Yet another outlet air idea

[Bob Axsom]

I've been think about this area for a long time now and this is my latest thought:

- Add a ~2" cuff to the rear of the outlet to gently turn the air inward toward the centerline
- add a cernterline fairing consisting of two sections (forward an aft) that retains the full height of the outlet all the way to the trailing edge
- the fwd section of the center fairing would swell from a smoothly curved leading edge to the interface with the aft section.
- many aft sections could be built to test the effect of different shapes - the best would seem to be one that is "fat" at the front to restrict the outlet area then curve inward going slightly concave to pick up the bypass flow around the "Cuff" perhaps accellerate the aircoming past the forward part of the center fairing
- all three pieces would be independent but when installed all three would be interconnected with screws, platenuts and dimple washers.

Thoughts?

Bob Axsom

[AX-O]

Bob, I am sure this makes sense to you but I am lost. Can you draw something on paper and scan it.

[LifeofReiley]

good info Bob... excellent idea. I think you're on to something.

[Bob Axsom]

Originally Posted by AX-O

Bob, I am sure this makes sense to you but I am lost. Can you draw something on paper and scan it.

I spent my day using my RV building skills making an 18" diameter aluminum cone squirel barrier for my back yard bird feeder. These kind of jobs seem to occupy my time here in the Arkansas country but I think about speed a lot. I haven't drawn anything and I will evolve the actual configuration from the the dimensions of the existing parts of the airplane.

To help with the visualization just imagine sitting on the ground with your head in front of the wing level with the bottom of the fuselage. You see the line of the bottom of the cowl pass under the FAB but instead of truncating at the firewall it continues back for 1.5 to 2 feet under the fuselage before it truncates or another version may curve up to the fuselage.

Laying under the airplane with your head just aft of the firewall looking straight up at the bottom of the fuselage, you see an extension of the center portion of the cowl about 2 inches past the firewall with the edges curving in toward the center - not much but not a straight line. From the center you see a long structure that is several inches wide as it emerges from the cowl and curves in toward the centerline of the fuselage then gently curves back toward its trailing edge creating a concave section on each side.

Laying under the fuselage again but farther back and looking at the outlet area you see the two exhaust pipes in the cavity between the center structure (fairing) and the cowl extension cuff.

This allows the "A" builder to enclose the NLG support structure in a shroud (which I expect it to do nothing but, why not) and provide some directional flow control in this area that seems to have a lot of turbulent flow and drag. Ref. the tufting video or photos that appeared here earlier and Larry Vetterman's fairing development.

Bob Axsom