Longboard: learn how to make a homemade single fin | Photo: Shutterstock

Here's a step-by-step guide on how to make a homemade 10-inch single fin for a longboard or funboard.

Commercial surfboard fins are generally expensive, but the truth is that they're hard to make and require a lot of precision technology.

You can always shape it like a board maker, though it can be challenging and time-consuming.

Nevertheless, it is not an impossible mission, and above all, it's fun and can enrich your knowledge of hydrodynamics.

Don't expect to get a perfect fin on your first attempt. The more you practice, the better the outcome.

With the right tools, materials, and a bit of patience, you can create a rideable custom single fin for your longer boards.

Some of the following tools can be replaced by non-electrical hardware.

Read the do-it-yourself tutorial, follow the video, and create your first-ever surf fin.

Fins: it can take a couple of days to shape a custom-made stabilizer for your longboard | Photo: Shutterstock

Tools

  • Mixing cups and stir sticks;
  • Scissors, utility knife, or rotary cutter;
  • Mask/respirator;
  • Gloves;
  • Rail marking gauge;
  • Spiked/ribbed resin roller;
  • Squeegee;
  • Chisel;
  • Tape;
  • Sandpaper (80, 120, 220 grit);
  • Wet sandpaper;
  • Band saw;
  • Paint filters;

Materials

  • 3/16'' thick clear acrylic sheet;
  • 18'' x 15'' layers of 7.5 oz plain weave fiberglass cloth;
  • 50 oz polyester/epoxy laminating resin;
  • 22 oz hardener;
  • 5 oz resin tint pigment;
  • Universal mold release;
  • Acrylic gloss clear coat;
  • Finishing resin (optional);

1. Lamination

  1. Cut the 36 layers of fiberglass fabric using the rotary cutter;
  2. Lay the acrylic sheet on a flat surface;
  3. Tape the acrylic sheet off on all four sides;
  4. Spray the mold release over the panel;
  5. Measure out five or six ounces of epoxy, tint it, and run it through the filter;
  6. Pour 20 ounces of epoxy resin into a container;
  7. Add two ounces of the epoxy and tint concentrate;
  8. Mix it up to distribute the color well;
  9. Pour 9.5 ounces of hardener;
  10. Mix it for at least two minutes;
  11. Pour some epoxy directly onto the acrylic surface and disperse it around the panel using the squeegee;
  12. Remove the excess;
  13. Lay one sheet of fiberglass and pour more epoxy onto it;
  14. Place two more layers of cloth and pour the resin, making sure it gets fully saturated and without air pockets;
  15. Add two more layers and pour the epoxy;
  16. Use the resin roller to smoothen and even the fiberglass out;
  17. Repeat the process until you have 16 layers of fiberglass down;
  18. Let it rest for six hours;
  19. Pour six ounces of epoxy resin into a container and add the tint concentrate into the mix;
  20. Pour your new color formula onto the nearly-cured 16 layers board;
  21. Lay four clear acrylic sheets and apply the correspondent epoxy resin;
  22. Let the new layers sit overnight;
  23. Repeat the processes from steps 11-18;
  24. Take a little bit of clear resin and squeegee that across the weave to help fill in that top layer;

2. Shaping

  1. Work a chisel underneath the fiberglass board so that you can bend the acrylic and detach it;
  2. Lay the board on a flat surface;
  3. Mark off your fin templates;
  4. Use a blade on the band saw that is appropriate for fiberglass;
  5. Cut off the template;
  6. Clean up the perimeter by hand with a sanding block or some sandpaper. You want a nice square perimeter so that you know that when you're shaping your fin, you're not coming out of that true shape;
  7. Drill out for the pin on the back or front of the fin, depending on your template. You can use a 3/16'' x 9/16'' stainless steel spring pin;
  8. Taking the base down close to the final thickness - around one inch in diameter - using a router table;
  9. Start sanding the fin's starboard trailing edge using a 60-grit silicon carbide sanding pad;
  10. Make even passes to try to bring out the fiberglass contour lines and work them about two-thirds of the way across the trailing edge of the fin;
  11. Try to keep an even bevel and push that all the way forward, maintaining a pretty consistent width;
  12. Now, take some heavily angled passes on the leading edge, leaving a little bit of margin on either side of our pencil line, wrap it around, and try to blend the leading and trailing edges together to develop a parabolic curve like an airplane wing;
  13. Flip the fin and take down the trailing edge of the port side;
  14. Be cautious - you don't want to blow into your base too much, but you also want to shape it enough;
  15. By now, the rough shape should be looking good;

3. Sanding

  1. Switch to the 120-grit silicon carbide sanding pad;
  2. Starting sanding again on the starboard side, just pushing it a little further and smoothing out any of the undulations that shouldn't be there - you'll begin to see the colors come up even more;
  3. Switch to the soft flex 220 grit pad and pass it around the whole surface area;
  4. Take a strip of a 60-grit sanding disc that doesn't get used to round the leading edge over and spend some time there making sure that it's symmetrical and parabolic;
  5. Now, work on your trailing edge to a finer taper with 120-grit sandpaper, making sure it doesn't get too sharp;
  6. Continue working sandpaper on the base of the fin and all edges and surfaces using 220-grit sandpaper;
  7. Make sure the base is going to fit in the fin box. Test it on a loose box, in the surfboard, or measure it using calipers;
  8. Insert the stainless steel spring pin;
  9. Drill a hole for the hardware using a 3/16'' drill bit;
  10. Rinse the fin with fresh water to remove the dust;

4. Finishing

  1. Sand the whole fin for one minute using 320-grit wet sandpaper;
  2. Repeat the process with 320-grit wet sandpaper;
  3. Clean the fin with denatured alcohol;
  4. Spray finish it;
  5. Install your custom-made surfboard fin and surf;

Top Stories

We can't choose our height, and 80 percent of it is genetic. But if you're into surfing, taller and shorter surfers feel noticeable differences in getting acquainted with boards, paddling for, and riding a wave.

Cole Houshmand and Caitlin Simmers have claimed the 2024 Rip Curl Pro Bells Beach.

At 32, Laura Enever is slowly building a name in women's big wave surfing. And to make her vlogger debut on YouTube, the Australian chose Cloudbreak.

Ryan Crosby is the new chief executive officer (CEO) of the World Surf League (WSL).