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.

Fiberglass shouldn't peel up like this (2nd test not working so well)
Too many others have success, so I had to figure out what I was doing wrong.

After our first polyester resin 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.
Cleaning the old test material off with acetone

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.

I mixed up my resin and catalyst again according to the manufacturer's instructions.
Test 2 was 2 layer of 26 ounce roving, prepared properly with fin roller
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 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.

I 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.

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 catalyst.    I poured out 6 ounces of resin and added just under four ccs of hardner.   (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,
I 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.
I 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.
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 :)

If you are receiving this blog via email or on a device that won't play the embedded video, click this link to the video.  The link is  https://youtu.be/poiiKJuQetg

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.


  1. You need to invest in a MEK measuring/dispensing bottle ! It's a squeeze bottle that sends the MEK into a graduated container on top, no mess, no fuss !http://www.fibreglast.com/product/MEKP_Dispensers_166/Supplies_Tools_Dispensing

    1. I have been watching there videos for a while. I ordered that and some filler for fairing as well.