The Catfish - A fully working submarine

thingiverse

A functioning submarine created for Thingiverse's #MakeItFloat challenge, designed to eventually be equipped with a fish finder and map lake beds. Reviews: "a fun, unique design" - Derek Bower "incredible build" - omega-00 3DPrint.com article: http://3dprint.com/81607/3d-printed-mini-submarine/ ## Inspiration The initial inspiration for this sub came from a boat on Thingiverse. A fishing trip was planned, and an RC boat would be ideal to play with while out on the lake. The necessary hardware wasn't available, so the boat was modified to fit a water pump. A newer version of that pump, modified by me, can be found here: http://www.thingiverse.com/thing:883212 On the lake, some fishing line was tied to it for a tether and a hook with bait attached to the bottom. It caught a catfish! He was a small little guy and was released back into the lake. While it was a success (it caught a fish!), the boat had problems taking on water. Any amount of motion in the water was enough to splash, flood, and sink the thing. The centrifugal pump needed to be primed to get it pumping, so a future version of the boat would need a second priming pump. ## Submarines Can Control Their Own Buoyancy Submarines can float or sink at will by controlling their buoyancy. Archimedes' Principle states that an object will sink if it weighs more than the water it displaces and float if it weighs less. Imagine an empty soda bottle with the cap screwed on tightly, taken down to the bottom of a lake and released. Since the bottle is filled with air, it will quickly float up to the top of the lake with an amount of force equal to the weight of the water that is displaced by the bottle. ## How Submarines Control Their Depth Submarines control their depth by adjusting how much air and water is stored in internal ballast tanks. There are holes in the bottom that are always open to allow water to freely enter and exit. To surface (float), air is pumped into the tank to pressurize it, forcing water out through the bottom. When it's time to submerge, the air valve is opened to allow air to escape so it can fill up with water. The desired depth is reached when the air valve is closed. ## Overview This submarine has 3 pumps, 2 servos, and 1 additional DC motor: 1. Main propulsion (centrifugal) pump: http://www.thingiverse.com/thing:883212 2. Second water pump for priming the first pump: http://www.amazon.com/gp/product/B00D82W60O 3. Diaphragm air pump for surfacing: http://www.amazon.com/gp/product/B008SNYG9C 4. Rudder servo (left/right direction control) 5. Air valve servo: http://www.thingiverse.com/thing:138112 6. DC motor for reeling in the float deck (a small motor pulled from a CD-ROM drive) The surface procedure would go like this: With the air valve closed, pump air into the sub until it has enough buoyancy to return to the surface. You might also choose to reel in the float deck while surfacing. The air pump will need to overcome the pressure of the water surrounding the submarine to push the water out. The deeper you go, the more pressure there will be. You will need to experiment with how deep you can actually go before the air pump is no longer effective. Go to Instructions to keep reading: http://www.thingiverse.com/thing:920376/#instructions