This is an instructable for making a small rubber band powered paddle boat. I sketched it on Autodesk Inventor and used a 60 watt Epilog laser cutter to make the parts. Quite a bit of experimentation was required to get this to kind of work.
I made it at TechShop
Step 1: Draw It on CAD
I sketched it on Autodesk inventor. This is a really simple, 2 extruded solids part. I designed it to be built from 3/16" plywood that I was using for another project. This came about as an idea to use up extra space on the pieces of wood I was using for cutting. Only half of the paddle is drawn because it's 2 interlocking identical pieces. The slots are drawn 3/16" wide and half the width of the paddle.
I have included all the CAD files and a .pdf that it setup for a 6"x6" sheet of wood. It requires 4 pieces to be cut. 2 layers of hull and 2 paddle pieces.
Step 2: Gather Up the Pieces
Here are all the parts needed except for the second layer of hull. I only intended the hull to be 3/16" thick but when I tested it in the test tank (bath tub) it didn't have enough flotation and the motion of the paddle was burying the bow and sinking it.
Step 3: Make the Paddle Wheel
Glue the 2 halves of the paddle wheel together.
Step 4: Glue 2 Layers of Hull Together
Glue the 2 layers of the hull together to make the completed hull.
Step 5: Put It All Together
Use a rubber band to attach the paddle wheel. I found I had the best results with a #64 rubber band cut in half. It seems to work best with a weaker rubber band that will spin the paddle as slow as possible. When the paddle is spinning quickly, the torque seems to bury the bow under the water and it just sinks and spins the wheel. I had to try quite a few variations on the rubber band to get it to move.
Step 6: Give It a Try.
Try it out. I uploaded a .mov file here. I'm not sure if it's viewable or not. Hopefully it is.