Kevlar, Water Absorption Reported

The Aramid (Kevlar) fibers don't themselves absorb water but if they stretch inside the resin matrix they break free from the surrounding resin and significantly weaken the laminate. If there's a penetration the water can travel down these "tubes" causing further damage as seems to be described in Brian's post.

IMHO there isn't near enough information in the link about the construction (or damage) to make such a blanket statement that Kevlar shouldn't be used in hull bottoms. This sort of problem has been known about for a long time and specific methods of mitigating or eliminating it have been employed successfully. Higher elongation resins (ie. Vinylester and epoxy) allow the matrix to stretch more with the fibers and "hybrid" weaves using E or S glass and now occasionally even carbon fibers also combine their different physical properties and help the resin matrix stay bonded to the individual fibers. I've been building boats with epoxy/Kevlar/hybrid cloth skins for nearly two decades now and have yet to see any failures like the article described. There have been several impacts reported with floating debris and groundings but no problems with moisture penetration in the surrounding areas.

12 days of sanding bottom paint???? That in and of itself doesn't make any sense on a 65' boat.

I don't know, it's certainly not a job I would enjoy making 12 days out of.....You could sand it down with a DA and one guy in about 2 days......

As with any "newfangled" product, there always seem to be some teething pains Brian. I seem to recall some of the early all Kevlar hulls built by a very highly regarded boatbuilder had delamination issues that forensic analysis attributed to the pure Kevlar being to stretchy for the polyester resin and fibers were moving inside the laminate. The solution was a higher elongation resin and a hybrid weave with e-glass that improved the resin bond to the weave. As with anything it's a compromise, the Kevlar is "held" by the glass fibers well below the limits of it's full potential to stretch and mitigate penetration and the glass fibers will tear first but the hybrid laminates have almost twice the damage tolerance of plain e-glass so it can be justified. Many of the high end sport fish builders use or have used it on premium builds; Merritt, Hines Farley, American Custom, Spencer, Tribute and us.

End grain balsa core on the other hand still makes me shake my head. It does have excellent compression strength but add any moisture and it's mush in short order. I can't count the number of extensive repairs we've done on failed balsa structures, decks, hulls, cabins, hardtops, you name it. In fact I have to boats in the shop now getting just such repairs. Before the advent of honeycomb and higher density foam cores I can understand why it was so popular but nowadays I just can't fathom it's use.