OK folks,

In the very high and hot summer  temperatures here in Idaho my oil and CHT temps seem to run a little warm creeping up into the yellow range as specified by Rotax.. Last summer I added an  air scoop to the NACA duct for the oil cooler - dropped the temp very slightly, but it did decrease. Also added an air scoop to the radiator (vertical ULS) which again helped slightly. Picture attached.

Now am fabricating a "lip" for the bottom of the cowl to increase - maybe - air flow through the cowl.  Read that this will decrease the pressure at the cowl air exit thus more air flow.

Question - how much lip in height do I want and also should the height of the lip follow all the way around to the juncture of the fire wall??  Attached picture of my rudimentary efforts - please ignore the mess in my shop - the flare and lip will be better finished when done.

Phil Smith

CH 701

Views: 350


Reply to This

Replies to This Discussion

Hi Phil

The lip seem high and at a large angle to me. My understanding is that you need to have a low pressure but laminar flow. If it gets too turbulent the air will not come out of the cowling. 

Have you tried to make the hole for the landing gear bigger instead of adding a lip?



New from Zenith:

Zenith Planes For Sale 

Classified listing for buying or selling your Zenith building or flying related stuff...


Weather Maps

Custom Instrument Panels
for your Zenith

Custom instrument panels are now available directly from Zenith Aircraft Company exclusively for Zenith builders and owners. Pre-cut panel, power distribution panel, Approach Fast Stack harnesses, Dynon and Garmin avionics, and more.

Custom Upholstery Kits for your Zenith Aircraft:

Zenith Vinyl Upholstery Kits

Zenith Apparel from EAA:

Zenair Floats

Flying On Your Own Wings:
A Complete Guide to Understanding Light Airplane Design, by Chris Heintz

Builder & Pilot Supplies:

How to videos from HomebuiltHELP.com

Developed specifically for Zenith builders (by a builder) these videos on DVD are a great help in building your own kit plane by providing practical hands-on construction information. Visit HomebuiltHelp.com for the latest DVD titles.

Aircraft Insurance:


West Coast USA:

Transition Training:

Pro Builder Assistance

Pro Builder Assistance

Aircraft Spruce & Specialty for all your building and pilot supplies!

© 2019   Created by Zenith.Aero.   Powered by

Badges  |  Report an Issue  |  Terms of Service