X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sun, 28 Sep 2008 13:16:12 -0400 Message-ID: X-Original-Return-Path: Received: from web36905.mail.mud.yahoo.com ([209.191.85.73] verified) by logan.com (CommuniGate Pro SMTP 5.2.8) with SMTP id 3189940 for lml@lancaironline.net; Sun, 28 Sep 2008 04:04:46 -0400 Received: (qmail 78914 invoked by uid 60001); 28 Sep 2008 08:04:45 -0000 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=X-YMail-OSG:Received:X-Mailer:Date:From:Subject:To:MIME-Version:Content-Type:Message-ID; b=aHhwnqXwUwUcdTspFCpuieuy+AKcVTtKx+okqAjmtUDYFnGtfdTPCMvvSFClqKlNxfd4T0EqCrJaYdb5hYWqzb4PfeaDBt5Deew0TNAS3YwUpiXFg5+M9wLxLglUROLRc5HOmyTj0MX2oB1/Pb7uu7DOSy6+lqpRK9seyGvq8co=; X-YMail-OSG: 5XXQwJ0VM1krYrKsNddMVeBQBC_GIsNj5fro6SfUyd0z4zarj_9kRqpXn.XY1xfYlAatV.LwWPaRKwQqtA3bPBPTkR12251800TwOAzYZpg11c8AXBpgDCp6Nyv_WHYjeyBQwbXQ3XpGwQV5m72v6iUDyi1s6EqSeqesXQTZvkvs3XU- Received: from [99.133.182.222] by web36905.mail.mud.yahoo.com via HTTP; Sun, 28 Sep 2008 01:04:45 PDT X-Mailer: YahooMailRC/1096.28 YahooMailWebService/0.7.218.2 X-Original-Date: Sun, 28 Sep 2008 01:04:45 -0700 (PDT) From: Chris Zavatson Subject: Re: [LML] Re: Small tail vs. large tail X-Original-To: Lancair Mailing List MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="0-6215938-1222589085=:78832" X-Original-Message-ID: <673306.78832.qm@web36905.mail.mud.yahoo.com> --0-6215938-1222589085=:78832 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable <>=0AScott,= =0AThe longer engine mounts serves to move the CG forward.=A0 The increased= surface area of the MKII tail moves the neutral point rearward.=A0 The dif= ference between these two defines the static margin.=A0 As the static margi= n goes to zero, the aircraft becomes neutrally stable.=A0 This means the MK= II tail can handle a more rearward CG than the original for the same degree= of stability or conversely, has greater pitch stability for the the same C= G location.=A0=A0=A0 =0ATwo side notes:=A0 The long engine mount is actuall= y somewhat destabilizing in yaw and=A0pitch due to the added surface area p= rojected out in front of the CG.=A0 The larger tail can also handle a more = forward CG=A0since it=A0has more pitch authority at low speeds.=A0=0AThe=A0= added area in the tail simply opens up the available CG range in both direc= tions.=A0=A0Either tail may be perfectly acceptable as long as each is kept= within its individual CG capability.=0AChris=0A=0A=0A=0AChris Zavatson=0AN= 91CZ=0A360std=0Awww.N91CZ.com=0A=0A=0A --0-6215938-1222589085=:78832 Content-Type: text/html; charset=us-ascii

<<The Mark II tail alone exacerbates flight problems at rearward CGs since it adds such a large rearward moment. Thus the corollary recommendation that the long engine mount be used to move the CG forward.>>

Scott,

The longer engine mounts serves to move the CG forward. The increased surface area of the MKII tail moves the neutral point rearward. The difference between these two defines the static margin. As the static margin goes to zero, the aircraft becomes neutrally stable. This means the MKII tail can handle a more rearward CG than the original for the same degree of stability or conversely, has greater pitch stability for the the same CG location.

Two side notes: The long engine mount is actually somewhat destabilizing in yaw and pitch due to the added surface area projected out in front of the CG. The larger tail can also handle a more forward CG since it has more pitch authority at low speeds.

The added area in the tail simply opens up the available CG range in both directions. Either tail may be perfectly acceptable as long as each is kept within its individual CG capability.
Chris

Chris Zavatson

N91CZ

360std

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