Here’s the backstory: large surfer (260+#) who normally surfs singlefin longboards. He was taking a trip to BSR Surfranch, so he needed a board that would travel and would fit their wave, including a 7" maximum fin depth. So what he normally surfs wouldn’t work, and his surf style and stance aren’t conducive to a normal quad/thruster. So this is what we came up with: 6-10 x 24" x 3.5", foiled to ride/trim more forward under a relatively close stance. 66L under Boardcad, which for the length is actually saying something.
A big guy using a fin system needs a fin install that won’t fail so I used Gearbox and added a Josh-Dowling styled HD insert to further stabilize the main side fins. I installed those for the main side fins prior to shaping the blank. I chose Gearbox because of the design of the box allows for a single longer tab that won’t break and because the design of the box itself has more support. So here’s the blank:
For the inserts, I used a 1" thick panel of HD PU that I got a long time ago. Unfortunately the foam has discolored a little, which you can see in the pics. I didn’t notice it until it was contrasted with the virgin foam of the blank.
I glassed one side with several layers of 6oz before I templated the inserts, and the I installed them with the glass side down, so that the glassing will support the bottom of the finbox when it’s installed. As I say, I installed the inserts before shaping the board, then I laid my fin patch down before installing the boxes, with the primary lamination going over that. You can see that when I routed for the finbox the glass layer is at the bottom of the cavity.
I needed the reinforced front boxes because I was making a big fin. I set the board up with the Neal Purchase Jr Quartet combo, but upsized for the 260# surfer. I tweaked the template to 6.15" and redid the trailing edge. I ended up with a 26"2 fin area for the fronts, and just under 10"2 for the rears, clustered tight and forward with the trailing edge of the fronts at 12".
Per Robin Mair’s suggestion, I used phenolic paper micarta for the fins. It’s a little lighter than G-10 but seems to foil similarly - the foil is just harder to see. I paid $30 for a 1x2 panel and have enough left over to make a smaller thruster or quad set, so that’s pretty inexpensive for a 1/4" panel.
The finished board went to BSR over the weekend and apart from the wave itself being a 2ft mushburger and pissing everyone off the board itself worked as intended for the big guy. He didn’t have any problems paddling in and he’s got plenty of leverage to duckdive the board and drive the fin cluster.
I might have to tweak the fins, maybe make a smaller main with more rake; we’ll have to see how the board surfs in real waves.
I would like to offer my thanks to Mr. Robin Mair on this project. His Gearbox design is dirt simple and bulletproof to install, the box design and his process for the install along with the long tab design makes this a no-brainer; and the boxes will take FCS fins. If you build your own fins the 3" long tab has more surface area and no inside corners to provide the shear point so it’s hard to imagine one breaking. Also, his recommendation on the fin material was a good alternative to PE fiberglass or G-10.
For this one I was poking around on Joe Blair’s site including his comments about moving the fin cluster forward. I have long followed what Bruce Fowler’ has been doing with the Stoker shape and what Neal Parrish jr has been doing with his Quartet fin setup. I tweaked the trailing edge of the fins to follow the Brewer design and Greg Griffin’s explanation for the even release, and I took the cue for stabilizing the finbox from Josh Dowling’s approach (and the compsanders) to using HD inserts with EPS cores. That makes this mashup 100% derivative on the work of others, each far more savvy than I.
I like that insert. Especially like that glass is on the bottom. Have a friend who designed a jig and routs out the cavity in a peanut shape and installs Fusion boxes into HD Foam. Does not put glass on the bottom tho. Good idea.
