2007-03-01 02:15:36 · 5 answers · asked by Anonymous in Cars & Transportation ➔ Boats & Boating
Free surface causes a virtual rise in the vessel's centre of gravity. It is present when the liquid in a tank is free to move, it can be removed by filling or emptying tanks. As the vessel is inclined, the weight of the liquid in the tank shifts towards the low side. The centre of gravity moves in the same direction and parallel to the weight that is shifted. The more slack tanks you have on a vessel, the poorer your stability.
The effects of free surface depend upon the dimensions of the surface of the liquid in a partially full tank and the volume of displacement of the vessel.
I am a ballast controller on a semi submersible drilling rig in the North Sea.
2007-03-01 02:38:28 · answer #1 · answered by Alex Y 1 · 2⤊ 0⤋
While it is common to think of free surface as liquid in a tank, it is correctly described as anything that can move about when a vessel pitches and rolls. Fish in a hold, water on deck and in a bilge, loose equipment. As for the effect on stability, try this: Put two bags of sand in a wheelbarrow and try pushing it around. Then take the sand out and fill the wheelbarrow 3/4 full of water. (About the same weight as the sand) Try moving the wheelbarrow now.
2007-03-02 00:27:02 · answer #2 · answered by Campo 4 · 0⤊ 0⤋
As a boat rolls to the side the side that is deeper in the water generates more buoyancy and keeps the boat stable. If there is loose material that can move in the boat this will move to the low side and cancel out the self righting effect, possibly leading to a capsize. This is a BIG danger with boats like ro-ro ferries with wide open decks.
2007-03-02 04:17:10 · answer #3 · answered by The original Peter G 7 · 0⤊ 0⤋
The answer from Alex y is as good as i could have put it really. It was due to a small amount of water in the car space on the Herald of Free Enterprise shifting that caused it to sink. Its amazing what a small amount of water across the full length of a ship all moving to one side at once can effect its stability.
2007-03-01 19:51:20 · answer #4 · answered by 6 hail marys 2 · 1⤊ 0⤋
The answer to this question,given by Alex Y says it all!
2007-03-01 15:20:52 · answer #5 · answered by rockdodger 3 · 1⤊ 0⤋