Just an observer of the art of board building but do know something about cavitation and venturis. On cavitation...don't know if you could create a bottom design that would create the pressure to compress the air bubbles enough to create true cavitation. The entrained air coming into the slot is going to escape in the direction of least (negative) pressure, which will be in the direction of the water flow off the bottom and not into a compressed pocket (positive) on top of the slot. Air venturis or vents on top of the slot is interesting but will require an air entrance entering perpindicular to the fluid entrance/exit into the venturi. Venturis are touchy animals though and require a constant fluid flow in most cases to keep the vacuum through the air side. With the constant shifting of the board's bottom don't know if you could keep this vacuum. With air "vents" without venturis on top of the slot I would assume that you could relieve the postive pressure on top of the slot and create a negative pressure at times. Don't know what type of effect you are trying to achieve but think this would cause the board to sit down or get sticky.headwax wrote:Quadfin, Bud
with a tri I think you'd have some strange effects happening around the centre fin - eg what I think is "cavitation".
As far as needing more horse power? Every time I see a body board riding hooting along I realise how little planing area we need. On the opposite spectrum, who would have thought a barefoot skier could, well... barefoot ski?
Then there's modern windsurfers. The more planing area they have the slower they go.
In industry, specifically water treatment, we use Dissolved Air Flotation (DAF) to create a blanket of very fine bubbles to create what is basically a flotation blanket. The fine bubbles create a surface tension (drag) because of the increased surface area of the fine bubbles. I have a unit that uses a venturi to create these bubbles and it requires at least 25 PSI of incoming pressure to create enough pressure drop to pull a vacuum through the air side of the venturi. Would think the creation of large bubbles would be more beneficial and achievable in a surfboard bottom, but not sure how to create or control those proper size air bubbles. Will cease rambling and get back to work.