Gel over fairing compound, wont set up.
03-09-2017, 09:30 PM
#11
First off I would like to thank Dave for his time and knowledge. He doesn't know me from a hole in the wall, yet he spent a good 15 minutes on the phone with me helping to figure out what was going on. This is what I learned.
Although I thought what I had used as fairing compound was West system it was not. It was Total Fair fairing epoxy from Jamestown Distributors. Regardless I still had wiped it down with a acetone rag and that as I found out is a no no as it brings the amine to the surface and will not allow a polyester top coat to cure. After talking to Dave I scraped off all the uncured gel and sanded the rest off back down the the fairing compund. I wiped down the entire area with cold water and let it dry for and entire day at 65 degrees shop temp. I then mixed up a new batch of gel and sprayed it on, topping it with PVA this time. The next morning I found again that the gel over the epoxy had not cured at all, the rest was hard and sandable. I scraped it all off again and called Jamestown Distributors tech line. After explaining what was going on I was told that there is some issue with their Total Fair fairing compound and that polyester based gel coat will just not cure over it, period. About ready to grind out the whole repair I called Merton's Fiberglass distributors in Massachusetts upon the recommendation of a friend, and asked what I should do, and what my options where the replace the epoxy fairing compound. They sell System Three Resins and I was informed that their SB-112 epoxy can be used as a tie coat between epoxy and polyester resins and gel coats. I now have added 3 lightly brushed on coats of the SB-112 over the total fair epoxy and have let it cure for 3 days at 60 degrees. Tomorrow I'm going to rough up the surface with some 120 grit and try again. I will report back with the results.
I will say that if I hadn't gone overkill and used polyester resins in the first place I would not have run into this issue and saved myself weeks of time. Also on a separate note,I have discovered tinting gel coats is like voo-doo magic for a few reasons. It seems that the perceived color of the gel has alot to do with whether it is liquid or cured, the thickness of the cured section and the surface finish of the test spot vs. the gel on the boat. I found that if I got the color close while it was liquid it was too dark after it cured. If I got the cured color close on a 180 grit sanded patch area it would be too dark after it was wet sanded and buffed along with the surrounding gel coat. Also, the thicker the repair or deeper the filled scratch, the darker the repair will appear after buffed. In the end I ordered the factory gel for Formula boats, and although it is not a perfect match it is closer then I was able to come after 8+ hours of mixing samples and testing them.
Lastly, the gel lays out much smother with less orange peel with as little as 10% styrene thinner added. I also shot a test piece with 25% sea-hawk patch aid and it laid out well and cured hard without a PVA top coat. I tried Hi-gloss additive as well at a 1:1 ratio and while it spays like paint and cures rock hard I found that it left a pinkish tinge to the cured gelcoat that was not there with the other mixtures. Use a cheap HVLP spray gun, TRUST ME, they work better then the higher end guns. Think 15 dollar harbor freight gun, I drilled the tip to .084" and it worked 10 times better then the two other guns I had used. I hope this helps someone else, if you need anything clarified call me at the number in the first post and I will be happy to help if I can. Steve
Although I thought what I had used as fairing compound was West system it was not. It was Total Fair fairing epoxy from Jamestown Distributors. Regardless I still had wiped it down with a acetone rag and that as I found out is a no no as it brings the amine to the surface and will not allow a polyester top coat to cure. After talking to Dave I scraped off all the uncured gel and sanded the rest off back down the the fairing compund. I wiped down the entire area with cold water and let it dry for and entire day at 65 degrees shop temp. I then mixed up a new batch of gel and sprayed it on, topping it with PVA this time. The next morning I found again that the gel over the epoxy had not cured at all, the rest was hard and sandable. I scraped it all off again and called Jamestown Distributors tech line. After explaining what was going on I was told that there is some issue with their Total Fair fairing compound and that polyester based gel coat will just not cure over it, period. About ready to grind out the whole repair I called Merton's Fiberglass distributors in Massachusetts upon the recommendation of a friend, and asked what I should do, and what my options where the replace the epoxy fairing compound. They sell System Three Resins and I was informed that their SB-112 epoxy can be used as a tie coat between epoxy and polyester resins and gel coats. I now have added 3 lightly brushed on coats of the SB-112 over the total fair epoxy and have let it cure for 3 days at 60 degrees. Tomorrow I'm going to rough up the surface with some 120 grit and try again. I will report back with the results.
I will say that if I hadn't gone overkill and used polyester resins in the first place I would not have run into this issue and saved myself weeks of time. Also on a separate note,I have discovered tinting gel coats is like voo-doo magic for a few reasons. It seems that the perceived color of the gel has alot to do with whether it is liquid or cured, the thickness of the cured section and the surface finish of the test spot vs. the gel on the boat. I found that if I got the color close while it was liquid it was too dark after it cured. If I got the cured color close on a 180 grit sanded patch area it would be too dark after it was wet sanded and buffed along with the surrounding gel coat. Also, the thicker the repair or deeper the filled scratch, the darker the repair will appear after buffed. In the end I ordered the factory gel for Formula boats, and although it is not a perfect match it is closer then I was able to come after 8+ hours of mixing samples and testing them.
Lastly, the gel lays out much smother with less orange peel with as little as 10% styrene thinner added. I also shot a test piece with 25% sea-hawk patch aid and it laid out well and cured hard without a PVA top coat. I tried Hi-gloss additive as well at a 1:1 ratio and while it spays like paint and cures rock hard I found that it left a pinkish tinge to the cured gelcoat that was not there with the other mixtures. Use a cheap HVLP spray gun, TRUST ME, they work better then the higher end guns. Think 15 dollar harbor freight gun, I drilled the tip to .084" and it worked 10 times better then the two other guns I had used. I hope this helps someone else, if you need anything clarified call me at the number in the first post and I will be happy to help if I can. Steve
03-10-2017, 07:09 AM
#12
Registered
Good info.
Where on your boat was the repair?
I have been a firm believer in doing repairs with epoxy after my experience of working with it building epoxy wood composite sportfishers, but Dave has sold me on using Vinylester instead these days.
He claims it's secondary bond is as good as epoxy and you don't have to deal with 2 different chemicals not playing well together when trying to re gelcoat.
Where on your boat was the repair?
I have been a firm believer in doing repairs with epoxy after my experience of working with it building epoxy wood composite sportfishers, but Dave has sold me on using Vinylester instead these days.
He claims it's secondary bond is as good as epoxy and you don't have to deal with 2 different chemicals not playing well together when trying to re gelcoat.
Last edited by tommymonza; 03-10-2017 at 07:13 AM.
