How to Design a Helicopter

[Tompete Kerman]

So I've made a fairly simple Bell-style small helicopter replica, and while I can get it up in the air by manually setting the torque limit to 10, the tail rotor limit to the same, and using throttle to control the blade deploy pitch, I'm somewhat at a loss on how to make the main and tail rotors synchronize or rotate/pitch at the proper relative speed/angle to keep it level and straight mid flight.

Does anyone have a succinct tutorial on this subject? Example craft to show? 

EDIT: Good news, got the main rotor all but figured out, bad news: still cant get the tail rotor to correct rotation. Can anyone help with that?

Edited February 21, 2020 by Tompete Kerman

[OHara]

Propeller controls were significantly improved for version 1.9.1, and I haven't seen a tutorial yet.  

So far I've done the same as you in 1.9.1.  I can point out some things that maybe you know about, but just to be sure:

1)  a site on which craft are shared   http://kerbalx.com/?search=helicopter%20~stock

2) Helicopters in general are not stable like fixed-wing craft.  The best you can do is make it statically stable so it tends to return to stationary hover, but it will swing past that stationary hover, and the swinging grows with time.

3) Trim  (alt-w alt-a alt-s, etc. on Windows, or right-shift-w etc. on Linux) can hold the craft in steady motion, but due to the differential lift on the blades you need some pitch (alt-w) and  roll (alt-q) to hold steady forward flight.  
(Manufactured helicopters have a built-in mechanism to make pitch input give the right mix of pitch/roll cyclic control, but arguably (link) KSP's lego-construction should not.)
 

 

[AHHans]

IMHO it is best for all kinds of rotors (in KSP) to keep the RPMs constant and control (whatever you want to control) by changing the blade pitch. But if I understand you correctly you also arrived at that conclusion.

If you only ever need 10% rotor torque, then I'd suggest to lower the motor size in the VAB/SPH. That way you don't need to carry unnecessary weight around with you.

And finally to your actual question (yes, yes, I do get to that): with the new changes in 1.9.0 you can indeed get classic main-rotor / tail-rotor helicopter to work. If you set the blades on the main rotor to do pitch and roll control and the blades on the tail rotor to do yaw control (with the control direction to the front), then SAS can use the tail rotor to keep the craft from spinning. Even without a counter-rotating rotor setup. I put a small test helicopter that does this on KerbalX: Basic Helicopter

In a heavier craft (with a more powerful and thus torque generating main rotor) you may have to "trim" the tail rotor to keep it from slowly rotating. You can either do this with the manual trim as @OHara explained, or by setting the deploy angle of the tail-rotor blades to an appropriate value.

[Rpatto92]

On 2/21/2020 at 4:41 AM, Tompete Kerman said:

So I've made a fairly simple Bell-style small helicopter replica, and while I can get it up in the air by manually setting the torque limit to 10, the tail rotor limit to the same, and using throttle to control the blade deploy pitch, I'm somewhat at a loss on how to make the main and tail rotors synchronize or rotate/pitch at the proper relative speed/angle to keep it level and straight mid flight.

Does anyone have a succinct tutorial on this subject? Example craft to show? 

EDIT: Good news, got the main rotor all but figured out, bad news: still cant get the tail rotor to correct rotation. Can anyone help with that?

I know it's over 3 years later but it's taken that long to sake off all the bugs and build a working single-rotor. 

Here's a guide I put together: