Boat Stability Flashcards
2 principle types of stability
Gravity and buoyancy
Gravity- downward force on a boat
Buoyancy- upward force on a boat
Or
Longitudinal (fore - aft)
Tends to keep the boar from pitching end over end
Transverse (Athwarship)
Tends to keep the boat from rolling over (capsizing)
2 primary forces that affect the boats stability
Static (Inside boat)
Flooding or grounding
Adding weight on one side of a boat centerline or above its center of gravity, usually reduces stability
Dynamic (Outside boat)
Ice, Current, Waves
Strong gusts of winds or heavy seas especially shallow waters may build up a dangerous sea tending to capsize a boar.
Indicators of an unstable boat
Listing, healing,
What are some causes for the loss of stability in a vessel?
Free surface effect
Baffles - the movement of a liquid (fuel, water) to one side of a partially filled storage tank as the vessel rolls from side to side. This shifting of weight is very dangerous to a vessels stability.
Downflooding
Water enters the vessel through an opening in its hull or superstructure due to the vessels trim, heel, or submergence. Reduces the vessels stability.
Free communication with the sea
Righting moment
The measurement of its tendency to return to an upright position after being tilted by an external force
Restrictive Casualty
Discrepancies that restrict the operation of the boat such that it can perform some activity but not all activities safely, can only be operated if the OIC has issued a written waiver. A verbal waiver is authorized, as long as it is followed with a written waiver within 4 hours.
Disabling Casualty
Casualties are those which make the boat not serviceable.
Major
Discrepancies that degrade the effectiveness of the boat to perform one or more missions. Shall be documented and a plan to correct these discrepancies shall be formulated and carried out by the unit.
