yes you are right! both are bending water - maybe we just have a terminology mixup. I normally use "wrap" to mean water wrapping the rails and "flow turning" to mean water following/being bent by the hull contour. So if you you mean that water "wrapping the hull" creates lift then I am in agreement with you. I am sticking to my guns that water wrapping the rail creates downforce not lift - but maybe you were not saying that as I originally thought? --> edit I may have contradicted myself with what I wrote below about that! Food for thought."flow turning" is essentially the same as "wrap"
That experiment is a nice illustration of what I call "flow turning", bend water to the left - force in the opposite direction created to the right.I did the spoon experiment for you. See how the water "wraps" around the spoon? You can feel this in your hand as it grabs the spoon, moving it to the right.
This "warp" can be thought of as the rail holding in to the face.
Remember, this wrap is a long spiral. If the radius is too tight, the water won't wrap and will release, ending the forces at work.
Its also a nice theory on "hold" - the larger radius rail allows the water to wrap not release - which means rounded soft rails hold better because they get pulled into the face. That's what you are saying isn't it?
Except, its just a "nice theory", the boars I have ridden tell me the exact opposite - the chunky rounded rail boars I have owned seem to have the rail pushed out of the face causing the board to sit more on the surface and feel skatey - less hold (which can be fine for a groveller). My pinched rail boars allow me to penetrate the wave face more with my rail, get more purchase from the hull thus give me more hold. Experience trumps theory.
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