Thread: fibreglassing

Mat is used with poly resins and isn't necessary or desirable with epoxy. The cloth you use will determine the amount of abrasion resistance you can absorb, before real damage sets in.

Generally 8 ounce fabric is used. This wets out easily, doesn't eat up a bunch of resin and smoothes out easily too. The heavier weight fabrics will require more resin and be harder to fill the weave.

My 'glass sheathed, plywood decks are two layers of 6 ounce cloth over three coats of straight epoxy. I usually do the whole thing "wet on wet", meaning I coat the deck, wait until it's tacky, coat again, then again, but on the third go around, I toss down the cloth and wet it out too. This creates a chemical bond between the layers and is the strongest way to adhere the fabric.

I use three straight coats of goo first to insure the deck is well sealed. It's probably sealed with just two, but the third ties the cloth into the well sealed deck.

8oz might be a bit hard to find.

The common weights in Australia are 6oz (200gsm) and 10oz (300gsm).

The 6oz will be fine unless the boat is used for really heavy work ... commercial fishing ... workboat for harvesting oysters.

MIK

He's already put epoxy all over the plywood and it's now obviously too late for a chemical bond.

You're going to need to rough that deck right up again or you won't get a good bond between the glass and the deck. You should also work out where your seams will be - you should overlap the glass sheets by about 50mm. To avoid having lumpy seams, use a sanding disc to scallop out the deck where the seams will lie to at least the depth of one layer of glass.

You shouldn't need to wet the deck out before you lay the glass. Just lay the first sheet on (don't fasten it anywhere as this just causes more problems) and wet it out with epoxy using a squeegee. Don't let the epoxy form shiny pools anywhere. You'll have put enough on once the glass looks wet.

Once it goes tacky, then cut the unwanted bits off with a Stanley knife, including any spots where the glass has lifted up or has voids under it. Use bits of glass thread (rovings) with epoxy to fill these spots if necessary. Then, while the whole lot's still tacky, apply a second coat of epoxy with the squeegee. Try to keep it thin but it should cover the weave.

It's actually good to put glass on a deck in the afternoon of a warm day. The cooling plywood will suck the epoxy/glass onto it and also minimize the formation of annoying air bubbles - it's an advantage of applying the glass to a bare, sanded deck rather than soaking it with epoxy earlier on. Don't put the epoxy on a warming deck.

Even though the deck has already been painted with epoxy, you're still likely to get bubbles forming as the epoxy warms up while curing. Use an epoxy high-build over the glass in less than 24 hours and you'll still get a chemical bond without sanding.

THEN, once the high-build is really dry, start sanding and applying more high-build until it's all smooth.

Rick