Heavy lift quadcopter/hexacopter

Hey all,

Im fairly new to RC aeronautics and aircraft but have an idea and a need for a multi-rotor copter that will function of 4 blades while running around, but will have an extra 2 ducted fans that will engage when it needs to lift a autonomous submarine that myself and my team have developed(I am a 3rd year naval architecture marine engineering student as well as an officer in the Australian Navy). This is the challenge:

This Is my main question:

I am fairly novice at programming, i need some help in how would i make the copter go to the sub autonomously, then need to drive it manually( have FPV camera and gear) to pick it up, then to fly autonomously back to have with the extra 2 ducted heavy lift fans??? 

this is what it will do:

  • Carry the sub to a nearby location(using 4 rotors and extra 2 ducted fans to carry the weight of sub), the sub will be deployed and do its thing
  • copter to return home(running on 4 rotors) , while the sub is doing its thing
  • return to the location of the sub to pick it up to return home

So the sub is fully equipped with just about everything you can think of with respect to electronics and sensors and has room for more if need be.

I have full access to my own 3D printer swell as carbon fibre and kevlar so no need for holding anything back. 

Please feel free to ask any questions and any help or suggestions at all would be really appreciated.


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  • Im interested myself in eventually building a quad or hex capable of lifting 50lb payloads. I realize thrust per prop depends on it being a quad or hex. Lets say I went the hex route, 6 motor/props with a 50lb payload. What would a copter capable of lifting itself plus 50lbs need to weigh? I realize it would depend on the motors, props, frame materials. What motors would you recommend? What about prop size? Lets say the frame was carbon fiber. Can someone explain the best way to calculate thrust/lift requirements, motor size, prop size, batteries needed for 15-30 minute flights. Is there a basic formula or online calculator available for these sorts of calculations, for example: "For a hex to lift a 50lb payload, rule of thumb the vehicle will weigh 2 times the payload weight or 100lbs. The total lift needed at minimum would be over 150lbs of thrust/lift or 25lbs per motor. To be functional, double the min required thrust per motor to 50lbs. The motor/prop combo required for this is "X", which would require "Y" mAh in battery power to fly a vehicle weighing "Z" for 15-30 minutes. (Is there an online calculator for this?)

    I realize this would be a lesson in aeronautical engineering but Im very interested in learning the calculations and how to figure out the best equipment to use based on the calculations.

    Id appreciate any guidance or links to learn the answer!

  • Hi Harry,

    I've been following this along and I was wondering what it was you were aiming to lift with the beast of a Multi Copter you are building?  Are you going to be lifting and placing breeze blocks or timber for the construction industry or will you be slinging an IMAX camera under the quad?  



  • An update for the project, below are some pictures of the design so far, and before any of you go all "this isn't right"  on me its just a rough plan trying to get the layout done and the general look i want it to have but any suggestions would be greatly appreciated :)


  • Maybe I'm missing the advantage of having the additional ducted fans? Here's a large quadcopter lifting nearly 45kg (pushing the limits of the craft, but you get the idea).


  • Bob,

    Im using 6 Xcelorin 7500KV Brushless Motors, with a max running RPM of 60,000 RPM. Running on 7.4V lithium ion batteries.


  • Hi Harry,

    Just a few thoughts.

    That is one serious undertaking.

    I take it 30 pounds is the weight of the submarine.

    So lifting vehicle weight would be on top of that probably over 30 pounds.

    So gross vehicle weight loaded would be over 60 pounds for a vertical lift multicopter.

    I do not think at this time that our hobby electric is really up for that kind of capacity for any sort of duration.

    Still you can get motors, Props, ESCs and Batteries that will lift it for short duration anyway.

    Second thought, unless you really know something special, Skip the ducted fan, just make a primary vehicle Quad, Hex or Octocopter with the lift you need, the way you are talking about doing it just adds more dead weight during non-transport section. Multicopters run most efficient at partial throttle anyway so adding a secondary system that was only used during sub lift would be a net loss of duration. If prop diameter is limited, ducts can pick up a bit of efficiency, but if prop diameter is not limited a bigger diameter prop will beat a ducted fan almost every time (and ducts are even more weight). 

    The first thing you ought to consider is making your USV sub lighter, a lot lighter, maybe like the one on Kickstarter.

    The smaller and lighter a Multicopter is the better it works.

    As it stands now, I don't think your main problem is Software, its physics and the technology we have available right now.

    That said you probably can build a multicopter with killowatt plus motors, humongous ESCs and really expensive and big batteries that will lift a 30 pounds weight for a little while anyway.

    If you want duration you probably need to consider a motor generator or Hydrogen fuel cells (hope you've got a government sized budget).

    Good Luck!

  • What motors are you thinking of using?


  • AN update, have calculated that it will have a lifting capacity of about 14kg's, all i need now is help with some code, anyone  have and idea on where i can start looking/trying?

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