DIY Fiberglass Boat Floor Repair

DIY Fiberglass Boat Floor RepairI found this great guide on that I think all of you should read. Your boat’s floor can root over the years and so it becomes dangerous for you and your crew to move safely around the vessel. At some point you will have to consider repairing or replacing your boat’s floor. It is very important to assess the damage correctly so you don’t start the repair and by the time you are done you realise you forgot to renovate the foundations for the floor. These are usualy made out of wood and are covered with fiberglass. Moisture can start to build up inside the fiberglass cover and just imagine what will come out in a few years. Check out the Fiberglass How-To Guide and Basic Fiberglass Molding Techniques to get a general idea on what you have to do. Also Boat Plans for Boat Builders might shead some light on the topic.

Assessing the Damage

Locate and correctly mark the areas of the fiberglass boat which have been damaged. Keep the required materials ready so that you can start working on the repairs.

The damage often results in delamination, so tap the area with the back of a screwdriver to see the extent of the damage to the laminate. Solid sounds crisp and sharp, while the delaminated part sounds dull. You can always compare by tapping one side that is good, and then the damaged area to notice any differences.

Repairing the Damage

The repair process is devided into eight easy and understandable steps. if you follow them I am sure you will make a fine job restoring your boat’s floor.

1. Step One

First off, when you locate the damage you will need to use a small saw to cut away the damage and the surrounding delaminated area (circles work best). You should have a circle or oval to work from.

2. Step Two

Next, you will need to de-wax the area before you grind it. If you fail to remove the wax, the grinding will get mixed with it and this will cause a weak bond.

3. Step Three

Use a disk sander with a 36-grit disk to grind a bevel around the hole. The bevel length should be at least 10 times the thickness of the hull.

You should wipe down the area with a rag that has been soaked with acetone. Slather on some wax paste around the area where resin could drip down.

4. Step Four

You will need to place some sort of “backing” in the hole for supporting the layers of fiberglass as you fix them. A piece of smooth plastic or waxed Formica will serve well for the backing. Place the backing in the inside of the hull so that you can work on the outside.

5. Step Five

Next, prepare the fiberglass to fit the hole. You will need to apply two layers of cloth, and then alternate layers of mat and cloth. The number of layers will be determined by the thickness of the hull, a good rule is a layer for every 1/32 inch. Cut the first layer of mat one inch larger than the hole, overlapping the bevel by 1/2 inch all around. Each piece after that should be a half-inch larger around the circumference.

6. Step Six

The catalyst for resin that can be used is methyl ethyl ketone peroxide. Polyester resin usually requires one to two percent of hardener by its cumulative amount (or volume). Four drops of hardener is good enough to catalyze an ounce of resin. Stir it well, or else it could be under-cured and weaken the entire patch.

7. Step Seven

Next, it is time to begin the lay-up of the fiberglass layers (which you prepared in step five) and the polyester resin between them. Never do more than four at a time, and make sure you compress them while also getting out all the bubbles; consider using a squeegee. Continue layering up until the repair is flush, and then finish it by cutting some mat and cloth. Apply them over the patch and smooth them with a roller. Seal this layer with PVA mould release.

8. Step Eight

Finally, remove the backer from the surface, fill the imperfections, and add gel-coat paste as needed. You can polish off the final surface.

Read the whole tutorial including the list of tools and materials needed for the job at

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