How to Build Your First Surfboard
by Stephen Pirsch

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If you are using polystyrene foam read the next chapter first.  The following instructions will work for any hard foam, but are now best suited for polystyrene block foam.   If you have found a polyurethane, or polystyrene blank which is close to what you need (without shaping modifications) you will be able to skip a lot of the steps here.  Ideally (with polyurethane foam) you can plane off the crust (if it has a crust), lightly sand, do a few details and, you are done shaping.  Shaping a surfboard from a square block is much more labor intensive.  If you are not sure then do not skip anything.

Note:  I get a lot of emails questioning the usefulness of videos, and the differences in the methods advocated in this book compared to pro shop methods.  The videos available show how pros build boards using power planners, power sanders, routers, air brushes etc.,  It is all entertaining, but I feel it is not very useful for a first time builder.  Not only are you unlikely to have access to these tools, but if you did, you probably should not use them because they are more likely to cause you to ruin your first board.  Please know although much effort has been made to save you from problems, you will have problems that cannot be foreseen.  I feel, however, you will have much fewer problems if you use mostly hand tools, and instructions made for, and influenced by, first time builders.  I believe you will be much happier making your first board if you keep it simple, and realize it will not be perfect.

Practice on scrap foam first.  Put special emphasis on practicing shaping the rails.  You can shape a 1/10 scale replica of your board.  A full thickness piece as shown below is good for rail practice..


Once again, if you are shaping block foam, please follow the directions in POLYSTYRENE - shaping the rocker before cutting the outline.

Do the following:

  1. Put your blank bottom up on your rack.
  2. Draw a straight line, (across the width) about 1/2" from one end of the blank, flip the blank, and mark another line directly beneath it (use a framing square etc).
  3. If you do not have a stringer, ( I recommend no stringer if you are using block foam) draw a center line. 
  4. Line up the 1/2 template, with the center line, and with the line across the end of the blank.  Also, the board you are going to copy can be placed directly on the blank.  Trace it on the blank with a "Sharpie" pen.
  5. Flip the template over and trace it on the other half.
  6. Flip the blank, and repeat.  Double check.  The two templates must line up, or you will have major problems later.

  7. Take a hand saw (almost any saw will do) and slowly cut about 1/2" outside the lines.  If you are very careful you can try cutting at 1/4".  Try to make sure the saw is cutting at a 90 degree angle to the blank.  If not the extra 1/2" should make up for the crookedness.  Check by looking at the template lines underneath.
  8. Turn your blank rail up on the racks.  Take your #12 or #16 block and gradually, keeping a 90 degree angle, sand the foam down closer and closer to the lines.  Stop when you are about 1/8" from the lines all around (top and bottom).

    Note that it is important to get in the habit of using long strokes running end to end when doing most of your blank shaping.  After you get some of the initial unevenness of your saw cuts removed, practice using longer and longer strokes.  Count 10 stokes on one side then 10 on the other.  If you start off doing things evenly, and continue doing things evenly, you will have much fewer problems, and much less work overall.  Please resist "scrubbing" from one area to the next.

    If you are using TDI polyurethane foam you will notice it has a 1/8" hard outer crust.  Be careful, the crust takes a lot of work to remove, but after barely going through it, it becomes softer and softer.  A TDI polyurethane board will be much stronger if you keep it close to the original molded shape.  Also, once through the crust you can gouge a dip without trying to.  The cheapest and easiest tool to use for crust removal is a small (smallest) block plane. This tool may later be used to plane the stringer.  Set the small block plane blades at a shallow depth so only the crust is being removed.  Please use continuous end to end strokes.  You can also use your #12, or #16 sanding block.  Note:  MDI polyurethane foam and polystyrene foam is the same density throughout (no crust).
  9. Place the blank bottom up on the rack.  Level the blank and level the center of the electrical metallic tubing over the center of the blank (if you have block foam you will probably be tracing the rocker template here - see POLYSTYRENE).  Take measurements as you did in DESIGN.  Compare the design numbers with the blank numbers. 
  10. If the rocker numbers are off more than 1/2" you may want to start removing stringer material and foam with your small block plane, or #12 or #16 sanding block. Also; the toothed edge of a hand saw can be dragged over the area - hold saw with both hands opposite the teeth on the smooth metal and pull lightly with teeth trailing across foam. Use a drill sander with #12 to #50 disk, or a power planer, as in POLYSTYRENE, if you have a lot of material to remove.   Please make sure you will have enough blank thickness when you finish planning the rocker.  If you simply must remove more than 1/8" past the crust (polyurethane blank only), try to do it on the bottom of the blank (the top needs to be stronger)  Plane the stringer (if you have one) to the proper rocker numbers, then plane or sand the foam.  Take care to not "scrub" the foam in one area, causing a dip. Again, please adopt the habit of counting your strokes in 10's. Stroke mostly end to end with the same number of strokes on all parts of the blank - this promotes symmetry.  All the curvature must blend into the whole. I recommend initially leaving at least an extra 1/8" of length, width, and thickness in the blank. This will give you the security of having a little extra foam to correct mistakes.  The ideal situation is to have ordered the correct dimensions when you bought the blank.  If not go slowly here. I recommend that you make round rails and make the bottom and top flat side to side. This

  11. Next, I highly recommend marking what will be the furthest protruding rail points about every 3" - 12" (3" at the tight curves, and 12" at the straights) around the entire circumference of the blank.  If the rails are round this will be at the center of the rail.   
  12. Connect the dots from the furthest protruding rail points using 2' x 1" roofing felt as a straight edge. This will create a continuous line parallel to and between the top and bottom rail lines (not shown in photo above).  Leave this line until the end of your shaping.  If it gets sanded, re-mark it.  All this trouble will ensure symmetry, and save you from a major mistake.  Most first timers find shaping the rails the most ddifficult part of shaping the blank.  The tendency is to be too thin in one place.  To fix one small thin area, often the entire blank has to be thinned to make it symmetrical.  Go slow on the rails. 
  13. After the rocker is acceptable and the flats of the top and bottom of the blank are rough sanded, start on rail curvature.  Again, the rails are the hardest part of the blank for most first time shapers to get even.  Do the rails very gradually, and symmetrically (evenly) with light pressure.  Turn the blank rail up and sand the rail with the # 12 or #16 block.  Sand 10 times on one side then 10 on the other.  Flip the board with the other rail up and sand with the same counting, and same pressure.  This simple counting will make it much easier to keep your board symmetrical, and will eliminate much work later on.  As you start finishing your curvature you will have to use proportionally lighter pressure on the thinner areas.
  14. Stay away from, or only touch very lightly, the black areas in Figure 11 (avoid on top side only).  Although I mentioned previously that you should use end to end strokes, do not stroke longwise through the nose curvature.  Stroke with your block parrallel to the stringer until you reach the top nose curvature, then you must stop.  Finish the top nose curve with the block turned sideways (perpendicular to stringer) or you will gouge a dip (a very common and very hard to fix problem).  Also, do not sand off your mid rail line, (from the paragraph above) yet.

    Figure 11

  15. Small holes can be filled with interior/exterior lightweight spackling.
  16. Take your racks and blank outside and align the stringer with the direction of the sun.  As the sun changes position change your racks to keep the light perfectly even.  This will make it very easy to see all the little dips and bumps you might otherwise miss.  Get back 10' - 20' and view the board rail up, top up, and bottom up. Also turn the board vertical (careful the wind does not blow it over) and view it, aligned with the sun.  Note:  even shade is O.K. (overcast clouds and buildings).  Tree shade is the worst.  Note:  If you can afford 8' fluorescent lights mounted at the same height as your board rails on each side, this outdoor moving will probably not be needed.
  17. Correct any large, obvious unevenness with your #12 or #16 block.
  18. Take your #50 long block and start sanding the bottom.  Sand with block parallel to the stringer.  Use a light, continuous motion longwise from end to end.  10x's back and forth on one side then 10x's on the other.  Keep sighting down the blank for uneven spots.  If uneven repeat.  Don't try to remove dips and bumps by scrubbing at them in one place.  Blend them into the whole with continuous long strokes. Don't try to correct uneven spots that are less than 1/8". 

  19. Make sure the tops of the racks are level with the torpedo level.
  20. Slide the level across the bottom of the blank holding it parallel, then perpendicular to the stringer.  You can put it on top of something that is very flat and about 2' long (long block-wood side down) A long level is nice too.  If you are making a board with a flat bottom side to side (recommended), and the level bubble is outside the center lines, sand until it is (not perfect just within the lines).  Look underneath the level/block as you slide it along the length of the blank.  
  21. You may see high and low spots on the foam and /or stringer.  Mark the high spots with the "Sharpie".  Plane down the stringer to just below the foam level with your block plane.  Sand off the marked areas until within 1/8". 
  22. Run the long block parallel to and very lightly around the bottom rails (just a few light passes to eliminate hard to see dips).
  23. Turn the blank top up and use the long block only on the rear 2/3 of the top -stay away from the nose curve.  Do not push any block longwise (parrallel with stringer) through the nose curve - turn blocks perpendicular to stringer when sanding top nose curve (See 26).
  24. Plane the stringer as before.
  25. Start sanding using the #50 small block as you did the long one.  Keep sighting aligned with the sun.  If you see dips and bumps you should even them out with the long block.
  26. Now, #50 short block in hand, start blending the areas in Figure 11 into the whole.  Please go lightly here.  Keep the block sideways as you push through the top nose curve.  There is a strong tendency to gouge a dip here.
  27. Please round  the nose tip.  One California eye surgeon I talked to does at least one eye surgery every week that is due to thruster nose tips.  Most of these cases result in one eye blindness, usually caused by their own boards.  I personally have known two people blinded this way.
  28. Next turn the board rail up.  Your black rail lines should still be there.  Sanding longwise only, run your long block very lightly above below and finally at the line.  Try to do exactly the same number of passes in the same areas in the same direction on each side.
  29. Take a sheet or belt of #50 sandpaper.  Stretch it between both hands and push it down firmly enough to make it curve around the top rail curve.  Now walk it down the entire length of rail.  Do this quickly and ease up on the nose and tail.  Do both sides until the rails are blended perfectly.
  30. Step back and view the sun aligned board again - rail up, top up, bottom up, and vertical.  Fix any unevenness etc.
  31. Pass the block plane at least one more time on the top and bottom stringer until it is even or just below the foam.  If you leave the stringer sticking up the glass is likely to crack.  You may notice that the block plane doesn't work around the top nose curve.  Adjust your block plane to a slightly deeper depth (only for this area).
  32. Finish the fine details in perfectly even light.

Put it somewhere safe and leave it alone until you glass it, which should be soon!  Note that if you are making a tri or twin fin board, you may want to install the boxes now - before you laminate.  See FINS.

Practicing with Materials video (1of 2)

Practicing with Materials suppliment video (2of 2)


2003 by Stephen Pirsch, All Rights Reserved.

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