Fiberglass Blister Repair & Prevention

Blistering is caused by the permeability of fiberglass resin and the damage water can do by osmosis.Osmosis blistering, if left alone, will sooner or later destroy the integrity of your boat's hull. Often times when a fiberglass boat is hauled, you'll be able to see blisters on the bottom.A quick fix is to sand over the blisters to open them up and let the water ooze out. If there is no sign of delamination of the fiberglass itself, clean out the blistered area and let it dry out COMPLETELY. Depending on where you live, preferably the Sahara Desert, this drying period could take a few days or even weeks and weeks. Heat lamps or heat guns can be used to help speed up the drying process.After the hull appears to be dry, it's strongly recommend to have someone go over the bottom with a moisture meter.

This process will tell you if the damage has been contained to just the blistered areas or if you have a much bigger problem. Using the moisture meter is a very important step, especially if you have a cored bottom. When the bottom moisture content of the hull is the same as the topsides, then repairing the blistered area is the next step.Apply a coat of Bottom Protect High Build Epoxy Sealer to the exposed cloth and matting. This step seals the exposed fiberglass from any further water penetration and makes a good base coating with which the epoxy filler can bond.Next, fill any open areas with KBS NuFill Epoxy Filler. After the filler has thoroughly dried, sand it down to the contour of the boat and apply one more coat of epoxy sealer to seal off the filler layer.

At this point, you have several choices:

• Paint the bottom and hope for the best •Go out and buy "Boat for Sale" sign • Apply a barrier coat on the bottom of your boat and then paint it with your choice of bottom paint. (Highly Recommended) READ THE INSTRUCTIONS that come with the product!The Bottom Protect Primer has to be any where from 12 to 20 mils in thickness for it to be effective. For example, one coat of paint will only give a maximum of three (3) mils thickness, so obviously multiple coats will be needed.The instructions will list drying times and temperature limits for application. The good news is that these barrier coats can be applied, coat on coat, with the previous coat still “green”. So, depending on the temperature, 3 or even 4 coats can be applied in one day with no sanding required between coats.This may sound like a lot of work and expense, but if done properly, you will have a boat that is highly resistant to any further osmosis blistering. However, if you should have a grounding, hit a floating object, or do anything that penetrates or compromises the integrity of the barrier coat, it must be repaired ASAP.Remember, water is a wonderful thing, just not inside the hull of your boat!