X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 21 Oct 2013 07:36:45 -0400 Message-ID: X-Original-Return-Path: Received: from nm5-vm2.bullet.mail.ne1.yahoo.com ([98.138.90.153] verified) by logan.com (CommuniGate Pro SMTP 6.0.7) with ESMTPS id 6546916 for lml@lancaironline.net; Sat, 19 Oct 2013 06:05:09 -0400 Received-SPF: none receiver=logan.com; client-ip=98.138.90.153; envelope-from=casey.gary@yahoo.com Received: from [98.138.90.55] by nm5.bullet.mail.ne1.yahoo.com with NNFMP; 19 Oct 2013 10:04:34 -0000 Received: from [98.138.101.178] by tm8.bullet.mail.ne1.yahoo.com with NNFMP; 19 Oct 2013 10:04:34 -0000 Received: from [127.0.0.1] by omp1089.mail.ne1.yahoo.com with NNFMP; 19 Oct 2013 10:04:34 -0000 X-Yahoo-Newman-Property: ymail-3 X-Yahoo-Newman-Id: 360088.68671.bm@omp1089.mail.ne1.yahoo.com Received: (qmail 90178 invoked by uid 60001); 19 Oct 2013 10:04:34 -0000 DomainKey-Signature:a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=X-YMail-OSG:Received:X-Rocket-MIMEInfo:X-Mailer:Message-ID:Date:From:Reply-To:Subject:To:MIME-Version:Content-Type; b=j3tt0IWDR6pdPHaJysxp5oIDNWX4r8uI8I20tw2QmQ+gVxHOy2WrzyabCIRy6Kk5vvnX+Br+vE5J6nglExXrjSilR/CpeOEoXFQ98R9IN8gCeMZEXqpLknBXclhk2PTd0yl9T1CFTW8IxG4m00lb5wnUQ52IUKDG4C49wG41ohg=; X-YMail-OSG: tkH9DQkVM1kkr_jpotB2U8kf658myZExbXlvIA25gRdiwcG pgbmP6pn30Feb4OZ9.8LLeiY8QsgU0yDenSTAdOgy7zr1yDu7UMngNJyrF33 aODpm9AZLDEnigw9j6eYG3BPYZhr65_s5E1d5Azq5hyLlWedZJqYFxdoaYvv pn.N2y3Bo1U_XfbALQAC5TDs5QTbD.MhSn4ES8ybdkKYeGDI_Bywow9FYQ0K XzDT.7sJCa0jnkhg.ReElrbHOizlnZTOPE5X.PtQiVpVTY3Nt7s0WrjQ5gZU 6nEnns4vTj4YEU4EuaukJXRTs_pb7LrzhDSQB8TCemVH.qcC7NpNBySJHh3t 2J1hQUV.H59Of8KiyDVF4ymDd1HtOa6c9qkKVoBk_wu.CPOIYM4TMavy7yXi NdDw3zqc21skGeCydKjCfX0u1SgEenuoqR45_r6h8RJsJAxPzqykNEFzNOlP npLSyVLUAtxcN4xRnILZMEP52Jh82an2wNCS.nVPWukr2wdPjRfDliYHlfkR 1S.3jpoGpi0Hk5RUA5Wvi.uZkF1jBipU.2wHbd93tM4H_kVNchpuOrYUVWMt WUCllfBdPP4Yap1d26O_Ik7M- Received: from [97.92.63.83] by web120105.mail.ne1.yahoo.com via HTTP; Sat, 19 Oct 2013 03:04:33 PDT X-Rocket-MIMEInfo: 002.001,VGhlIGlkZWEgaXMgdG8gcHV0IGEgZHJvcChzKSBvZiBvaWwsIHByZXN1bWFibHkgdWdseSBibGFjayBvaSB0aGF0IGlzIGhpZ2hseSB2aXNpYmxlbCwgb24gdGhlIHNwb3QgeW91IHdhbnQgdG8gZXZhbHVhdGUuIMKgVGhlbiBnbyBmbHkgZm9yIGVub3VnaCB0aW1lIGZvciB0aGUgYWlyIGZsb3cgdG8gInN0cmVhayIgdGhlIG9pbCBpbiB0aGUgZGlyZWN0aW9uIG9mIGFpcmZsb3cuIMKgSXQgZG9lc24ndCBhbHdheXMgd29yayB2ZXJ5IHdlbGwuIMKgR3Jhdml0eSB3aWxsIGFmZmVjdCB0aGUgdHJhamVjdG9yeSABMAEBAQE- X-Mailer: YahooMailWebService/0.8.160.587 X-Original-Message-ID: <1382177073.87527.YahooMailNeo@web120105.mail.ne1.yahoo.com> X-Original-Date: Sat, 19 Oct 2013 03:04:33 -0700 (PDT) From: Gary Casey Reply-To: Gary Casey Subject: Yaw X-Original-To: Lancair Mailing List MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-1460980517-1184998850-1382177073=:87527" ---1460980517-1184998850-1382177073=:87527 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable The idea is to put a drop(s) of oil, presumably ugly black oi that is highl= y visiblel, on the spot you want to evaluate. =A0Then go fly for enough tim= e for the air flow to "streak" the oil in the direction of airflow. =A0It d= oesn't always work very well. =A0Gravity will affect the trajectory of the = streak, and in the back of the plane the boundary layer is sufficiently thi= ck that little streaking may occur - at least in a reasonably short time. = =A0And then, of course, the time spent in the desired flight regime (say, c= ruise) must be enough longer than the other conditions (taxi, climb, etc) s= o that the streaking is accurate. =A0The method doesn't cost anything, so i= t's usually worth a try. =A0And then different kinds of oil will produce di= fferent results - I haven't experimented with this.=0A=0AAnd I agree that a= single dorsal fin would be better than the twin ventral fins. =A0Ventral f= ins are used when there is limited vertical clearance, like on a jet when a= tail "rub" is possible. =A0They are also used when increased pitch stabili= ty, especially in high AOA condtions, is desired. =A0Neither is a factor in= our planes. =A0I looked hard at building a dorsal fin, but finally gave up= and just bought the ventral fin from Custer. =A0The thing that tipped me o= ver the edge was the difficulty of providing a tail tie-down. =A0In retrosp= ect I should have stuck with it.=0AGary=0A=0AHow do you execute the "oil dr= ops" method?=0A=0AFWIW I ended up with a single strake on my IVP .=0A(What = I really wished for was a longer rudder but I didn't have the =3D=0Aenginee= ring/flight test budget for that....)=0A=0AOn Oct 18, 2013, at 7:56 AM, Gar= y Casey wrote:=0A=0AI certainly concur with the comments below.=A0 I instal= led them on my ES =3D=0Aafter doing an A/B test.=A0 They increased the "fee= t-off-the-rudder-pedal" =3D=0Astability by about 30%.=A0 I measured a drop = in cruise speed of about 2 =3D=0Aknots.=A0 Painful, but I'm still glad I di= d it.=A0 There seemed to be no =3D=0Adifference in low speed pitch trim.=A0= And I agree that the alignment of =3D=0Athe strakes with the local airflow= could be better.=A0 If I were doing it =3D=0Aagain I would carefully evalu= ate the local airflow, probably with oil =3D=0Adrops, and take a wedge-shap= ed slice out between the strakes, most =3D=0Alikely toeing them out by mayb= e 5 degrees.=A0 That said, I have evaluated =3D=0Athe airflow with oil (eve= ntually the engine blowby oil will reach the =3D=0Astrakes) and I don't see= any real problem.=A0 Maybe I'm imagining a =3D=0Aproblem when there isn't = one.=A0 I was told by someone (professional test =3D=0Apilot) who has flown= all types of Lancairs that on a IVPT they are =3D=0A"absolutely required,"= on a IV they are "essential" and on an ES they =3D=0Aare "nice."=A0 FWIW= =0AGary Casey=0A ---1460980517-1184998850-1382177073=:87527 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable
The idea is to put a drop(s) of oil, presumably ugly bla= ck oi that is highly visiblel, on the spot you want to evaluate.  Then= go fly for enough time for the air flow to "streak" the oil in the directi= on of airflow.  It doesn't always work very well.  Gravity will a= ffect the trajectory of the streak, and in the back of the plane the bounda= ry layer is sufficiently thick that little streaking may occur - at least i= n a reasonably short time.  And then, of course, the time spent in the= desired flight regime (say, cruise) must be enough longer than the other c= onditions (taxi, climb, etc) so that the streaking is accurate.  The m= ethod doesn't cost anything, so it's usually worth a try.  And then di= fferent kinds of oil will produce different results - I haven't experimented with this.

And I agree that a single dorsal fin would be better than = the twin ventral fins.  Ventral fins are used when there is limited ve= rtical clearance, like on a jet when a tail "rub" is possible.  They a= re also used when increased pitch stability, especially in high AOA condtio= ns, is desired.  Neither is a factor in our planes.  I looked har= d at building a dorsal fin, but finally gave up and just bought the ventral= fin from Custer.  The thing that tipped me over the edge was the diff= iculty of providing a tail tie-down.  In retrospect I should have stuc= k with it.
G= ary

How do you execute the "oil drops" method?

FWIW I ended up with a sing= le strake on my IVP .
<= span style=3D"font-family: 'Helvetica Neue', 'Segoe UI', Helvetica, Arial, = 'Lucida Grande', sans-serif; font-size: 13px;">(What I really wished for wa= s a longer rudder but I didn't have the =3D
engine= ering/flight test budget for that....)

On Oct 18, 2013, at 7:56 AM, Gar= y Casey wrote:

I certainly concur with the comments below.  I installed th= em on my ES =3D
after doing an A/B test.  The= y increased the "feet-off-the-rudder-pedal" =3D
stabil= ity by about 30%.  I measured a drop in cruise speed of about 2 =3D
knots.  Painful, but I'm still glad I did it.&n= bsp; There seemed to be no =3D
difference in low s= peed pitch trim.  And I agree that the alignment of =3D
the strakes with the local airflow could be better.  I= f I were doing it =3D
<= span style=3D"font-family: 'Helvetica Neue', 'Segoe UI', Helvetica, Arial, = 'Lucida Grande', sans-serif; font-size: 13px;">again I would carefully eval= uate the local airflow, probably with oil =3D
drop= s, and take a wedge-shaped slice out between the strakes, most =3Dlikely toeing them out by maybe 5 degrees.  That said,= I have evaluated =3D
<= span style=3D"font-family: 'Helvetica Neue', 'Segoe UI', Helvetica, Arial, = 'Lucida Grande', sans-serif; font-size: 13px;">the airflow with oil (eventu= ally the engine blowby oil will reach the =3D
stra= kes) and I don't see any real problem.  Maybe I'm imagining a =3D
problem when there isn't one.  I was told by someone (= professional test =3D
<= span style=3D"font-family: 'Helvetica Neue', 'Segoe UI', Helvetica, Arial, = 'Lucida Grande', sans-serif; font-size: 13px;">pilot) who has flown all typ= es of Lancairs that on a IVPT they are =3D
"absolu= tely required," on a IV they are "essential" and on an ES they =3Dare "nice."  FWIW
Gary Casey<= /span>
---1460980517-1184998850-1382177073=:87527--