Featured Image - Adding Layers of Glass to new Core

Adding Fiberglass to the Deck where the Core has been replaced

After all the work on the deck with replacing the core, it was time to start to get the glass laid down over the core. While this post is a week or so after the last one related to replacing the core and smoothing a layer of thickened epoxy over the top of it, I did do this about 48 hours after that work and just took me a bit to get to writing the post. LOL, I was busy taking advantage of all the time I could to get work done on deck and remove epoxy resin from myself.

Side note, it doesn’t seem to matter how much I protect myself with long sleeve shirts, thick gloves, etc., It never seems to fail that I end up with resin somewhere around my wrists. I usually don’t notice it while I am cleaning up, I see it the next day when there are about ten arm hairs permanently bonded together with only one way for resolution. And that is RRRIIPPPP, AAAAGGGGGHHHHH, OOUUUCCHHH, That smarts!
Then I repeat this process next time I do work with epoxy.

As I looked at my project ahead, it was to ensure that I got at least one layer, preferably two layers of fiberglass mat down over the deck core. This plan meant that I had to cut the glass ahead of time to the correct size and shape and prepare all of my tools and utensils so that I was ready when the epoxy clock started ticking.

I had bought some fiberglass mat (1.8 oz cross-strand mat) from an old naval shipyard supply. They had 30,000 linear yards of it, and I bought 20 or so yards that were about 40″ wide. Fiberglass rating goes by its weight. So in this case, 1.8 oz means that 1 square yard of material weights 1.8 oz. You can Cutting Fiberglass matt sheets to sizeestimate that it takes about the same weight in resin to thoroughly wet it out meaning every square yard I cover will weight approximately 3.6 ounces.

I rolled this out on the deck and cut several sheets of it. The first one I cut to fit inside the opening in the outer deck surface. Essentially this layer was just going to cover the new core. The next layer was slightly larger, and each subsequent layer would be wider to integrate to the ground edge of the adjacent deck as we added layers of cloth and thickened the new surface.

Prewetting the surface with epoxy resin and hardnerEvery time I do any epoxy work where there was a gap of time of more than an hour or so since the last wet layer, I start by cleaning up the surface. I very liberally use acetone and douse a cotton rag with it (old T-shirts work great) and then wipe the entire surface ensuring that the cloth is still wet when I do. I then use a clean cloth and wipe it once more.

laying the first layer of fiberglass
I started by wetting out the entire surface using a small chip brush. I may have been better served using a roller, but not being sure how fast I would have to work, I was fine just using this process. After brushing the entire surface with a layer of mixed epoxy, it was time to lay the cloth down into place on top of this. It was windy this day, so I had to put a few small weights down on the glass until I was able to get it pressed into the wet epoxy and wet out the upper surface.After lining the cross-strand mat in the location I wanted, I started by pouring some epoxy in lines on top of the mat in a small section. I started at one one and worked my way down to the other. At first, my goal

pouring epoxy resin onto the glass and soaking it

is just to get the surface thoroughly wetted out and then I do some more accurate work of ensuring every part of the surface is saturated and that there are no air bubbles between the mat and the surface below it.

I use a criss-cross pattern with my brush using more of a dabbing motion than a brushing motion. It doesn’t go on like paint, and your goal is to permeate the mat with epoxy so don’t worry about trying to get a “smooth” finish like you would when using paint on a wall.

Using a fin roller to remove all air bubbles

I then used a “fin roller” to remove any air bubbles from below the surface and ensured a good bond to the substrate below the mat. When using a fin roller, you are not attempting to race or go fast. Doing so can start to lift the mat from the surface in back of the roller if you do. Use the fin roller in slow strokes, and it is best to go from the center of your work toward the outer edge to avoid lifting the edges.
I then used small pieces of cross-strand mat first layer of cross strand to bridge gap to existing deckripped (not cut) along the edge to start to bridge the gap between the core and new mat and the edge of the existing deck. I did this in 2 layers. The first one was only 2 inches wide or so, and the second layer was about 6 inches wide. Now that I have that gap filled, I will start to build thickness on the entire surface.

I am doing this with a 28 oz (shoot it maybe 24 oz, I don’t recall now) woven roving mat. This material is a cross thatch pattern that is much thicker. I really like the way this stuff goes down as well. I started in one place only to get a feel Building thickness with woven rovingfor how the woven roving will lay down. Now that I know, I will get a larger quantity of this and cut large sheets out the size of the opening.
As an FYI, West Marine sells woven roving. It ran me just under $50 for a sheet that was not as big as this hole in the deck. There are many places online to buy fiberglass mat of this weight that ranges from $6-$10 per yard at 50 inches wide. It pays to shop around, just be sure the mat you get is compatible with your resin (Epoxy, Polyester or Vinylester).


Feel free to repost this article with embedded video to your favorite sailing group, sailing club or even point them to our youtube channel or Facebook page for more info as well.

The tools we use for this job are listed below if you find this a convenient way to shop for them.    If you use these links, you get the same great Amazon pricing, but we get a small affiliate link credit.  Thank you.

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