Cowl Flap

[racaldwell]

Here is one possibility of reducing drag if you want to spend a week making parts and putting this together. I am not yet flying this so I can't speak yet of what it gains. My other desire is to not rapid cool my engine when I shut down for soaring flight.

The basic dimensions are derived from the Sonex Jabiru installation instructions. I have 3-1/2" x 7" x 2 = 49 sq in. when open. It's actually more given the exhaust pipe slots. The articulating front lip is 1" but only extends 13/16" below the cowling. If necessary later, this lip can be increased easily.

I modeled this 3D in Inventor to get the linkages and pivots correct. However, I didn't model the firewall and the sloped firewall interfered. I had to redesign the actuator and mount it from the engine mount. That is the carbon fiber bracket. I am currently installing a spring so it is spring loaded open.

There are more pictures on my EAA Building Log; just look up Xenos.

Rick Caldwell
Xenos 0057

Cowl Flap Closed on Bench Sm.jpg (195.5 KiB) Viewed 4233 times

[racaldwell]

Some data for using a cockpit controlled cowl flap to reduce drag. This is from glide data recorded by the GRT Sport EX in my Xenos with the short (acro) wing tips installed.

Best glide speed is 55 kts IAS for this comparison.

Cowl Flaps open: Glide angle = -3.795 deg., VS = -370 fpm, L/D = 15.1:1

Cowl Flaps closed: Glide angle = -3.380 deg., VS = -328 fpm, L/D = 16.9:1

So that is about a 12% improvement by closing the cowl flaps to reduce drag.

Easy pickin's for drag reduction.

Rick Caldwell
Xenos 0057 15.7 hrs

[GordonTurner]

Nice work Rick.

[bvolcko38]

Do you have pictures of your cowl flap/s?

[racaldwell]

Hi Bill,

Other than those posted above, take a look at my EAA builders log under XenosA or RicksXenos. Plenty of pictures there.

How about some pictures of your cowl flaps? Any comparison data to present?

Rick