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

: The dynel should give some ding resistance, as would another layer or two or
: three or four . . . (stop me when it gets thick enough) of plain ol'
: fiberglass cloth.

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.

: There is a definite reaction between the graphite and epoxy resin which has
: been moted in several areas. The graphite apparently does make the epoxy
: quite a bit stiffer and tougher -- which means better ding resistance.
: there are also some reports that adding graphite to the wetted area of the
: hull will reduce water friction, but these have been countered by claims
: that the data are not conclusive.

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.

: A stripe or two of graphite filled epoxy might be all you need. There have
: been reports that scratches on the darker material are not as obvious as
: scratches on a white or clear finish.

When epoxy-filled glass gets dinged, the glass stretches and fractures, creating a whitish bruise - see the pic below from One Ocean Kayaks. The test panel was whacked with a hammer, screwdriver and a sharp rock. So if the finish color is white, the damage is not so obvious. On clear wood the damage would be more obvious, and on any dark color the damage would really stand out. The boat manufacturers figured that out a long time ago. Steel hulls are often black or dark blue, but glass hulls with few exceptions are white.

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 )