What might be helpful to consider is if somebody defined “drive” --“someone” should be sure to include all possible factors— the fins: surface area, toe-in, number, configuration, flex, cant, foils; the board: rail contours, bottom contours, thickness flow, planshape outline, flex, tail shape; the surfer’s style: pumpy, coasty, back foot, front foot---- that all contribute to a surfer (or his/her surfboard!) converting gravity combined with forward wave motion into lateral motion down the line.
What I think is really interesting is what happens in terms of the thruster’s center fin’s leverage and stabilizing influence on the foward fins, how it adds its own surface area to the overall control surface area and simultaneously prevents the inside rail fin’s over-rotation/stall/cavitation when its angle of attack is increased during a bottom turn or pumps. It basically slows the pivot just enough to where that stall doesn’t happen or happen so completely and adds in its own lateral assistance so the rails can hold. The combined effect of all three fins and a back WP, along with concaved bottom, effective rocker, etc allow the rail to penetrate, hold in, and be useful throughout a turn as a lateral springboard, and all together produce hold and drive.
All of the opposing planes of the control surfaces (toed-in rail fin, center fin, bottom concave, rail) counteracting each other also produce drag, when trimming, or when straight-off, so the question really becomes one of passive “drive” or active. I think on active drive, pumping for acceleration, thrusters take the cake, for all the opposed control surfaces’ impart stability and you can smoothly transition force between them all (sometimes).
Maybe by deleting some of the leverage-induced drag, and keeping some of the leverage–quads may become more of a force to be reckoned with. Perhaps two smaller rear fins moved closer to the outward corners of the tail.
But anyway–if you mean active drive, a board that can be pumped explosively and controllably and speed added in by the surfer working against the combined control surfaces, you’re talking about a huge component of what allows all the turns and pivots of modern shortboard surfing, like the front tires’ camber that enables F1 race cars to initiate turns so quickly and corner so fast. Opposing control surfaces in effective sizes and configurations. So you move much toward the passive drive side of the equation, and you start robbing capabilities from Kelly, et al. Active drive = drag, and available speed and control. Passive drive = effortless speed.
If you think twins are the driviest, I think you’re really talking about passive drive: big speed, big keel fins, WP forward, straight rails – 2:1 WP to tail tip width ratio. Fish.
This is all with shortboards in mind, mind you.
