Boat repair?

[BOB L]

I finally got around to trying to patch a few holes in the boat and after sanding for what seemed like years and getting every piece of matt material cut just right I mixed up the resin and hardener and got everything wet and where I thought I wanted it. I went to check my work this morning and there are a few spots where everything looks great but about 80% of the work is still tacky. I am guessing that I did something wrong in the mixing of the resin and hardener or that storing them over the winter in the unheated shed did something to them. Now how do I correct my mistakes, sanding the tacky spot just seams to mush it around to a new spot. Acetone and a rag does not seem to work either. Any advice would be welcome and it looks like I will have at least another year of sanding just to remove the spots that do look ok on the outside cause who knows what they are like under the matt.

Bob L

[risingsn]

I finally got around to trying to patch a few holes in the boat and after sanding for what seemed like years and getting every piece of matt material cut just right I mixed up the resin and hardener and got everything wet and where I thought I wanted it. I went to check my work this morning and there are a few spots where everything looks great but about 80% of the work is still tacky. I am guessing that I did something wrong in the mixing of the resin and hardener or that storing them over the winter in the unheated shed did something to them. Now how do I correct my mistakes, sanding the tacky spot just seams to mush it around to a new spot. Acetone and a rag does not seem to work either. Any advice would be welcome and it looks like I will have at least another year of sanding just to remove the spots that do look ok on the outside cause who knows what they are like under the matt.

Bob L

Hi Bob, I had this happen to me about thirty years ago. You may not have completely mixed in the hardener. Since it sounds like it has partially cured, a little extra time may finish the job.

[Brian Nystrom]

In a situation like this, heat is your best friend. You didn't specify whether you used epoxy or polyester resin. If it's the former, if heating the area to ~100F for a day doesn't cure it, it's not going to cure and you'll just have to scrape it all off and start over. Use a space heater or a work light as a heat source.

The same is somewhat true of polyester resin, but it will eventually cure over time. One other important thing to understand about polyester resin is that most common types will not cure in the presence of oxygen; that is, they need to be sealed off from air. This is typically accomplished by covering the area tightly with polyethylene or Mylar, or by spraying the area with PVA (polyvinyl alcohol), a liquid wax coating. If you don't seal the surface, the resin underneath will cure, but the surface will remain tacky. In this case, you can scape off the gooey surface and see if the the resin/glass underneath is hard.

There are also "waxed" polyester resins available that will cure in the presence of air. They contain a wax that migrates to the surface and seals it. When the time comes to apply gelcoat - a form of polyester resin - you want to use "finish" or "waxed" gelcoat, for the same reasons.

BTW, you may notice that I said "scrape" rather than "sand" above. Sanding won't work on partially cured resins, it just makes a gooey mess and wastes sandpaper. The best tool I've found for working with fiberglass and resins is a carbide scraper with a 2" wide blade. Bahco makes a really nice one for ~$20.

http://www.amazon.com/Bahco-America-650-2-...r/dp/B0015YNI3G

[BOB L]

Thanks for the insight, it was a polyester resin so I will work on the repair with that in mind.

Bob L