It's Fiberglass Time

Now that we've finished our molds for the flotation tanks, I'd like to take a minute and talk about the finishing process we went through. It's very important the inside face of the mold be as defect free as possible. The gel coat will cover this surface and it will show every nick, scratch, and bump. You want the gel coat to come out of the mold as smooth as possible to minimize the amount of sanding. Also, don't skimp on the wax when coating the mold. We used Meguir's mold release wax. It goes on easily, dries quickly, and buffs out without a lot of effort. After the wax dried we sprayed on about three or four coats of Polyvinyl Alcohol (PVA). This is another mold release compound. Hopefully between the wax and the PVA you won't end up with a fiberglass structure stuck to the mold.

Finally, with all the prep work done, we're ready to start laying some glass and resin. The first part of this process involves putting on the gel coat. We used laminating gel coat so we wouldn't have to worry about adhesion problems between the coats. Since I had never worked with gel coat before it took a little time for me to understand that you get no points for neatness in this operation. The object is to get the gel coat on as fast as possible and make sure you have a good heavy coat. You want to be especially careful to make sure that you have a nice thick coat in the corners and on the flanges. These two areas are the most prone to being thin which could result in a problem when wet sanding the finished product. If you sand through the gel coat you'll have to touch it up and that leads to more sanding! And possibly more touch up...and more sanding...and well, you get the idea. After two coats of gel coat we were happy with how it looked and were ready to start fiberglassing.

Since this is July in Atlanta its hot; which means that the resin is going to set up faster than you realize. You may need to adjust the amount of hardener you're using to give you enough working time to get the glass down in an orderly fashion. We found this out the hard way with the first batch of resin. By the time Bruce got it mixed, handed it to me, and I started to wet the mold, the whole thing gelled up in the cup. So we dumped that out and mixed a new batch with less hardener. The other issue we had was that we had not pre cut the glass pieces we needed for the lay up. This was a major problem because it meant that we were scrambling to cut glass while mixing resin at the same time. This did not go well. We had a number of problems getting all that done at the same time and getting the material down on the mold in a timely fashion. The resin started to harden up on us and we ended up just stopping and letting everything solidify. We then came back, ground some areas off, and then built up another layer. The moral of this story is cut all your pieces first and have them laid out and ready to go. It will make the process a lot easier.

So, as you would expect, we did much better on the second one than on the first. I precut all the glass pieces and was able to lay the glass up in a more orderly fashion. I also did a better job getting the gel coat on - again, no points here for neatness, just get it on in a heavy coat. The net result of this experience was that the second tank was about a full pound lighter than the first one. And of course it looked better as well - even if no one will ever see the inside of it!