Matteo V wrote: ↑
Tue May 21, 2019 12:50 pm
rynhardt wrote: ↑
Tue May 21, 2019 9:44 am
If you are comfortable with those assumptions then I can comment, otherwise I can't.
Go for it. You have got me curious!
So.. under fairly steady state conditions, while under kite power, and edging on a typical reach/tack, the waterline under the board looks like the photo below.
The board is providing lift against the water through a combined angle of attack against both the direction of travel and the pull of the kite.
The waterline is probably a good indication of equal pressure, and is a visual confirmation of the spray root as per Savitsky fig 2.
We can transform the coordinate system a bit to reflect the pressure distribution, and the section in contact with the water can then be approximated by a series of flat planes orthogonal to the pressure distribution.
I drew some rectangles to indicate the series of flat planes - note that they are aligned to the pressure distribution and not aligned with the coordinate system one would typically assume for the board.
The red and orange rectangles are the areas of highest pressure (and lift, and drag), so I'll chat more about them in the next post.