Prototype design concepts from the book “Surfboard Fin Design: Just the Basics” available from Amazon here.
Due to my frustration with the surf conditions relative to my current boards on the east coast of Australia, I have finally decided to take the matter into my own hands. The old boards I have still work great in Western Australia, but there is no where near the power here that you’d find in Margs. Also since leaving WA and coming here I’ve gained 7-8 kgs or more and that makes a ridiculous difference. Especially when the conditions are marginal. I have been out on so many days with other surfers and watched whilst the 75kg guy gets wave after wave till his legs are burning from cutting back so many times. I only get 2 or 3 waves floating at about the mid 90kg mark (now heaver than that) on a 6’8″ , 2 3/4 thick board and the 105kg guy on a 7’8″ mini mal has no hope in hell of catching anything.
So I’ve grabbed some blanks to shape. Testing tail width first. I’ve surfed a couple of boards around here wafer thin, but with wide tails and they seem to work.. My current board has the 14.5 inch rounded tail at the standard 1ft from the tail. I figure I’m going to throw the first few boards away, so I’ll also try some weird radical ideas whilst testing tail widths. The tail width here is 18″ (457) right to the tail. Going on snowboard theory, I’ve bent the rails in and then in the profile I’ve made them as close to 89 degrees as possible. The rails have rocker lengthwise and I’ve concaved out the underside so the centre is dead flat tail to nose 2/3 of the way up the board. This flat I’ve drawn into a concave tail so that as the air compresses in under the board it can exhaust out the back once planing. The blank was not big enough to do full length snowboard style rails so I had to cut the snowboard rails shorter. Probably next time I’l just make it from a block of EPS and vacuum bag some divinicell on top and go the epoxy route instead of polyester. Standard surf blanks are not really geared to trying weird shapes. I want to incorporate flex so that as the turn is lent into, the board bends with the turn like a snow board, but that can happen on a later board. I think I’ll probably test it without fins first to (a) purely test the planing ability of the 457 tail and (b) if it does get me going see if I can turn on the rails without fins. Either way the fun is in the design process and not so much the surfing.
The deck is also concave as I skated for years and know the difference between the old 80’s flat skate decks compared to the >90’s concave decks. Christ knows why surfboards didn’t follow the trend. I’ve seen a couple, but it’s close enough to none for it to be none in mainstream surfing.
Now that it’s shaped I really can see that I wanted to go 510 (20″) or 535 (21″) in the tail. That was the limitation of this blank, so it’s a starting point.