In article ,
News f2s wrote:
You're quite right of course. Proper reasons for abandoning ship
(for a life raft) are fire and uncontrollable leakage such that
the vessel is about to sink.

The reasons I gave above are reasons for transferring to a larger
vessel, which wasn't the point of the previous poster, but is the
most common type of abandonment, the one being discussed earlier
in the thread.

I would think that some boat interiors would become uninhabitable if
the boat were dismasted. This happened in the Fastnet Race, and I'm
sure it's happened other times.



--
Capt. JG @@
www.sailnow.com

"Jonathan Ganz" wrote in message
...

I would think that some boat interiors would become
uninhabitable if
the boat were dismasted. This happened in the Fastnet Race, and
I'm
sure it's happened other times.

The boat becomes very much more stable, giving it an extremely
rapid natural rocking motion. If this is sparked off by waves, the
boat is all but untenable.

The problem is that in those conditions a liferaft also rolls
viciously, and is likely to be overturned from time to time. Three
of us experienced that liferaft motion in a wind over tide, 2
metre breaking waves, just off Appledore in the Bristol Channel.

It was a training exercise that went wrong. The lifeboat call-out
was delayed. We were blown downwind into the race. Like being in a
washing machine. Lots of minor injuries, one broken arm. Never
again. We were stuck in this rotating hell for about 15 minutes,
then when the lifeboat arrived it took a further 20 minutes to get
us all aboard. By that time all of us were cripplingly seasick -
and we were experienced sailors, used to offshore racing, who
prided ourselves on our strong stomachs. Yuck.

JimB

"News f2s" wrote in message
...

"Jonathan Ganz" wrote in message
...

I would think that some boat interiors would become uninhabitable if
the boat were dismasted. This happened in the Fastnet Race, and I'm
sure it's happened other times.

The boat becomes very much more stable, giving it an extremely rapid
natural rocking motion. If this is sparked off by waves, the boat is all
but untenable.

The problem is that in those conditions a liferaft also rolls viciously,
and is likely to be overturned from time to time. Three of us experienced
that liferaft motion in a wind over tide, 2 metre breaking waves, just off
Appledore in the Bristol Channel.

It was a training exercise that went wrong. The lifeboat call-out was
delayed. We were blown downwind into the race. Like being in a washing
machine. Lots of minor injuries, one broken arm. Never again. We were
stuck in this rotating hell for about 15 minutes, then when the lifeboat
arrived it took a further 20 minutes to get us all aboard. By that time
all of us were cripplingly seasick - and we were experienced sailors, used
to offshore racing, who prided ourselves on our strong stomachs. Yuck.

JimB

I think you mean "because more *unstable*" right? I'm not sure what would
have been worse... a washing machine with sharp objects or just an empty
washing machine with soft sides. I think I'd like to avoid both!

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

"Capt. JG" wrote in message
...

The boat becomes very much more stable, giving it an extremely
rapid natural rocking motion. If this is sparked off by waves,
the boat is all but untenable.

I think you mean "because more *unstable*" right? I'm not sure
what would have been worse... a washing machine with sharp
objects or just an empty washing machine with soft sides. I
think I'd like to avoid both!

No, I meant stable! Take the top weight of the mast off, and the
centre of gravity of the boat drops down, so the righting moment
goes up.

Add to that the fact that the mast's inertia has gone, and the
boat now reacts very much more quickly to any disturbance - then
rolls back and forth, one cycle every couple of seconds.

JimB

Nope. It doesn't work like that. You would think it would, but it doesn't.
We had a dismasting on the bay (one of my students). It was caused by a
hairline crack. They were pounding up to the Golden Gate area from Alcatraz
on a typical 20-25 knot day in 3-4 foot chop. After the mast came down, the
boat was almost uncontrollable as it drifted back down hill. Finally, after
they cut away the mast, they were able to motor back to the slip, and
according to the crew who we interviewed, it was the worst part of the trip.
The boat was so unstable a couple of people got sea sick.

You said it yourself in your final paragraph... that is the definition of
instability.

In addition, if the conditions are bad enough to roll a boat, the mast would
act as a break when it goes into the water. This would actually slow the
roll effect.

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

"News f2s" wrote in message
...

"Capt. JG" wrote in message
...

The boat becomes very much more stable, giving it an extremely rapid
natural rocking motion. If this is sparked off by waves, the boat is all
but untenable.

I think you mean "because more *unstable*" right? I'm not sure what would
have been worse... a washing machine with sharp objects or just an empty
washing machine with soft sides. I think I'd like to avoid both!

No, I meant stable! Take the top weight of the mast off, and the centre of
gravity of the boat drops down, so the righting moment goes up.

Add to that the fact that the mast's inertia has gone, and the boat now
reacts very much more quickly to any disturbance - then rolls back and
forth, one cycle every couple of seconds.

JimB

No, I meant stable! Take the top weight of the mast off, and
the centre of gravity of the boat drops down, so the righting
moment goes up.

Add to that the fact that the mast's inertia has gone, and the
boat now reacts very much more quickly to any disturbance -
then rolls back and forth, one cycle every couple of seconds.

"Capt. JG" wrote in message
...
Nope. It doesn't work like that. You would think it would, but
it doesn't. We had a dismasting on the bay (one of my students).
It was caused by a hairline crack. They were pounding up to the
Golden Gate area from Alcatraz on a typical 20-25 knot day in
3-4 foot chop. After the mast came down, the boat was almost
uncontrollable as it drifted back down hill. Finally, after they
cut away the mast, they were able to motor back to the slip, and
according to the crew who we interviewed, it was the worst part
of the trip. The boat was so unstable a couple of people got sea
sick.

You said it yourself in your final paragraph... that is the
definition of instability.

For clarity, I'm only talking about the rolling stability. There
are two types of roll stability we're perhaps confusing here.

First, static stability is the tendency of a boat to right itself
once it has been heeled over. After a single disturbance the boat
will rock side to side a couple of times until the motion dies
off. If static stability decreases, the boat will right more
slowly after a disturbance. If statically unstable, the boat will
roll upside down. If, on the other hand, static stability
increases, the boat tries to right itself more quickly than
before. The rocking motion will speed up.

If the rocking motion dies away, you have dynamic stability too.

Dynamic instability is when an oscillation builds up instead,
until either something breaks or there's a breakdown in the
circumstances. The best example of this is the 'death roll'
enjoyed by a downwind boat with too much sail up for the wind. Our
relevant example is when the wave frequency disturbing a dismasted
boat is the same as the (quicker) tendency to rock back and forth.
The rocking amplitude will then increase (instead of dying away)
until it reaches some peak value, when there's usually some hiatus
before the whole lot starts off again.

Incredibly uncomfortable. Dynamic instability, caused by excessive
static stability raising the boat's natural rocking frequency to
match the wave frequency.

JimB

"News f2s" wrote in message
...
No, I meant stable! Take the top weight of the mast off, and the centre
of gravity of the boat drops down, so the righting moment goes up.

Add to that the fact that the mast's inertia has gone, and the boat now
reacts very much more quickly to any disturbance - then rolls back and
forth, one cycle every couple of seconds.

"Capt. JG" wrote in message
...
Nope. It doesn't work like that. You would think it would, but it
doesn't. We had a dismasting on the bay (one of my students). It was
caused by a hairline crack. They were pounding up to the Golden Gate area
from Alcatraz on a typical 20-25 knot day in 3-4 foot chop. After the
mast came down, the boat was almost uncontrollable as it drifted back
down hill. Finally, after they cut away the mast, they were able to motor
back to the slip, and according to the crew who we interviewed, it was
the worst part of the trip. The boat was so unstable a couple of people
got sea sick.

You said it yourself in your final paragraph... that is the definition of
instability.

For clarity, I'm only talking about the rolling stability. There are two
types of roll stability we're perhaps confusing here.

First, static stability is the tendency of a boat to right itself once it
has been heeled over. After a single disturbance the boat will rock side
to side a couple of times until the motion dies off. If static stability
decreases, the boat will right more slowly after a disturbance. If
statically unstable, the boat will roll upside down. If, on the other
hand, static stability increases, the boat tries to right itself more
quickly than before. The rocking motion will speed up.

If the rocking motion dies away, you have dynamic stability too.

Dynamic instability is when an oscillation builds up instead, until either
something breaks or there's a breakdown in the circumstances. The best
example of this is the 'death roll' enjoyed by a downwind boat with too
much sail up for the wind. Our relevant example is when the wave frequency
disturbing a dismasted boat is the same as the (quicker) tendency to rock
back and forth. The rocking amplitude will then increase (instead of dying
away) until it reaches some peak value, when there's usually some hiatus
before the whole lot starts off again.

Incredibly uncomfortable. Dynamic instability, caused by excessive static
stability raising the boat's natural rocking frequency to match the wave
frequency.

JimB

Ah, well, then for the other kind of stability, you should get a multi. :-)

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

On Sun, 29 Jan 2006 11:18:35 -0000, "News f2s"
wrote:

Add to that the fact that the mast's inertia has gone, and the
boat now reacts very much more quickly to any disturbance - then
rolls back and forth, one cycle every couple of seconds.

That was my experience, quicker motion and greater amplitude of
rolling. Very unpleasant.