Underwater Quadcopter


This may sound crazy.  How about a quadcopter designed for underwater use.  Brushless motors operate perfectly well submerged and the rest can be waterproofed quite easily.  Idea being that one would use small props, basically the quad would operate in a different medium but essentially it should still stabilise as it does in air.  I thought about escs (which don't like water) getting hot but they could be exposed, covered with tectyl or some other waterproofing spray.

As a fail-safe, waterquad would be slightly buoyant so in case of power loss, it would merely float to the surface.  One would then have keep throttle on all the time to stay submerged and power up to sink as opposed to normal operation.  I know that 2.4ghz does not work underwater but the older 35mhz systems do.  For fpv, 1.3ghz could be used ??  Also I wonder which flight controller would work best, kk2 maybe for cost-effectiveness. 

Has this been attempted before and if so, any success?   Couldn't seem to find anything on this concept.  I'm itching to start building but somebody please stop me if I'm wasting my time. 

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          • Ah yes I see the four props and thus the craft is vertical in flight then drops down to horizontal for under water. You would only be able to control depth whilst moving forward or backwards but maybe some applications would be happy with that. You still wouldn't be able to control it more than about 5 cm under water though :) 

  • Ok, now I'm day dreaming but wouldn't it be awesome to make one of these a hybrid?  Deepfly Dragon using ducted fans?

    • Wow that would be something but $1.5 million just for the water version I think it may be slightly out of my play list bracket.. :)

      A word of warning to anyone that reads this and thinks model ducted fans would be ideal for a ROV. The ducted fans you get in model aircraft are only built for thrust in one direction. You reveres the fan (and thus the thrust) and the darn things come apart....obviously I'm not sure if this is the case for all set ups but I believe it is the norm...

  • Why not build a Octocopter with four normal props for flight and the second set for underwater flight?  If assuming you can make it water tights, it would be an interesting project to try.  Of course software would be needed to switch on and off the two types of props based on mode of operation but I like the idea that you could fly it out to water entry point then submerge it and run underwater then surface and fly back.

    • The flight ones will work fine for the up and down element (z axis)  of a near neutrally buoyant craft so if you don't want to vector these some how to give X,Y control then (minimally) you only need one other motor with forward/reverse and a rudder. 

  • Ever since I learned that brushless motors worked underwater I had this exact idea. I think the main issues would be getting accurate signal underwater, and dealing with the propeller sizes, because you'd need much smaller propellers underwater to move around. if you could overcome those problems it just might be the coolest thing ever.

    • Developer

      Your best bet for thrusters are either of these https://www.bluerobotics.com/store/

      • yes i have seen these thrusters.. but i have to use same motors for both air and underwater operations..

        • The same type of motor will work underwater but it will require a different prop to run at the same rpm.  Something that can fly and swim using the same motor/prop combination is not possible by the laws of physics.

          • I agree , that's  why you don't turn them at the same RPM. You need a brush less outboard that is capable of slow speeds, Many can't but some can...

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