Several Fiberglass Repair Tips

We use fiberglass to repair boat, tanks and many other G/FRP products. Here are some tips when you doing repair.

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

How to Prepare Fiberglass before Apply Gelcoat

You can add a gelcoat surface to your fiberglass boat if you wish to change its color, if you have damaged the outside of the boat somehow, or there are other reasons for replacing the fiberglass shell which the boat came with using a gelcoat resin. If you plan to do this, following a few simple tips can help you to prepare your fiberglass for the application of this coat.

Step 1 - Get Your Fiberglass Clean

The most obvious step in preparing your fiberglass body for a gelcoat is the one which many people miss, and that is simply to give your boat a cleaning. Fiberglass can attract dust particles like paper on a comb, so you need to make sure that the surface you will be painting is scrupulously clean. You should first sweep the surface with a wide brush, and then clean up the area more closely using a brush with rigid bristles. This will help to remove debris from the corners or between panels. Sweep all of your debris into a dustpan, and then clean out your brush carefully, ready for when you will next want to use it.

Step 2 - Sand Your Fiberglass

Sometimes, the surface will need a new coat of gelcoat because the old surface has become oxidized through contact with the air and salt water. If this is the case, you should strip away the old gelcoat surface using a specially designed planer. This will cut into the pigmented resin and ensure that the gelcoat is completely removed from the surface of the fiberglass boat. You can purchase these sanders from local hardware stores, and it may be possible to rent them from marinas and other boat-specialist stores. Once you have the gelcoat planer working, connect it to a vacuum cleaner or other waste disposal unit in order to ensure that the dust and dirt will not be left on the boat surface, where it can affect the appearance of the new gelcoat.

Step 3 - Wash Your Fiberglass

After you have sanded down the old gelcoat, it is a good idea to give the surface a good wash with some soap and water. This will remove any old gelcoat that is adhering to the fiberglass, and it will also wash away specks and stains from the surrounding surfaces. A good wash will ensure that your fiberglass has a smooth surface, and therefore that the gelcoat will pour or spray evenly onto the boat. Once you have washed the fiberglass, give the area where you will be pouring your gelcoat a good buffing with some sandpaper. This will give your surface a slightly raised edge, which will help the gelcoat cling to the fiberglass.

More about fiberglass boat, please visit our web.: https://www.wbcomposites.com/

How to Use Fiberglass Cloth to Make a Transparent Lay-up

Fiberglass cloth can be wet-out in a transparent fashion, but is not necessarily intended to be used in this way by those selling it. Many builders of boats other than strippers use epoxy/fiberglass which will be painted.

Usually, a more open weave glass will wet-out better and produce a more transparent lay-up than tight weave fiberglass cloth. You can use some tight weave 4 oz. glass that would not wet-out to a transparent level and remained looking slightly white.

Use open weave 6 oz. e-glass and 4 oz. s-glass for strippers.

Fiberglass cloth absorbs epoxy resin slowly, so give it time to absorb. The epoxy must displace all the air surrounding each fiber in each strand in the cloth to become transparent. It's best not to over work resin into a small area until the glass is totally wet-out because this can introduces bubbles. Apply resin to the cloth and move on, to coat the next area, giving the resin a little time to soak in.

Fiberglass cloth is coated with a special sizing to make it compatible with epoxy resin. This sizing is sensitive to water and can be damaged or removed if water comes in contact with it. The result will be a glass weave that looks white. Be careful not to have water on a surface or on your hands, that could come in contact with fiberglass cloth. Be wary of a "sale" on cloth that might be water damaged.

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How to Fiberglass a Boat Floor

We know fiberlgass can reinforce the boat. Belows are working process to fiberglass a boat. When you "fiberglass" a wooden boat's floor, you don't use fiberglass. Fiberglass mat is used in boats to provide a foundation for the epoxy resin and hardener; you already have a wood deck to provide that foundation, so you don't need to add fiberglass cloth: the deck is already a firm foundation. You can proceed directly to the process of adding the resin and hardener to protect your deck from water, fish that jump into the boat and friends who now track mud all over the place.

Step 1

Cut the plastic milk container with your jack knife so that it forms a container in which you can mix the resin and hardener, and into which you can dip your paintbrush.

Step 2

Mix the resin and hardener in the milk container, in small batches that can easily be applied by a paintbrush before the resin dries. Mix the ingredients according to the instructions on the resin.

Step 3

Dip the paintbrush into the resin mixture and apply the mixture to the floor (deck) of your boat liberally. A "thin, even coat" is great for paint, but you can slather the resin on like a heavy coat of paint. Work the resin into every nook and cranny in the floor, and into the joint between the floor and the sides of the boat as well. As you empty the container of the mixture, mix more and repeat the application process until the floor is completely covered.

Step 4

Apply the last brush stroke, completely covering the floor of the boat and filling in the joint between floor and sides. Let the boat sit, undisturbed, until the resin has completely cured. This may take up to 72 hours, depending on how thickly you applied the resin.

Step 5

Sand the floor with a palm sander and 100-grit sandpaper (the "grit" number is a measure of roughness) until the lumps are gone. Wipe up the sanding dust with a clean, damp cloth and allow the floor to dry once more.

Tips & Warnings

If any caulking needs to be done, do it before you start mixing the resin and hardener, and allow it to cure completely before proceeding. Work from the center, out to the sides. If any caulking needs to be done, do it before you start mixing the resin and hardener, and allow it to cure completely before proceeding. Work from the center, out to the sides. Resin dries quickly once the hardener is mixed in. Try a "test patch" on some scrap wood to see how much "working time" you have before it begins to harden. Resin dries quickly once the hardener is mixed in. Try a "test patch" on some scrap wood to see how much "working time" you have before it begins to harden.

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How To Repair A Fiberglass Boat?

When you need to repair your fiberglass boat you will find is how easy it is to repair. While a damaged wood boat requires expensive and intricate work, a fiberglass one can usually be repaired with just a few materials, even by people with only basic knowledge and skills. Another great quality of a fiberglass boat is that, once repaired, it looks as good as new. After the new layer of fiberglass dries, it becomes part of the boat, rather than a superficial patch.

To repair a fiberglass boat, start by cutting away the damaged area. To make sure you're stripping away all the damage, always remove an area at least half an inch (1.27 cm) larger than the damage you see at first view. This type of boat is always waxed, so before you attempt to repair the hole, wash the area with a solvent. Getting rid of the wax will not only make the process easier, but it will also prevent the inner surface of the boat from cracking and weakening. Next, using a disk sander, grind the area surrounding the hole until you get a distinct, uniformly dull look on the surface, and then apply a heavy coat of paste wax.

There are several materials you can use to repair a fiberglass boat, but for the inexperienced boat owner, it is best to buy a repair kit. Start by taping a piece of Formica or Plexiglas to the inner surface of the boat, making sure to cover the hole thoroughly. This will serve as backing. Next, mix all the materials that come in the kit – usually some type of resin and a hardening agent. Fill in the damaged spot until it's level with the hull of the boat, and then smooth the area with release paper or cellophane for a high-gloss finish.

If your fiberglass boat only has superficial damage, such as scratches and cracks, sand the area and remove the wax with a solvent before applying a store-bought plastic filler such as Gelcote. Wait for the plastic filler to cure before applying another coat. Two coats are usually enough to repair standard damage in the typical fiberglass boat. Finish by sanding the filler to a smooth level and follow with a coat of primer.

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