Hollow Wood Surfboard - Plywood and Cedar

Over 20 years ago, I tried surfing for the very first time and fell in love with it. It is one of those intangible loves, where the sum of the experience cannot really be quantified. I still cannot exactly tell you what it is that brings that joy… maybe it is the expanse of the ocean, the power of the waves, the feeling of a clean peak and ride out, or just the sheer joy of being on the water. 

After my first experience, I knew that I had to have a surfboard. There wasn't a lot of materials available inland where I live, but I learned what I could online and built my first surfboard following the style of Paul Jensen Surfboards. It was a big and heavy hollow-wood beast with cork rails. And it was flawed and somewhat obstinate, yet I loved it. I built and cycled through other boards after that, but I always held on to that one. It's now 20+ years old and retired, but still hangs in my garage. Life and careers and family got busier, and for a long time I didn’t work on any new boards. Then two years ago I bought a set of paddle board plans from Sliver Paddleboards and built an 11’2” SUP for my wife. It was a fun build, I learned a lot, and fell back in love with board building. (I highly recommend anyone buys his plans or kits, and then uses the incredible amount of resources on the site to build their own.)

This last summer, our family spent a week on the beach. Our son is now old enough that he could surf with me and we had a blast. (Except for the jellyfish incident). At the end of that trip I decided I wanted to build another surfboard, combining what I learned from all my previous experiences. It was a fast build, and this board took 10 days from start to finish.

1 sheet - ¼” birch plywood

1 sheet - ¼” cabinetry grade cedar finishing plywood

2x – 8’ cedar 2x6

Titebond 3 glue

“PL premium” deck adhesive

“Door and Window” expanding foam

4-oz fiberglass cloth

Entropy epoxy resin

Tablesaw

Jigsaw

oscillating cutter

planer

router and bits

The plan dimensions can be seen in the drawings above. It had to be under 8 feet total though as I don’t need the extra length, and most importantly, plywood doesn’t come in lengths over 8 feet. And I wanted to use that as my decking. So, the overall design was finished at 243mm x 58mm, or roughly 8'0 by 22-5/8”

My goal was to create a board that would be rideable in small to medium surf. And I needed to account for my increasing age and weight, and lagging skill. So I needed a decent amount of flotation out of it. I decided that I would build a mini-Mal style of board, with a fairly easy entry rocker, high volume, and rails that increasingly hardened out towards the tail which would be a squared-up pintail. That way I could still get a decent release out of the tail for turns on the drop. I used Shape3Dx (free basic version) to create my overall Board shape. It is a dedicated surfboard shaping software. Like all 3D design the software, it does have a learning curve to it. That took me a couple of evenings of playing around before I finally ended up at the shape that I wanted. 

Once I had the shape figured out, I sectioned the board every 200 millimeters. Then I printed out each of these section lines to PDF, imported it into Visio, and offset the lines to account for the deck skin, create cut outs, and intersecting joints. (There is an option on paid versions of Shape3Dx that allows you to automatically generate these. But I knew that I would need to modify them further so I decided to do it manually.)

Where my build design differs from all others I have seen online is in how I created these skeletons. Most other builders will cut out the skeletons ("Fish bones") completely, and then support them by building build one or two rocker tables. Those rocker tables follow the stringer profile, and allow you to use force when gluing on bottom skins and the deck skin. If I were to be building multiple boards, rocker tables would make sense as it would be reusable. But for a single one-off board it is a lot of extra work (and then discarded materials) that I could bypass by creating cutaway ribs.

I planned to keep my lateral ribs attached to a supporting piece of plywood. I would place them along a strong back (like building a canoe) and then cut them away later on once I had finished the rails and deck skin. I wasn't 100% certain whether this would work.. But having done this once I would definitely now repeat it. So when you are looking at the rib kit that I generated, you will see that each rib is attached to a precisely measured height in line with its position along the rocker. You'll also see that there is another line on each one that shows the reverse rocker it gets cut down to and used when the bottom skin gets attached later on.  

• Full Plans are attached below. They are sized on "Architectural D" sheets which can be printed at Staples or other stores. These can be glued onto your wood and cut by hand with a jigsaw.

Because I had created my design digitally, I also used digitized tools to cut it out. In my case, this was done utilizing a laser cutter. But these designs could also be imported into a CNC machine. They can also be printed on full size sheets of paper and then glued onto quarter inch plywood and cut out.

Whatever method you use to cut them out, you will need to do so out of quarter inch plywood. At the end you should have a set of funny looking ribs that look like the ones shown.

Instead of a rocker table, you will need to build a strong back. Just like if you were to build a canoe. In my case I took two 2x4 pieces of lumber and attach them together into a T shape. Then I fastened this onto the top of two sawhorses. Last of all, I snapped a chalk line down the centre of my top piece of wood and then attached my rib sections every 200 millimeters, centred and squared..The stringer was cut as 3 pieces, and these were attached and then smaller clamping pieces glued on to make them connect.

The rails for this board were made out of 3/8 x 1/4 inch cedar. Each of the strips was cut to dimension and then milled with a set of router bits called Cove and Bead or canoe bits. This puts a male rounded profile on one side and a female rounded profile on the other so that they can close up around complex curves. I milled 14 strips for each side of the board. I had tossed around the thought of doing a larger "Foundation strip" like in my drawing, but decided against it due to lack of flex.

Be very careful when running a router. I have developed an immense respect for routers after I accidentally ran two of my fingers through one last year. There was a lot of blood and some broken bones. To this day, I cannot feel anything with the primary fingers on my dominant hand, and I miss that.

Starting at the bottom of my board, I began attaching these to the skeleton. The nicest method is to use clamps and do them one at a t time. But I was on a short deadline, and willing to have the little bit of scarring from stapling. They were glued along the length and I stapled them to the skeleton utilizing a electricians cable stapler. (This is a type of staple that has a rounded crown and is really easy to grasp and pull after the fact.)  Ratchet straps were also used to help hold them. Usually I would do about four strips per rail and then wait for a couple of hours before coming back and doing a few more. This gives them some chance to stabilize and for the glue to harden, as some of the curves are quite tortured. Altogether, the strips for the rails were done in two days.

With the rails all glued up, I then pulled all the staples that were being used to temporarily hold them in place. The glue was hard at this point and the rails hold together. Once I had all of that metal removed, then cut the ends flush and attached solid blocks for my nose and tail. I then planed down the rails and blocks to smooth them to the deck junction.  

At this point I also filled the rails with expanding foam. If you've ever worked with expanding foam before, you know exactly how sticky this is. I like having a little bit inside of the rails to grip the circumference and hold the rails together in case there are any places that I had missed gluing up on. Be careful the type that you select though. It must be a very low expansion “door and window” type or else it can bulge and distort your rails.

For the top and bottom skins I had bought cabinetry grade quarter inch cedar plywood. (This is not the “Purist” method, as a lot of builders will mill and laminate all their own pieces of solid cedar together and create their own skins. Or strip-plank like a canoe. But I was on a short timeline for this board.) I ripped the board in half lengthwise on my table saw and then placed it over the top of the board and traced around the outline. I then squeezed a thick bead of deck adhesive onto all of the exposed wood and glued the deck on. To clamp it I used a assembly of ratcheting straps. Once the adhesive had dried, I removed all the straps and then did a quick pass along the rails with a planer to take off the bulk of the excess.

With the rails and the deck all glued on, the board has a massive amount of stability. I used a short angle screwdriver to remove each of the skeleton webs from my strong back and then flipped the board over. When I had cut out all of the skeletons on the laser, I had also engraved a line across the bottom to show where I should be cutting too. I did a rough cut first with a flush trim saw and then used an angle grinder to bring each of the skeletons back down to that line. 

Last of all, I put in a couple of supports where I knew that my fin box was going to be. Because I'm using a fin box, I needed to have the whole area solidly blocked to support the fin box on the inside.

All of the pieces that I cut away from the skeleton had another line engraved on them that showed the reverse rocker. I used a jigsaw and cut away to each of those lines and then fasten them back to the cleats on the strong back. This then formed my reverse rocker table that would allow me to flip the board and clamp the bottom skin on.

The bottom skin goes on exactly like the top skin. Before I flipped the board and placed it onto the reverse rocker table, I put some old blankets over top of it so that I wouldn't scar the deck wood. Every exposed surface along the skeleton and along the rails got a bead off deck adhesive. The bottom plywood skin was then clamped down using ratchet straps again.

Once the bottom skin was dry, I built a quick set of shaping stands. These are basically a glorified Y shape that allows you to place the board on its side or flat so then you can work on it with tools. To protect the wood of the board from dings, I used an old piece of carpet over top of each one. I then started the process of sanding and planning. I used a cordless planer and set my depth to the absolute minimums that I wouldn't take off too much material in each pass. Each of the two skins was slowly brought down until it aligned with the rails. Once that was done, a belt Sander was used to do the final smoothing of the wood.

One of the most beautiful things about a hollow wood surfboard is the fact that your rails are already built into the design. You basically just need to go and smooth them out. This is way different than freestyle shaping rails on foam or cork, where you need to be so careful about the symmetry and shaping. You will probably find some voids as you're going along. Fill those with wood filler as you go. (I do not suggest using glue and sawdust as that dries harder than the surrounding wood and makes it difficult to sand.)

As much as a plain wood board is beautiful, I decided to do a deck inlay to put a little bit of colour into it. I used pre-glued cherry veneer strips and stained them a light blue. I planed off the top skin from the plywood in the nose where I wanted the inlay. Then I ironed them on to set the adhesive. After that they all got a light sanding to give a weathered look.

After a lot of sanding and filling, I was finally happy with the state of the board. The next step would be doing all of the fiberglassing. But before you do that, you must put on a sealer coat. Otherwise during the glassing, knots, voids, or even just the wood cells will suck the epoxy in from underneath your glass and leave you with “dry spots.” These show up as a whitish area where you can see the weave of the fiberglass cloth. 

I put long screws in the top of my shaping stands and then balanced the board on top of that. That way wouldn't stick to the carpet that I had covered them with. Then I mixed together 9 ounces of epoxy and hardener. This got poured on top of the board and then squeegeed off so that the board was sealed but did not have a thick layer.

I used a Futures 10.5 inch fin box on this board. I have done glassed on fins before, but I wanted to have the option to change out things as needed. I measured up the fin box and built a jig. Then I taped that jig onto the board in line with my centre stringer. Carefully using a router, I then made cutouts for the box and the lip. Once that was done, I glued in the fin box using a thickened mixture of epoxy. The top of the fin box was taped off and file used to take the tape down.

Even homemade boards need a logo. Our family has a Viking blood and it seemed fitting for a wooden watercraft. So I designed a surfboard shape around a helmet and set of bearded axes and vinyl cut it. This board has now become the 1st official model by my unofficial personal brand of "Saga Surfboards" This vinyl gets placed directly on top of the sealed wood and will be glassed over.

Before I started the bottom glassing, I used painters tape to form a perimeter drip line around the bottom of my board. This started just passed the apex of the rails. I made this as even as possible as later on I would be trimming along it with a razor knife.

Once that was done, I gave the board a final clean to get any last bits of dust off. Then I mixed up 12 ounces of epoxy and hardener. The glass was pre cut and laid over top of the board and the epoxy was poured down the centre. Starting from the centre, I spread it across the bulk of the fiberglass. Then I went back over top of it one more time to work it evenly in towards the taped off rails. The goal is to completely saturate the fiberglass while leaving only the minimum amount of epoxy still trapped in the fibers. You should be able to see the weave everywhere on your board. Be careful that you don't overwork the epoxy, as that creates microbubbles that once again will give you a whitish look to your finished product. This first coat is called the lamination coat.

Let this lamination coat dry until it is no longer tacky on the surface. Then using a razor blade, trace along your tape line and pull off all of the excess overlapped fiberglass. Then mix another 9 oz set of epoxy and hardener together. Using a clean paintbrush, spread this across the fiberglass. It will fill in all of the weave an even everything out. We call this the fill coat as it fills the weave. Let this cure until it is fully hardened.

When the bottom fiberglass was completely hard, the board was flipped. All the tape was removed and the edges of where I had cut, called the lap joint, were sanded smooth. A new tape perimeter was placed just below the apex of the rails again. Once again, I cleaned up my workspace to eliminate dust and then laid out fiberglass on the top. The deck lamination coat was done identical to the bottom skin as well as the fill coat. A razor blade was once again used to cut the fiberglass against the tape and then that excess fiberglass and tape was removed.

Hollow boards need a vent because of the massive amount of air trapped inside of them. This vent gets opened anytime that the board is not in the water and being ridden. Otherwise, if a sealed board is left in the sun, that air will eventually create enough pressure to rupture the board. For my vent I epoxied a stainless steel nut into the deck. A hole is drilled through that to the inside. This gets sealed off with a stainless steel screw and rubber washer.

Instead of utilizing a leash plug, I decided to make a leash loop. I just like the way they look. This is done by removing a bunch of fibers from a piece of scrap fiberglass and then twisting them into a rope. That gets saturated in epoxy and then placed over top of a small piece of tape on the deck. Flare the fibers where they meet with the deck. Once it hardens, the tape is removed, it is sanded smooth, and then given another coat of epoxy.

With all the hardware in place, I gave the board a final sanding. Then I mixed a final batch of epoxy and brushed it on. This becomes the final gloss coat. Last of all, I carefully took an angle grinder and ground through the fiberglass that was over top of my tape-sealed Finbox. This opens it up so that you can insert your fin.

Some people like to do multiple sandings and then coatings with spar varnish at this point. I accept that mine will get scratched and dinged and prefer to ride my boards. So that is exactly what I did.   First coat of wax was applied and the vent was closed.

There is always some bias that goes into riding your own board, but I found that it performed beautifully. I found it easy to catch waves with, and the tail was free enough that I could turn easily with it. At just over 20 pounds, it is heavier than a comparable foam board but not drastically so.

Having built a board now with this cutaway method, I will definitely repeat it. I'm always interested i making new shapes, not repeating old ones. For small one-off projects it eliminates a lot of the extra work associated with rocker tables. And with that speed, being able to have a little over a week turnaround from cutting wood to riding is fantastic. I'm already dreaming up my next design…

Second board design and another free set of prints! I had found that the last board build went so quickly and well with the cutaway rib method. So I decided to make another one.

Design idea: Board shape is somewhere in between a fish and a big guy funboard. There is a fair bit of volume to it as well. Partially for the fact that I'm just a casual surfer, and partially also for the fact that super tight bends on the rails are very difficult to make Because wooden boards are stiffer than foam ones, it has a little bit of extra rocker in it to make up for the flex you would normally have on a shorter board. This design can be either built out longer, leaving you with a board out to about 7’6” range, or cut down shorter leaving you with a fish around the 6’ range.

Build: Use the same steps as in the board above. You might need to use a clothing iron to heat and steam the strips a little bit to get them around the tighter radius of the nose on this one. If you are going to cut it down, do so after you have finished building out the entire rails.

Deck and bottom skins: I bought 1/8 inch door skin plywood, and then glued on thin strips of cedar. To do this, I laid the 1/8 inch door skin over top of a thick sheet of plywood, then stapled the thin cedar strips onto it. These stapled all the way through the cedar and the door skin to hold it flat against the backing plywood. Once it was all dry, I pulled the staples and sanded it all down.

Fins: Once again I used the Futures fin setups. I set mine up as a quad on a swallow tail. If you have never bought and installed these before, you need to know that the finboxes closest to the back need to be the”1/2” depth and the further forward finboxes need to be ”3/4” depth. So for a quad setup, you need 2x 1/2 in the back and 2x 3/4 in the front, and for a thruster you need 3/4 in the front and ½’s in the back. 

• Full Plans are attached below. They are sized on "Architectural D" sheets which can be printed at Staples or other stores. These can be glued onto your wood and cut by hand with a jigsaw.