from Dave Parmenter’s Surfboard Design Analysis:
BOARD ONE
Kingdom: surfboard
Phylum: longboard
Class: classic longboard/neo-traditional longboard
Description: The surfboards of the classic longboard era were a drag – literally. No, they were (and still are) great to ride, it’s just that virtually every component of their design intentionally or unwittingly contributed to the forces of drag. The bottom contours, the templates, the rail shapes, rocker and fins all served, for one reason or another, to slow the board down.
Classic longboards of the '50s and '60s, as well as the modern replicas of such boards, have a clear design link to the wooden olo boards of ancient Hawaii. These boards had basically rounded, convex bottoms that attempted to reduce the drag on their enormous lengths by pushing the water aside from the centerline as the board plowed through the water. This application of a shape known as the “displacement hull” shows that in earlier times, board-builders had only canoes, and later, boats to draw their inspiration from.
The inherent drag and suction of this type of bottom granted the rider enhanced control and easier handling – there were no fins on boards prior to 1935 – if not contributing much in the way of planing speed. By the '50s, turning ability was further improved by placing more pronounced hips (the peak or wide-point of the board’s one-dimensional outline curve) farther back toward the tail. The resultant contour drag acted as a sort of power steering that let surfers of the day – at a further cost in drag – to pursue tighter turns and hotdogging.
Rails on the classic longboard were mostly of the 50/50 variety, completely round and bulbous with little or no release or breakaway edges; the water had no choice but to wrap completely around the rail onto the deck. Once again, user-friendly but slow.
Another feature of the classic longboard that relied on drag forces was the rocker profile, which usually had its peak, or apex, well behind the center of the board, and employed a heavier tail kick with a flatter nose lift. When the rider pulled the board into a tight trim along the top of the wave and moved onto the nose, this rocker design – along with many of the other previously mentioned features – created a counterbalance of drag and suction that allowed a full-grown man the ability to perch indefinitely on the very tip of the coasting surfboard.
The length, width and comparatively flat bottom rocker of the classic longboard overcame many of its drag-inducing features, giving these boards their distinctive Cadillac glide and stability, but there was a relatively low terminal velocity: these boards would only go so fast before they’d shimmy, hum and basically try to buck the rider.
Dimensions (in decimal inches):
Length: 9’8"
Nose: 16.5 inches (at 12 inches down)
Widepoint: 23 inches
Tail width: typically 15 to 16 inches (at 12inches up)
Thickness:
Nose: 1.7 inches (at 12 inches down)
Thickest point: 3 inches
Tail: 1.9 inches (at 12 inches up)
Foil: Thickness usually peaks a little behind center, with the main volume pooled around the behind-center hips and rocker apex. Thickness tapers down to a fairly thin nose and holds a medium volume as it meets the fin/tailblock area. This conjunction of foil, rocker and outline creates the characteristically slow feel of the board when turned from the tail and provides for the marked increase in speed when the rider moves forward to the optimum trim position (usually in the front third of the board), changing the whole angle of attack of the planing surfaces.
Rocker:
Nose: 3.5 inches
Tail: 3.75 inches
The apex, or peak, of the rocker curve is placed much farther back than modern boards and is centered back at the thick-point/hip area. The amount of nose-lift tends to be a lower measurement than the tail. Once again, a feature that shows the separation of the trim position of the board and the sweet spot for turning.
Bottom shape: Bottom is basically convex, as is the deck. This rounded, displacement hull-style bottom fades to a slightly flatter surface near the nose and behind the fin. This tubby hull design has its roots more in boat design – and one method of dealing with pushing a large surface with a weak power source through the water – rather than the modern, flatter planing hull-type of surfboard that skims on top of the water, but requires more power to keep it up on step and planing.
Rails: Rails are the classic 50/50 shape, with the apex at the center of the rail. Some 50/50 rails were completely round-shaped and others were more elliptical or almond-shaped. It’s a user-friendly, soft and stable rail shape but, being edge-free (water-flow wraps around rounder rails but doesn’t do so as easily around a sharp edge or corner), it’s slower and almost impossible to surf with modern body English.
Tail shape: Rounded squaretail, which carries the rail line to its maximum extension, providing the greatest amount of tail area and thus allowing for more flotation and speed in slower, weaker waves.
Stringer: .375 inches redwood/spruce/redwood T-band
Glass specs: Two layers of 10 ounces. Volan cloth top and bottom.
Fin setup: The classic longboard fin is a crude affair, little more than a stabilizer. These squarish, clumsy rudders were designed when the sciences of aerodynamics were still just so much unfathomable mumbo-jumbo. Tips were as wide as the bases, had near-vertical leading edges and were poorly foiled. So much drag was created that you can see them throwing off rooster tails in the old surf films taken at faster waves like Sunset.
Performance envelope: 1 to 4 feet
Optimum generic example: Any early to mid-'60s Hobie production board, or similar brand of that era
mose well go out in a blaze of glory!