Mailing List flyrotary@lancaironline.net Message #3854
From: JJ JOHNSON <JJJOHNSON@ACCESSCOMM.CA>
Subject: Re: [FlyRotary] Re: rooster-tail drag
Date: Wed, 15 Oct 2003 13:23:26 -0600
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
I have never seen a NACA scoop used to vent air FROM the aircraft BACK into airstreams.
I have reviewed all the NACA papers on scoops and have never seen this effect described.  Please point us to any reference on the subject.
 
Respectfully,
Eric
 
 
Eric, I have to admit I've never seen this analyzed on paper however I've seen it in practice and the builder swore by it. He had extended the edge of the opening back a bit 1/4-3/8" as well as rounded the ramp into the opening as to smooth the transition. I just took his word for it that it could be used either way. You've got me thinking now but I see why it wouldn't work? I guess maybe the converging ramp sides might pre-maturely force the air out into the slip-stream but other than that..  I guess worst case scenario is to eliminate the converging ramps. One thing that I would steer clear of [or at least I will on my a/c] is the shark gill type exits. I have read somewhere that they are one of the worst types of exits for air.. now where I read that I don't know.. but I'm going to try and find out. Maybe there are some other aerodynamics types out there that can help me/us w/ this?
 
Please don't take what I say as the gospel truth..  I'm no expert, but I try to learn/know all I can about the subject.
 
Jarrett
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