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Re: [Phys-l] hurricane question



Nice experience sailing! My wife's former boss and his friend once rented a time share on a 32 foot sailboat and he took me along several times up and down the Barnegat Bay which is long but narrow. So, while it was a learning experience I never really got the *feel* for sailing.
Yes, the large cruise ships have several stabilizers. The current designers and ship builders (the Royal Caribbean fleet is built at the Aker Shipyards in Norway) build the ships with pitch and roll stabilizers all computer operated with automatic sensors. We were attending an ice show onboard during the time they were steering around the hurricane and no one fell down from the movement of the ship. They even have a minigolf course, and that is really challenging in rough seas!
We were constantly changing course and our track kept heading in a general direction around the hurricane at about 7 K. The ship's tv station showed this course and it looked like what you would see on a pirate movie when Johnny Depp is trying to avoid the British fleet by zig-zagging all over the sea. By the time we got to St. Thomas the hurricane was way out in the Atlantic. The itinerary was supposed to be Antigua, St. Marteen and then St. Thomas, but Omar struck St. Marteen and Antigua head on and damaged the port so these visits were avoided this time by order of the US Coast Guard. As the Captain said, "I will not attempt to take this $700 million ship and it's precious cargo... you folks... into port at St. Marteen with 10 foot swells and a damaged dock."
Ever the inquisitive teacher, I looked out for and eventually saw the volcanic island of Monserrat. On a previous trip we saw it spewing ash and smoke as we passed in daylight. But this time we approached the island from about 10 miles away at dusk and while the cone was evident I couldn't see any activity. (Wikipedia says there are still over 4000 people living there.) I did get some neat photos however and showed them to my class.
All this has nothing to do with physics but it's interesting nevertheless. Sorry for the diversion, folks.

Marty


On Nov 8, 2008, at 2:54 PM, John Clement wrote:

Large ships may be more stable, but some small ships can also be very
stable, but not in a hurricane. Sailing ships do not roll much when the
sails are up. I went on a very small ship aroung the Bahamas with a tiny
passenger capacity, but it was a sailing ship. It sailed at night, but had
an engine just in case the winds were not good. So at night we had a good
rest with only a little gentle rocking. But during the day it put down
anchor and then it wallowed. But we all jumped into the ocean to either
dive or snorkel around the fantastic coral formations.

The one problem with sail is that if you have a good breeze in the early
morning, half of the ship rolls out of the bunks, while the other half
snuggles in.

I was under the impression that large ships also have a stabilizer to dampen
the rolling. Sail only dampens the sideways roll. And of course we steered
well clear of a hurricane, and raced it to Miami. But it didn't follow us.

John M. Clement
Houston, TX



Jack,
I looked up the size comparison of the Nimitz class carriers and the
current fleet of cruise ships. We were on the Adventure of the Seas
(Poyal Caribbean). That ship is 1020 feet long and has a tonnage of
137,000+, top speed of 22 K. This is what they call the Voyager class
of ships which has several other sister ships all built between 1999
and 2002. Royal is now building the largest cruise ships called the
Oasis class which will be 1181 ft with GNT = 220,000. The QM2 by
comparison is 1132 ft and GNT 148,000.
Wikipedia lists the Nimitz carriers as 1115 ft and 104,000 tons with
top speed of 30 K.

These cruise ships are remarkably stable and in 20 ft swells in the
fringes of Omar the ship hardly ever *rocked and rolled*. We once
cruised the north Atlantic out of New York on a smaller ship, the
Nodic Empress (since rechristened but I don't recall the new name) to
Bermuda. Now, that was a real *rock and roller* making the entire
dinner table retreat to their cabins the first night at sea. My
friend and I were the only ones left *alive* at the table at the end
of the evening and even my wife, intrepid sailor that she is, was in
bed that night by 7 pm.

On our previous cruise (Voyager of the Seas) they had a complete
oceanographic lab on board and we jumped at a chance to go on a tour.
The University of Miami set it up with a team of scientists and the
only thing the cruise line demanded was that they give tours daily for
passengers who signed up. Otherwise the scientists and the lab were on
board *rent free* for the week. Fascinating! My wife jokingly
asked if they needed teachers to give tours. They actually said yes,
so I wrote when we got home, sent them my credentials (no ocenaography
experience needed, so they said), but we never heard from them. Oh,
well... I suppose we will always have to pay our own way.... ;-)

Marty


On Nov 8, 2008, at 1:31 PM, Jack Uretsky wrote:

Hi Marty-
I was struck by "these huge cruise ships". As one who has been
through a numbeer of hurricanes in the Atlantic, mostly on 30,000 ton
aircraft carriers, your cruise ships are not that huge. Nothing, in
fact,
made by man is THAT huge, when mother nature really gets into one of
her
frenzies. Our carrier was a midget, in the late forties, compared
even
then with the Midway class, and one of those, steaming in our
company, had
aircraft wasshed off the flight deck. We pitied the poor destroyer
sailors, tossing and bobbing as they kept their stations on the edge
of
our task group.
I think that Brian summed up the present state of knowledge of
hurricane dynamics pretty well. Weather prediction is one of the
future
targets of future large scale computer evelopment.
Regards,
Jack



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Forum for Physics Educators
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_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l