Re: NACA Inlet question

Bob Holliston

Yes and yes. I had those corners on the NACA for awhile (mainly because I noticed Klaus did) and noticed no difference so I cut'em off. When I built a new lower cowl a couple years ago I incorporated dedicated tunnels (two into four) that blow on the cylinders. The cooling is better than with the ramps but the OT is now 190 instead of 180. Damnit, I wanted a FREE LUNCH! With the tunnels it is easier to tweak them than the ramps to even up CHT's Three of my cyls. are around 338 - 349, with one at 318 in cruise so I need to shrink the low one.... when I get the ambition. Also, with the ramps the CHT's were only about 15 F higher, so not that bad. 

On Tue, Aug 3, 2021 at 2:33 PM Joe Dubner via <> wrote:
Thanks Don, Roch, and Todd.  Three in the plus column; no negative (so far).  Thanks too, Bob -- you make four.

I did try VGs ahead of the beginning of the ramp but when I designed and placed them in accordance with this Kitplanes article ( they were honkin' huge and wound up being mounted on the speed brake.  Totally unsatisfactory but they did improve airflow somewhat.  I'd like to see a picture of others' VGs if they are effective.

My oil flow tests show outflow at the inlet with air spilling over the little "strakes".  Maybe it would be worse without them, maybe not.  I'm tempted to take Bob H's advice and cut them off for comparison.

Bob, you have an O360 Long-EZ with no particular cooling issues, right?  Maybe we can talk.


Join to automatically receive all group messages.