below is a picture of my final product:

how this product works is that you wind up the rubber bands in the front onto the wooden stick, the boat will move after you release it. the boat, with the help of the wheels, should drive into water and continue moving with the propellers on the back  wheels. the only use for the front wheels is to hold the boat up.

the energy change is from the elastic potential of the rubber bands winding up, and being released into kinetic energy for the wheels to move and push the boat forward.

in the end, there are still many flaws to the functionality of my product. the biggest problem is that despite my efforts, i couldn’t get the boat to move nearly as far as i wanted it to, which made it look kind of stupid in the end. the rubber bands also take more effort to wind up than i hoped. some minor flaws were that the wheels could’ve used some extra manufacturing to be smoother and less bumpy while rolling, i could’ve achieved that by ether drilling the hole more accurately, or by sandpapering the wheel after i drilled the hole. on top of that, i definitely think that the boat doesnt look very nice and could use some better designs for aesthetics.

the schedule that i made in the beginning also didn’t work very well, because along the way, i realized some things that needed to be fixed or taken a closer look at, so i ended up deviating from the plan quite a bit. in the end, i mostly just did whatever in needed to do according to the situation, since i ended up scraping a lot of my plan and changed my origional battery + motor plan to the rubber band contraption instead.

my product can be made for kids who would want to play with it as a toy. (even though nobody would want to) its safe because there isnt any electrical devices involved, and isn’t too complicated to make it run a little bit. my product is also safe for the environment, because it is completely rubber band powered.