JTA

Well, since you are designing a chopper thats going to be much larger then anything you can purchase in a hobby shop, im afraid you will probably end up having to fabricate most items like swashplates, rotors, gearboxes, and the like... Have done a little bit of reaserch into larger rc helicopters, and yours is going to have to be something like the Yamaha RMAX, which was designed for agricultural crop spraying. It was designed to carry 22 Kg (aprox 48 lbs) and is powered with a 246 cc horizontally opposed 2 cyl liquid cooled engine. You are looking to lift about half that weight so you will want approximately half the engine power, at about a 125cc engine. But you have to remember that just because the engine is half the displacement, doesn't necessarily mean that its going to produce half the power... it may be less, it may be more. That will require research along with taking in to account its weight/power ratio. Yamaha RMAX helicopter specs I would probably suggest using a single rotor design for your first prototype anyways because of its 'simplicity'. its still a complicated system, but when you get into dual rotor aircraft there is much more to take in to account on the design aspect. Im not sure how familiar you are with R/C helicopters, helicopters in general, and the physics of flight of a rotational winged aircraft... so assuming its a minimal amount I would probably suggest starting this whole project off by purchasing an r/c helicopter kit, assembling it yourself, and learning to fly it manually... this experience would give you a mountain of knowledge on how helicopters work mechanically and their physics of flight. While you are learning to build and fly a normal r/c chopper you could use a program such as Solidworks or something similar to do your design phaze of your project... This is not something you are just simply going to piece together bit by bit with 'spare' parts. Or if you want so save time and have lots of money, just buy yourself an RMAX I know i want one now haha As we say in the aviation business; if you want to fly higher, faster, and carry more weight... Forget about aerodynamics theory... Its MONEY that makes aircraft fly... hahaha

Ive been into model aviation for years, and building a 'ground up' rig especially if its your first go at R/C choppers is going to be one COMPLICATED ordeal! with stock 'hobbyshop' choppers (.40 - .60 size) you'd be lucky to haul 5 to 10 lbs (with a VERY high fuel consumption rate and a smokin' hot nitro engine ready to puke its piston out through its head...) for a ticket price of around $1000 to $2000. And that's before any of your fancy autopilot gear... I wish you luck I believe it is a worthwhile project (Even the Canadian space agency is looking for something similar to what you are describing, a gps oriented autonomous r/c helicopter - although they prefer electric powered units) I'd suggest starting out with how and what you are going to use for navigation, gps seems to be the best bet I would think, then you will have to think about what components are going to be onboard the craft. The more components you have on the craft will be cutting into your 'useful load'. If i was going to do it, I would probably start by finding a way to stream gps, and 3 axis aircraft orientation data via wireless connection (bluetooth, or wifi maybe) to a ground based computer, and link that somehow with the remote control and having the computer interpret the orientation data and the gps data while controlling the craft through the controller.(probably some fancy programming involved there). I know i can hook my futaba controller up to my computer via usb, not sure what the limitations of working with it would be though. Never looked into it. Like i said before, I wish you luck in your project! And any other R/C stuff I can help you out with Id be glad to although when it comes to figuring out how to implement an active 3 axis programmable autopilot Im at a loss... LOL for R/C anyways.

Might want to try replacing the water with some vinegar... ... Also, C02 can be purchased in pressurized tanks from gas suppliers. The same suppliers that sell gasses like acetylene, oxygen, helium, etc should be able to help you out... You would just have to hook the tank up to a timed regulator of some description and let the system do its magic...