Red wrote:
As I understad it, Kevlar is not only difficult to get a good bond with,
its not all that great for collision protection as it is for puncture
protection.


"Kevlar" as applied in structural composites (ie boat building) is
cloth made of fibers, same as fibgerglass is cloth made of glass
fibers. No magic here.

BTW it may be interesting to note the structural properties of
fiberglass, some other composites, and steel. It is relatively easy to
build a composite that is as strong as steel. It's also easier to
scale the structural properties to the size of the vessel. This latter
property is why steel doesn't make good small boats.


Besides, your answer doesn't address what I was asking - something that
can be applied on an older existing hull. I believe Kevlar would not
bond well enough on old polyester to make this practical anyway. Is this
correct?


No. Kevlar bonds just fine to existing hulls. I know of several boats
that have had this done. It would be better to apply it to the inside
of the the hull, where impacts put the laminate in tension, rather
than the outside (compression) face. However this is not always
practical, and it certainly helps the impact resistance of
"conventional fiberglass" to have a layer of Kevlar cloth on the
outside. A big problem to beware of is that Kevlar can't be faired...
sanding into the cloth leaves frizzies that will NOT lay down no
matter how much resin or paint you try to cover it with. So any
attempt to armor an older hull should have a thin layer of matt or
finishing cloth sandwiched over the Kevlar.

It would also be a very good idea to add positive flotation.

Fresh Breezes- Doug King