After riding the same 8'6" Robert August board for 13 years, I found it had developed a lively flex zone somewhere near the middle, around the cracked and swollen stringer. It was time to strip the wax and send the board into wall-hanging retirement, but I couldn't afford a new board to replace it. Why not build my own? Could I do that for a couple hundred? I didn't want to work with foam. What about a hollow wood board? Hmm...


As part of this daydreaming and fantasizing I tried making a surfboard in a free 3D modeling program on the computer. This got me thinking about the basic curves involved in defining the shape of an entire board. It turns out you can describe the basic shape of most boards - meaning every point on a board's surface - with as few as four curves. (Well, maybe even three, if you're not too particular about rail profiles, but either way, it seemed like a manageable number to start with.)

With my Web programming background and a little research into the math used to describe curves, I started developing a web page to graphically adjust those board curves, and a rendering engine that takes those curves and builds a 3D mathematical model of a surfboard. (I didn't bother looking at existing board design software, since I assumed it was geared toward expensive foam shaping machines. Besides, it's more fun to figure these things out without reminding yourself that it's already been done.)

With the ability to take virtual cross-sectional slices through the board at any angle, I wasn't limited to traditional rib and stringer hollow board designs (descendants of Tom Blake's water sled). I was sketching all kinds of alternative rib patterns: random, radial, plan-shape-parallel - anything not square.

the quarter isogrid

Out of one of those scribbly sketches jumped a simple, obviously good, intersecting rib design. It's the design you see in the photos here, the grid of triangles and hexagons. Not quite a honeycomb, not quite a conventional isogrid, I call it the quarter isogrid. The quarter isogrid is better suited than the conventional isogrid for a notched rib assembly, since ribs only intersect two at a time. Intersections are simpler and the average notch depth is shallower, retaining more of the ribs' strength, and simplifying reinforcement efforts.


After graphically "shaping" the basic board-defining curves, I run those curves through the board modeling and rendering program, and have it produce the patterns for the interlocking ribs. These two-dimensional patterns are then formatted for a computer-controlled router. Sheet stock such as cardboard or wood is clamped onto the router table, the cutting program is started, and in anywhere from one to ten hours I've got all the pieces ready to assemble. (How long it takes depends on the size and speed of the router. A large format CNC router or laser cutter makes for reasonable cut times. My tiny router takes forever, but it was affordable.)

Assembling the board is simply a matter of lining up the first few pieces correctly, and then sliding all the sequentially numbered ribs into place. I've had this take 45 minutes to three hours. Doing it late at night with tea is faster than doing it on a hot afternoon with beer. This is one of the most rewarding steps. At the end, you have this perfect see-through skeleton outline of your board. You can see the rail profile transitions, and any concave or vee you put in the bottom. It looks so good you put off glassing it for a few days just so you can come back and stare at it every once in awhile.

Glassing is a challenge, but I'm getting usable results so far by initially draping pre-saturated fiberglass cloth over the core, and pulling it tight over the structure to smooth it out. Improved techniques and alternative materials should speed and improve glassing. This is the focus of my development efforts right now.

Resin Research epoxy is one of the key ingredients that has made this project successful so far. I look forward to trying a good Bio Resin when it becomes available.


From the beginning I set out to make a board with cheap and preferably natural materials. Foams have been structurally adequate and affordable for surfboards. High-performance alternatives are often more expensive or more difficult to work with. With the ribs-from-sheet stock approach, many alternative natural, composite, plastic, and other types of materials become readily available, at commodity prices, to replace foam cores.

I wanted to purchase as few tools as possible, and keep the construction process simple and cheap. I don't have much woodworking experience, or foam-working experience beyond ding repair, and I didn't want to buy all the saws, planers, clamps and other tools you need to make conventional foam or modern hollow wood boards. I tried to leverage the tool I was good with - the computer - as much as possible. The other tool I chose was a CNC router, which, for my purposes, takes the place of several cutting and shaping tools. With my software and the router, and a $30 sander, cheap garage production became feasible.

It was also my intent to build a board that performed at least as well as a conventional board. With my second prototype, I had a real board, and a slew of ideas about how to make these boards better than conventional boards, yet price-competitive.


There are several directions to take this board-building approach. Initially I would just like to put out a nice showroom-quality board that performs as well as a conventional board, costs less to produce, and is significantly composed of renewable and recyclable materials. From there the materials, design, and process can be refined to optimize price, performance, and customizability, among other things.

Cardboard was supposed to stand in for wood for a first prototype, but it worked so well I decided to stick with it. I pay a premium for buying cardboard sheets in small quantities and it still comes out as a cheap alternative to foam. What other surprise sheet stock materials are out there to replace foam?

Because the board core assembly originates from a computer model, it would be possible to extend that model to simulate the dynamic performance of the assembly, given the material properties of the sheet media and the skin components. A dynamic simulation would help determine optimal rib pattern scale, rib thickness, and notch configuration. Of course, it could be used to engineer flex, or other performance characteristics. (And when the flex hype goes stale, the dynamic model could be extended to help tune parabolic inertial resonance enhancers.)

This board building system is well suited to end-user board customization. My board design software is simply a web page on a private server. It could be made public, allowing anyone to graphically produce a board specification for my rendering system. The web page allows a user to upload images and plot data to use as guides in shaping the basic board curves. Custom fins could be designed and placed in a way similar to how board curves are edited. Additional output formats could be offered, including photo-realistic 3D image rendering and foam-shaping machine code.

What else can we build this way? Paddleboards, kayaks, wings, armchairs, platforms, domes - lots of things.

prior art

I call this a new approach to building boards, but as with most new things, it's really just a fresh version of something old.

Tom Morey built a cardboard surfboard in 1965 to promote a water-resistant cardboard product, called "Surfcore" (or was it Surfcor), produced by International Paper Company ("Where good ideas grow on trees."). Based on his account and this video, it looks like he made a block of flat-stacked sheets. He built three boards. The first one weighed 54 lbs. The rails were lumpy and there were lots of leaks to patch. He was able to ride the boards at Makaha, though, for a T.V. commercial and a two page spread in Reader's Digest. Not bad.

We inherit the rib and stringer approach from boat building, by way of Norman F. Carmichael, Tom Blake, and countless others who were too busy paddling and trimming to bother recording their constructions in the patent records. Surfers are always taking the art of wood board construction to new levels. Check out Tom Wegener's traditional wood boards and Danny Hess' modern high-performance wood-framed boards. Amazing.

Grain Surfboards takes the CNC approach to making beautiful wood boards and board kits. It sounds like their software and sparse ribs constrain their ability to quickly and arbitrarily alter board features. They make up for this by having a nice selection of standard models. Molded board makers like Aviso take the same approach. They say they can make a custom board, but however nicely they say it, it sounds like it's an expensive pain in the ass. Still, I'd love to have one of the Grain Surfboards standard models, and I wouldn't mind trying someone else's Aviso.

why I prefer my approach

Translucent boards.

Every board can easily be a custom board. The design software is graphic and simple and developed specifically for surfboards, the rendering software is sufficiently parameterized, and the 2D cut pattern output can be fed to the simplest of 2D CNC cutting machines.

The rib materials are widely available and cheap. A wide variety of alternative rib materials are already available as sheet stock. Specialty materials can be developed to engineer performance. Any sheet material can be dropped in with little or no change to the process.

The manufacturing process is fairly simple and affordable, at the cost of making the design process more complex. That complexity is managed by the computer. What's left is an intuitive graphic design process, followed by running the robotic router, followed by assembly and almost conventional glassing. It works at the garage level. Whether the process can be made fast and scalable remains to be seen. I think it can.

The basic approach I've established so far is a good platform for further innovation. I will try alternate rib patterns, like curved ribs cut as 2D patterns and splined through notches. The core can support established and new skinning materials and techniques. Strong fin mounts for existing and new fin systems can be securely integrated into the core structure. The design and rendering software could be extended to do dynamic modeling, analysis, and prediction of board performance. There are new artistic possibilities. You could put lights inside and run your own little bait barge. Too many ideas come to mind.

- Mike Sheldrake

(done here)