KT, Dave Kalama and Jimmy Lewis all well understand that sharper rails produce water release and rounder rails produce control through the water with water following the rail or sucking as some people on here like to call it. They have been using this understanding and balancing its subtleties for decades to get surfboards to work well in turns and on a steep wave. In fact this is the basis for design (physics) in all naval architecture for at least 100 years and can be seen in both displacement and planning hulls but is more critical in foils and propellers where water is moving at higher velocities. Think water ski's, speed record setting windsurfers, pipeline surfboard guns and particularly fins where control or release is a higher priority.

A cutback on a surfboard uses the softer rails around the front foot to allow the board to engage with the water and provide some control into the turn buy grabbing the water (sucking) and as we complete the turn we transition to the back foot where the rails are sharper and this allows us to pull out of the turn by releasing the water from the sharper rail on the tail. The best foil surfers like surfboard rails (soft) around their front foot because in white water hits where the foil become inactive you want the board to provide control in the foam so some sucking is good. Again subtle and a balance. Now introduce the fact you are touching down from a foiling turn and the foil is still mostly in control but needs some temporary support (control) but not too much. Some might like more support by sacrificing release. I learnt to foil by mounting a foil to a twin tip and the sharp edges provide no control before being on foil as it releases on the whole edge as designed and definitely can't track to give support so no directional stability.

I am not disputing what you are all feeling and enjoying in the boards that favor your style and circumstances but its not because of the design elements you might think. Rails, bottom surfaces, rocker line, volume, volume distribution, flex are all working together to balance release and control at different speeds angles and circumstances.

Taavi you board works better (releases) standing further back because you are likely engaging less of the round sucky rail and bottom shape.

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AnyBoard said..
I am not disputing what you are all feeling and enjoying in the boards that favor your style and circumstances but its not because of the design elements you might think. Rails, bottom surfaces, rocker line, volume, volume distribution, flex are all working together to balance release and control at different speeds angles and circumstances.

Taavi you board works better (releases) standing further back because you are likely engaging less of the round sucky rail and bottom shape.

This is what I am trying to explain. Before writing off a certain design one needs to ride it and really understand it. Find out what volume works the best for a particular shape / rider's weight, where are the touchpoints that behave well for that shape, etc. The fashion of standing very far forward on a board is one good example. It might work well with some shapes, but would ruin the riding characteristics of another one. And then, of course, and perhaps even most importantly - really find out what kind of riding style one is after. Because different gear provides different riding sensations, and this is what makes foiling beautiful and keeps it interesting, I think.

I guess you did not listen the podcast I was referring to, @ 58:00 minutes, open.spotify.com/episode/4qmYIf3cBdlqFcjrlARmNO

Keeping the thread alive. Stumbled upon yet another board with a nice shape, with displacement style nose and round rails going pretty far until the shape turns into having more flatter surfaces in the back. Nicely pulled in nose and tail. I wonder why brands keep coming up with such designs, if people with no experience riding with such shapes find such rails and bottom shapes "sucky" and not good "because of physics".



Oh, and this is how such bottom shape behaves when touching the water. I see no problems.

I look forward to testing that board in the spring actually.
Different shapes for different styles and desires.