Red wrote:
I hear ya on the flotation!


A lot of people seem to think it isn't practical. It would indeed mean
giving up some interior space, but IMHO many production boats could
have positive flotation installed and give up maybe 15~20% of useable
stowage. A lot of space could be used for flotation that is up in
tight angles & inaccessible spots.

The reason I asked is that I read an article somewhere way back on some
boatbuilding site that kevlar wouldn't bond adequately to old poly
resin.

Can't think why that would be. It's just fancy cloth. More would
depend on the surface prep & type of resin.


.... I'm curious though, why would it be better for the kevlar to be
on the inside? Wouldn't that make it less effective in a collision due
to the layer being in tension so it wants to seperate? I would have
thought that being on the outside would be better to provide a barrier
to the forced entry. Could you explain further? Thanks


I can try. A laminated structure almost always fails in compression...
same as a mast BTW. As force applied increases and the structure
bends, at some point the strength of the bond between layers starts to
fail and the inner face of the bend, the skin that is under
compression, starts to buckle. This is where local tears in the skin
form. After this point failure occurs, the whole thing comes apart
like a zipper until the strain is relieved.

Kevlar is very very strong in tension, and along the tension face or
skin will distribute load over a much wider area than conventional
fiberglass cloth, thus avoiding critical point loading in the opposite
compression face.

OTOH if you're thinking of an object piercing the hull like an ice
pick, having the Kevlar layer on the outside might not make much
difference. In any event, having it on the outside is better than
nothing.

Fresh Breezes- Doug King