Hover Endurance

[chewala]

I would like to make an RC helicopter that can hover for as long as possible before draining the batteries. I don't care about aerobatics. For this task, which is better, variable RPM rotor or variable pitch (collective) rotor?

Any other tips for maximizing hover endurance?

[Aztek1701]

Hi Chewla,

Welcome to the Forum

How long were you planning to hover for becuase it sounds like you have an application in mind such as Aerial video.

If you dont care about aerobatics then then best way to go (in my opinion) is to have collective pitch and SEMI symetrical blades. Semis are condsiderably more efficient than fullys symetrical blades since the bottom aerofoil is basically drag until the heli is inverted. Also motors work best when going at a constant speed without too much load. As far as motors go.. at the moment, the longest loiter time is offered by the "gasser" type of engine.

Therefore to get the longest hover time, your looking at a gasser (petrol powered) machine with semi symetrical blades and set to run at the lowest practical head speed.

Hope this Helps... Azzy

[chewala]

Thanks Azzy.

So I'll try to look more into semi symmetrical blades with fixed RPM and collective control. I'm a little disappointed that there's not much info (at least that I can find) out on the web about the performance characteristics of various blades. For example, some kind of efficiency ratings for various blades as a function of pitch and and RPM or something like that. Have you found that information anywhere?

I would like to avoid using a gas powered combustion helicopter, even if it will significantly reduce the endurance.

I've read some info about fuel cells containing almost 3 times as much kW*HR (per unit weight) as Lipoly batteries. Sounds like that would be a great way to improve endurance, but do you know if anyone has experimented with fuel cells on a RC heli or small RC UAV?

[Aztek1701]

Hi there,

No im not aware of that kind of information being easily available. You could try looking at the better blade manufacturers, such as SAB and BBT but Im not sure if they publish the info your looking for. Part of the reason I think is the companies dont really go to that much detail because the blades performance is dependant on so many factors.

Im not aware anybody using fuel cells to generate the power to run helis yet. though Im sure as this type of power source comes to market, that people will start playing with the idea. I think we are probably some years off before we start to see them. To the best of my knowlege, the highest power battery available at the moment is the emerging A123 or LiFe cell type. I suspect that fuel cells or the "nano?" batteries will be the technology after that.

Take care.... Azzy