Oil Breather Tube Orientation

RW,

I think, what you are suggesting is that, by supplying higher relative pressure, to the hose, may create a venturi. The venturi could create a vacuum in the breather, exacerbating the tendency for oil droplets to be drawn out of the tank. I agree - a possibility I had not considered..

I am not sure what you mean, in the context used, by "neutral pressure" - please expand?

The term "neutral pressure" suggests to me, the same as. The same as what?

My understanding of the NOTCH is that the pressure downstream of the notch, should be not be a vacuum ie any tendency to have a vacuum at the end of the breather should be nullified/counteracted.

My limited understanding of how to do this, is that a positive air pressure,  equal opposite to the negative, needs to be introduced to the breather, thus creating a neutral pressure, that will not draw oil droplets out of the tank. This is not the same as introducing a "neutral pressure"

Without air pressure sensing (altimeter) equipment and multiple hoses within the cowling, I don't see how anything but a guess can achieve anything like an acurate equal/opposite air pressure (where to place the NOTCH & how big should it be???).

The best I can do without more precise direction/testing equipment, is try for a posative air pressure, at the end of the breather hose, in the hope that this will overcome the possibility of a low (negative?) pressure area, in the cowling exit air (breather exit) to be  transferred to the breather .

The best way to do this would be using a Y fitting with the posative air pressure, being directed against the flow of breather air - no chance of a venturi effect. I will explore the availability of a Y fitting (may have to make one)😈

Sean, by neutral pressure I should have used the aviation term, static air pressure.  As it relates to  aviation is defined as: