Builders' Forum Archives
Big Problem Glassing Hull
Posted by Matt Croce on May 31, 2005
Help. Up until now, things have been going great; yeah, I made the odd mistake here and there, but everything worked as advertised, and the screw ups were my fault due to inexperience.
But now, just when I thought things were going great, Iím having a pretty bad problem with glassing the hull.
Iíve attached a link to a PowerPoint file to illustrate the problems Iíve been having, but Iíll summarize here:
Laid the glass cloth on the hull (hull had been sanded smooth with 220 grit and brushed clean per instructions and recommendations off of the user forum)
Applied epoxy; tried to go with a fairly light coat, just enough to wet out the hull. I thought the first coat went great Ė glass followed the curve of the bow no problem, wetted out well; in general it was much easier to do than the inside of the cockpit. When this coat had dried, it was just as the book said it would be; the weave was visible over almost all of the boat, except in a few spots where Iíd laid it on a little too thick. Generally, the boat looked and felt good, almost like snakeskin.
Applied second coat of epoxy. Tried a couple of different applicators including a plastic spatula, a yellow foam roller, and a chipping brush. Best combination seemed to be the foam roller and the chipping brush to smooth out the many bubbles caused by the roller. However, the coat appeared to be too thick; I wanted to keep it neat and light, so I used the spatula to scrape off the excess; my goal on this coat was just to fill in the weave. As I pulled the excess off, I noticed that it was whitish instead of clear, like it had a lot of air in the epoxy; I assume from the foam roller.
Once it dried, it looked pretty good; shiny in some places, weave still showing through in other places, just like the instructions said it should. I wanted to sand this coat down lightly, mainly on the shiny areas, and get it nice and smooth for the final coat.
I started sanding with 120 grit on an ROS; the keel panels looked okay, although as I sanded, I noticed that it was almost like I had some surface bubbles; if I sanded a bit further, they went away. However, as I got closer to the bow, where the keel panels start to become more vertical, I noticed that these werenít really bubbles, but areas where the 2nd coat of epoxy was separated from the first; as long as I sanded through the 2nd coat, the problem went away. Well, the bow was one of the areas where the glass was thicker, and I switched to 80 grit on the ROS, and ended up cutting through the glass to the wood, so I stopped sanding, and waited a day, to think things through.
Today, I went out with a carbide scraper, and it was much worse than I thought. The second coat barely adhered to the first, especially on the sheer panels. I was able to scrape off huge strips of it, almost like stripping wallpaper. Unfortunately, it didnít ALL come off that easily, so I was left with a really bad looking case of psoriasis on my boat (see PPT file).
Iíve continued sanding and scraping, trying to remove the bad coat of epoxy, but I have some concerns. First, Iíve sanded through to the wood in three places trying to get this crap off. Once by the bow, along a chine, once about 2/3 way back along a chine, and once near the stern at the top of the sheer panel.
My concern is this: Because the weave of the cloth was still present when I applied the second coat, in order to remove the second coat, which filled in the valleys of the weave, Iím having to sand into the glass. And, based on the fact that Iíve sanded through to the wood in some spots, Iíd guess that Iím thinning out the glass over the entire boat. What do you recommend? Should I continue to sand until all of the bad epoxy is gone, and then reapply a new coat, or do I need to continue sanding until Iíve gotten rid of most of the glass, and reapply the whole thing, glass and all??
Second, why did this occur? Iíve thought about a couple things, but canít say anything definitively. Amine blush was my first thought, but I only waited about 18 hours between coats; outside temperature was 60-70 degrees during that time. The first coat was dry, not sticky to the touch. Iíve never had any blush before; Iím using the slow hardener that came with the kit.
This is the first time that I havenít used the ďtentĒ (see pictures) that I set up for working in cold weather (Virginia Beach, the temps just got above 70 degrees last week). Maybe the tent kept some pollutant in the air off of my boat before. Or maybe the space heater, cranked up to 80 degrees, made the epoxy harden better??
I also have a dryer vent nearby; itís about 5 feet from the edge of my workspace; I donít know if we were doing laundry that day, but we may have been, it might have been contamination from the dryer vent??
The only other thing could be that I got lazy mixing the epoxy, and it didnít cure right, but itís strange, because the epoxy actually is hard, just not adhered.
Do you have any suggestions to avoid this in the future?? Obviously, the hull will now be freshly sanded. Iíve washed it several times as I sanded with clean water, and wiped it down with Lacquer Thinner; Iíll do it again before I do the next coat of epoxy. I will use my tent set up again, and will make one of the ďelectric mixerĒ looking things out of a dowel and some screws to mix the epoxy. And finally, Iíll be brushing the epoxy on, to ensure that the roller introducing air into the epoxy isnít the cause of the problem. Beyond these steps, Iím at a loss.
Sorry this is so long, but if you have any idea what happened, please let me know.
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