# Cruising the Seas

1. Mar 2, 2005

### trubey

Hello.

This is my first message on these boards, so I apologize if I repeat anything that has been discussed before. And if I'm in the wrong section, I won't be upset if you redirect me elsewhere.

I belong to a message board aimed at people who take frequent ocean cruises. One subject which keeps cropping up is that the best rooms (i.e. less rocking-and-rolling) are in the center of the ship. I've been wondering if this is a myth. It sounds logical, though. So, on my next cruise I would like to experiment by checking different decks, front and back.

Finally, my question: Is there some sort of instrument which I could use to detect the relative stability or motion?

Thank you, physics experts! Susan.

2. Mar 2, 2005

### FredGarvin

I would think that if you are talking about a rocking motion (the same as a roll along the longitudinal axis for aircraft) then the theory could hold water. Sorry for the pun. If you were talking about pitching motions, I would think they might be a bit less, but you would still see them.

As for a device to detect the motions. That's an easy one. Get a clear, glass bottle and fill it half full with liquid. Use a marker to draw a line at the water level all the way around the perimeter of the bottle when it is calm and perfectly level. Now, simply set it down in the area you are interested in and watch the water level in relation to the marker line on the bottle. The rocking and rolling of the ship will cause the water to level to change (i.e. tilt) various ways inside the bottle. If you want, make small marks on the bottle at the locations the water level moves to at the various locations on the ship. That will give you a comparisson between locations.

Hope this helps.

Last edited: Mar 2, 2005
3. Mar 2, 2005

### Staff: Mentor

The reason motions are less noticeable at the center of gravity is that there is no displacement. Ie, if you are to the left of the center of gravity and the ship rolls right, not only do you roll with it, but it lifts you as well. Same goes for pitch. The center of gravity of a ship is generally at the centerline (duh), near the waterline, and 2/3 of the way back. Since most cruise ships have stabilizers, I'd be more worried about pitch.

I don't really get seasick, but the closest was when all the way forward in a ship that was pitching so much I felt like I was going to leave my feet.

Last edited: Mar 2, 2005
4. Mar 2, 2005

### Wudan

Ever try skipping down the hallway of a cruise ship when its really movin.
Here's a hint you might want to wear a helmet.

5. Mar 3, 2005

### trubey

I just wanted to give a thank you for your responses.

Now I know that when I do my testing with my jar, I should be sure to wear a helmet if I leave the centerline.

OOps, as I reread the responses, I just thought of another relevant question: As my ship travels from Europe to America, are waves more likely to be in one direction or equally distributed?

Susan.

6. Mar 3, 2005

### motai

That sounds like it probably depends on the current at that particular time, that is, unless there is a particular place where strong waves are constant (the seas south of Tierra del Fuego for example).

7. Mar 3, 2005

### Staff: Mentor

For the most-part the waves will follow the winds and currents, which typically go clockwise in the north Atlantic. If your cruise is north-north atlantic (say, Denmark to New York, you'll be headed near directly into the waves for most of the trip. Diagonal south toward Florida and they'll come at you from the sides, but you'll have several days of dead calm (barring an actual storm) in the middle of the ocean.