuming that is multiple coats of the resin to build up a thick layer?

Everyone is making it look so simple, I've never done it so any tips would be great.

ramittome · Apr 5, 2017

Stretchable fleece for the shape after you have all the curves and everything built you want from the wood, resin on too of that and let it sit. Then start laying your fiberglass and resin on top of the fleece.

charonblk07 · Apr 5, 2017

Tin foil is your friend. Line wherever you want to mold with 2 layers of foil, seal seams with painter's tape. Apply layers of fiberglass directly over the foil. This is used for negative molds like the storage areas under the seats. If you're trying to make a positive mold then use the fleece over a MDF skeleton. With fleece you need to pull it as tight as you can to remove the wrinkles so you have less body filler work.

When it comes to fiberglass, more resin is not a good thing, you want as much matting as possible with the least amount of resin. The mat should be whetted out but you shouldn't have pools of resin anywhere. Most boxes I build from fiberglass use a light chop mat for the initial shape using 2 layers then I'll use 3-4 layers of a heavier woven mat for strength.

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shadoweng · Apr 5, 2017

charonblk07 said:
Tin foil is your friend. Line wherever you want to mold with 2 layers of foil, seal seams with painter's tape. Apply layers of fiberglass directly over the foil. This is used for negative molds like the storage areas under the seats. If you're trying to make a positive mold then use the fleece over a MDF skeleton. With fleece you need to pull it as tight as you can to remove the wrinkles so you have less body filler work.

When it comes to fiberglass, more resin is not a good thing, you want as much matting as possible with the least amount of resin. The mat should be whetted out but you shouldn't have pools of resin anywhere. Most boxes I build from fiberglass use a light chop mat for the initial shape using 2 layers then I'll use 3-4 layers of a heavier woven mat for strength.

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When you are layering, do you wait for them to completely dry before the next layer or do you start the next layer while it is still tacky? I am looking at building a fiberglass box for my truck.

charonblk07 · Apr 5, 2017

shadoweng said:
When you are layering, do you wait for them to completely dry before the next layer or do you start the next layer while it is still tacky? I am looking at building a fiberglass box for my truck.

I will lay out the first two layers using the chop mat to get the shape then let that cure overnight. I'll then remove the fiberglass molds, scuff sand the surface with 150 grit, vacuum the dust and wipe with a damp rag, then I'll lay the next 3-4 layers using the woven mat. I do it this way so the shape is retained by the fully cured chop mat before I add the strengthening layers. I know some guys that will do it all at once but it really depends on the size of the surface you're working with; for me, I find most fiberglass shapes can warp from the heat from that much resin curing all at once. If you're connecting a fiberglass mold to a MDF board make sure the fiberglass shape is fully cured before making the connecting joints.

Fiberglass materials for a box build

icetraxx

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ramittome

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charonblk07

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shadoweng

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charonblk07

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