: Usually I agree with you Paul, but in this instance my experience is
: different.

: My boys have ground off 4 or 5 iterations of more plain ol' glass, and I'm
: looking for something more "kid-proof". Anything will work if
: you always launch and recover wet, but accidents will happen and E-glass
: isn't up to the challenge, no matter how thick.

I was thinking of MINOR dings, not kids-who-aim-for-rocks-just-to-see-if-dad-built-a-good-one-this-time. Have you considered a solid metal covering -- maybe armor plate

: Yeah, I've read those threads and can't imagine how it could be true. Maybe
: some folks are confusing carbon fiber with carbon powder. Carbon fiber
: composites have some Really Flashy Numbers for strength and impact
: resistance - how does 305,000 psi tensile strength sound? (See
: http://www.matweb.com/SpecificMaterial.asp?bassnum=O1780 ) I can't find
: any test data for carbon powder, only anecdotes from this and other BBSs.
: But isn't all that stuff isolated from the water by varnish anyway? Sounds
: like cognitive dissonance at work.

For a few reasons -- the biggest one is skepticism -- I have not played with carbon filled resin. But, as I understand the process, you mix in a relatively large amount of graphite. We are not talking about the small amount of printer toner needed to make the resin turn black, but more on the order of the amount of filler that is used to "fill" the resin and amke it sag resistant for fillets. This much carbon provides an extremely opaque layer, but as best as i can figure, for it to reduce your friction you would need to lightly sand the finish to remove any surface resin.

Here is how I see it: Magnify a tiny area in your mind, if you can, and imagine the graphite as being beads or marbles. The resin is holding many in suspension, and those on the very surface are being held by the glue that is behind them, and the have been flattened a bit as the outer layer of resin and a part of the carbon bead was removed wiht the sanding process after the resin hardened. Even a very thin layer of graphite is extremely good at blocking UV light, so the resin should be protected from damage by sunlight. The only area where light can actually reach the resin is at the edge of each of these beads. Now, if the resin should eventually fail in these areas the microscopic bead of graphite will fall off, and expose a fresh layer of graphite, so over time the surface will slowly ablate, or wear away. The exposed graphite is "slippery" in its own way, and just might give slightly less friction. but I still want to see some numbers on this before I put out any cash. The "lead" in a lead pencil is made in a similar way, but they use clay as a binder to hold the graphite, and the varying "hardnesses" of pencils is related to the relative amounts of graphite vs. clay. Of course as you write a small amount of clay/graphite rubs off of the pencil lead and sticks to your paper. I envision something like that happening with graphite suspended n epoxy resin: Get the mixture right and small amounts may slough off.

I'm thinking this may be really more useful to racing sailboats that are willing to spend for recoating the hull as needed, and their owners who will spent a few buck more to get a fractional increase in speed.

: When epoxy-filled glass gets dinged, the glass stretches and fractures,
: creating a whitish bruise

If the finish is clear, or translucent, you can see the whitish bruise easily. (and I've seen plenty like that !) I'm thinking that the use of LOTS of graphite might make the fill coats totally opaque. Then you won't be able to see through it to identify any problems with the underlying glass. Scratches should (if the theory is right, and the concentration of graphite is high enough) look just as gray as the surrounding area. All you'll do is scrape off a layer of graphite and unless you go completely through the graphite and into the glass or wood, you'll just see a gray scratch in a gray area. Since the finish is not coated with varnish you won't get any diffraction from the disturbance in the varnish film, either, which also makes a ding stand out. Of course such an opaque finish can hide potential damage that should be repaired, so there may be another flaw in this concept.

: Vaclav's tests are shown in the link, where he tested Dynel, Olefin, Xynole,
: Syntex, E-glass and S-glass. Syntex looks like a clear winner (pun
: intended )

Am I missing something on that picture, or is it mislabeled, or am I just not reading things right? Was the panel delaminating before he hit it? the screwdriver holes in the glass ( on the right of the picture) are well defined, and you can plainly see them, with no apparent additional damage around them. If the wood was sealed before glassing this kind of damage is easily fixed. The rest of the panel looks like it did not get punctured by the screwdriver (good for the puncture resistance of the fabric) but the delamination looks pretty bad, as you can plainly see the weave and translucency of the fabric. If that was from the impact damage, I'd stay with plain glass. If that was from the fabric not being able to bond well to the panel (before getting abused) then I'd stay with plain glass.

PGJ