calculating planing surface area

[yagon]

I'd like to build a new sailboard with a skiff-like bow (vertical stem). I've written the following articles about my concept:

http://www.lbwindsurfing.com/raceboa...eboard-design/
http://www.lbwindsurfing.com/raceboa...oard-design-2/

I'd like to do some calculations on the surface area required to support various weights (while the board is on the plane), but it's been 20 years since I studied fluid dynamics.

Can anyone help with the formula to do such calculations?

[Doug Lord]

These papers should help-"Drake 2" has the formulas for calculating planing area:

[yagon]

thanks for this feedback - it is most helpful. Some questions:

1. The formulas to calculate the lift from the planing surface - how do these compare to the formulas for other non-sailboard hulls?

2. Where can I obtain a copy of the figures listed in teh first document?

[Doug Lord]

1) I don't know-this was all I needed-and I haven't worked with it yet. There are MANY threads on this forum about planing....Drakes formulas are a bit simplified for the case of a nearly flat board...The simplest way to proceed is to watch and measure actual windsurfers. Get the exact weights, a Davis windmeter and preferably a GPS speedometer and you can get a pretty accurate idea of what is required in terms of planing area on a board. I would use that info as your #1 reference and back it up with Drakes formulas.

2) You could try e-mailing Jim Drake-his e-mail address is at the end of the document. He has not responded to my e-mail.