Return-Path: Received: from [65.54.169.98] (HELO hotmail.com) by logan.com (CommuniGate Pro SMTP 4.2b2) with ESMTP id 3204093 for flyrotary@lancaironline.net; Mon, 03 May 2004 16:14:10 -0400 Received: from mail pickup service by hotmail.com with Microsoft SMTPSVC; Mon, 3 May 2004 13:14:01 -0700 Received: from 4.174.4.152 by bay3-dav68.adinternal.hotmail.com with DAV; Mon, 03 May 2004 20:14:01 +0000 X-Originating-IP: [4.174.4.152] X-Originating-Email: [lors01@msn.com] X-Sender: lors01@msn.com From: "Tracy Crook" To: "Rotary motors in aircraft" Subject: Re: [FlyRotary] Tail Wing Incident Date: Mon, 3 May 2004 16:13:59 -0400 MIME-Version: 1.0 X-Mailer: MSN Explorer 7.02.0011.2700 Content-Type: multipart/alternative; boundary="----=_NextPart_001_0009_01C43129.A45D3AD0" Message-ID: X-OriginalArrivalTime: 03 May 2004 20:14:01.0930 (UTC) FILETIME=[2CEDB2A0:01C4314B] ------=_NextPart_001_0009_01C43129.A45D3AD0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable I probably am overpropped at static and low speed. I told Clark Lydick t= o build me a speed prop. I figured that being overpropped on take-off doe= snt matter if you have lots of HP and can get off the ground in 1200 ft a= nd climb like a banshee anyway. I'll be sending the prop back for adjustm= ent once I get solid numbers, but I don't think I'll want him to cut it b= ack much. john Slade =20 What sort of top speed, and cruise speed do you expect? What would be co= mmon for an O-360 powered plane? =20 Cheers, Rusty (wishing the RV airfoil wasn't so draggy over 220 mph) I used to think the same thing (draggy airfoil) but I think the problem = with RVs over 220 is related to wing / tail / fuselage incidence. At 22= 0 I get the visual impression that I am in a dive during level flight. The early Citation jets used the same airfoil as the lowly RV. Tracy Tracy, =20 As you known, the airflow over the horizontal tail is such as to exert= down force on the tail (Nose up) to overcome the forward pitching moveme= nt of the CL of the wing airfoil. I suspect that at the higher airspeeds= the airflow over the wing could be changed sufficiently that the tail su= rface might be providing less downforce (nose up ) than required. In o= therwords the downforce on the horizontal stab is sufficiently lessened = that the nose lowers until the horizontal stab finds a new equilibrium po= int at your higher airspeed. As nose goes down, more of the upper surfac= e of the horiz stab is exposed to the airflow causing more down force/nos= e up until the new equilibrium is reached. Just a thought. Ed Hi Ed, I thought the major reason for down force on H stab was to resist the for= ce due to CG being ahead of CL. Or maybe that's saying the same thing yo= u said? CL does not move much on the 23013 series airfoil in normal flig= ht envelope. In my limited understanding of the aerodynamics (in non canard aircraft),= it is always "all about the wing" and what it requires to do what is = asked of it. =20 At any given speed, the pitch requirement for level flight is X, end of = story. The hor. stab and elevator delivers the amount of down force requ= ired to make it thus. If this happen to be at an angle where the H. Stab= & elevator are shaped like a shallow inverted V and the fuse is plowing = through the air in a nose down attitude, it's going to make drag. The fi= x is to lower the incidence of the wing relative to the fuselage and to l= ower the incidence of the H stab relative to the wing. This is what all = the serious RV racers are doing. =20 The only reason I don't do this is that it increases drag at more normal = flight speeds. Everything is a compromise. Tracy ------=_NextPart_001_0009_01C43129.A45D3AD0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

I probably am overpropped at static and low speed. I = told Clark Lydick to build me a speed prop. I figured that being overprop= ped on take-off doesnt matter if you have lots of HP and can get off the = ground in 1200 ft and climb like a banshee anyway. I'll be sending the pr= op back for adjustment once I get solid numbers, but I don't think I'll w= ant him to cut it back much.

john Slade
=

<= FONT face=3DArial>What sort of top speed, and cruise speed do you = expect? What would be common for an O-360 powered plane? =

Cheers,

Rusty (wishing the RV airfoil wasn't so dragg= y over 220 mph)
=

<= SPAN class=3D109152418-02052004>I used to think the same thing (draggy airfoil) but I think the p= roblem with RVs over 220 is related to wing / tail / fuselage incide= nce.   At 220 I get the visual impression that I am i= n a dive during level flight.

The = early Citation jets used the same airfoil as the lowly RV.<= /FONT>

<= SPAN class=3D109152418-02052004>

Tracy<= /DIV>

Tra= cy,

=
<= SPAN class=3D180273302-03052004>   As you known, the = airflow over the horizontal tail is such as to exert down force on the ta= il (Nose up) to overcome the forward pitching movement of the CL of the w= ing airfoil. I suspect that at the higher airspeeds the airflow ove= r the wing could be changed sufficiently that the tail surface might be p= roviding less downforce (nose up ) than required.   = In otherwords the downforce on the horizontal stab is sufficiently = lessened that the nose lowers until the horizontal stab finds a new equil= ibrium point at your higher airspeed. As nose goes down, more of th= e upper surface of the horiz stab is exposed to the airflow causing more = down force/nose up until the new equilibrium is reached. Just a tho= ught.

=

Ed

Hi Ed,

I thought the major reason for down force on H stab was to resist= the force due to CG being ahead of CL. Or maybe that's saying the = same thing you said? CL does not move much on the 23013 series airf= oil in normal flight envelope.<= /DIV>
In my limited understandin= g of the aerodynamics (in non canard aircraft), it is always = "all about the wing" and what it requires to do what is asked of it=

=

At any given sp= eed, the pitch requirement for level flight is X, end of story= The hor. stab and elevator delivers the amount of down force requ= ired to make it thus.  If this happen to be at an angle where t= he H. Stab & elevator are shaped like a shallow inverted V and t= he fuse is plowing through the air in a nose down attitude, it's going to= make drag. The fix is to lower the incidence of the wing relative = to the fuselage and to lower the incidence of the H stab relative to the = wing. This is what all the serious RV racers are doing.  =

=
The only reason I don't do this = is that it increases drag at more normal flight speeds.   Every= thing is a compromise.

Tracy

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