Twin Fins

Two fins sit near the rails with no center fin to create drag. The result is raw speed — water flows freely between and under the board without the braking effect of a center fin. Twins plane earlier, accelerate faster, and feel looser than any other setup. As Geoff McCoy put it: "the principal of twin-fins is that one fin slows, and the other one revolves around it."

The tradeoff is hold. Without a center fin, twins can slide out in steep or critical sections. Designers compensate with toe-in (the fins angle slightly inward), cant (fins tilt outward), and template shape. Channels and bottom contours are critical stabilizers — MR refined the twin into a slightly wide swallow template with steep panel vee, hard rails, and moderate rocker.

Modern twins come in two families: keel fins (wide base, short height, like a fish fin) and upright twins (taller, narrower, closer to a thruster side fin). Keels are fast and drivey on fish and retro shapes. Upright twins are more maneuverable on performance boards. As one Swaylocks rider noted: "you can't beat the feel of a twin in the pocket."