how could I use this to then get the intake pipe to face the same direction as the wind vane?
The rotary encoder could control a small stepper motor that is attached to the intake pipe.
Robin2 - The intake pipe can either be fixed to the hexacopter, or mounted such that it can rotate on a servo or stepper motor..
I don't know much about hexacopters (apart from the spelling) but it seems to me if it is easy to rotate the 'copter it would be simpler to have the intake fixed to it so that you have only two differentially moving items - the wind vane and the ('copter and intake).
Of course it might be easier still if the windvane was attached to the intake and they could, together, rotate separately from the 'copter.What about using a large windvane and no electronics?I doubt if a stepper motor would be suitable in an airborne vehicle, they are heavy and very power-hungry.
But the larger wind vane is more weight,
Could you perhaps tell us what your purpose is, within your application. It's quite probable that there are better solutions that don't involve any fins or air intakes.
Will the prop wash from the copter blades make rotating a collector to face the wind a moot point unless its opening is far enough above/below/outside prop wash effect?
Edit: Sorry, did not read the whole thread in detail: the wind direction will only be measured while the object is on the ground... OK, forget my arguments.But another problem might be "ground effect": wind direction and speed are influenced much by vegetation, hills etc. on the ground. so on airfields the wind meter is placed with some distance (several meters) above the ground.