Breaking Ground: Propeller efficiency as a function of velocity.

[JP_Magoo]

Quick question about propeller efficiency in breaking ground. I've noticed that the thrust a propeller output at a given deploy angle is a function of airspeed. I was wondering, for maximum efficiency, if you could someone automate the deploy angle to be proportional to your current airspeed and therefor have maximum acceleration and top speed without doing it manually.

[Curveball Anders]

11 hours ago, JP_Magoo said:

Quick question about propeller efficiency in breaking ground. I've noticed that the thrust a propeller output at a given deploy angle is a function of airspeed. I was wondering, for maximum efficiency, if you could someone automate the deploy angle to be proportional to your current airspeed and therefor have maximum acceleration and top speed without doing it manually.

Not that I know of yet (been looking for a similar thing).

The issue isn't unique to KSP, it's a common issue with all prop (and fan) driven aircraft, actually even with boats...

As you wrote, the effective angle of attack of any blade is relative to the airspeed.

So either you select an airspeed where you prop/fan will be as most effective or you'll have to tweak it depending on the situation.

As far as I know there's no current way to use airspeed as an input to the KAL, or any similar.

 

[AHHans]

I don't have much to add to what @Curveball Anders wrote in regards to the actual question. But some comments from me:

I'm a firm believer of the "change the blade pitch to change thrust, not the rotor RPM" school of design. For best performance I keep the PAW of one of the prop.-blades open during flight and fine-tune the blade pitch manually. (Well, with an action group of course, so that all blades have the same pitch.) For more convenience I use a KAL to map the main throttle to blade pitch: from minus-something at zero throttle via pitch == 0 at 1/3 throttle and starting/take-off pitch at 2/3 throttle to maximum useful pitch at maximum throttle. I also use low pitch as airbrakes to lower my airspeed for landing, and zero (or negative) pitch for braking on the runway.

If you haven't seen it already, there is quite a useful description on how propellers work in these design notes.

[Curveball Anders]

The nerdy can start with this from Wikipedia Variable-pitch propeller

 

[AHHans]

12 minutes ago, Curveball Anders said:

The nerdy can start with this from Wikipedia Variable-pitch propeller

And then try to understand how helicopters actually work? But I don't want to scare new players that much.

[Curveball Anders]

2 minutes ago, AHHans said:

And then try to understand how helicopters actually work? But I don't want to scare new players that much.

Choppers are an extra, variblade props is enough for me poor brain

 

[Spricigo]

On 6/4/2020 at 2:45 PM, AHHans said:

And then try to understand how helicopters actually work?

[insert ugly helicopter joke here] 

I took a look at this and it seemed like too much management for my limited game time. But I'm nerdy enough to enjoy learning the theory behind it. 

[Curveball Anders]

I've started to ponder if it might be possible to create an auto pitch thingy with kOS.