Kiteforum.com

Follow up,
Got a couple of 9.1m jumps last week for a new personal best so stoked! Found it actually goes upwind pretty well, took a while for my technique to adapt because my previous design board goes upwind with hardly any effort at all. The high rocker does exactly what I wanted, when I'm picking up lots of speed but through chop the front lifts nicely and I don't get those surprise flicks off. It's a bit different with bubbly surf, my longer board was easier to ride through that with but the new board is easier to jump over it with anyway!

Think about those tips with sharp corners. Look at what they are doing when you ride.
Amazing you built that in what looks like your living room.

TomW wrote: ↑

Sun Apr 22, 2018 9:42 am

Think about those tips with sharp corners. Look at what they are doing when you ride.
Amazing you built that in what looks like your living room.

Here's a comparison of my last 3 design's outlines:
F2 is brilliant up wind and fun on waves. I get massive accumulated jump height on this board.
F3 I can go faster without getting caught by chop, it carves harder because of the high rocker.
F4 is in construction. Narrower again but fuller tips for that last bit of pop.
None of them have particularly sharp corners but only the F4 has no concave and is suited for flex.
What do you mean by "sharp corners"?
Do you mean the underside edge or the angles where I'm joining the rails? Soft under edges of rails bring in the "Coander effect", which will make the water follow a round corner rather than leaving cleanly.

Just round those sharp corners in the outline. They are non functional and catch water.

TomW wrote: ↑

Wed Apr 25, 2018 10:00 pm

Just round those sharp corners in the outline. They are non functional and catch water.

TomW as in TW surfboards?
It's a twin tip I'm designing, not a surf board. If I wanted drag from the coander effect then I'd redesign it. The rounded end board tapers from the top so it doesn't induce coander effect. (hard under side corners)
Conventional hull boats have smooth sterns and speed limitations. Planing hulls have sharp sterns and can go much faster.
I suggest you look up the coander effect so you can resolve our difference of opinion.
Here's a link showing the effect over a spoon: https://www.youtube.com/watch?v=AvLwqRCbGKY
From the moment a stream of water starts flowing along a surface, that stream will be resistant to separation from the surface while the path over the surface is smooth. Any trailing edge of a kite board will entrain water around curves, more so with soft curves.
By breaking up the perimeter of my board I'm also breaking up the flow of water where it would otherwise stick to the rail(smooth rail outline) or flow around the back and up (rounded under edges.)
I believe this effect is used on parts of the sides of surfboards intentionally for grip but I'm avoiding it on purpose in my last two designs.
Makes it easy to fit kwila rails too