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Cardboard Kayak

This was a project undertaken due to extra material and time on a laser cutter, and turned out to be the second of three projects I was able to cut and build from an overstock supply of hexcacomb cardboard. My primary project was the Geoshift chair that you can find here, and seen in the background of some of these pictures.

Hexacomb cardboard is a surprisingly strong material, and it cuts super fast on a laser, really a nice material for prototyping.

I have wanted to build this Kayak, in one form or another, since I picked up George Putz's "Wood and Canvas Kayak Building". The book is excellent, I can't recommend it enough. Seriously, this guy is like the Ron Swanson, but realer. Super clear instructions, cheap materials, really a nice accessible project for someone like me (who knows basically nothing about building boats).

The challenge for me is that my only build space is a rather small living room, so doing a proper build of a wood and canvas Kayak has been shelved as a future endeavor. But when I found I had some extra time on the laser bed at Pagoda Arts, I figured what the heck, let's have a proper test of what can be made from Hexacomb.

Do be warned, this instructable does not take you to the point of a seaworthy voyage yet, but I do have some ideas on how to move forward with waterproffedness, and am hoping some discussion might follow in the comments. I am always grateful for suggestions. The structure is light and strong though, even without glue, so I feel this is a good start.

Ok, enough exposition, (though why the heck someone would build a boat out of paper does deserve some explanation I think)

Materials and Laser Cutting

For this build, you will need the following:

  • The CAD file to be cut (attached to this instructable)
  • 4 sheets of 4'x8'x1/2" hexacomb cardboard (I purchased mine from Peidmont Plastics, under the product name "Falcon Board"). You can see in the cut file that it is really just over three sheets, so if you have some extra 1/2" material for the seat plate you might be able to save on a sheet of hexacomb.
  • Access to a large bed laser cutter. I had my pieces cut at Pagoda Arts in San Francisco. When getting it cut, make sure that the blue letters + numbers on the CAD file get etched onto the parts, or this puzzle will get a lot more complicated.
  • 2" clear packing tape (I used blue tape in the pictures, but have since switched it out. The clear gives a cleaner look and sticks a little better)

Assembling Keel Plate

Assembly starts with the keel plate, this is basically the spine of the boat. I have cut this and other pieces up due to the limited length of the 4'x8' sheets. The boat is 16'-6", so some pieces are split in half, some in thirds.

Lay out the pieces for the keel on a flat surface, matching up "AA" to "AA" and "BB" to "BB". Once aligned, tape over the whole joint to pull it together. Flip the part over and tape over the whole joint on the other side. You can go ahead and repeat this process with all of the pieces that key together (they are all labeled with double letters).

Adding the Ribs

Start slipping the rib pieces onto the keel plate. Each rib plate is numbered, and the front and back of the keel plate are labeled with an "F" at the front and a "B" at the back. (I know, not proper boat terminology. I guess I'll always be a land lubber)

Start with rib plate 1 at the front of the keel plate and work your way to plate 11 at the back.

You can start to see the shape of the boat now, things are heatin up!

Lower Stringers

The lower "Stringers" are the bottom plate of the boat. Slide these into the lower slot on the rib plates with "F" oriented towards "F" on the keel plate, and "B" oriented towards "B" on the keel plate. Make sure they are pushed all the way in, the long edge of the lower stringer plates has tabs that should be pushed all the way into the corresponding slots on the keel plate.

Side Walls

Slide the side plates down onto the vertical slots in the rib plates, making sure the tabs fit into the slots in the lower stringer plates. "F" should be oriented towards "F", as in previous steps.

These parts get bowed as you put them in, I started towards the middle and worked them a little into each slot, working along the length. It gets a bit tight so take your time. The pressure from these bowed plates puts the assembly into tension/compression which tightens it all up.

Deck and Seat Back

Drop the bench plate down into the cockpit before putting the top on. The front slides into a deep slot, so I ended up having to score the middle and bend it as I put it in. It is not a structural piece so no biggie. (It also sits a little high. In the future I would suggest notching the surface to conform to the structure below so the plate drops lower. You need all the knee height you can get)

The top deck gets a bit hard to put in, just keep working it. You will have to angle them a bit to clear the tabs from the side walls. Once you get it slid onto the rib plates and tabbed into the keel plate, you can push the deck down onto the wall tabs. You may have to pry a shim down into the slot on the deck to get the wall tab to align, they want to pull in due to their curvature. Just make sure it is lined up as you push the deck down so you don't damage any of the tabs. The tighter the stronger, its worth the fuss.

Once the deck is installed, you can drop the seat back down into the tabs on the bench deck. Make a bunch of vertical relief cuts in the seat back so it is able to curve and conform to the bend in the deck.

Next Steps

And there you have it! a structurally sound, lightweight cardboard kayak form, ready for a waterproof skin, or just to be hung as a nice show piece.

So, I've got a few concepts on how to move forward with the project (input from the instructables community is very much welcome):

Option A: Shrink wrap skin. I love this idea because of the consistency of the "packaging material" theme. Also, not a totally insane idea, there is some precedent to shrink wrapping boats. Shrink wrapping a boat is a technique used to to winterize boats, here is a nice how to video showing how the process is done: link

My though is to flip the process upside down and shrink wrap up around the deck, then shrink wrap over the top to seal it. The cockpit is an issue, I'm thinking a sleeve of some kind that gets gasketed in with the shrink wrapping process (this is where I feel some uncertainty in this process, I can see that sentence being much more complicated than it sounds)

Depending on the strength of the shrink wrapped skin, I would add additional layers for reinforcement. Maybe add a strip of stronger material onto the edge of the keel plate before wrapping to protect from collisions

Option B: Tailoring up a skin from a waterproof material, with a zipper along the top for disassembly. I like the idea of preserving the possibility of disassembly, but I think this option is a bit ambitious for my skill level. Its got all the problems of the previous option, with the added difficulty of waterproof seams. But it would be cool...

Option C: Wrap the boat up in any material, with a sleeved cockpit, then have the whole thing covered in Rhinoliner, Like I did with the GeoShift chair. Its a nice waterproof material, but it would totally permanentize the boat, which I am trying to avoid.

Option D: If all else fails, I can use this as a formwork to build George Putz's wood & canvas kayak as originally intended. It is all made as a shell of thin lumber, so it could be assembled as a top and bottom around the cardboard form then taken off and glued up as one shell. This will have to wait until I have more space though, my living room isn't currently equipped for the woodworking I would need to do for this option.

Thank you for allowing me to air out my ideas, they were starting to get confused cooped up behind my eyeballs. Any input from the instructables community would be greatly appreciated, the future of this boat is still a soft concept floating in space waiting for more refined ideas.

Keep making stuff!



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