SQUAT

["Arthur H. Smith" <arthurhsmith@compuserve.com>]

Last night I watched a program about the investigation into when  the QE ll
ran aground off Marthas Vineyard. The Captain and pilot both followed
proper procedure and the only thing left was the charts showing the depth
at 39 feet. The QE ll has a draft of 32 feet so there should have been
adequate clearance. At first it was thought the charts could be wrong so
NOAA redid the depth sounding and found a few spots a little less than 39
feet in depth.

The final finding was, as a ship moves through the water the force of the
water moving under the ship creates a hole around the ship in the water and
the ship actual sinks. While the water level along the water line stays the
same the depression at the water line is closer to the bottom. This
phenomenon is called "squat," so as a ship moves it squats down in the
water. The full extent of the effect was not totally understood so at 25
knots the QE ll sank 8 feet and the 7 feet of clearance disappeared. Hence
it ran aground in water that was 39 feet deep.

It ended with the announcer saying that after 20 years experience the
captain of the QE ll didn't know "squat."