A question:
Question Roy!
When you surf 4-5 foot of your board is almost always out of the water not being used for anything. Seems like a waste to me. Whats the logic?
Your premise that the part of the board which is out of the water is doing nothing is incorrect.
Firstly one needs to realise that planing craft ideally change the amount of wetted surface area used according to speed... more area when going slowly less when going faster. so, a surfboard which is intended to be used over a wide range of speeds needs to have a large area available and to reduce it as speed increases.
One could still argue that the nose area which is out of the water at higher speeds is useless at that time and is merely being carried along for use when the board slows down. Of course the area is being carried for use at slower speeds but it also serves other purposes even when out of the water.
One of these purposes is as a counter weight. Mass in the nose balances mass in the tail, making a well balanced board. The counter weight aspect is also used for control and drive, it gives motive power to the nose of the board which can be used to drop the board down the face ( when trimming for example) when forward rail length is released. surfboards are powered primarily via gravitational energy, this energy is gained in proportion to mass and in the position where the mass resides.
Another purpose is aerodynamic lift, the nose acts as a wing.
