Hull speed calculation

[fredrosse]

heel angle

on a reach or a run

hard on the wind

windward

These look like English words, but are Greek to me??

Just read in this months’ ASME publication about a sailboat making slightly over 65 knots, that’s over 75 MPH, and that’s FAST! Does not look like any sailboat I've ever seen, with a solid sail no less.

[gondolier88]

The America's cup class catamarans now regularly cruise at 50mph with top speeds of 70+mph, but with a waterline length of 45ft, but a beam across one of the hulls (they never achieve high speed with both in the water) of about 30-40". The 'solid sail' is in fact a carbon fibre wing- instead of a horizontal wing on a plane giving vertical lift, it is a vertical wing giving horizontal 'lift', ie. forward motion. However, they require real skill to handle- the heel angles of these beasts is astounding, and the 'dry' hull is often 20ft+ out of the water, it only takes a gybe to go wrong and that 'wing' will pitchpole the boat over it's stem- you try hitting the water at 40+ feet and 50mph, that's going to hurt! I think there was loss of life last year in fact.

Greg

[Albert]

Applied to my "Min Deern" (Elliot Bay, LWL 21' 6", Displacement 2400 pounds), the Gerr's formula renders a hull speed of 8.94 knots... I might need to take an extra factor out of some orifice... Even though this formula introduces the variable "displacement", it still disregards the actual shape of the hull. I would rather stick to the well known formula (1.3 ... etc) which renders good results for our type of hulls under "normal" load conditions.