planning hull running surface

[gtflash]

How much wetted area does a planning boat hull run on when at speed?

Bit of an open ended question, but i have spent ages looking at youtube videos, of racing boats and im still undecided. Id guess at less than 1/3

 

[Mr Efficiency]

1/3 of what, the below chine area ? The below static waterline area ? Depends on a number of things, principally the speed, weight of boat, hull shape, trim angle etc. Why do you want to quantify this ?

 

[Olav]

gtflash,

you might want to get familiar with Savitsky's 1964 method for estimating the running attitude (trim, rise) and resistance of a prismatic planing hull. There are also several approaches to include non-prismatic (warped) hulls as well.

A member of this forum (Dingo) did a superb job and made an Excel spreadsheet which you can download here.

 

[gtflash]

Thanks Olav, I will research more on that.

Mr efficiency, I was thinking high speed craft, +70mph. I kind of decided in my head that at lesser speeds, hull sizes and weight would create different resolutions, however over a certain speed all hulls would be balancing on an equally small surface as a % of running surface. Yet watching videos it didnt appear i was right