Originally Posted by maytrix
If it really was that close, then I'm not impressed and don't think it took guts. It took stupidity...
I don’t believe that “squat” can be precisely calulated; only very nearly estimated.
The "squat effect" is the hydrodynamic phenomenon by which a vessel moving quickly through shallow water
creates an area of lowered pressure under its bottom that causes the ship to "squat" lower in the water
than would otherwise be expected. This is due to a reduction in buoyancy caused by a downward hydrodynamic force created by flow-induced pressures. It is caused by similar forces as lift
in aircraft, except that the low pressure area is beneath the hull
. It can lead to unexpected groundings and handling difficulties.
Squat is believed to have been one of the causes of the 1992 grounding of the Queen Elizabeth 2 (QE2) off Cuttyhunk Island, near Martha's Vineyard
. At the time of the QE2's grounding she was reportedly traveling at 24 knots (12 m/s) and her draft
was 32 feet (9.8 m). The rock upon which she grounded was an uncharted shoal later determined to be 34.5 feet (10.5 m), which should have given her room to spare, if not for the "squat effect." NTSB investigators found that the QE2's officers significantly underestimated the amount the increase in speed would increase the ship's squat. The officers allowed for 2 feet of squat in their calculations, but the NTSB concluded that her squat at that speed and depth
would have been between 4.5 and 8 feet.