Sender: <marv@lancaironline.net> (Marvin Kaye)
To: lml@lancaironline.net
Date: Thu, 04 Dec 2003 10:39:39 -0500
Message-ID: <redirect-2783320@logan.com>
From: "JJ JOHNSON" <JJJOHNSON@ACCESSCOMM.CA>
References: <list-2782695@logan.com>
Subject: Re: [LML] Re: Vortex Generators
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Paul wrote;
>Hence my question, why are we interested in doing that to
> these high performance airplanes?  I understand that you can lower your
> stall speed, but who wants to do that at the expense of decreased
> performance?


Paul, I'll take a stab at it. I think the reason that this person isn't
experiencing any drag increase [ or performance decrease] is probably
directly linked to his a/c. We all know that Lance designed our Lnc2's w/
the NLF-0215 airfoil, which is a natural laminar airfoil. The problem arises
when we as the builders built this a/c w/ this airfoil. There is no way that
we are all getting our outter skins to form this airfoil exactly. If memory
serves correct the 0215 has NLF [natural laminar flow] out to about 55%
chord --> In best case wind tunnel conditions <--  and I think that is the
key. In the real world we are probably only getting 35-40% NLF so if a
person was to put their VG's at 25-30% chord there would be little effect to
the laminar flow characteristics. The reason I feel we are only getting the
little NLF that we are is because of the variables in leading edge shape as
well as skin waviness and ruffness[not to mention bugs, rain or paint
chips]. Not to sound like the total pessimist, the 0215 is a great airfoil
and even though it is being used in the higher end of its intended Re#
[remember this airframe/wing was originally intended to be flown w/ an
0-200]. Another point which I can't remember what the effect was, is the
reflexing of the flaps, this enables us to fly at a different AOA than
optimum and which I believe [don't quote me] isn't helping our NLF situation
either.

In the words or a wiser man "Asbestos flame suite on and ready.."

Jarrett Johnson
235/320 55%