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Re: Material: s-glass
In Response To: Material: s-glass ()

: I am having trouble searching info about s-glass comparded to
: regular glass. Does anybody use 4oz s-glas instead of 6 oz.
: regular? I need to reduce weight alittle and would use this on
: the deck mainly. Thanks Joe

You might save a pound, maybe only 1/2 a pound, switching these on just the outside of the deck. Inside of the deck would be another pound saved. Maybe.

Here is how it works: the best mix is to use an equal weight of resin to glass. That rarely happens. To fill the weave and get a smooth coat we usually use excess resin. It takes about a gallon to a gallon and a half of resin to cover a solo kayak. At 8 pounds to a gallon, your resin is going to weigh 8 to 12 pounds. So your glass will weigh about the same. Total weight for glassing is 16 to 24 pounds (Typically). The rest of the weight of your boat is the wood. That typically ranges from 22 to 35 pounds.

First-time builders tend to go heavy with their materials. They don't trust the strength of these materials because they haven't got any experience with them. And they waste a lot, so they may use 1.5 gallons of resin, but only 1 gallon remains on the boat after sanding off boo-boos. So, these numbers are probably a bit on the high side. Even so, the strip-built boat is considerably lighter than a fiberglass kayak.

Going with thinner glass means the resin coating can be thinner, and still fill in the weave pattern. Working with 3-ounce or 4-ounce glass you might build a boat with 3 to 3.5 quarts of resin (about 6 to 7 pounds) and glass of the same weight. A total of 12 to 14 pounds for the fiberglass work. You save anywhere from a pint to a quart of resin compared to a careful worker using a thicker 5 or 6 ounce glass.

If you want to save weight, go for savings in the hull (bigger area to cover, more room for waste), use 3/16" strips instead of 1/4" strips, weigh your boards at the lumberyard and buy the lightest ones, use 3 ounce glass (S or E), make a large cockpit (less wood), and/or build a smaller boat. Or, build a skin-on-frame boat design. Not a lot of wood to them, no glassing, and the hull and deck are fabric. It's not too hard to get a SOF kayak in the 20 to 25 pound range, and most will be under 35#.

Just curious. What model boat are you working on, and why the worry about such a small weight savings? If you were building the entire boat to win some contest for 'superlight" (and I don't know of any such contest) then 6-ounce glass would never have been part of the plan.

I'm not too sure exactly what info you need on s-glass, but has some good info on glass online. You might browse there. one thing: S-glass stands for Strength. the other glass cloth was originally designed for use as an electrical insulation, and is called E-glass. E for electrical. As it happens, the E-glass, besides being a fine insulator has great strength and serves as the base of most fiberglass products. There are a million recipes for glass. Using one which gave stronger fibers they created S-glass. For a given fiber diameter and weight it is stronger by about 25 to 30% (if I remember correctly). It is not as common, so the price is higher. People who want greater strength frequently go to the really expensive materials, carbon fiber, kevlar, spectra, or mixes of these instead of glass. That kind of cost is usually a budget-breaker for the home builder. sells these and has some prices and info on them in their catalog. It takes a bit of digging to find it on their web site, but it was there when I last looked.

Hope this helps.


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