70's Design Forum Series - #1. (Info taken from G&S Ad in International Surfing Magazine April-May 1973)
With our Fish and Swallow Tail designs, the two pintails, points A and C have water flowing on either side and up thru the middle from point B (see image diagram) giving an increased resistance to lateral motion or, in other words, better holding ppwer. It's like having tri fins with no side effects. This holding power is quite evident in steep critical, high and tight parts of the wave, in bouncy, choppy, or backwash conditions, and in hard driving turns and cutbacks.
Thrust or acceleration out of a turn depends on deflecting speed efficiently and upon capturing the wave's power at the instant a turn is being completed. "Capturing Power" is done by resistance or bite from fin, rail, and bottom surface. With our Fish and Swallow Tail design, there is an increased rail line A-B-C , giving more bite, We have inside rail B-C working like a booster fin on a right turn (Rail B-A becomes effective on the cutback or left turn) giving extra push when you need it coming out of the turn, but not causing drag or resistance when going into the turn or when trimming and gliding after the turn. Also, because of the presence of the holding power, a wider tail is possible (Fish and Summer Fish), giving a larger thrusting surface without risk of spinning out. More power and drive can be put into the turn for the same reason, the traction keeps the tail from sliding out.
RELEASING THE SPIRIT
Freedom, Sensitivity, and Maneuverability HAPPEN with Area A-B-C taken out of the tail. The split tail sinks easily and moves or pivots through the water with less resistance for quick directional changes.