Just finished this 6'10" Single fin for Paul Efanos of Brunswick Heads. Paul is a connoisseur of traditional late 70's single fins. He had seen a single fin I made up for myself a few years back and recognized a few elements that constitute a period correct board of this style.
Proper foil, or thickness flow, from tip to tail in conjunction with rail foil is major componentry as well as a particular rail shape. The apex of the rail will be low, however, it's tucked under in a tight radius, allowing the board to be both sensitive and forgiving at one time. If this is done improperly the board will have a tendency to dive and be overly sensitive. While moving this rail apex down, you can pack a lot of meat into the shoulders where paddling power and great momentum is produced while still having a rail that penetrates into the face of the wave. The rail foil change as you move towards the tail puts control and sensitivity into the back foot area and interacts with the wave face more effectively in steeper, more critical spots.
Paul's board, shown here, has a 6oz Yellow Semi-Opaque bottom, and clear 6x4oz deck with a 4oz tail patch. Just to keep things correct I've added a Red Opaque resin pinline.
This board model is available in any size from 5'6" to 8' and actually represents a quite refined surfboard design, generally underrated and imminently capable in any circumstance.
