Builders' Forum Archives
what weight of glass ?
Posted by LeeG on Jan 14, 2007
You can't make it look as good as new but you can make it tougher. Once the glass is broken and waterstains show up all you can do is stop further waterstaining. Did you use 6oz glass when making the kayak? If you're breaking through 6oz that's rough use. If you used 4oz then that kind of wear is normal. I wouldn't remove the old glass. Just sand through the varnish and fill coats to the top of the old glass, if the gouges depress varnish below the level of the sanded epoxy then you have to remove that varnish that's pushed down below the level of the adjacent epoxy. If you mask off an area where the gouges/scratches are most numerous it should be a long tapered diamond with flat sides or an elongated football shape. Fill the gouges with some epoxy thickened with a little cabosil (not enough to cloud it). Scrape flat when green then glass some more 6oz over that area using the masked area to mark off the glass. If you want a LOT of durability a "football" (below waterline high wear area) of 4oz over the regular 6oz will do it. 6oz football over 6oz hull glass is way over kill but I could see it for a big person launching/landing in rocky places. When it comes to rough use durability you really do want a substantial fill coat, sanding fill coats to the top of the glass before varnishing just make the glass more vulnerable to gouges. Durability/impact resistance starts with 6oz e-glass and three fill coats. If a person wants more then adding a 4oz football will do it. If money is no object then get some s-glass. It's priced about the same as kevlar, maybe a little less. It's repairable like e-glass, as abrasion resistant as kevlar without fuzzing and stronger than e-glass. It wets out with a little ghosting of the threads visible from a couple feet away unlike e-glass which pretty much disappears. Don't bother with kevlar,polyester cloth (dynel). Kevlar doesn't have that much protection against impacts (by weight) that can dent the wood, it'll stay together but it's not as hard as fiberglass. Also the 5oz kevlar will use a LOT more epoxy for it's weight, between wetting out and the thickness of fill coats to ensure you don't sand into the cloth and raise fuzzies requiring more fill coats. You could probably use 7.5oz of glass for the epoxy needed in 5oz of kevlar. Polyester and especially Dynel cloth soak up HUGE amounts of epoxy. If you covered a large area with those cloths the amount of epoxy used would be almost twice as much and it would be as pretty as a wet t-shirt with large weave. Not.
In Response to: reglassing hull bottom by Patrick Forrester on Jan 7, 2007