I designed this balloon powered boat awhile back in Tinkercad. It works ok does not last long though.
Step 1: Supplies I Used
Step 2: Tools
- 3D printer
Step 3: How I Designed It
Lined up 3 cylinders. Added wedge to help it cut through the water. Stuck cylinder into center. added second one on top to help grip balloon. Cut hole in for balloon. Added holes to allow air to come out the back. I added lego bricks to from thingiverse http://www.thingiverse.com/thing:50437. However I printed this on my old printer and they did not work well.