buoyant force expirements: forcamaran, floatingisland, funnel, hovercraft

thingiverse

I'm really new to 3D printing, but I'm totally fascinated by it. The S.T.E.A.M make it float challenge is pretty interesting and challenging, so I'll try to design a boat that can carry as much weight as possible compared to its own weight. All in all, I came up with four designs to exploit different physical phenomena of buoyancy. 1. Forceamaran: I started with a super simple structure to test how much a 3D print can carry. The bottom has a triangular shape to center the weight, and on top are small arms for stability. First test: 14g 3D printed weight, 39g coins carried - boat carries roughly 2.8 times its own weight. Next Step: Mimic a trimaran. I designed two support boats for both sides, which is essentially a copy of a trimaran. The difference is that the support boats have tilted bottoms. If you apply weight to the supports, they'll tilt and apply force to the middle boat (body), hopefully improving the weight it can carry. Result: the force from the supports on the body isn't enough to improve the weight significantly. The Forceamaran's weight was 45g, carrying 56g of coins - that's about 1.24 times its own weight, which is much worse than just the body. But at least it's way more stable with the supports. 2. Floating Island: This design uses buoyant force from pressure differences in differently steep water. It consists of a cube and a stick on top. The cube is 5x5x2 cm and the stick is 10 cm long. Let's do some math: Force = Pressure [Pa = N/m²] * Surface [m²]. On the bottom plane of the cube, there's a force of 1200 N/m² * 1/400 m² = 3N. On top of the top plane, there's a force of 1000 N/m² * 1/400 m² = 2.5N. The buoyancy is the difference between these two forces - 0.5N. Since weight force G = m * g (gravitation force), this construction should be able to carry ~50g. Result: The Island's weight was 18g, carrying 45g - that's exactly 2.5 times its own weight. It's super unstable, making it hard to apply any weight. Improvement: As the Force formula suggests, the bottom surface of the cube should be as big as possible and the top plane as small as possible. The bottom and top planes should also be as far apart as possible to achieve a big pressure difference. The infill of the cube should be as light as possible - air is good, helium would be better. I designed a new Floating Island but didn't print it yet. On the bottom of this new design, there's a force of 2900 N/m² * 1/100 = 29N. On top of the cube, there's a force of 2000 N/m² * 1/10,000 = 1/5N. The difference between these two forces is 28.8N - this design should be able to carry ~3kg. 3. Funnel: This design uses buoyant force from Archimedes' principle. The more fluid you displace, the higher the buoyant force will be. So I created a simple 3D design with the same structure as a funnel just in cubic shape - it's easier to print. Result: The funnel's weight was 17g and it carried 368g! That's ~21.6 times its own weight! This is by far the best result I've achieved so far. Improvements: I chose an angle of 45° (1cm in z direction for every cm in x or y direction). A smaller angle could lead to even better results as more water is displaced with the same amount of material. 4. Hovercraft: Last but not least, I wanted to create a good-looking design that can float. As I'm a huge fan of hovercrafts, I tried to mimic their design. If I got time, I'll design a fan that will blow air in the chambers to make it levitate above the ground and an engine to power the fan on the back. Thanks for reading through this far!