Greener Waves

Extended play: Shaping an EPS foam surfboard

1. Get your kit and template.
   Greenlight kits (greenlightsurfsupply.com) run from 6'6" to 9'8". I made a 6'6" twin-fin "fish." Whatever style you make, keep a similar board on hand for reference as you work.
   
   Download and print your outline template, tape the sheets together on the reference marks, and cut out the curve. For a rigid template, trace it onto cardboard. Alternatively, trace the outline of a favorite board.



2. Glue and cut the blank.
   Glue the halves of the EPS foam blank to the bamboo stringer, keeping surfaces as level as possible to minimize sanding later. Stand it on edge, weight it or clamp it, and let the glue dry.
   
   Trace your outline onto the bottom of the blank, then cut the foam out with the handsaw, keeping the blade perpendicular to make the edges (rails) as square as possible. If you're making a swallowtail, don't cut out the tail yet; save it for last (Figure A).
   
   

   Figure A

   
   
   With double-sided tape, stick 36-grit sandpaper to your 12" sanding block, and use it to square up the rails all around.



3. Level the deck and bottom.
   Use the mini hand plane to level the bamboo stringer wherever it protrudes above the foam (Figure B). Then use your 24" sanding block to level the foam and stringer across the deck. (Figure C). Repeat to level the bottom. If you want a thinner board, continue sanding foam evenly in this way. Don't overdo it!




Figure B



Figure C




4. Add rocker and vee (optional).
   For steeper waves, put more "rocker" curve in the bottom by sanding more foam off the nose and/or tail. For easier turns, shape "vee" into the bottom. Mark the stringer 1"-20" from the tail, and mark each tail corner ¼" down into the foam. Sand the bottom gently, outward from the stringer and backward toward the tail, angling down to your ¼" marks, creating a slight pitch from rails to stringer. Easy does it - I gouged my rail a little bit.



5. Shape the rails.
   Following Greenlight's diagrams, draw the rail bands with a marker. Use long strokes with the rasp to bevel the foam between the bands, roughing out the rail curve (Figure D). Leave the rail's bottom edge sharp near the tail (more bite for turning), but round it farther forward (more forgiving). The transition is about 20" from the tail.
   
   

   Figure D

   
   Use the 100-grit drywall sanding screen to round your bevels into finished rail curves (Figure E). Make them as even and symmetrical as you can. Gently blend the transitions to the sharp rails in the tail.




Figure E




6. Blend the deck into the rails.
   With 60-grit on your 12" sanding block, blend the deck into the rails. Keep moving; you don't want high or low spots lengthwise. You do want to “crown” the deck crosswise, i.e. make sure the stringer remains the highest point.
   
   Run your hands down the deck and rails; will water flow smoothly? Measure, compare with your reference board, and shape until it feels right.



7. Shape the nose and tail.
   Use the handsaw to cut out the swallowtail, then a round rasp or file to round off the top of the stringer. Make a small sanding block with 60-grit, and shape the tail to match the rail — bottom sharp, deck blended.
   
   In the nose, plane down the stringer on the deck and the bottom. You want extra bottom rocker (or "flip") at the very tip, so you won’t bury the nose when taking off on waves. Then sand the foam evenly down to the stringer, thinning the nose. Clean up rails and blend to the deck as before.

Links

• Swaylock's Surfboard Design Forum
  
• Stephen Pirsch’s how-to
  
• Surfboard template, and plans for shaping and glassing rack
  
• Greenlight Surfboard Supply
  

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