Wha’s SUP, water lovers? A stand-up paddleboard (or SUP) is one of the newest incarnations of the venerable surfboard, and we’re going to build one that has all the wonderful qualities of the old wooden longboards. In fact, this 10’5″ longboard SUP
can do double duty as both a paddle craft and a wave-rider.
I grew up around boats and the beach. The surfboard is a natural for attracting any young beach kid’s interest. After hurling around some awfully heavy solid wood boards in the past, modern materials and techniques drew me back in. As I became interested in building lightweight sailing boats, I started to fuse modern composite technology with old-school wood. This CNC SUP project pulls in the best influences from drastically different worlds.
At the core of this CNC SUP longboard is a “rib and spine” skeleton that makes it hollow yet strong. Using a CNC router and the vector images that I provide, you’ll be able to create this internal frame in a few quick steps. The covering of the board and the final finishing are phases of the project where you can go in any number of directions. I’ll show you one way, and will hint at others. The beauty of making a surfboard is that there are infinite varieties in the final covering.
Anatomy of a Surfboard/Paddleboard
Finally, this SUP has excellent safety. It uses what I call a “NeverSink” system for its rails (the curved edges of the board) which result in a board that can survive a fracture and yet never fully sink!
Creating the CNC board is a twelve-step program:
- Obtain the materials, tools and space
- Think about time and schedules
- Use the SVG files to create G-code
- Cut the ribs and spine on your CNC router of choice
- Assemble the internal frame
- Choose a tactic for covering the deck and bottom
- Plank the deck and bottom
- Create the nose and tail pieces
- Create the NeverSink rails
- Cover the rails and body with epoxy and fiberglass
- Create the stabilizer fin
- Finish work
Software and Data
You’ll need a Scalable Vector Graphic (SVG) viewing or editing program, such as the freely-available Inkscape application. With this editor, you can view the included files and alter them as you see fit. You can print the SVG file with numbered pieces to aid you in building the board’s skeleton.
You’ll also need access to a G-code generator. You can find these online, for free, such as MakerCam. When you upload the SVG file, you will have to select your type of cut (such as a profile) as well as the sequence and bit size. For the purposes of this tutorial, it is assumed that you know how to perform this step. It is also assumed that you know how to import this G-code into your CNC platform and operate the machine safely. To learn more about G-code, see Get to Know Your CNC: How to Read G-Code and Make: Getting Started with CNC.
Materials
The SUP is a hollow wood craft with extruded polystyrene foam rails. The structure is encapsulated in layers of epoxy and fiberglass cloth, making it a true “composite” watercraft. The oldest longboards were entirely wood, with no epoxy sheathing, and many worked well. You can choose to go that route, for sure, but take some time to read through my assembly process and notes and perhaps you might find a new route that’s even better! Then, you will absolutely have to write it up and share it. If you do some digging around on surfboard builders’ forums, you’ll find an amazing variety of tactics and material choices. This is just one of my tested creations.
The Skeleton
The primary material for the board is wood. I suggest plywood. You can go the ultra-reliable route and purchase “marine grade” plywood, which is usually made out of okoume, or you can go less expensive and use the most knot-free plywood you can find and simply know that encapsulating it in epoxy will repel water and add strength. “Marine grade” plywood is the better choice, to be sure, and it is virtually free of any “voids” between the laminated plys. However, there are some very good non-marine grade choices out there. You will make the internal frame out of this plywood. I suggest one sheet (48″×96″) of ¼” plywood.
The Skin, Nose, Tail, and Fin
The covering for the board is another area of great freedom. Many people choose to use cedar strips and plane them down to ¼”. You can use plywood or other woods, but be sure they’re as knot-free as possible. I try to use found wood or recycled flooring or fence wood; of course, for such pieces I have to do a lot of repair with epoxy, but if you’re comfortable with this, by all means try it! For the top and bottom skins, you’ll want enough wood to approximately equal two 48″×96″ sheets of plywood.
The wood that you use for the nose and tail blocks should be thick enough for these ends, or you can simply laminate smaller pieces together to make blocks that are about 24″ wide × 2½” thick × 3½” long.
The fin is usually made out of scrap plywood and laminated with epoxy and fiberglass cloth. It’s usually slightly thicker than ¼”, so you may want to laminate two fin profiles together and simply sand/shape it down.
The Rails
You will need one 48″×96″ sheet of 2″-thick extruded polystyrene (XPS) foam. This is usually called “pink foam” insulation, and can be found in the big box home improvement stores. A blue form of this also works. Please be aware that the dust from cutting, sanding, or burning this type of foam is toxic, as we will talk about later, so be prepared.
Space to Build
You will need at least enough space to fit the board in and flip it over as you work on it. A room 16′ long and 7′ wide is as small as you would dare manage. You can bring the board out through a normal door or even a garden-level window. Be aware that the board is about 125″ long and 32″ wide, and negotiating tight turns or stairs may need to be taken into account. When in doubt, make a mock-up with scrap wood or cardboard and see if the object can make it out. Think about where you will cut materials while the board is progressing. Where will you glue up the skin and where will you keep the internal skeleton when they are not paired?
Stop. Breathe. Think.
Making a surfboard is a whole-body experience, and also a whole-mind experience. It is no wonder many people find ways to attach the metaphysical to the art of surfing, and consequently, to the building of the boards. Why are so many SUP riders doing yoga on their boards? There is something going on here, and you’d be remiss to miss out. Building a board is like making another type of fish for the earth. Stop and think of the form, the water, the people and the shapes. Let’s also pause a bit and think about some important aspects involved in making this new creature.
Timing and the Schedule of Chemicals
So you have your materials and tools. Great. Think about the order in which it is all going together and the manner in which you will bring material in and out of your space. As pieces are being glued up, can you progress with other parts? Look through the steps carefully and determine where you can optimize your build process. Take for example, the fin: you may have time to work on this while the top skin is gluing up to the frame. Not all steps are concretely sequential.
The use of epoxy and fiberglass cloth to create the skin covering necessitates careful thinking. Here, you will need about one day per rail (of which there are two) and one day per skin (again, two). Therefore, you will need at least four days for just putting on the epoxy and fiberglass. Then there is the sanding. Then the painting and/or varnishing. While your epoxy and paint and varnish are drying, you won’t want a lot of dust flying around; what can you do in the meantime? Think of scheduling your tasks so that suspended particulate matter doesn’t interfere with your clean, drying surfaces.
Another piece to consider is the material list. Most of the time, you can get the wood quick enough, but odd items such as the vent leash plug may take a while, if ordered. Make sure your assembly isn’t hung up on some tiny item in transit.
The Look of the Board
Many people like the “bright” look of a clear wooden surfboard. This is easily done with a layer of epoxy and then varnish (since the epoxy is not UV-stable, the varnish protects it). For my purposes, since the rails are made out of foam and the skin is made of found wood, I choose a bright look on the decks and painted rails. You can paint the whole board or only parts. That’s the great thing about surfboards: they are amazing canvases!
How to Plank the Board
Here, again, we have a lot of room to maneuver. Boards are usually planked longitudinally, which is running lengthwise. An alternate way is to lay the planks diagonally, as I have shown here. If you plank diagonally, your planks shouldn’t be more than 3″ wide or they’ll be too hard to bend — they must conform to the curvature of the top, bottom, and spine of the board’s frame.
Whichever way you decide to plank, you’ll likely have to do it in stages. You can lay out the boards and edge-glue them together first, and then place that skin on the frame, or you can glue the planks together in batches on the frame itself. Both ways will be shown here.
Fin Style: External or Internal Box
I’ll show you how to place an external fin on the board. A modern alternative is to use an internal fin box so you can use removable fins. If you choose to go this route, you’ll have to plan out how the box is to be laid into the skin (above) and then how that skin will sit on the frame. You do not want to mount your fin box on the skin and then find out that it’s in the way of the internal spine (or vice-versa).
Vent and Leash Hook Plug
This CNC SUP is a hollow wood board. Since it is encapsulated in epoxy and fiberglass cloth, the composite structure is watertight. Being hollow, however, it has air inside it which will expand and contract with heating and cooling (such as on a car’s roof). To mitigate any cracking of the skin due to expansion, you’ll affix a vent in a block and place it in the top skin near the tail. You can search the Internet for “surfboard vent plug” and find all sorts. The best will have a leash attachment where you can tie on a surfboard leash that attaches to your ankle: very handy to keep your board nearby when you decide to take a spill!
Safety
Before you begin, think about safety. Building a surfboard involves cutting various materials. Eye protection is a must whenever any type of power tool is used. Hearing protection is also important, especially if your power tools are louder than a kitchen blender.
Gloves for your hands are necessary when you work with epoxy. Do not skimp on this. Don’t try to “get one more use” out of a disposable glove. You may go through the entire box, but that’s fine. Get used to putting them on and then disposing of them, one inside the other, each time you change mediums or when the epoxy gets too tacky on them. Don’t go opening doors with epoxy on your gloves. Do not scratch that itch on your face. Epoxy and fiberglass and skin are not great mates, despite all the wonderful new “eco” brands.
Dust masks and respirators are essential any time you’re around wood dust (near the CNC router) or cutting XPS foam. The insulation foam, particularly, is quite noxious, and the dust particles are not meant to be inside your lungs. While a set of disposable masks is great, I recommend a cartridge-type respirator that covers mouth and nose.
Have a first aid kit ready, always. Have an area to clean up. Keep your phone handy not only to take pictures, but also to call a friend if you need help. Don’t try to tough things out. Stop. Breathe. Think.