X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from elasmtp-banded.atl.sa.earthlink.net ([209.86.89.70] verified) by logan.com (CommuniGate Pro SMTP 6.0.7) with ESMTP id 6548877 for lml@lancaironline.net; Mon, 21 Oct 2013 09:00:11 -0400 Received-SPF: none receiver=logan.com; client-ip=209.86.89.70; envelope-from=colyncase@earthlink.net DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=dk20050327; d=earthlink.net; b=ZZd0bESSenGaHRo+bwOs1v5+R4HqNc0Mo9QuiR21Qmi4jeXeTMbhnRaczazT5WMC; h=Received:From:Mime-Version:Content-Type:Subject:Date:In-Reply-To:To:References:Message-Id:X-Mailer:X-ELNK-Trace:X-Originating-IP; Received: from [70.105.250.9] (helo=[192.168.1.24]) by elasmtp-banded.atl.sa.earthlink.net with esmtpa (Exim 4.67) (envelope-from ) id 1VYF55-0000Tv-UN for lml@lancaironline.net; Mon, 21 Oct 2013 08:59:36 -0400 From: Colyn Case Mime-Version: 1.0 (Apple Message framework v1085) Content-Type: multipart/alternative; boundary=Apple-Mail-402-326249574 Subject: Re: [LML] Yaw Date: Mon, 21 Oct 2013 08:59:35 -0400 In-Reply-To: To: "Lancair Mailing List" References: Message-Id: X-Mailer: Apple Mail (2.1085) X-ELNK-Trace: 63d5d3452847f8b1d6dd28457998182d7e972de0d01da9408c0a02b9e1cce586a0aeab49934b86e2350badd9bab72f9c350badd9bab72f9c350badd9bab72f9c X-Originating-IP: 70.105.250.9 --Apple-Mail-402-326249574 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii re: tail tie down, I left mine right where it was and provided a hole in = the fin so I can still get a rope through it. On Oct 21, 2013, at 7:36 AM, Gary Casey wrote: The idea is to put a drop(s) of oil, presumably ugly black 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 direction of = airflow. It doesn't always work very well. Gravity will affect the = trajectory of the streak, and in the back of the plane the boundary = layer is sufficiently thick that little streaking may occur - at least = in 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 = conditions (taxi, climb, etc) so that the streaking is accurate. The = method doesn't cost anything, so it's usually worth a try. And then = different 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 vertical = clearance, like on a jet when a tail "rub" is possible. They are also = used when increased pitch stability, especially in high AOA condtions, = is desired. Neither is a factor in our planes. I looked hard 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 = difficulty of providing a tail tie-down. In retrospect I should have = stuck with it. Gary How do you execute the "oil drops" method? FWIW I ended up with a single strake on my IVP . (What I really wished for was a longer rudder but I didn't have the =3D engineering/flight test budget for that....) On Oct 18, 2013, at 7:56 AM, Gary Casey wrote: I certainly concur with the comments below. I installed them on my ES =3D= after doing an A/B test. They increased the "feet-off-the-rudder-pedal" = =3D stability by about 30%. I measured a drop in cruise speed of about 2 =3D knots. Painful, but I'm still glad I did it. There seemed to be no =3D difference in low speed pitch trim. And I agree that the alignment of =3D= the strakes with the local airflow could be better. If I were doing it = =3D again I would carefully evaluate the local airflow, probably with oil =3D drops, and take a wedge-shaped slice out between the strakes, most =3D likely toeing them out by maybe 5 degrees. That said, I have evaluated = =3D the airflow with oil (eventually the engine blowby oil will reach the =3D strakes) 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 pilot) who has flown all types of Lancairs that on a IVPT they are =3D "absolutely required," on a IV they are "essential" and on an ES they =3D are "nice." FWIW Gary Casey --Apple-Mail-402-326249574 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=us-ascii re: = tail tie down, I left mine right where it was and provided a hole in the = fin so I can still get  a rope through it.

On Oct = 21, 2013, at 7:36 AM, Gary Casey wrote:

The = idea is to put a drop(s) of oil, presumably ugly black 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 direction of airflow. =  It doesn't always work very well.  Gravity will affect the = trajectory of the streak, and in the back of the plane the boundary = layer is sufficiently thick that little streaking may occur - at least = in 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 conditions (taxi, climb, etc) so that the streaking is accurate. =  The method doesn't cost anything, so it's usually worth a try. =  And then different 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 vertical clearance, like on a jet when a tail = "rub" is possible.  They are also used when increased pitch = stability, especially in high AOA condtions, is desired.  Neither = is a factor in our planes.  I looked hard 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 difficulty of = providing a tail tie-down.  In retrospect I should have stuck with = it.
Gary

How do = you execute the "oil drops" method?

FWIW I ended up with a = single strake on my IVP .
(What I really wished for was a longer rudder but I didn't have = the =3D
engineering/flight test = budget for that....)

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

I certainly concur with = the comments below.  I installed them on my ES =3D
after doing an A/B test.  They = increased the "feet-off-the-rudder-pedal" =3D
stability by about 30%.  I measured a drop in = cruise speed of about 2 =3D
knots.  Painful, but I'm still glad I did it.  There = seemed to be no =3D
difference in low speed pitch trim.  And I agree that the = alignment of =3D
the = strakes with the local airflow could be better.  If I were doing it = =3D
again I would carefully = evaluate the local airflow, probably with oil =3D
drops, and take a wedge-shaped slice out = between the strakes, most =3D
likely toeing them out by maybe 5 degrees.  That said, I = have evaluated =3D
the = airflow with oil (eventually the engine blowby oil will reach the = =3D
strakes) 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
pilot) who has flown all types of Lancairs that on a = IVPT they are =3D
"absolutely required," on a IV they are "essential" and on an ES = they =3D
are "nice."  = FWIW
Gary = Casey

= --Apple-Mail-402-326249574--