Quote from: Dommo on April 05, 2020, 01:02:51 pm

Quote from: stevez on April 05, 2020, 05:43:30 am

I've decided there's a lot of room to explore for a board that still floats, can be kneeling started. Maybe a sinker next time!

Here is a draft design. Dimensions are 4'6" x 24" x 5". So it's really short, twintip kiteboard length, and reasonably narrow, but still has 90L volume which should be plenty for my 76kg.
It's really ugly and boxy with square straight rails (though the edges won't be quite this sharp).
Not cutting away the edges and not having beveled rails (which appears to be current generally accepted best practice) maxes the volume and spreads it to the perimeter as much as possible.
There is good rocker / scoop but by starting it further forward also maximises volume - the back 2/3rd is pretty flat. This is a tradeoff.

The main design principle is any part that displaces water as it moves does so by pushing water down.
So any forward speed will push the board up and the water will go underneath.
It should hopefully plane at a very low speed and lift off easily.
Pointing noses mean pushing water to the side, which is a waste of energy for a wingfoil board. Sorry @stenninger  (though your board wins hands down on the looks department!).

One of the nice things about my own build is I get to test out my armchair theories 

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 Bevels are best known for allowing the board to release from the water easier, BUT, their lesser known characteristic is that they are also very important for providing directional stability - i.e. moving in a straight line. No bevels and a totally flat hull will be very hard to keep moving in a straight line, especially when pumping the board. The end result will be that the board will skew left or right rather than move straight. The greater the angle of the bevels (i.e. the more vertical they are) the more they help with directional stability, but too vertical (100% vertical = no bevel, or, a normal surfboard type rail) and the water wraps around the rail and will prevent release.
But then again, what the hell do I know? If I could build my own boards I would also try to buck the design trends. Respect to you!!!!!!!!!!!!

Hi Dommo,

In my experience, they do the opposite. If the bevel continues all the way to the tail, it will let the board slide sideways, making it harder to track upwind.   

I also don't totally agree with your comment about the water wrapping around the rail and preventing release. If the Rail ends sharp it will release better. 

--
Gunnar

What I said was based on discussions with Jimmy Lewis while deciding on the design for a custom board he's making for me. I say for me - it's actually the same shape as his Flying V production board - he just changed the size slightly to suit me better, but he explained why he made his boards the shape he does. I thought I understood it...apparently not

Pointing noses mean pushing water to the side, which is a waste of energy for a wingfoil board. Sorry @stenninger  (though your board wins hands down on the looks department!).

I did make that one last year and I'm still using it.
So I will have a direct comparison.

Quote from: stevez on April 05, 2020, 05:43:30 am

Pointing noses mean pushing water to the side, which is a waste of energy for a wingfoil board. Sorry @stenninger  (though your board wins hands down on the looks department!).

I did make that one last year and I'm still using it.
So I will have a direct comparison.

So cool that you made this shape a year ago, and from the action shot it looks like its effective - nice!!! I'd love to hear how your 2 board designs compare. Let us know when you get the chance to ride your new 'pointy' board Is the new one smaller?

... I'd love to hear how your 2 board designs compare. Let us know when you get the chance to ride your new 'pointy' board ...

ok, got a chance to try the new 92l board today in changing conditions with my 6m wing.

I love it!

I think I can pump it up even a bit earlier than the larger 107l board. This might be caused by the 2,5kg less weight and the less volume and weight in nose and tail.
It feels pretty playful... nice!

92l seems to be the lower limit for my weight if the wind drops and one tries to get home in choppy conditions without enough (almost no) power from the wing.
But even this works pretty well.