NACA vent IN the cowl cheek

rph142 · #1 10-07-2010, 11:25 AM

Would a NACA vent work if it was mounted in the cowl cheek? It wouldnt take much to cut and mount them to my fiberglass cowl cheeks.

Thanks,
Rob

szicree · #2 10-07-2010, 11:38 AM

I would think that such a convex surface would be an area of low pressure. You might end up pulling air out of the cockpit.

elippse · #3 10-07-2010, 03:13 PM

Is this for cabin air, engine or oil cooling? Don't use a NACA duct (curved divergent submerged duct) unless you have the design data and can size it appropriately for your application. There is also a parallel-wall sumerged duct that is part of the same family that is much better when you want very high duct airflow. It is better than the CDSD when the velocity of the air through the duct is 0.5 or greater than the free-stream velocity. It uses a square aperture which interfaces to a round duct easier than the 4:1 to 6:1 CDSD aperture and also uses the 7 degree ramp for best pressure recovery. It should be 8.1 times as long as the aperture height-width to give the 7 degrees. A steeper ramp than this invites separation.

KatieB · #4 10-07-2010, 08:23 PM

Quote:

Originally Posted by elippse

There is also a parallel-wall sumerged duct that is part of the same family that is much better when you want very high duct airflow. It is better than the CDSD when the velocity of the air through the duct is 0.5 or greater than the free-stream velocity. It uses a square aperture which interfaces to a round duct easier than the 4:1 to 6:1 CDSD aperture and also uses the 7 degree ramp for best pressure recovery. It should be 8.1 times as long as the aperture height-width to give the 7 degrees. A steeper ramp than this invites separation.

Um, does that come in English?

elippse · #5 10-07-2010, 08:40 PM

Well, Katie, that must be some of the Latin I got in Catholic schools showing through!

n5lp · #6 10-07-2010, 08:50 PM

Is this what you are talking about? I don't know how well it works, I just took the picture.

Ironflight · #7 10-07-2010, 09:36 PM

I thought of your recent pictures when I saw the question Larry - thanks for posting it! I do wonder how effective it is on that curved surface though - true NACA ducts are harder to implement than people think. In my case, I have other plans for the cheek cowls, so I am looking elsewhere for cooling air....

Paul

szicree · #8 10-08-2010, 07:41 AM

Not sure if it works, but IMHO it doesn't look very good.

Dmadd · #9 10-08-2010, 07:45 AM

LOL!!!!!!
I was thinking the same thing Katie.

DM

Quote:

Originally Posted by KatieB

Um, does that come in English?

rph142 · #10 10-08-2010, 08:27 AM

Yeah I thought they would look interesting there, then I happened across pictures of johns plane "hack job". I just talked to him about their effectiveness and it's sounds like they don't work very well at low pattern speeds. It looks like I'll be pulling fresh air from somewhere else. I might end up stuffing the inverted oil tank in the cheeks.