Adrian Smith wrote:
How long should a modern GRP hull lasts as compared to one made 10 years
ago?


The material, design, type & execution of the lay-up will
matter a lot more than whether it popped out of the mold
last week or 10 years ago.

About the only maintenance issue is if it's cored, then the
skins must stay bonded to the core and no water should be
allowed in (ie deck fittings properly thru bolted & bedded).

If you're talking *only* about the structural integrity of a
fiberglass hull & deck, it should last forever within a
certain range of stress. The more strongly it's built, the
wider range of stress it can take. Once it is loaded /
stressed enough to break a few of the bonds within the
lamination, it is said to be "fatigued" just like metal that
gets bent back & forth. Fiberglass has some advantages over
metal in that it can bend further without fatigue, and can
accumulate a higher number of fatigue cycles, but that
number is not infinite. Another good thing about fiberglass
is that it's relatively easy to re-bond bulkheads & other
structural members inside.



And how old is considered too old when taking a boat offshore into potential
rough conditions?


The old-fogey brigade will insist that older is better, for
a number of reasons. Old fashioned hull & rigs can be more
seakindly (altho old running rigging & deck fittings can be
awful to cope with). Some will even claim that 'back in the
old days' the boat builders did not know how strong
fiberglass was, so they made it incredibly thick & strong.
The fact is that engineering data was available on
fiberglass from the early 1950s on, readily available to
those who cared to look... is ignorance a good excuse?
Another fact is that resin/fiber ratios in many older hulls
is poor.

It's more of an issue about the functioning of all
systems... rig, plumbing, electrical, electronic (if any)
than the age of the hull.

Hope this clears some things up.

Fresh Breezes- Doug King