Aerodynamics is a long and hard study. The length of the rotor blades is only a fraction of the factors you need to get right before your chopper can liftoff. For instance: the shape of the rotor blades, the number of rotor blades, the speed of the motor, the torque of the motor, the number of rotors, the length from rotor to tail propeller, the point of gravity, the total weight, the desired speed, the aerodynamic shape of the body, the desired environment, the amount of noise.
My advice is that you start to estimate the amount of hardware you need to collect and compute enough data to actually navigate. Then find a commercial helicopter with enough payload to carry that..
sorry for sounding so negative, building a F__ing helicopter is really difficult.
You're prolly right, but I'd say it would be easier than a plane.
I fancy a helicopter bot 'cos I reckon it would be easier to fly-by-wire. You know. It should be easy to get 4 similar rotors/motors/gearboxes. If you have 4 rotors holding you up and you know what the effect of increasing the revs on a particular one will be, then the computer should be able to deal with the rest. (Actually, for a 4-rotor job, you'd prolly need 2x screws going in eaither direction to stop the whole thing rotating.)
Sure, there would be a real trick in selecting the rotors and motors. BUT I'd get Frits do select them. He seems to get really really really lucky when guessing what parts to use and throwing them together.
OKay, I have attached a Tamiya 540-type motor (from one of those 20 year old monster truck models) to a 12x6 airscrew. It drew about 6A from 7.2V and didn't really get up to full speed. I McGuyver'd a 4:1 reduction gearbox and powered it up and it had sufficient lift to bend the 20mm x 2mm aluminium bar it was mounted on.
That equates, basically, to just enough lift to lift the 6x C-dell battery pack (and little to spare).
Photos and videos to follow.
Any first year R/C pilot will tell you this prop is supposed to be mounted on a petrol engine. I don't have a petrol engine. Bearing in mind the weight of the prop, it's no wonder I got a faster prop speed by putting in a REDUCTION gearbox!
Here's me vid.
Are you going for the hovercraft or helecopter? - you have spare motors & props to provide thrust or stop counter-rotation respectively? ....
And as for your piloting skills - this question comes to mind, "What happened to the plane which was attached to this propeller?"
I haven't thought it through at all. I just wondered if I had enough juice to lift a battery off the ground. The answer is "just about."
I'd say I'd consider 4 rotors in the horizontal, independantly speed controlled. Would need a 2D accelerometer to stay level and this would have full authority over the rotors, so the height and direction would be secondary and tertiary inputs respectively.
Alternate props would rotate in alternate directions so the heading could be controlled.
for an idea see www.mikrokopter.de (there is an english version too).
That is pretty wicked cool :)