Builders' Forum Archives
Re: glassing - mmm!
Posted by terry on Feb 18, 2005
I don't know if you have a carbide-bladed scraper. If not, today is a good day to buy one. Many, but not all (I've heard) home centers have them. You can use the scraper to save a LOT of sanding work, as well as a LOT of recoating and maybe even some reglassing. You do this by going over the hull and scraping off all bumps, drips and dust before you do much sanding. I say much sanding, because a quick pass over the entire boat (except for the spots you should hand sand) will highlight where these imperfections are and make it easy to scrape all of them off.
It's best to attack these bumps with the scraper within a day or so of epoxying, as the partially cured eopxy will scrape off more easily. You can still scrape off cured epoxy, but it takes more effort.
On the other hand, if you try to skip the scraping and just sand the entire boat down to smooth finish, you will almost certainly sand through the glass in areas near the bumps because, while you're concentrating on sanding a bump down smooth, you'll also be sanding down the thinner epoxy surrounding the bump, and it's esay to sand right through the glass and into the wood.
Experienced builders use the scraper a lot to save sanding time and damage. I use it for those reasons, but mostly because I'm lazy: it's less work to maximize the scraping and minimize the sanding.
You had mentioned that some areas are not fully wetted out. Are they silver-colored and is the glass weave still quite visible? If so, these areas are voids that should be refilled. Otherwize, when you sand the boat, the glass over these voids will get very thin and will be a weak spot in the finish that can easily fail and allow water into the wood underneath (a bad thing). Some voids can be drilled and filled with epoxy, others you have to cut out and refill with thickened epoxy or fairing compound.
Lastly, you generally need more than two coats of epoxy to get the glass weave filled uniformly over the boat. But a thorough sanding after the second coat provides a good foundation for the third, very, very thin coat that will be much easier to sand. Apply this last, profoundly thin coat with a roller (some builders wipe it on with a rag, or use a wide squeegee) in small sections, and immediately tip off with a foam brush to smooth it and catch any drips. A light power sanding, filling of small dents and holes, and a thorough hand sanding of this cured last coat will give you a ready-to-paint boat.
Good luck, and do enjoy your first, hand-built launch day.
In Response to: glassing - mmm! by ray on Feb 18, 2005