Deadrise and Chine Flats

[CET]

When calculating the degree of deadrise on a planning hull with chine flats (lifting strakes), should one include the angle of the bottom panels only , or should the angle be calculated from the outer edges of the chine flats, which would seem to be the “effective deadrise”. Just wondered whether there is a customary way of doing this. Thanks.

[RANCHI OTTO]

I take a corrected deadrise angle as follows:

Deadrise correction factor = (b1 + b2 + b3)/(B/2) > percent of flat length to half boat breadth

Effective deadrise = deadrise x deadrise correction factor

example:

Deadrise = 22 deg.
B/2 = 2 m
b = 0.05 m ( angle = 0 deg.)
Total number of b = 3

Deadrise correction factor = (0.05 x 3)/2 = 0.075 or 7.5%
Effective deadrise = 22 - 7.5% = 20.35 deg.

[CET]

Ranchi Otto,

Thanks very much for the information!!

Charlie