How I re-cored and glassed my delaminated deck


Jul 17, 2017
San Diego
Figured I'd write up a tutorial around how I fixed my delaminated deck in case it would help others. I pulled the deck in order to replace fuel fill hoses and also to add a new Bluewater bait tank to the deck. I knew the bait tank would add 345 pounds to the deck so wanted to make sure it was solid. Upon inspection I saw extensive delamination due to some dings and items that the previous owner screwed to the deck without sealing.



I did this whole job using expoy from US Composites. Epoxy is strong, adheres better mechanically, and has way less VOC’s that vinyl ester or polyester resin. It is more expensive and you have to very precise about your mixing ratios, but in my opinion it is worth it. Get metering pumps for the resin and the hardener so it is easy to mix the right ratio. I also used a small scale I bought off of Amazon so I could mix up smaller batches if I needed. For tools make sure you have a ton of disposable gloves, keep acetone handy, shop towels and paper towels, go buy a ton of tongue depressors, buy a bunch of quart mixing cups from Home Depot, buy a bunch of cheap chip brushes from Harbor Freight, and get at least one fiberglass roller to roll out air bubbles (make sure to wash this in acetone after use so you don’t have to buy a new one every time you use it).

Step 1:
Remove all of the old core and fiberglass material, leaving just the top fiberglass skin. This step was by far the least fun. I used a oscillating tool to carefully cut around the edge, then peeled the glass and core off. Luckily so much of the deck had delaminated that most of the core material popped right off. For any stubborn areas I used a sharp chisel and CAREFULLY scraped it off.


Step 2:
Sand the fiberglass down evenly and to scuff it up for better adherence. WEAR FULL SLEEVES, THICK GLOVES, A RESPIRATOR, AND GOGGLES! When sanding fiberglass shards will get everywhere and will feel like you have small cactus splinters wherever you didn’t cover. The dust is obviously very bad to breathe in or get in your eyes. Don’t just wear glasses, wear goggles. And I would recommend a real respirator, not one of those dust masks.


Step 3:
Lay down a layer or 2 of new base fiberglass mat. For this layer of mat I put down 2 layers of 1700 bi-axial mat. This is basically 1708 mat without the chopped standed mat layer.





Step 4:
Glass in the new core. For this material I used divinycell. Make sure to cut templates out of cardboard before cutting the new core material. Then drill holes in the core material so when you epoxy it down air doesn’t get trapped. I mixed the epoxy with cabosil (aka fumed silica) to make it into a runny glue consistency, then layed down the core. I then layed down some 3mm painters plastic and then stacked a ton of weight all over it to get it flat.




Step 5:
Put down bottom layers of glass mat. For the bottom fiberglass layers I put down 2 layers of 1708 bi-axial mat.



Step 6 (optional):
My old deck had a stiffening foam lattice structure glassed in so I figured I would cut it out and re-glass it back in. Stiffeners for fiberglass actually come from the shape of the glass once it hardens, not necessarily the material of the stiffener. There are some methods where builders will actually glass hollow stiffeners. For this I used some 1708 strips.



Step 7:
Add any screw holes, bolt holes, or access holes and make it watertight. You just went through all of this work, don’t get lazy here. Any area where a screw or bolt penetrates the deck should be sealed properly. I won’t go into the methods here as Google is your friend. But do not skimp on this.

Some tips for glassing:
1) Prep work is key. Pre-cut all of your mat and have it ready. Make sure you plan out what you are doing and know how long it is going to take. Once you start, you do not want to have to stop.

2) Epoxy set time is slower so don’t feel the same need to rush as using vinyl ester or polyester.

3) Epoxy will GET HOT in the cup. There is a term called exothermic runaway, meaning the heat from epoxy will make it cure faster, which makes it hotter, which adds more heat, which causes it to cure faster, on and on. You get the idea. Do not mix up giant batches. Do small batches as you use it. Also, do not leave epoxy in a cup deeper than a 1/2” unattended. It can melt and potentially catch something on fire.

4) If you are mixing up a cup and forget your ratio or mix, toss that cup. Yes it’s a painful lesson and you’re throwing away material, but you do not want to have a situation where you have uncured resin. Always make sure to pay attention when mixing. It is very easy to get sloppy during this step, and it will bite you hard if you do.

5) Epoxy wets out slower than vinyl ester or polyester resin. Take your time. You do not need to rush.

6) I found a good method to wet out mat with epoxy was to use a chip brush by soaking it in epoxy, then pushing it onto the mat and letting the epoxy soak in. DO NOT BRUSH the epoxy on. You will introduce air bubbles into the epoxy and it is not that much faster. Soak the brush, press onto the mat, let it soak for a second or two, re-dip the brush, move over an inch, press the brush down, let it soak, rinse and repeat. Once I got a section of glass wetted out I would use the roller to SLOWLY roll out air bubbles. Do not run this back and forth like a rolling pin. Slowly move the air bubbles.

7) Try not to epoxy with low ambient temps. Check the type of epoxy you have to see the recommended temp window, and be diligent about trying to work in that range.

Hope this helps someone out there. If you have any questions let me know.
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