# Nautical/Stability/GM

posted by .

I have previously understood a ship's GM determined her role period. However I have just read that if weight on the centreline of the ship is moved laterally outwards to the sides of the ship this will slow the ships roll ie. increase its roll period. I understand the GM of the ship will not alter under these circumstances because as the weight is moved laterally the COG will not change.

Comments please.

Thanks

Mike

• Nautical/Stability/GM -

GM is not changed, but the righting arm is. If you move G/2 to each side perpendiular to GM, so that G is unchanged, then heel the ship, then draw (or calculate the righting arm for each G/2 mass), the NET (one side is positive, one side is negative) righting arm is increased, due to the distances from each G/2 to the vertical BM line. One then has has a net increased righting arm, with a decreased mass (G/2). The ship will be not so tender, and have a longer roll period.
The idea is to make a vessel less tender so that it does not take on the shape of a high wave and roll over, but rolls more slowly. In practice, shifting fuel ballast or cargo in heavy seas is dangerous and is usually to be avoided.

## Respond to this Question

 First Name School Subject Your Answer

## Similar Questions

1. ### CALCULUS

At noon, ship A is 40 nautical miles due west of ship B. Ship A is sailing west at 23 knots and ship B is sailing north at 19 knots. How fast (in knots) is the distance between the ships changing at 5 PM?
2. ### Calc

At noon, ship A is 50 nautical miles due west of ship B. Ship A is sailing west at 15 knots and ship B is sailing north at 18 knots. How fast (in knots) is the distance between the ships changing at 6 PM?
3. ### calculus

At noon, ship A is 30 nautical miles due west of ship B. Ship A is sailing west at 25 knots and ship B is sailing north at 25 knots. How fast (in knots) is the distance between the ships changing at 6 PM?
4. ### calculus

At noon, ship A is 10 nautical miles due west of ship B. Ship A is sailing west at 15 knots and ship B is sailing north at 15 knots. How fast (in knots) is the distance between the ships changing at 3 PM?
5. ### calculus

At noon, ship A is 10 nautical miles due west of ship B. Ship A is sailing west at 15 knots and ship B is sailing north at 15 knots. How fast (in knots) is the distance between the ships changing at 3 PM?
6. ### calculus

At noon, ship A is 10 nautical miles due west of ship B. Ship A is sailing west at 15 knots and ship B is sailing north at 15 knots. How fast (in knots) is the distance between the ships changing at 3 PM?
7. ### Trigonometry

Navigation A ship leaves port at noon and has a bearing of S 29° W. If the ship sails at 20 knots, how many nautical miles south and how many nautical miles west will the ship have traveled by 6:00 P.M.?
8. ### Calculus

At noon, ship A is 50 nautical miles due west of ship B. Ship A is sailing west at 19 knots and ship B is sailing north at 24 knots. How fast (in knots) is the distance between the ships changing at 3 PM?
9. ### calc

At noon, ship A is 30 nautical miles due west of ship B. Ship A is sailing west at 17 knots and ship B is sailing north at 16 knots. How fast (in knots) is the distance between the ships changing at 6 PM?
10. ### Maths

At 3 pm ship A is 20 nautical miles south west of ship B. Assuming that the y- direction is north and the x-direction is east, the velocities of ships A and B can be expressed in knots in vector form as Va=(12,+5) Vb=(-8,-9) (i) Find …

More Similar Questions

Post a New Question