Feature Image - Fiberglass Testing - 3rd time is a charm

Polyester Testing – 3rd time is a charm !!!

If you are an avid reader of this site, you likely know we are removing our teak deck and going back down with a nonskid Fiberglass deck. The big question has become what material to use, Epoxy or Polyester resin. We have been doing tests on the removed parts of the deck to validate strength, ease of application, and cost. Our epoxy test (see post here) yielded results different than what we expected, and the first polyester resin test failed, and I had a strong suspicion it was something I was doing wrong.
Cleaning the surface with AcetonePeeling up test 1Too many others have success, so I had to figure out what I was doing wrong.

After our first polyester res
in test had failed, I attempted to do the test again within a few days. I jumped to a snap decision that my issue had been that I didn’t have the correct amount of catalyst in the resin and it was due to my use of an insulin syringe without the needle to measure and dispense the catalyst. So I re-did my test. I started by removing the old material which was not dry nor hard. I was able to just lift it right up off of the surface. Before I could re-test this whole mess, I had to clean and prep the surface again. I used Acetone in liberal doses and several old rags to wipe the entire surface down. It took quite a while, but I was able to get the test surface back to its pretest state.

Test 2 - Applying 2 layers of Roving and fiberglassI mixed up my resin and catalyst again according to the manufacturer’s instructions.
The temperature was about 72 degrees Fahrenheit, so I added a bit more catalyst than the instructions called for and decided to do two thick layers at one time to allow the thicker build ups to generate a little more heat and help the curing process. Once thoroughly mixed, I applied a coat to the surface, then added my roving and saturated it with a brush and the fin roller process.
I allowed this to dry for about 24 hours, and it felt a little drier than my previous test, but it was still a bit tacky. I decided to give it another full day or so, and after a full 48 hours, I checked on it again, and I was still able to just roll the material right up from the surface.

Test 2 - Fail Fiberglass test with 2 layers of rovingTest 2 was a failure!

I contacted the manufacturer, and they suggested that at 72 degrees, it may be too cold for the length of the full cure if the temperature is dropping down later in the day. I put the whole test on hold and decided to come back and try it again when the weather was warmer.

Fast forward a few weeks, it was warmer, we were expecting a couple of days in the mid-80’s.

Cutting a new test piece from old marine deckI mixed up a small batch and let it catalyze on a piece of wood, and it did, it hardened. It was going to be my window of time.

In the interest of time, or maybe just frustration at the thought of cleaning that damned old test surface again, I cut a new piece of test material from the removed portion of the boat deck. Just like in previous tests, I ground part of the deck down relatively smooth but still left some of the fairing compound, gel coat and various other materials that added over the last 40 years between the original surface and the teak boards.

Grinding down the deck to glass (Test peice)In another spot, I ground all the way down to bare fiberglass. There are two primary things I am testing in addition to the gained experience of how to do this work before attempting it on the boat.
1) I want to understand if Polyester or Epoxy will be the material I will use (I am basing it on cost, ease of application and strength of adherence to the existing material)
2) I also want to understand the extent of my preparation work. Mainly do I need to grind everything down to bare fiberglass or not. My epoxy test yielded interesting results demonstrating that the overall strength was better on the existing material rather than the bare fiberglass.

After cleaning all surfaces of the new deck section with acetone, it was time to get ready for my work. I always lay out the material I need close to my job. In this case, seven mil Nitrile gloves, mixing cup, mixing stick, resin catalyst (MEKP – Methyl Ethyl Ketone Peroxide), some towels and the syringe I am still using to measure my catalystMixing the Catalyst at 2%. I poured out 6 ounces of resin and added just under four ccs of hardener. (There are 29.57 CC’s in an ounce, so 3.6 CC’s of hardener is 2%).
In this case, seven mil Nitrile gloves, mixing cup, mixing stick, resin catalyst (MEKP – Methyl Ethyl Ketone Peroxide), some towels and the syringe I am still using to measure my catalyst. I poured out 6 ounces of resin and added just under four ccs of hardener. (There are 29.57 CC’s in an ounce, so 3.6 CC’s of hardener is 2%).
Like before the surface of was covered with a light coat of the catalyzed resin and then it was time to add the first layer of fiberglass. With the temperature where it needed to be, First Layer of Cross StrandI was feeling good about this test and wanted to mirror the way I would apply it to the boat deck. I am planning on doing one layer of cross-strand mat, followed by a layer of 26 ounce woven roving and then a final layer of cross-strand mat. This method will provide a smoother surface on top to apply fairing.

I placed the glass mat to the surface and gently pressed it against the wet surface from the layer of resin just applied. Using the Fin Roller on each layerI dabbed more resin on top of it and used the fin roller with slow strokes from the center toward the outer edges to remove any air bubbles and completely saturate the mat.

I repeated this process carefully with the roving and the top layer of mat. This time, rather than storing the table with my test in the storage locker (metal building with no light and a bit cooler) I left it out in the sun for a couple of hours. Within just 3 hours it was already good and hard and dry this time as well. This test is feeling much better.

My next step will be to add a layer of catalyzed resin with wax in it; this allows the material to harden up and make it possible to sand it. If I were to attempt to

Test sitting outside

Test material sitting in the sun at my storage unit complete with note that says “Please don’t touch, test in progress”

If I were to attempt to sand the “layup resin” which does not have wax, it would gum up the sandpaper in seconds. I will then try to add a thin fairing layer to test out how best to apply it.

Then I will break the whole darn thing, remember this is a destructive test to determine which is a better and stronger bond to the existing surface. The only way to determine that is going to be to separate it from the surface.

Next week, we will be destructive 🙂

The supplies 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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