Question:
flat spots on sides of a glass sailboat?
I'm helping self-survey (pre-survey survey?) a sailboat for a friend,
and am quite concerned about large flat spots on the sides.
The boat is a 1978 O'Day 28, and the spots in question are in the same
place on both sides: directly below the mast cables (sheets? Sailboat
terminology escapes me sometime) at about the waterline.
The flats are about 2 square feet in area and do not appear to
correspond to impact damage. My mechanical engineering "almoast degree"
tells me that the mast cables are now or were once strung way, WAY too tite.
(The line of action of force from the outer cables go directly through the
flat spots, exactly where I'd expect a near-syllindrical shell to buckle
when loaded in the way.) Safe assumption?
While on the topic, what is the assumption of safety? Is this something
that can be written off to one-time damage that adds a little drag on an
otherwise very nice potential acquisition? Or is this yielding of the
structure a critical problem?
Answer:
- Overstressing the shrouds (mast cables to you) might deform the hull around
the keel or the deck similar to pulling back the string of a bow but will not
flatten out the area you describe. That sounds like the result of improper
bracing while out of the water. If the stands are placed where there is no
bulkhead or other structural member behind the hull to take the load it can
deform the area.
I do not believe I would expend any money on a professional surveyor for this
boat.
- Are they directly below the shrouds -- wires that hold the mast up on either
side of the boat?
If so, it could be where the chainplates -- the fixtures that actually
attach those wires to the hull -- are glassed/molded into the hull. There
may be reinforcement to spread the loads better. You should be able to
check inside the hull and see the hardware. Without a better description, I
don't know if it is damage or just a sloppy glass/mold job in the original
hull.
- There is a bulkhead directly beneath the areas flattened.
The spots are sufficiently high up on the sides (the flats start at
about the waterline and extend approximately one foot up) that I still
suspect the shrouds are/were too tight.
The O'Day 28 in question is rather a beamy boat, and the hull sides are
nearly verticle therefor I can't imagine the damage being caused by poor
blocking.
To answer the response of John R. Weiss, I have not been able to get
access to the inside of the hull to check whether the chainplates were
affixed in the vicinity of the flats. It does not appear to be damage as
there is no gelcoar damage, and the suspect spots are on _both_ sides.
And, Glen, I read with great interest the annuls of the Rutu project.
Several coworkers who are fine hobbyist crafstmen in their own right were
duly impressed, as was I. Very nice work.
