> Does anyone have any experience using s-glass instead of E-glass. I was
> looking at a piece earlier today and it seems like it may be a superior
> product, and easier to work with than E-glass??? I have built a few plywood kayaks with 4 and 6 oz. S-glass. If you substitute S for E of the same weights the boat will have greater impact strength. It will also cost more. One can substitute 4 oz for 6oz E glass but just be aware that there will be much less rigidity on large panel shapes. I built a Pygmy Coho with 4 oz S-glass, the bottom of the hull was a bit more flexible than I anticipated. I am just beginning to temper my inclination to overbuild boats. Ater having built 5 kayaks I think how one builds is much more important than what raw materials are used. I made about 3 dozen test panels with a variety of cloths;S,E-glass,polyester,dynel,kevlar,carbon. Dealing specifically with the differences with S and E. S-glass is a little stiffer so if your want it to lay over a tight radius curve you may want the threads on the bias. Otherwise I haven't found much difference in handlayups. There are many types of weave and weights in cloth. The most common 4oz and 6oz cloths are around 20x20 and 17x17 threads, the 4oz S-glass doesn't wet out as clear as 6oz Eglass but the differences aren't noticable from a couple feet away. All these opinions based on limited experience. Comparing a test panel of 4oz s-glass to 6oz e-glass, the 4 oz panel is slightly more puncture resistant,or at least a puncture didn't lead to large spreading fractures. In a crude 3 point bending test (my foot against a panel leaning against a step);the 6 oz panel fractured primarily along one axis, with the glass and wood breaking, The S-glass panel bent completely (multiple axis roughly parallel)without the wood breaking through, with puncturing impacts the e-glass tended to fail along the direction of the threads, the fractures on the s-glass traveled a shorter distance and less along the orientation of the threads. Whether this is due to the higher thread count in the lighter s-glass or higher strenth in individual threads I don't know. Anyway J.R. Sweet in N.Carolina is and excellent source for all this stuff, . One of the test panels had 4oz S-glass over 4oz polyester,although this may be as heavy as one layer of 10oz E-glass, it sure was tough. Anyway my short experience tells me it is great stuff when cost isn't an object otherwise using the squeegee well is more important.