Geometry in Surfboards


I have this project to do for my Geometry class. I need to answer the question, “Where is Geometry?”, and one of the choices was to interview a surfboard builder. My teacher directed me here.

Can you help me out? Any information would be greatly appreciated.


When I was younger I was too lazy to do my homework.

It seems that tradition continues on the internet.

there is not a whole lot of simplistic geometry in surfboards.

i.e. simple equations to represent all facets of the design.

I suggest you look at rocket/missile design and the 16:1 ratio,

much more simplistic, geometric shapes, and interesting.

All built around straight lines and circles.

*** Or even the Crusader Artillery Program and parabola’s ***.

And how One Mobile Artillery Gun can replicate a Shell Barrage

that used to take 5-6 Artillery Guns.

Trust me…, this surfboard thing is too esoteric from a simplistic

geometry perspective. Its a dead end for your level.

geometry in the sence that it is all about smooth flow: curves blending together seemlessly

good luck on your project (do some homework/research - do some searchs in the “search for” box at the top of the page)

geometry is the old math…it only works on wood …foam is for right brainers who build impulsive shapes in record time…on a lark…ambrose…three before monday to make the plane…hey kid try the Computer Assisted Design guys they think in forulae

What a great question. I wish my Geometry teacher had detached himself from his protective podium long enough to ask us to open our eyes and have a look around instead of pouring sand from the desert called proofs down our throats everyday.

Geometry is everywhere in surfboard construction. It starts perhaps when we sight down the stringer of our fresh blank and check to see that stringer is suggests a straight line. If not, we make some marks on the two ends and draw one ourselves to serve as a reference line. From here, depending on whether we have a template or not, we draw a series of reference lines perpendicular to the stringer or our reference line we drew because the stringer was cattywhompus. We mark our nose, widepoint, and tail widths. Then, we place our template on one side of the stringer and trace out half an outline before reflecting in our mirror line stringer, flipping the template, and tracing the other half of our outline. From here we cut out our template. We then use a t-square and sanding block, planer perhaps, to square up or true our outline.

Perhaps the board we are building was inspired by a picture we saw in a magazine or on the internet. If so, we used our knowledge of geometric proportions to enlarge the picture into a functional outline. Perhaps we are building a front foot driving hull and notice how, on some of the most fine tuned examples, all the curves, outline, rocker, and hull, appear to coincide around something called The Golden Section, approximately 2/3 up from the tail. Same for many of the boards that are meant to be driven with the back foot, except for 2/3 back from the nose.

Once we have our outline cut out we might stand it up and check the outline. Is is too parallel or not parallel enough? We keep in mind for whom the board is being built and maintain a certain volume in the blank. We start shaping the rocker and notice the entry rocker on many boards accelerating 1/3 back from the nose through the tip. We’ll adjust the crown of the rocker to coincide with the surfer’s preference for front foot or back foot surfing. Depending on what type of surf the board is being desinged for, we’ll measure 1/4 up or 1/3 up from the tail for our tail rocker break. The curves then blend, we don’t necessarily want 3 different planes in our bottom curve.

We might think about how to increase the surface area of the bottom of our surfboard without making it “too” wide, and reveal channels, or concaves, or hull. If we’re shaping a hull we might sight down the straight line stringer and measure out to The Golden Section, make a mark and have our hull accelerate from there out to the rail. Same thing for the hump in the s-deck or for marking the start of a step-deck.

Once the board is shaped it’s then up to the glasser to place the fin box perpendicular to the stringer or perpendicular to the plane that is the bottom of the surfboard. Perhaps the board is a tri-fin, suggestive of a triangle, and the glasser must place the center fin perpendicular to the stringer while the side fins are placed at two different angles, toe-in and cant.

Now, if we’re big time, once the board is finished, we might depend in part on advertising to market and sell our surfboards. We notice in the best ads, the ads that seem to whisper in our ears and encourage us to reach for and extract money from our wallets, that our boards are placed in areas on the page that correspond in one way or another to The Golden Section.

This barely scratches the surface. There are others here with much more knowledge who might add a thought or two.

Good luck with your project.


if i were you i would just cut and paste that last post and print it up! Thats what i would do


… to sharpen planer blades hold them at a 30 degree angle (approx.) against the stone. Once sharp at 30 degrees, increase the angle a little and sharpen some more, create a slight chisel tip, to keep the blade from chipping.

It’s heresay but I once heard of a shaper who had a vision of surfers surfing through space on triangles and that vision was, in part, the inspiration for wide points moving behind center on surfboards.

Speak to surfboard blank manufacturers and some will speak to you about the either pentagonal or hexagonal structure of their chemical bonds in their foam, a reason, perhaps, why their foam seems at once less dense and stronger than some of the other foams.

Hello Ambrose, I notice that you refer to the left brain/right brain concept, and imply that geometry is not useful to the right brained shaper. I think that the idea that right brained or creative thinking cannot use formal geometric curves is based on the notion of creativity as personal expression. There is another analysis of the nature of creative expression that suggests that creativity is what we do when we are in tune with the Creator, and that it is an impersonal process. This second notion is the way of the mystic. The first notion, that is, that creativity is a personal expression, is the way of the individualist. If we accept that creativity the result of using oneself as a channel for ideas from the Creator, then the use of perfect geometrical forms is inevitable. What individual can design a more perfect curve than the circle, parabola, or ellipse? Trying to ‘improve’ on nature’s perfect curves is a tall order!

The Imp Lied is correct the Implicit Creator is indinguishable from our human form.To consider less dampens the pure creative process…Channel ? contemporary rhetoric ,I submit, for another control attempt by the structure dependant “scientific” mind…applied geometry is and has been every where in nature and craft set up house keeping.

Like columbus discovering the new world and Americus Vespuchi naming it after himself,a fine joke to the People who had inhabited this alternative culture for many centuries…Pathagoras discovered that geometry that tile setting masters had used to lay out tile floors certainly for centuries before Pathagoras.The Plan guys are geometry dependant ,the do guys that are trained and in the groove can"wing it through w/out layout lines, templates,golden fleece or an audience at a seance…ultimately the tree was first and within the tree was all knowledge. Hearing the tree speak was the trick,coaxing the tree to speak to us and reveal its dreams of flying over the sea. Always trying to get a little taller to feel the breeze , hearing tales

of the endless sea

from the visiting birds,filled with nutrients gleaned from sea creatures consumed in passing and left in fealty to the lofty monarchs of the coast range.the tree when It speaks to the comcerned doesnt speak in geometric formulae but in direct concern for dryrot ,a bad year 40 years ago ,a greai growing season 5 years ago , a list of endless fires…and always getting back to the sea,The paternal overthrow of world culture worked dilligently to discredit the pagan methods and co-opted everything they could of merit and renamed it and claimed to invent it and collect from all who would buy in…I have been of the opinion that perfection is on a sliding scale on a slippery slope where ever you decide is perfect although the elctron micoscope will receal a higher margin of error awareness…WE are perfect and , everything we make is perfect by default or until we are revisited by “THE CRITIC” capable of talking up any flaw…right brain?.. ambrose… when you aren’t right there is only one alernative …left…as it may work better for some .belss their hearts. provide them wih theory and and paper and pencil…

Ambrose, You appear to be contradicting yourself. First you say that

applied geometry is and has been every where in nature”, and then that

“the tree when It speaks, . . . doesn’t speak in geometric formulae”

Offering oneself as a channel for higher forces, or allowing oneself to receive inspiration as a blessing, is an age old practice. Brushing this meditative process off as a “Contemporary rhetoric” and “another control attempt” is foolish.

Regarding the left and right brain distinction, realise this: For the best results both hemispheres, and thus both the creative and analytical mind, should be functioning correctly. It is not a case of one or the other, or “Ancient Hawaii versus Modern Science”! We have been given many mental faculties, why not use them all?

As the one who pointed lee sits on the right hand of the fool on the hill I thank you for recognising my foolishness,as it is a compliment to have my devotionals credited.These forays into the greater mind are likely to be the only posssible salvation of this miserable human species.To claim to have channeled higher forces has been used in memorium by hucksters and gypsys to bilk old women out of their savings …I realized at a young age that disecting materials like dry rotting wood down by the creek was access to the life and times of the tree from which the branch fell…the best hemisphere is the one that doesnt get us into untenable and unkind situations that there is no getting out of… ."science "has a questionable track record and is as suspect as “channeling” {the term channeling is not in my old dictionary as is currently used as a reference to hearing or sensing fom beyond physical senses} ancient hawaii is not the concern the druids and world wide nurturing based cultures ie pagan like mother earth get it? not patriarchial like the overthrow of that was done by war helmets force and “SCIENCE” control organizatons of every shape and color …my point is that using all our facilities is not the best Idea some would best be left time to rest and reflect before wrecking more cool stuff …old growth is better than plantation grown.wild salmon is better than farmed salmon ,because scientists are just guessing,they get more accurate all the time, but I sure am glad I didnt eat that brain fed beef sausage from devonshire’s advanced ag.lab with the mad cow virus, or that farmed salmon with the mad fish diseasefrom canada either or the mad science PHOPAWS yet to be…I left my Left brain to science but my right brain is going to be with the great spirit …You’re gonna miss me roy .I promise not to let anyone burn you in effigy at swaylolicks annomyus… ambrose… Your only supporter in the whole world … only because someday you Will ride a foam board without a helmet or a wetsuit or zinc oxide and have fun

actually no contradiction - nature is geometric - but applies no formulae - just like shaping really - if it works it gets kept, if not it becomes extinct. evolution is pretty much trial and error.

With you on the druids ambrose - bur roy - they too worshipped wood

Mr. Stewart will have more than one supporter at SA although he certainly does not appear to need support. Not only are his boards interesting and beautiful to look at, but his remarks stimulate banter that is more fun to read than watching “American Choppers” re-runs. Mike

aye sylvie an thats wwye we love 'em an ourselves cause thats the druid way and ancestors were amongst the trees I would speculativly guess … ambrose …proud to count Pinicchio as a distant cousin

clearly one of the top ten threads going on right now.

in a land with no television, ambrose would have scores of women at his feet.

as for roy, i think ive actually seen you surfing: n.z. two years ago at the beach break on the way out to manu (sp?) bay.

it was either you or someone else with a scary big board. i must confess that the board was moving at a good speed and it most certainly did turn- a tele-ski turn instead of a snowboard carve. interesting to say the least. i didnt see the red wetsuit, so maybe im mistaken.

please continue, i feel a soul coming back in.

the spline is a basic geometric shape of surfboard templates [its real name is second order polynomial: y = a + bx + cx^2: complex math but easy enough to draw]. Many beautiful boards are drawn by tracing along a flexible wooden spline bent around 3 or 4 nails stuck into the blank, and then drawing the mirror image on the other side of the stringer. Like a lot of geometry, an accurate drawing is easier than the math behind it. In this case the use of the wooden spline is a far easier way to lay out and refine the template than is the math and associated measurement of tic marks to approximate the curve. Sure elipses, circles and sine waves are great, easier to calculate and draw, but those shapes rarely match the free flowing curves that mother nature and most surfboard shapers set loose in the sea. To me, surfboard geometry is all about drawing and re-drawing which i love, but if i ran a milling machine then I would be happy cranking away with equations in search of the same shapes.

oops sorry. it took so long to compose my paragrgraph that i missed the change in thread direction

Bee Tail

Fractal in design

not geometric

Ambrose …sensei!

For the first time since Paul Gross (he did a bit on a Swaylock’s thread, writing the entire thread, including “responses” from many of the regular posters at that time - it was generous and brilliant and hilarious and he got everyone dead on), I need to print another thread for the sheer wonder of the writing. Thanks for those last two posts, the lying imp and that one next to the fool on the hill.

A beautiful mixture of levels, encompassing those things which can’t be expressed directly in verbiage, touching many points, all with wit and fantastic imagery.


And thankee Roy for your ferment/foment, the energy.

from the sidelines (as usual)


Some folks like to get trapezoidal, or at least trapezoidalesque: