Have any of you shaped a longboard, with a single finbox & no side fins, with a slight single conave running most of the length of the bottom, then blending into a slight double concave around the single finbox? Did it perform well for you? Or is this “single to a double” best left for a tri fin or a 2 + 1 set up?
are you wanting it to be more of a noser or a performance board???
are you wanting it to be more of a noser or a performance board???
Tentoes: I’m looking for it to be more of a semi-performance style single finbox longboard: 9’6"long, 23"wide, 3"thick, 18"nose, 14 3/4"tail. Not for nose riding, but for easy wave catching, smooth cruising, and some “turnability”. What do ya think about a slight double concave at the tail bottom blending around the finbox? Usually one would use this on a trifin or 2 + 1 set up. Just wondering what effect it would have, if any, on a single. Usually one would shape in a vee here, but I was just “brain farting”. I guess I really need to go surfing.
Tentoes: I’m looking for it to be more of a semi-performance style single finbox longboard: 9’6"long, 23"wide, 3"thick, 18"nose, 14 3/4"tail. Not for nose riding, but for easy wave catching, smooth cruising, and some “turnability”. What do ya think about a slight double concave at the tail bottom blending around the finbox? Usually one would use this on a trifin or 2 + 1 set up. Just wondering what effect it would have, if any, on a single. Usually one would shape in a vee here, but I was just “brain farting”. I guess I really need to go surfing.
Not for nose riding, but for easy wave catching, smooth cruising, and some “turnability”. Make it a hull for smooth fast trims, pull the nose in a bit, make the tail thin so you can lay it over on an edge and jam it off the tail. I have a 9’4 like this that I’m getting wired and having lots of fun. Ride on Dan
Not for nose riding, but for easy wave catching, smooth cruising, and some “turnability”. Make it a hull for smooth fast trims, pull the nose in a bit, make the tail thin so you can lay it over on an edge and jam it off the tail. I have a 9’4 like this that I’m getting wired and having lots of fun. Ride on Dan
Concaves are a huge asset to relatively narrow shotboards. As you increase surface area the margin for error with multiple concave bottoms (counter productive influence on the design and thus performance) increases dramatically. If you plan to ride your 96 like a shortboard limit the concaves to the surface area under your stance. Place a long smooth continuous rocker throughout the board and insure that the rocker accelerates away from the concave area through the tail and fins. Since you’re not going to do any nose riding pull the nose and tail of the template in a fair bit. This will give you more curve in the template which will reduce the surface area of the whole board (reducing the negative effect of the concaves) and make the board turn a lot easier (a template with a fair amount of curve in it turns easier than a more parallel template.) Mike Diffenderfer made some excellent single fins (66 to 76 in length) in the late '60s and early '70s that featured a rolled bottom from nose to wide point - single concave under the stance - and a crisp little vee in the area of the fin. They were really fast and loose ! Try to visualize your 96 as a blown up version of those boards.
Concaves are a huge asset to relatively narrow shotboards. As you increase surface area the margin for error with multiple concave bottoms (counter productive influence on the design and thus performance) increases dramatically. If you plan to ride your 96 like a shortboard limit the concaves to the surface area under your stance. Place a long smooth continuous rocker throughout the board and insure that the rocker accelerates away from the concave area through the tail and fins. Since you’re not going to do any nose riding pull the nose and tail of the template in a fair bit. This will give you more curve in the template which will reduce the surface area of the whole board (reducing the negative effect of the concaves) and make the board turn a lot easier (a template with a fair amount of curve in it turns easier than a more parallel template.) Mike Diffenderfer made some excellent single fins (66 to 76 in length) in the late '60s and early '70s that featured a rolled bottom from nose to wide point - single concave under the stance - and a crisp little vee in the area of the fin. They were really fast and loose ! Try to visualize your 96 as a blown up version of those boards.
For those of you who remember these Diffenderfer boards, what are the details of this design? (Come on Jim.) Was there a really low entry rocker in conjunction with the roll in the nose? Did Diffenderfer put a “speed box” in the rocker line underneath where you paddle? What was up with these boards?
For those of you who remember these Diffenderfer boards, what are the details of this design? (Come on Jim.) Was there a really low entry rocker in conjunction with the roll in the nose? Did Diffenderfer put a “speed box” in the rocker line underneath where you paddle? What was up with these boards?
The Diffs were some of the first shortboards with any functional rocker distinction. The entry rocker was low compared to some of the elf shoe entries used by other prominent shapers of the era. No “staged rocker speed box” as these boards had smooth continuous rocker profiles. Just as the continuous rocker finished decreasing under the surfer’s stance the rocker accelerated through the fin and tail. The rocker profile in the Diffs was a magic blend of entry - speed - and release ! This concept for rocker is the backbone of contemporary shortboard, hybrid, and gun rocker.
The Diffs were some of the first shortboards with any functional rocker distinction. The entry rocker was low compared to some of the elf shoe entries used by other prominent shapers of the era. No “staged rocker speed box” as these boards had smooth continuous rocker profiles. Just as the continuous rocker finished decreasing under the surfer’s stance the rocker accelerated through the fin and tail. The rocker profile in the Diffs was a magic blend of entry - speed - and release ! This concept for rocker is the backbone of contemporary shortboard, hybrid, and gun rocker.
Soooo, back to my original question. I now guess that it would NOT be functional to add a slight double concave around the single fin on a longboard…right?
Soooo, back to my original question. I now guess that it would NOT be functional to add a slight double concave around the single fin on a longboard…right?
Grant. That’s up to you. A “performance longboard” doesn’t seem like the best board for single to double concave around the fin. You’ve already got plenty of surface area and lift to catch a lot of waves with ease and carve some nice turns. You could pull it off if you’re very clever and very careful, but a nice convex bottom is the best solution.
Grant. That’s up to you. A “performance longboard” doesn’t seem like the best board for single to double concave around the fin. You’ve already got plenty of surface area and lift to catch a lot of waves with ease and carve some nice turns. You could pull it off if you’re very clever and very careful, but a nice convex bottom is the best solution.
You might want to check out Harbours website. In the description of his HP-1 model, he mentions using a “tunnel hull” in the fin area. I’m not exactly sure what this does but you could probably post a question on his BB and get a response from him. To me it seems a double concave would increase drive through the turn. If I were doing what youre thinking of doing, I’d put in a little extra vee through the tail along with the concaves.
You might want to check out Harbours website. In the description of his HP-1 model, he mentions using a “tunnel hull” in the fin area. I’m not exactly sure what this does but you could probably post a question on his BB and get a response from him. To me it seems a double concave would increase drive through the turn. If I were doing what youre thinking of doing, I’d put in a little extra vee through the tail along with the concaves.
THANKS everyone. Regarding my 9’6" semi-performance single fin: I’ll definitely be putting in a slight tail vee, but will withhold the double concave idea for now. I’ll make a very flat bottom with a slight concave running from aprox. 18" behind the nose thru the beginning of the single fin box. Sounds like a “rush” (of water) to me!