On Thu, 30 Mar 2006 22:26:02 GMT, Rosalie B.
wrote:

High quality boats almost never have integral tanks - for water or
fuel.

Our water tanks are build into the hull. I think our boat is quite
high quality.

And no doubt it is. I think my my statement about "almost never" is
still true however, even though the reasons are not necessarily clear.

There may be less of an issue with integral water tanks as opposed to
fuel, certainly leaks/safety are less of a concern. There have been
many, many instances of fiberglass fuel tanks degrading because of
fuel/resin interactions, especially with ethanol/gasoline. There's no
reason to think that those same interactions wouldn't take place place
with the resin in a hull, with even more serious consequences.

My first cruising sailboat was a Westerly 28 which was reasonably well
built in most respects. It did have an integral water tank however
built in underneath the V berths. The tank eventually began leaking,
probably from being repeatedly being stressed at its aft bulkhead. We
never did find a totally satisfactory cure and would probably have
needed to rip out the V berths, reinforce/rebuild the tank, and put
the whole thing back together.

Here's another data point. In the process of switching from sail to
power several years ago we spent quite a bit of time looking at
offshore sport fishing boats made by Bertram, Hatteras and Viking. We
already had some experience with our old Bertram 33 and had come to
appreciate just how well it had been built. All three of these
builders have (or had) a reputation for building tough high quality
boats that could go offshore and take a pounding. Not a single one
that we looked at had integral fuel or water tanks. They were all
fiberglass hulls of course and that may be part of the reason but I'm
not sure. It is true that many steel hulled boats, and some with
aluminum hulls have integral tanks but it is not clear if that is
coincidental or structural.

Perhaps Roger Long could cast some light on the question?