3D Printed Kayak: A Skin-on-Frame Siskiwit Bay

This is a guest post by Dave Arruda.

At some point early in the pandemic (probably day 2 of lockdown) I took a look at my PRUSA MK3s+ 3D printer that was growing dust on my desk and said to myself “yup, I’m going to 3D print a kayak!” That started the adventure that has led me to a 3D printed kayak. It’s a version of the Siskiwit Bay SOF.

The journey started with a lot of computer aided design (CAD) work (and by a lot, I mean A LOT). I chose to use OnShape, a cloud-based CAD software, as my platform and set to drawing the stations, stems, seat, cockpit rim, and all the various braces and brackets needed to assemble the kayak. Most of the dimensions were taken from Bryan’s original Siskiwit Bay SOF drawings with some minor tweaking here and there. After what seemed like forever in my office (probably about 2 weeks) I had myself a virtual model of the skin-on-frame kayak that I always wanted and finally had the time to build!

From there it was a matter of setting my good-old PRUSA MK3s+ 3D printer to work to make all of the parts. I chose to use polyethelyene terephthalate-glycol (PET-G) filament for its mechanical properties, UV resistance and general waterproofness. The parts were printed at 20% infill in an attempt to save material and weight (more on that later). The first real problem that I encountered was the fact that the stems and most of the stations were much larger than the build surface of my printer. This required me to go back to the virtual drawing board to section these parts into printable-sized chunks that would later be joined together using some stainless steel hardware. After failing forward for a while I ended up with a box full of all of the parts that I needed to build the frame and a second, much larger box, full of all the mistakes I made along the way. All-in-all I went through about a dozen 1kg spools of filament and a set of bearings for my printer!

After all that I decided to follow a more traditional approach for the rest of the build. The stringers were ripped from a sheet of 1/2in thick Baltic birch plywood down to 1in wide strips. The strips were finished with a black gel stain and then glued and lashed to the 3D-printed stations and stems. I consulted Corey Freedman over at Spirit Line Kayaks in Anacortes, WA and he sent me an 840 X-Tra Tuff Ballistic Nylon skin and urethane coating kit. The skin went on pretty easy using the welting cord technique. The hardest part was getting the skin to mate with my 3D-printed cockpit rim. I ended up redesigning the rim with a notch around its circumference near the bottom. I glued a piece of nylon rope into the notch and used a hook needle to secure the skin to the rope embedded in the cockpit rim. It took a while but the cockpit came together great!

The finishing really had me hung up for a while. I had put so much time and energy into the project by this point that I really wanted it to finish well. I had envisioned a translucent skin that would allow you to see though to the black frame underneath but I just couldn’t seem to get any of my samples to come out the way I had envisioned. That’s when I went crazy and decided to dye the kayak black! When I reached back out to Corey to purchase some acid dye he nearly had a stroke on the phone. “Well, it’s your boat you’re about to mess up and you’re a** you’ll be sweating off next summer”, he said. I was adamant about adding color so Corey reluctantly advised the use of rare earth pigment which is suspended in the urethane rather than in the fabric and I decided to take his advice. After all that hemming and hawing the finishing really came out great and up close the kayak has a really authentic look to it. I plan on adding back in some orange highlights on the bow and stern and some orange deck rigging to balance with the cockpit rim as soon as the weather gets better.

We finally took the kayak down to Billington Sea Kayak in Plymouth, MA for its maiden voyage. I couldn’t think of a better place to launch from than the kayak shop that started my obsession over 20 years ago. It was cold November afternoon and near sunset when the hull hit the water. “Wow, IT DIDN’T SINK!” was the first piece of good news. Overall, the kayak handled well and was really fast over the water. However, the CG was a little high which made the boat a bit unstable for my liking but not any worse than some of the racing kayaks from my past. I’ll have to try to drop the seat down about a half inch and that should make a big difference. Finally getting to sit in the cockpit on the water felt amazing but it was short lived as my daughter Natalie wanted to take a spin. I was over the moon about this because I had forced her into a few kayaks in the past but this time she took it upon herself!

As fun as this project was for me I WOULD NOT recommend building a kayak this way to anyone. For one, the process was hyper-laborious and resource inefficient. Much of that was due to my fail-forward approach and the fact that 3D printing takes FOREVER and requires a complete reset every time you make a mistake in a part. I would probably make a bunch of changes to revision 2.0 if I ever get the hankering to make another one like this. Most notably, I would start by building a custom 3D printer that would allow me to make all of the stations and stems as single parts thus eliminating most of the hardware and probably shedding a good 8-10lbs off of the kayak. I would also consider removing at least four of the stringers. These changes would get the final weight back down into the low 40lbs range (it’s currently hovering around 52lbs which is obviously way too HEAVY for a SOF kayak). However, producing this craft was an incredible and formative experience for me both as an engineer and a long-time kayaker. It really called on many of my passions and I ended up with a unique kayak that I’m really proud of. I already have plans to build another kayak…just not this way!

This is the time that I should thank a few people that helped me on this journey. First a shout out to Bryan for posting the inspirational Siswikit Bay SOF plans and for making so many other great kayak plans accessible to us all at Paddlinglight.com. Second, a heartfelt thank you to Corey over at Spirit Line Kayaks for all of the great conversations and kayak building advice that he provided, even if I only listened to some of it! Finally to my inner circle: Doug at Billington Sea Kayak for your sage kayaking wisdom, Mom and Dad for helping with the construction, Erin for putting up with all of the late-night cursing and keyboard smashing as I tried to tame the CAD software and whisper the 3D printer into cooperating, and Natalie for melting Dada’s heart by being the first person to claim a seat in the cockpit; you’ll be an amazing kayaker one day!

-Dave Arruda aka KayakDave