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Deciding on shape is probably the most important part of making
a surfboard. Thrusters and longboards have their place, but
many surfers are riding designs which do not maximize the fun possible
on the type of waves being ridden. Often it seems the image
a surfer thinks he will portray is affecting his design decision.
The best way to simplify the decision is to ride as many different
surfboards as possible. This is important. It is unlikely
you will ever know what is best suited for you if you do not experiment.
One hour surfing a different board is better than ten hours reading
about design, or listening to opinions. Most surfers will
let you try their board for a few minutes. Try your friends'
boards or rentals. Find one you like, then copy it or modify
I love seeing all types of surfboards, but I feel that the biggest
design drawback is simply building too small. This appears
to be a common problem with all types of surfboards. My friends
and I are happier surfers now that we are designing for the average
conditions of ourselves and our home break. Many people quit
trying to surf simply because their board is too hard to paddle
and catch waves.
Generally accepted truths about surfboard design:
A relatively wide, thick, long, flat shape is generally better
for small or slow waves.
A relatively narrow, thin, short shape with more than average
bottom curvature is generally better for fast, hollow, or large
waves (not double overhead plus).
A relatively long fin(s) or one placed towards the tail end
will make turns having a larger radius and having a feeling
of projection (energy is transferred strongly from one direction
A relatively short fin(s) or one placed towards the nose will
make shorter radius turns and will have a feeling of looseness
(board will turn easily but slide somewhat).
Sharp down turned rails are better suited for hard, leaning,
gouging turns in smooth water conditions (sharp and down turned
only in the rear quarter transitioning to rounder rails in the
Round rails will make smoother, slower, speed conserving turns. Round
rails are more forgiving, and are much better suited to choppy
A shape with more curvature in the outline (other things being
equal) will tend to turn easier, and create more planing drag than a more parallel outline.
Whatever preconceived notion a person has about the type
of board he wants to ride is more likely to determine what he
rides than what is best suited for the conditions!
The site, essentialsurfing.com, and the Clark Foam catalog, have
good, free, design information.
If new to surfing, ride mostly small, or slow waves, or just enjoy
early wave entry gliding, use the following guidelines: 1/2"
thickness for each 25 lb. of body wt. and 2' longer than height.
To be more exact use: .50 cubic feet of foam per 25 lb. of
body weight (the US Blanks, and Clark Foam catalog has the cubic foot numbers for
each blank for free online at www.foamez.com ).
For example; a 150lb. surfer divided by 25 equals 6.
6 times .50 = 3 cubic feet of foam. Add at least 5%
(1/4") for shaping losses which brings the example to
3.15 cubic feet. Simply look at the displacement number (cubic
feet of foam) in the catalog for the blank with a close number.
If you pick a blank within 10% of your number you will have a good
wave catcher. Remember to add 10 lbs to your weight
if you wear a wetsuit often when surfing. These guidelines
are maximums. More is not likely better in this case.
A board designed using the math above gives a huge advantage in
crowded conditions, by allowing early wave entry.
There are many alternatives to the standard thruster and longboard
shapes. Instead of using a longer blank you could use one
that is shorter, wider and, thicker. One & one half inch
in width or, one quarter inch in thickness is approximately equal
to six inches in length (width and/or thickness through the entire
blank, not just the center). A board 6.5' x 22" x 2.25"
will catch waves about the same as a board 7' x 20.5" x 2.25".
A board 8.5' x 23 " x 3.25" will
catch waves about the same as a board 9 x 23" x
3" . A shorter board will turn easier and go from turning to
planning faster than a longer board.
If you cannot decide what rocker to use, consider five inches at
the nose tip, and two inches at the tail end. An easy way
to form a useful rocker on any surfboard is: Divide by 2.5.
Divide the total nose end or tail end rocker by 2.5. This
will give the rocker at one foot from the nose or tail ends.
Dividing this new number by 2.5 will give the rocker two foot from
the nose and tail ends. Example:
5" divided by 2.5 = 2" at one foot point.
2 " divided by 2.5 = .8" at two foot point.
The curvature can be easily free handed between these points.
Any facets on the template or foam can be easily removed with sanding
blocks. The 2.5 curvature will create a larger planing area in the
middle of the board, compared with production boards. For
a rocker that is similar to production boards divide the nose measurements
by 2.25 and the tail measurements by 1.75.
A blank (with all its measurements) can be choosen from the Clark
Foam catalog and copied with polystyrene block foam - this is the
hard, cheap way. See POLYSTYRENE. Note: Although Clark
Foam is out of buisness, the old Clark Foam catalog is an excellent
design resource. Also; see the US Blanks catalog - both available at Foamez.
The easiest way to shape a surfboard is to pick the exact blank
needed. Anyone who orders a roughly shaped polyurethane blank,
and has to cut the entire rail with a saw, or plane in different
rocker, is probably working much harder than is needed.
Unless you are sure the blank will not have to be modified (blank
is exactly the shape you want), make a template (as outlined below)
on 30 lb. roofing felt, or trace the board outline directly on the
blank - the left over roofing felt will be used later to protect
the floor when glassing. Making a template will allow mistakes
on a very cheap surface, instead of an expensive blank. Also,
a template will make it very easy to exactly duplicate, or slightly
modify an earlier board. Resist drawing numerous lines, hoping
to visualize what looks right.
Make an outline template by doing the following:
Place the original board top down on 30 lb. roofing felt,
and trace out 1/2 the outline longwise (If traced 100%, it is
not likely to be symmetrical). Use the machine edge of the
roofing felt as the center line. Keep the pencil (white colored pencil, or silver ink marker is best for roofing felt) at ninety degrees to the rail edge.
This can be insured by taping the pencil to a torpedo level.
Remove the fin/s, and line up the outline template with the
stringer/centerline of the model board. Make sure it is perfectly
aligned with the nose and tail.
Feel around for the box hole etc., under the roofing felt,
and mark the center outside edge of each end of the hole.
With a sharp pencil, poke a hole in the felt and connect the holes
with a straight line (so the hole can be found). This will
save you the trouble of measuring when you install the fins -
mark the fin location/s by putting the template on top of the
board and mark the locations through the holes.
A rocker template can be made by doing the following:
Put the board rail up (at 90 degrees to the floor) with rolled
towels about 2' from each end, under the rail (to keep the board
Brace the board with a box etc., on each side (to keep it from
Tape a marker to a mixing paddle etc., and trace the rail outline
by sliding the mixing paddle along the flat surface of the board
(at 90 degrees to the floor) as the marker contacts the roofing
felt (tracing the entire rocker from nose to tail, top and bottom).
The paddle is needed to bridge the extra distance from the floor
at the nose and tail. Where the towels and boxes block a
continuous line, simply connect the lines after removing the towels,
boxes, and board.
If the above method is not practical, get measurements (or use
your own) at 3, 6, 9, 12, 18, and 24" for the last two feet
of nose and tail, and every one foot for the rest of the board length. Do
Measure from the stringer to the board edge using a framing
square etc. and a torpedo level at ninety degrees on the rail.
Mark these points on roofing felt, and draw straight lines
between the points.
Create the curvature by cutting slightly outside the lines
between the points.
Finish creating the curvature by sanding the edge of the roofing
felt with the #50 short block (see STANDS AND BLOCKS).
Roll it up, and put it in a box (see Figure 4).
Note: If you know the blank will not need to be modified
(recommended), these steps can be skipped.
Although there are many good reasons for making the measurements
below, I urge tracing the outline and rocker of an existing board
on 30 lb. roofing felt (as mentioned above), or directly on to the
foam blank. If measurements are possible , a piece of roofing
felt can simply be taken where the measurements would have been
made, and traced instead. Tracing is faster, easier, and
less prone to errors.
If you must measure, see Figure 1, 1a, 2, 3, and the directions
If you insist on measuring try these steps:
To get the needed measurements and transfer them to roofing
felt or, new foam blank (or better yet simply pick the blank with
these measurements) you will need a tape measure and 1-10' piece
of electrical metallic tubing. You can use anything perfectly
straight and as long as your board. Electrical metallic
tubing is available at Lowe's etc., for $1-$2. Make sure
it is straight (sight down its length while turning).
To get and transfer the measurements in Figure 2, you must
mark the center points of the original surfboard bottom and the
electrical metallic tubing.
Roughly level the surfboard by putting a level over the center
mark and parallel to the stringer (wood center piece of surfboard).
If the surfboard is on the ground you will probably have to put
something under the tail, if on stands slide it nose forward.
Balance the center mark of the electrical metallic tubing over
the center mark of the surfboard and parallel to the stringer.
Center a magnetic torpedo level over the center mark of the
electrical metallic tubing (magnet will stick). You will
probably have to shift the level of the surfboard to get
the electrical metallic tubing to level exactly (bubble in center)
over the center marks (see Figure 3).
Once level, get the measurements shown in Figure 2, (more
measurements are better - 3. 6, 9, 12, 24" from the nose
and tail ends, then every 1'). You may repeat this process
when you begin to shape your foam blank.
Take the following fin measurements: (1) distance
of fin box or fin(s) from tail end, (2) angle of fin(s),
(twin or tri fins only - you could cut roofing felt etc., to match
the angle or use an angle finder tool). (3) distance
of fin front edge and rear edge from stringer (twin or tri fins
only, see FINS).
Assuming no calipers, take approximate thickness measurements
at 3, 6, 9, 12, & 24" on each end, and each foot thereafter.
Do this by putting the board rail up, straddle it, and look directly
down. Line your eye with the end of a measuring tape, and
the bottom (flat vertical side) of the board. Move your
head to line your eye with the top and write down the measurement.
Repeat as needed. With practice, many people are accurate to within
It is much faster, easier, and less prone to errors to trace.
Measuring should only be needed if building from catalog measurements,
or creating a shape from modifications of other shapes.
Ordering a polyurethane surfboard blank that is exactly the shape
wanted can eliminate tracing and measuring (some measurements
may be needed to figure out which blank to choose).
If choosing a roughly preshaped, polyurethane blank, pick
the blank and rocker that is the closest to your desired measurements.
The less foam you shape off, the stronger your board will be, the
less work you will have to do, and less errors you will
make. Note: There are now two versions of polyurethane;
one which is uniform throughout (MDI), and another which has a crust
(dense 1/8" outer layer) - (TDI)
Polystyrene block foam will allow a design that would be impossible
with polyurethane foam. In contrast to TDI polyurethane, polystyrene
foam is the same density throughout, so buying oversize polystyrene
block foam is ok, and advisable.
Combine the smallest stringer possible, with more cloth in the
laminate. Epoxy glue joints, and stringer less blanks work
well also, if the amount of cloth in the laminate is increased.
Break tests done on surfboards indicate a surfboard with a light
stringer (1/12" is light) and heavy laminate is stronger than
a surfboard of the same weight with a heavy stringer and light laminate.
Multiple light stringers or epoxy glue joints are stronger than
an equivalent large stringer.
Check www.foamez.com , www.fiberglasssupply.com, and www.surfsource.net for availability
of polyurethane and polystyrene blanks. If available, you
can save money by having a blank shipped, and held at the central
shipping warehouse (to be picked up by you) in your city, rather
than delivered to your home. Polystyrene block foam is available
in all large cities.
Please do not short cut what is probably the most important part
of board building; your design. It is amazing the hours
of sanding and rubbing builders are willing to endure for a glossy
finish, while stubbornly refusing to think for one minute about
design. Ask yourself, "what are the average surfing conditions
of my home break, and what design will best allow me to take advantage
of those conditions?" Ride a lot of boards before you