"Roger Long" wrote in message
...
Thanks J, a great read about an impressive guy.

Speculation about things like this is a flame magnet but I think it serves
a valuable purpose in helping anticipate and mitigate threats. Being
right about the specific incident isn't the point, thinking about
possibilities that could effect you is.

Having spent some significant portions of my professional life calculating
and thinking about how vessels break, flood, and sink, I find the sinking
by the stern possibility mentioned quite plausible. The problem is that
it requires a hole in the aft part of the boat since vessels usually start
to trim towards the damage. Boats, especially light ones with light ends,
will also usually dissapate a lot of collision energy by the fine forward
end gradually lifting or turning the bow. A sharp heavy object, with it's
effective weight increased by being entrained in the water, could puncture
the forward part of the hull. The nightmare object in my mind is the
corner of a barely floating shipping container lost overboard.

A major hull breech aft is harder to explain but there are two
possibilities, the rudder and prop. An object awash and nearly invisible
might be spotted at the last moment. An instinctive quick turn to avoid
it when the boat was moving fast could swing the stern into it and hook
either the rudder or prop. The geometry of neither is such that much
energy would be dissipated by movement of the hull. Hull failure around
the rudder stock or the shaft pulling out of the coupling (many similar
boats have enough clearance behind the prop to let the shaft come clear of
the stuffing box and shaft tube) could have set off rapid stern flooding
and trimming. This quickly would have cascaded into back flooding through
the cockpit scuppers and then through the companionway which certainly
would have been opened to see why the boat suddenly seemed stern heavy.
It would have been very easy to have focused on plugging a leak and not
realized that the companionway had reached the waterline. The water level
would have still have been fairly low inside the boat at this point and a
wave, the stern heavy boat now having swung downwind, could have sent a
large slug of water down the companionway completing the sinking in
seconds.

There is a theory and possibility that Titanic could have survived the
iceberg impact if they had not attempted to turn, thus turning the
collision into the long sideswipe that opened up so many compartments.
The same thing can happen to modern sailboats with their delicate hull
appendages. A sailboat trimming by the stern as it floods will go down a
lot faster than one trimming by the bow.

I wouldn't want this taken as a recommendation to steer straight into any
floating object you see at the last second but, as anyone who has dodged
lobster pots in a separate rudder boat knows, the reverse turn back
"towards" the object is essential to avoidance. Often, when I spot a pot
pulled nearly under by the tide, I find myself close enough that it is
better to just hold the course and hope than to risk swinging the stern
into it by turning. I imagine it would be damn hard to remember that
though if something like a shipping container or giant log suddenly showed
up less than a boat length ahead.

--
Roger Long



The only thing about the scenario of sinking that doesn't quite wash (no pun
intended) is that there would surely be some debris. Lot's of things would
float and nothing has been found. Of course, it's a big ocean....


--
"j" ganz @@
www.sailnow.com