Return-Path: Received: from relay04.roc.ny.frontiernet.net ([66.133.131.37] verified) by logan.com (CommuniGate Pro SMTP 4.1.5) with ESMTP id 2634361 for flyrotary@lancaironline.net; Sun, 12 Oct 2003 23:17:35 -0400 Received: (qmail 4274 invoked from network); 13 Oct 2003 03:17:32 -0000 Received: from unknown (HELO frontiernet.net) ([170.215.97.8]) (envelope-sender ) by relay04.roc.ny.frontiernet.net (FrontierMTA 2.3.6) with SMTP for ; 13 Oct 2003 03:17:32 -0000 Message-ID: <3F8A0B70.AC0D0DB@frontiernet.net> Date: Sun, 12 Oct 2003 22:18:24 -0400 From: Jim Sower X-Mailer: Mozilla 4.77 [en] (Win98; U) X-Accept-Language: en MIME-Version: 1.0 To: Rotary motors in aircraft Subject: Re: [FlyRotary] Re: solo's & Delta T... no more emergencies References: Content-Type: multipart/alternative; boundary="------------FCFF47697048FD459E9E52ED" --------------FCFF47697048FD459E9E52ED Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit <... Do you have any references ...> No I don't offhand. I heard about it from the speed merchants in the canard community. They do some pretty slick (no pun intended) stuff. It might have been written up in the Central States Association newsletter. A lot of the discussion was on the Canard Aviators email list which I left a couple of years ago. Anyway, you should be able to minimize the effect by forming your louvers such that the air exits the traveling in a direction parallel with the air stream (flag against the fuselage). Oh - another example of rooster tail drag is the aileron hinge gap. Rutan planes have the ailerons hinged at the top surface of the wing, so it's easy to seal the gap. Most dramatic result is low speed roll authority, but air on from the lower (high pressure) side of the wing squirting up through the aileron hinge gap to the upper (low pressure) side not only compromises the aileron, but makes a rooster tail. These guys even take extra care sealing the cowl to prevent plenum air from squirting out from where the cowl joins the wing and fuselage. Hope this helps. I'll try and find references if I can ... Jim S. Ed Anderson wrote: > That is interesting, Jim. My RV has louvers on both sides > of the cowl, so if I understand what you are saying, I might > pick up less drag due to the turbulence created up front that > flows back over the entire fuselage. Do you have any > references about this effect other thanthe one already > mentioned? Ed Anderson > RV-6A N494BW Rotary Powered > Matthews, NC > eanderson@carolina.rr.com > > ----- Original Message ----- > From: Jim Sower > To: Rotary motors in aircraft > Sent: Sunday, October 12, 2003 9:06 AM > Subject: [FlyRotary] Re: solo's & Delta T... no more > emergencies > <... I've considered adding a set of louvers on the > right side of the cowl and ducting the right rad > outlet to exit the louvers ...> > If you try this, you might want to take care to > avoid "rooster tail" exit drag. Studies have shown > that is a real significant component of drag. > Canard folks have picked up significant airspeed by > making them go away. > Best ... Jim S. > > > -- Jim Sower Crossville, TN; Chapter 5 Long-EZ N83RT, Velocity N4095T --------------FCFF47697048FD459E9E52ED Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit <... Do you have any references ...>
No I don't offhand. I heard about it from the speed merchants in the canard community. They do some pretty slick (no pun intended) stuff. It might have been written up in the Central States Association newsletter. A lot of the discussion was on the Canard Aviators email list which I left a couple of years ago. Anyway, you should be able to minimize the effect by forming your louvers such that the air exits the traveling in a direction parallel with the air stream (flag against the fuselage).

Oh - another example of rooster tail drag is the aileron hinge gap. Rutan planes have the ailerons hinged at the top surface of the wing, so it's easy to seal the gap. Most dramatic result is low speed roll authority, but air on from the lower (high pressure) side of the wing squirting up through the aileron hinge gap to the upper (low pressure) side not only compromises the aileron, but makes a rooster tail. These guys even take extra care sealing the cowl to prevent plenum air from squirting out from where the cowl joins the wing and fuselage.

Hope this helps. I'll try and find references if I can ... Jim S.

Ed Anderson wrote:

That is interesting, Jim. My RV has louvers on both sides of the cowl, so if I understand what you are saying, I might pick up less drag due to the turbulence created up front that flows back over the entire fuselage. Do you have any references about this effect other thanthe one already mentioned? Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com

----- Original Message -----

From: Jim Sower

To: Rotary motors in aircraft

Sent: Sunday, October 12, 2003 9:06 AM

Subject: [FlyRotary] Re: solo's & Delta T... no more emergencies
<... I've considered adding a set of louvers on the right side of the cowl and ducting the right rad outlet to exit the louvers ...>
If you try this, you might want to take care to avoid "rooster tail" exit drag. Studies have shown that is a real significant component of drag. Canard folks have picked up significant airspeed by making them go away.
Best ... Jim S.

--
Jim Sower
Crossville, TN; Chapter 5
Long-EZ N83RT, Velocity N4095T
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