"DSK" wrote in message
.. .
KLC Lewis wrote:
Doug, Essie takes serious exception to the slanderous allegation that she
was "poorly built." I told her that you really didn't mean it, but I
think it'll be a while before she forgives you.


OK, re-phrase that statement so as not to be pejorative.

However, there is really no reason for a fiberglass boat to have any
measurable flex in it's hull, other than rigidity (and the strength that
is a commensurate by-product) not being high on the list of builder's
priorities. For example, many years ago a buddy of mine & I went in shares
on a fancy racing boat, a 1-Tonner. Several years past it's prime, of
course, or we would not have been able to afford it.

This boat had been built to be driven *hard* under sail, and stiffness
means speed to a racing boat. The tuning guide said that at times, it was
possible and desirable to place a tension of 10,000 lbs on the backstay. I
spoke to the builder and asked if the boat would really take this, and he
laughed and said "Heck yes, when we trialed that boat, we put 20,000 on
the backstay and measured a little less than 1/4" deflection along the
deck."

In years before and since I've worked on and sailed a number of boats, and
have found some that flex more, some that flex very little or not at all.
Perhaps it's just idle prejudice on my part, but the ones that flex less
seem to me to be more desirable.

Fresh Breezes- Doug King



Well, there's flexing and there's flexing. Essie is built exceptionally
stout for a boat of her size, having been built back in '63 before
scantlings for fiberglass boats had been developed. In those days they
really didn't know how thick things like hulls should be, so they erred on
the side of, "I dunno, Frank. Better lay up another quarter inch or so."

But a boat on the hard is unlikely to be supported the same way as the water
holds her. Essie's cradle supports the keel (full) for a good portion of its
length, then there are two supports foreward and two aft (P&S) -- for a
total of four. Over the length of a winter, with the hull alternately
heating up and cooling off (there are times even in winter when the hull can
be hot to the touch during a particularly bright day, only to drop below 20
degrees f at night), this "support" cannot help but put some unusual
stresses into the boat. When launched again in the spring, it takes a while
for the boat to relax into the water.

Again, with Essie we're talking fractions of fractions, but it's still
noticable. And she is WAY stronger-built than she needs to be. The flexing
we are talking about isn't "oilcanning" from scantlings that push the lower
limit.

KLC Lewis wrote:
Well, there's flexing and there's flexing.

Agreed.


.... Essie is built exceptionally
stout for a boat of her size, having been built back in '63 before
scantlings for fiberglass boats had been developed.

I've heard this a lot, but it's not 100% accurate. The Navy
was very interested in fiberglass for it's small boats
(gigs, whaleboats, utility boats, etc etc, which had been
previously built out of wood). In the early 1950s they paid
for, and published, a large scale engineering study of
fiberglass including how well it stood up to UV. Lots of
early boat builders used this reference.


But a boat on the hard is unlikely to be supported the same way as the water
holds her.

Agreed again. The cradle or jackstands should be positioned
to support the internal structural members, like bulkheads,
directly. And fiberglass will exhibit 'creep' under
consistent heavy load for a long time. But it won't creep if
it's not loaded past the point of measurable deflection.



.... The flexing
we are talking about isn't "oilcanning" from scantlings that push the lower
limit.


Actually, oilcanning is annoying but not particularly bad
for fiberglass. FG can withstand at least an order of
magnitude more cycles of flexing than steel before
fatiguing, in this respect it's far superior to metal.

If given a choice between a hull that had oilcanning in some
panels (for example, the big almost-flat section in the bows
of many boats) and one that flexed over it's whole length
from rig loads, I'd pick oilcanning. But it would be a lot
better to have neither.

Fresh Breezes- Doug King