I am starting to get up and running with enough new tools in New Zealand to actually build some fun things. I decided to start on a pretty easy project and build a rubber band powered paddle boat. It was a fairly small boat, only 14 cm long and made from 20 mm and 10 mm thick boards. The first step is to cut out the hull and the top deck out of 20 mm thick board and the two paddles out of the 10 mm thick boards. Next, you use a rasp or plane to round the bottom and front of the boat for hydrodynamics, and then a round rasp to cut in a groove for the rubber bands. Then go ahead and sand down the hull and the top deck and glue them together; exact positioning is not important. Next, press the paddle halves together to make a paddle; you may have to sand the grooves to ensure a good fit. Then use the round rasp to groove the center of the paddle. This allows a gap for the rubber band to wind up in. Now, a bit more sanding of the of the paddle and the boat is almost done. Put a rubber band around the grooves and insert the paddle wheel. Do one rotation and then add another rubber band. Then double rubber bands help to keep the paddle wheel in place when it finishes unwinding.
The boat was placed in the sink and worked great. I wish we had a swimming pool or hot tub to test it out in and see what sort of distance it could achieve.
This was the second iteration of the boat. The first iteration had a much smaller paddle wheel and didn’t work well at all. Also, the paddle was almost the same width as the cutout in the hull and didn’t let the rubber band wind up and, also, the paddle hit the hull and stopped rather frequently. So if you want to resize the boat, make the wheel cutout at least 25% larger than the wheel itself, and make the wheel extend at least one hull height into the water.
I hope you can have fun building your own paddle boat!

The plans. Exact dimensions are not that important.

The kitchen table is a great place for wood working with the addition of a few clamps. And a lot of sweeping.

A test fit of the paddlewheel before gluing the deck on. The paddle had to be sanded down a couple of times to fit well.

Making wood toys floats my boat.