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The finest thread ever.

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  • The finest thread ever.

    Something finny is going on around here.

    Enough of the puns, old dude latest post on his build thread was about fin making. It got me motivated to finally make one from start to fin-ish.

    I started with a $3 pack of bamboo cutting boards from the store. I had picked them up a while back with the intention of making fins, but never followed through.

    Step one was to make/trace an outline. I chose to copy an existing longboard fin with a twist. Instead of the normal tab with metal pin and screw hole for bahne boxes, I shortened the base to fit into a futures center fin box. My inspiration came from wanting a bigger center fin for a longboard that someone foolishly installed futures fin boxes into. Also was inspired by Awesome Surfboards Model T fin.

    Step two, cut out fin outline. I think this part is self explanatory.

    Step three, this is probably optional. Because the cutting board I started with was thicker than a futures fin box I had to narrow the tab area. I used a table saw to cut 1-2 mm deep rabbets on either side of the tab.

    Step four, foil the fin using your favorite shaping tools. My foil isn't pretty, but it should get the job done. I found that drawing a center line around the edge was helpful in keeping the sides even.

    Step five, sand.

    Step six, glass. Plenty of places on the Internet to learn about this.

    Sorry I didn't take more pictures of my attempt. The only picture I have is between steps five and six, but I plan to take more after I glass it.

  • #2
    It will become pretty, bamboo cutting boards are really good stuff for fins. Maybe you do not need to glass at all. Just some surface protection against water should do it, bamboo is really strong, the only problem may depend on the glue of the original cutting board. It has to be waterproof.
    I would try just a natural oil, like linseed or tung...
    If you are going to glass, try to glass the fin and the tab in once, you may need to adjust between those parts. Watch out, that the tab fits into its slot after glassing, meaning you may have to rabett the tabs sides a little more
    The best surfer is the one with the biggest smile on his face...


    • #3
      I already rabbeted the tab thinner than the box so I could build it up with glass for extra strength.


      • #4
        Glassing half of the fin. Easier said than done with both sides foiled. In hindsight I should have taken your advice old dude and glassed it all as one without the tab taped off. Hopefully it's not too difficult to get the tape out. Glass schedule is two layers of 4 oz glass, just scraps I have saved from previous boards. I did try to lay a bit of a halo around the outside, so we'll see how that turns out.

        Fin fact: you can see the fins brother cutting board underneath.


        • #5
          No pictures tonight, but I did manage to glass both sides of the fin. Everything except the tab which I feathered the glass to. I plan on laminating 2-3 layers of cloth on both sides going from the tab to a couple inches up the fin. Hopefully it will make for an extremely tough and durable tab. I suspect the typical futures center tab is not strong enough for this large of fin.

          I think next time I'll put a block or something underneath of the fin, so the resin can flow off of the edges and get a more even lamination. The halo while it looks cool has been a pain to do with a double foiled fin.


          • #6
            Here is it after sanding and test fitting and sanding until it fit.

            All the way until tragedy struck. The U shaped portion of the tab towards the back of the fin snapped off at the glue line of the bamboo.

            I am open to suggestions on a fix. My current plan is to carefully drill a hole diagonally up into the fin. Glue a nail into the hole. Fill the entire area with thickened resin, thickened epoxy, or the premixed sun cure in a tube. I'll probably use sun cure because I have it, it's easy, and I want to try the fin this weekend.


            • #7
              Didn't get any pictures today, but I did what I had planned. Drilled small hole diagonally into the fin, inserted small brad nail, covered it in sun cure ding repair. I'll post some pictures when i get it cleaned up again.


              • #8
                Bummer. Hope the repair works.
                I looked into making a fin once. You can get US to fcs adapters. You could use one of these as the base to avoid the problem of the week spot. Make the fin with 2 tabs like a fcs and glue/pin it into the adapter.


                • #9
                  One of these.


                  • #10
                    That's a good idea for next time. My whole problem started with a cheap longboard. Some no name pop out board from overseas. It was good and water tight, but just felt off when I surfed. It felt like the board was always unstable. Even when surfing on a wave it felt like trying to stand up when not moving on a wave. It felt like that all the time. I think the problem is that it was made with the standard futures thruster boxes and three relatively small fins. I say relatively because the board is 9'6" x 24" x 3" or at least that's what is scribed on it. Trying to get a decent sized longboard big single fin into the tiny futures box has been frustrating. A simpler solution would have been to route out and change the fin box, but I wanted to actually follow through with making a fin. I wanted something like this.


                    • #11
                      Well I test drove the fin today. It was awesome, like I was on a brand new board. I still have to gloss coat and finish sand the fin, but I couldn't wait to get it in the water. Super stoked on how well it turned out.

                      I didn't get any pictures in the water, but here are a few of it int the board and a comparison shot of the fin it replaced.


                      • #12
                        "Super stoked on how well it turned out"
                        Great! Why do you want to glosscoat etc. if it works, maybe its the "sharkskin" effect too
                        Did you try without the sidefins too? Since there is such a big difference in sizw, between the original and the new setup, it may be worth a try.
                        I hope I will have the same positive experiences with the three fins, I build for my newest board. By now I was not very much into fins, but now I will have a basis to compare, maybe it is worth to invest some time into. I think fins are quite neglected, at least by me, the most aspects where put on boards...
                        The best surfer is the one with the biggest smile on his face...


                        • #13
                          I actually didn't try it without the side fins, but I was also worried about it breaking off and having no fins. I probably will gloss it. Although, I'm already planning another one. This one turned into a proof of concept more than anything. Next try will be nicer/harder wood, less glass on the fin, and more glass on the tab. I might also try different resin. The poly stuff I used had a red tint to it. You can't tell against the wood, but the little bit of halo is a faint pink.


                          • #14
                            Dude that’s sweet... glad it fixed the board and rode well for you! Never thought to use cutting boards. Definitely cheaper and quicker.


                            • #15
                              If you do, just be sure what kind of wood it is. I tried making some more out of a really nice figured olive wood and the resin/glass didn't stick well. Literally peeled off when I was trying to sand it. It did make a cool half mold looking thing. Long story short olive wood is pretty, but not good for resin stuff.