Cut off exhaust for paint

[hecilopter]

I am getting ready for the paint shop and I'm trying to clean up everything as much as possible to reduce drag. One obvious thing hanging in the wind is the exhaust hanging about 2" lower than the absolute bottom of the cowl exit.

I'm thinking of pulling a straight line even with the bottom of the cowl exit, parallel with the fuselage and marking the pipes to cut off at an angle basically making them even with the bottom of the cowl exit. This would result in an oval shaped, down pointed exit for the exhaust. I would only be cutting off about 1 1/2" of the forward side of the exhaust exit and almost 0 from the rear side.

Has anyone tried this? I saw a post about cutting the whole downturn off and other things, but not this.

I would think it should help by getting the round pipes out of the air stream and shouldn't result in any additional noise or floor pounding since the exhaust is still pointed down.

Thanks!

 

[pierre smith]

No

Rusty,
If the pipes are cut off parallel to the exit, the outside airflow past those holes will block the exiting exhaust! IF you insist on cutting them off, cut PERPENDICULAR to the pipes so that they still point rearward. An engineer told me that you can also "squeeze" them with a vise, until they're oval, with the oval vertical, with the vertical part of the oval twice as tall as it is wide. This helps accelerate the exhaust to more closely match the outside air in speed, for reduced drag. Read the previous post about floor vibration and exhaust gas stained belly,

 

[gmcjetpilot]

Cool idea

Rusty, helps accelerate the exhaust to more closely match the outside air in speed, for reduced drag. Read the previous post about floor vibration and exhaust gas stained belly,

The exhaust tip restriction you mention works but the geometry needs to very with speed and altitude. IT works in theory and practice but it's more complicated than clamping the pipe down to an oval. If anyone want to play with this they can make differnt slip on pipe exit nozzles that provide "jet" thrust. Of course pointing aft parallel to the airstream is needed.