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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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?

What motors are you thinking of using?


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!


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


Thanks a heap Gary!

I have close friends studying aeronautical engineering to design to blades and will be making them myself so don't have to worry about sourcing them or anything and can make them specifically for what i want to do.

I have done some calculations and estimations about how much my design should lift and have run it past a mechanical engineer and aeronautical engineer and they got about the same and the aircraft will weigh about 8kg's and be able to lift an extra 13kg's with all the engines running st 40, 000 RPM (much lower then there max RPM) so  think it should be ok. 

With the electronics, I am getting 6 fan cooled 150A ESC's and with have a lithium ion 7.4V battery per engine, swell as the best solar panels  could find on the top to help give it a bit longer running time. 

The arms supporting the rotors will be carbon fibre and also foils, so they will provide some lift while moving forwards.

But yeah i have full access to carbon fibre production, kevlar and industrial grade high accuracy 3D printers. So all the blades and ducts and everything can be done to whatever design imaginable.


And The sub weighs about 7.7 kg's. and that can't change, its a constant. The sub is a world first and this quadcopter/hexacopter is a second thought to it and I'm doing this project as an extra side project for myself and if all goes well might sell the two as a package etc..

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).


yeah i have reviwed it and going with 4 bigger propellors, thanks for that :)

One thing to add that I'm sure you're already thinking of, but just in case. Larger motors and props like in that video of the 45kg lift are very dangerous and can maim or possibly kill. If this is your first experience with multirotors you might want to start with something smaller to get some practice in and do scale tests. The kit quad from 3DR is like $500 (just add radio and batteries).



I have been following along here a bit and I wanted to let you know a couple of things that you may not realize. 

For a heavy lift vehicle, you want smaller KV not higher KV, the smaller the KV, the larger the motor for the most part.  The 7500kv motors that you are reffering to are for cars.  They are 7500kv but they are geared lower in order to acheive the necessary torque needed for moving the car around the track.  Unfortunately, the larger the copter, the larger the batteries that are needed, then larger motors, then larger batteries, this continues indeffinitely due to inefficiencies in the basic design of quadcopters and hexicopters.  I have been working on building a hexacopter for a year and while I am not an expert, I have researched the topic quite a bit.  Also, with the low voltage that you are proposing to use, your multicopter will not have enough power to quickly change attitude in order to be stable.  Let me know if you want any additional suggestions.  To the others on this thread, correct me if I am wrong on any of this.

Thank you!


Thanks matt :) 

But yeah have changed my plans a bit since my original post, am using much lower Kv motors (around 3000kV, is this suitable??) with 11.1 V LiPo batteries with 4 larges rotors instead of the 6. I am going to gradually rogress the design as i become more competent and learn more. Going to start with a smaller one for prototyping then move to the full scale and eventually want to get it to 4 large rotors, each with 4 blades with a variable blade angle capability's. 

What are your thoughts?? I want to eventually get to the variable pitch for greater speeds, and also still going to need it to eventually carry a small load( the initial reason for starting this project). Any more tipson these plans would be greatly appreciated :)


I wouldn't bother with variable pitch blades unless you just want to be able to say "Look, it has variable pitch blades."

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