Coins Cat #MakeItFloat

thingiverse

These objects were designed for the Thingiverse Science Challenge: Make It Float. The challenge consisted of creating a 3D model of a boat or other floating object that could support coins in its local currency. To increase their chances of winning, contestants 3D printed their models and then tested, redesigned, and retested to optimize the amount of weight their boats could support using coins. The best solution for this contest was a box with dimensions that were a multiple of the coin diameter and as high as the printer's limits allowed. However, a box is difficult to push through the water due to its shape. We wanted to create a real ship for this challenge, so we chose a catamaran (double-hull ship) that could take coins with style and certain speed. The real ship, named Zephyr, is a wind turbine service catamaran that can run at 26 knots. A catamaran hull provides better speed and stability when carrying load, including coins. We created a video of our prototype advancing in the water with minimal resistance. We started designing from scratch using Rhinoceros to model the hull based on pictures and technical drawings from magazines. This process took a long time to complete. We also conducted CFD (computer fluid dynamics) simulations to check how the ship would behave in reality at 26 knots. We obtained a good approach with the real power onboard according to the magazine's specifications, which meant our design was similar to the one of the real ship. Regarding printing, we started with a one-piece prototype with the horizontal deck parallel to the printer base. However, this design had problems printing such a large plane deck, making it non-watertight (a bad idea for a ship). We produced a slightly smaller hull printed in vertical orientation, which presented a better finish but was too heavy to carry coins. Based on these two previous prototypes, we constructed a two-piece hull that was hollow inside its side hulls so coins could fit. The model is about 28 cm long, and the key is that weight is scaled with the third power of the scale, so if you construct a ship with double dimensions, you will have eight times more volume than the previous design. Our final design weighs 198 grams and can carry a load of 723 grams before sinking. It can advance well in water with a weight of 803 grams (with 605 grams of coins inside). We would like to thank the people at the model basin of the Technical University of Madrid (CEHINAV) for providing us with their facilities, including water basins and electronic weights.