Rubber band powered race boat

SummaryThis is a rubber band race boat I designed for the Maker Faire 2015 Moat Boat Paddle Battle Challenge. See it in action on a test run here: https://www.youtube.com/watch?v=8XWNFfDlJNM The propeller is a store bought model boat propeller because consumer 3D printers are not capable of printing high strength, high resolution models that propellers require. A large pitch propeller is preferred. I used a 2" T-pin as the propeller axle. I cut a slot in the tail of the propeller to secure it on the T-pin's head. I use Autodesk Fusion 360 to estimate the weight and volume and calculate whether the model has enough buoyancy.

Select the body to estimate in the browser Right click and choose "Properties" and a new dialogue box shows the volume, weight, etc. You might want to change the material to get the right estimate. measure volumes before and after hallowing out the hull with Shelling command, this gives me the volume and estimated weight Calculate Buoyancy: 1 liter can support 1 Kg. I used an online calculator.

Make the weigh of the boat about half of the buoyancy.

I then used Autodesk MeshMixer to check the center of gravity for the model.

To fine tune the boat's balance, I used a little stack of rare earth magnets. To hold the propellers after winding, I added a little hole to fit a drill bit. A small loop on the deck is used for dragging the boat back after it runs away. To reduce drag, I coated it with epoxy. Printing requires a bit of support as shown in after print picture here. No issues if you print it length wise.