1. Basic Fiberglass Repair Steps
Fiberglass repairs are a bit like doing paper mache. What you do is sand down the surrounding area to roughen up the repair area. Then you put fiberglass cloth soaked in epoxy on the area and wait for it to cure. If it is a deep hole, you put down enough glass to fill it back up. Then after the epoxy is cured, you sand down the repair to improve it's cosmetic apearance, and then apply your finish coat over top of the repair -- like paint or gelcoat. That is it, pretty simple. There are many techniques you can do while repairing, like multiple layers of glass in multiple sessions, special sanding techniques, special fillers to thicken the epoxy to make the sanding easier etc - but all of those techniques are all aimed at cosmetics to make the repair invisible after the job is done. Structurally sound repairs are very easy to make. Repairs that cosmetically completely dissapear are rather difficult to achieve.
2. What fabric weight should I get?
For small cracks & holes, I really like fiberglass cloth in 4oz to 6oz. 2oz is super light, and 8oz tends to be tougher to bend around curves. If the repair is going to need a thick build up, you can use multiple layers of cloth stacked up on each other. I also really like the fiberglass tapes - they don't have adhesive to them, they basically a narrow row of cloth that has a finished edge on the sides. My favorite is 4" wide tape at 6oz. Fiberglass also comes in a form called "mat", which is random fibers pressed into a flat surface, this is for boat molding and finish work, and there is also a really thick fabric called "roving" and is for molding boats also. Fiberglass Cloth and Fiberglass Chopped strand mat can be bought from zccyfiberglass.com
3. Dry your fiberglass before making repairs
Strange as it sounds, fiberglass and polyester resin (or epoxy) DOES absorb water. One neat experiment you can do is to take a square piece of plastic wrap and tape it onto the side of your hull after it has been in the water. You will be able to see the fiberglass sweat out moisture. Take the plastic wrap off, wipe it dry and re-apply the plastic square to see if it sweats some more. When it stops sweating, your boat is probably dry. It is a good idea to dry your boat before making repairs, or atleast after you grind down the area for repair, let a fan blow on it for 24 hours before putting the new epoxy & glass on.
4. How do you put on layers of fiberglass?
Most of the time I make the fiberglass cloth wet, then apply it to the repair area. Here are the steps:
- prepare the repair area by sanding it down
- lay dry fiberglass on the areas that need repair, and cut pieces to fit
- if I need multiple layers of cloth, I keep those pieces in their proper order
- mix up my epoxy in a plastic cup
- lay the fiberglass cloth(s) on a piece of cardboard, and use a paint brush to make the cloth wet with epoxy
- use the paint brush to make the repair area wet with epoxy
- pickup the wet glass and lay it on the repair area, and smooth with the paint brush and squeegee, make sure to get all the air bubbles
- squeegee out excess epoxy too
5. Precaution
I always wear protective gear like disposable gloves, face mask, safety glasses, apron, and have a fan blowing fresh air onto my face. I make squeegees by cutting squares from the sides of flat sided plastic bottles, or use squares of cardboard. To keep the repair area from growing, I mask off the surrounding area with masking tape and newspaper. If the epoxy is really thick, mix in a little acetone (like up to 5% of total volume) to thin it out, will help the epoxy penetrate the cloth better. Sometimes when using long strips of fiberglass tape, I'll dunk the piece of tape into a bucket of epoxy, then squeeze it as I pull it thru one hand to get the excess epoxy out of the cloth.
More about fiberglass cloth and fiberglass chopped strand mat, please visit www.zccyfiberlgass.com
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