Marin wrote:Whether the Bernoulli effect on each side of the hull reduces the resistance of the hull to the water I have no idea.
In the pressure domain surrounding a hull there are high pressure areas forward and aft and a large low pressure area midships. This is what causes "squat" and "bank effect."*
Squat is the phenomenon of the draft increasing with speed in shallow water. Bank effect is the tendency of the ship to yaw rapidly when passing close to another ship or the bank of a river or canal. It is what really screws people up when trying to rapidly motor out of the Ballard Locks and they appear to be stuck to the sidewall.
The effect doesn't suck the boat forward and reduce the power requirement, just the opposite, it takes more power since the draft increases. In a large ship, you can tell from the depths of the engine room when the ship has entered shallow water as the vibration increases a great deal and the power output increases to maintain the same shaft revolutions.
"But whether it does or doesn't, at 8 knots and 27,000 pounds it's not going to make a g*ddamned bit of difference to my boat or my fuel bill."
It would if you ran around in shallow water all the time. You might not care and it might not show up as a big increase in fuel consumption but it would make a difference.
-- Edited by RickB on Thursday 7th of January 2010 06:44:21 AM