Discussions

Hi there,

I'm right now reading a bit of theory on how to design my DIY quadcopters, and came across some interesting things.

First, this thread:

Pendulum Fallacy and Quadcopters

This is very interesting, but I'm not sure if anyone had success and how this theory can be explained (if working).

However, I was thinking if it would be more efficient to mount my propellers below the arms. My reasoning is that the outgoing airflow is cleaner as the arms take up a big portion of it if the prop is on top of them.

I thought that the air coming from above comes from a wide area at a rather slow speed, so the turbulence due to the arms doesn't really matter.

I then looked up how efficient pusher plane configurations are and came across this article:

Pusher Configuration Here it says that

"Efficiency can be gained by mounting a propeller behind the fuselage, because it re-energizes the boundary layer developed on the body, and reduces the form drag by keeping the flow attached to the fuselage. However, it is usually a minor gain compared to the airframe's detrimental effect on propeller efficiency"

So since a plane is in a constant stream of fast moving air, this stream gets disturbed by the fuselage and makes the pusher prop less efficient.

I wondered if this is the same for quadcopters - and I think it is not. There is no such constant airflow from above as we have for planes (for simplicity I'm only referring to hovering).

But I'm not sure if this is true or can be compared.. if of course the copter moves straight up fast, there again is this airflow like for planes. It's just a matter if it isn't more important that the 'outflow' is clean, but apparently it's not that easy...

Can anyone maybe enlighten me?