For this design, I wanted to present something unique from the standard castle build, but certainly represent mathematics. I chose to create a Nautilus shell sand mold, which represents the Fabonacci and or logarithmic spiral. Once printed, the mold can be filled with sand, and turned over onto the ground, and create a cool spiral visual. Make several at the beach and make an artistic expression!
I found a Nautilus shell image online, and traced the underside pattern, and sculpted the shell using surface modeling in SolidWorks, fleshing out the design into a solid model.
Print from bottom up. You may want to use rafts, or an adhesive on the build plate to keep part from curling.
There are a few really good designs that followed the design challenge, incorporating math with usable sand molds. If I were to win a 5th Gen MakerBot, I plan on donating a 3D printer I backed on a crowdfunfunding site to a local school, as soon as I would receive it. It is a smaller printer, but a great learning 3D printer.