Having successfully built three recreational kayaks constructed of marine-grade plywood using the stitch-and-glue method I had some surplus materials remaining and decided to pursue another boat project. The idea of stand-up paddleboarding (SUP) appealed to me — and to my sons also — so we decided to build a board rather than another kayak.
The above photo is of a Jarvis Boards’ San Marcos model beautifully crafted by a builder in Canada.
I spent about a year researching various plans - free and paid - and techniques for wooden board building. I learned what I could from reading and watching videos. As a kid I’ve surfed in the Atlantic and in lakes behind boats, but I’ve never used a stand-up paddleboard. How hard could it be? It’s all about balance, right? The designs offered by Jarvis Boards of Austin appealed to me so I took advantage of a really good Black Friday sale and purchased the printed roll plans (which my sons gave to me as a Christmas gift.) I also purchased Jarvis’ kit of plastic parts (deck lashing plugs and fin box) at the same time as it also was deeply discounted.
I chose Jarvis Boards’ 11’-4" long San Marcos model as it seemed geared towards casual users and offers stability. In my mind’s eye I could see me and my dog paddling around the lake. He loves riding in our canoe, but can’t fit in or on the kayaks and feels left out.
- I had plenty of left over Raka brand epoxy resin and hardener from my kayak builds.
- Although I haven’t unrolled it, I’m pretty sure I have enough 4 oz fiberglass cloth to fully encase the board.
- Okoume marine-grade plywood is the material of choice for the framing members, but since it is not available locally I elected to go with a sheet of 5 mm RevolutionPly from my local Lowes store. Comprised primarily of Poplar, RevolutionPly is purported to be more “green” and sustainable than tropical woods such as Okoume, Meranti or Luan. Also, Revolution is a fraction of the cost. So far while working with the plywood I’ve encountered no knots or voids. Since the framing members remain straight and are not twisted or contorted within the board this bending strength of the plywood was not a concern as it would be for a stitch-n-glue kayak hull or deck.
- Paulownia is the lumber of choice for the skin of the paddleboard. Paulownia is described as being the second lightest weight commercially available wood next to balsa, and it is much stronger. Originating in Asia, Paulownia is grown commercially in tree farms worldwide and is purported to be a sustainable product. I shopped around several specialty lumber yards in my area but could not find Paulownia. My best local option was Western Red Cedar lumber. Thankfully, Jarvis Boards decided to shift their warehousing operations and rather than move it they deeply discounted their remaining stock of Paulownia lumber so I jumped at the opportunity to purchase from them.
- The glue recommended by Jarvis (and some other builders) is a polyurethane glue such as Gorilla ™ glue because it is strong, fast drying, and foams up to fill voids within bonds. Others recommend Polyvinyl Acetate (PVA) which is what most folks recognize as standard wood glue. A hot glue gun is recommended for certain steps in construction where an immediate bond is needed and that can be cut or melted apart at a future step in the process. So, I’ll probably use each of these, in addition to occasional epoxy mixed with a wood flour thickener.
As you can see below I’m preparing to cut the 5 mm plywood sheets in half lengthwise.
The plans or patterns for the structural pieces are plotted on 2’ x 8’ paper, so I began by ripping the 4 x 8 sheet of plywood in half lengthwise. Then I diluted Elmer’s ™ glue 50% in water to affix the paper patterns to the plywood. A foam brush was used to apply diluted glue to the wood in sections as I rolled and smoothed out the paper. It dried overnight and in the process many of the wrinkles disappeared.
This technique of wet gluing paper patterns to plywood may not be appropriate for visible hull pieces of a kayak, but since all of these plywood components for the paddleboard were internal I accepted a bit of paper size growth or shrinkage due to the wet glue. For my kayaks, I kept the paper patterns dry: taping them to the Okoume plywood and using a pointed awl to transfer the shape outlines to the plywood by punching through the patterns. While cutting out the patterns I learned that either I diluted the glue too much or didn’t apply enough - as the paper was separating from the wood in some areas.
Jarvis’ plans come only as patterns with absolutely no instructions. I watched enough of their videos to understand the process, but it took a minute to understand all of the pieces on the paper sheets. To their credit, one sheet has exclusively longitudinal components (which must be jointed together to form their full length) and the second sheet is exclusively cross members. On the longitudinal center spine and rails sheet I used a highlighter marker to indicate which pieces join other pieces and on which end.
During my kayak build I learned about the benefits of a scarf joint (depicted below) and I am determined to join these longitudinal frame pieces with scarf joints rather than with butt block joints, which was depicted in all of the paddleboard construction videos I viewed. The butt blocks add unnecessary weight. The scarf joint is essentially a pair of matched wedges of wood with a large shared surface area between them to accept glue, making a strong joint.
To accommodate the length required for the joints, I measured and added 3/4" to the length of each of the pieces, sketching it on the pattern sheet with a pencil. Original outlines of the components were maintained so I’ll be able to confirm the final overall length is correct. When building my kayaks, the scarf joints were across 2’ wide plywood sheets prior to cutting out the hull shapes. I cut these scarfs using a circular saw and a wooden jig to hold the saw at an acute angle, then cleaned them up with a block plane. See related blog post. For these paddleboard frame members I’ll just use a block plane and perhaps a belt sander.
NOTE: I decided to go with 1" scarf joints and so have reduced the added length to just 1/2" rather than 3/4".
It seems other scratch builders cut out the voids in the structural members using a jigsaw. I decided to use my hole saw set with a drill in hopes of gaining some precision and maybe some speed. I did have some problems with the hole saw blowing out the material on the underside of the plywood stock, so I learned to go slower and apply less pressure as the drill turned the saw. I’ll fill these blowouts with thickened epoxy to ensure structural stability of the frame piece.
Comparing Jarvis’ plans with those of other paddleboards, the Jarvis plans are conservative in removing less material from the cross members. I took some license in determining how large to make the voids, using the closest sized hole saw. In some cross members (which are not beneath the load bearing area of the finished board where one stands) I removed extra material by drilling additional holes with a smaller blade. Again, the purpose in removing extra material is to reduce weight by creating more and larger voids in the plywood frames. According to Jarvis Boards, the target weight for this San Marcos board is 42 lbs. Other builders on the Facebook group have bragged about less and complained about more weight. It has made me weight conscious now at the beginning of the project when I’m able to do something about it.
During this first weekend working on the project I completed cutting out all of the voids, but did not start cutting out the frame components.
It required three more afternoons of effort over two weekends to complete the cutting out of the internal frame pieces from the plywood sheets. I used a jigsaw along the curves and a circular saw for the straight edges. The rough cutting was two afternoons (one for each plywood sheet,) then the third day was spent sanding all pieces down to their precise shapes as defined by the paper patterns. I used 80 grit on a belt sander for most of this task, with some use of a Japanese pull saw and of course a hand sanding block. Builders who purchase frame kits are really missing out by skipping this super fun step! They receive their components precisely cut by CNC router machines, saving a lot of time and perhaps some challenging labor. I invested sweat equity and a sore lower back.
By the end of the MLK Day holiday all of the interior frame components for the SUP were precisely cut and shaped. You see them above, stacked on top of the 5 boxes of Paulownia strips which I purchased from Jarvis Boards. An extreme (for us) cold front has reached south Louisiana to be followed this weekend with a reinforcing cold front. These sub-freezing temperatures will prevent any gluing, but I will be able to 1) clean out my storage room / workshop space, 2) set up my long workshop table, and 3) make the scarf joint cuts in preparation for gluing. I suppose I could try to use an electric heater or an incandescent light bulb to warm the work area, but in south Louisiana it will warm up soon enough.
Photos from my SUP project are presented in a gallery format below. Click any thumbnail for an enlarged version.