Return-Path: Sender: (Marvin Kaye) To: lml@lancaironline.net Date: Tue, 09 Dec 2003 18:32:31 -0500 Message-ID: X-Original-Return-Path: Received: from imo-r01.mx.aol.com ([152.163.225.97] verified) by logan.com (CommuniGate Pro SMTP 4.1.8) with ESMTP id 2883642 for lml@lancaironline.net; Tue, 09 Dec 2003 13:47:39 -0500 Received: from Sky2high@aol.com by imo-r01.mx.aol.com (mail_out_v36_r1.1.) id q.142.1e3daac3 (3964) for ; Tue, 9 Dec 2003 13:47:26 -0500 (EST) From: Sky2high@aol.com X-Original-Message-ID: <142.1e3daac3.2d0772bd@aol.com> X-Original-Date: Tue, 9 Dec 2003 13:47:25 EST Subject: Re: [LML] Re: Vortex Generators X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1070995645" X-Mailer: Thailand for Windows sub 250 -------------------------------1070995645 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit In a message dated 12/4/2003 5:25:30 PM Central Standard Time, dfs155@earthlink.net writes: I've related here before an episode wherein I encountered a really big cloud of bugs that apparently had glue for guts. I found that upon leveling out for cruise, I couldn't seem to get up to my normal IAS (I thought maybe the nose gear had been trapped, partly extended, by the nose gear door - a problem I had for a while early on). Tried recycling the gear but didn't help. Landed and found the leading edges coated with what felt like sand paper (Billions and Billions of squashed bugs). Once cleaned off, the problem went away. Don't remember the exact loss of IAS (maybe 20 kts) but was enough to get one's attention. I can only assume it was caused by loss of laminar flow. Dan and Cy, One of the design characteristics of the 235/320/360 wing (NLF-0215F) is that loss of laminar flow should only cause a rise in drag and little or no loss of lift. In the 2003 Kittyhawk to OSH x-ctry race, the descent into ARR (Chicago check point) resulted in the pickup of billions and billions of bilious green splats on any surface exposed to the air. I lost about 6 Kts IAS on the remaining leg to OSH and Mark Ravinski, in close trail of Larry Henney (a few minutes in front of me), called off their formation flight race since Mark couldn't see much thru the bug-goo covered canopy. I think your wing contamination was worse than ours. On one of my trips to the annual Labor Day Lancair fly-in, I encountered smoke from the usual seasonal forest fires (smoke was present up to 15,000 feet) as I flew over South Dakota and Monanta and made an overnight stop at Bozeman. Parking to the South, I had a good view down the wing into the setting sun. I saw overlapping v-marks, left by the smokey air, emanating from the bugs picked up leaving an Iowa refueling stop. The included angle of each vee was about 60 degrees and the smoke trails extended over what appeared to be 50% of the chord. If only I had taken a picture of the wing. The Navy performed laminar flow tests and found that leading edge contaminations closer than 1 inch apart destroyed the laminar flow. ---- Jarret and Jack, Jarret wrote: << 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.>> If you are interested, our wing is based on the following research: http://techreports.larc.nasa.gov/ltrs/PDF/NASA-81-tp1865.pdf Some of the design characteristics are to achieve about 40% chord laminar flow (LF) on the upper surface and 60% on the lower (yes, the bottom of the wing is important). The airfoil (NLF-0215F) uses the reflexed flap for for several things. Control of the pitching moment of the high camber airfoil and re-attachment of the turbulent air flow to reduce profile drag. Care must be taken in the corner formed at the intersection to the flap and wing trailing edge so that separation does not occur there. The wing was also designed for an efficient transition area from LF to turbulent boundary layer. Note that there are low drag turbulent boundary layer wings with "interesting" characteristics. The minimum profile drag occurs at an AOA of 1.52* (experimental wing). Yada...Yada...Yada.... Conclusion: Put some oil on your wing, go fly, interpret the results - much like reading tea leaves. You will be impressed. Scott Krueger MotorMouth, Charlatan, Bon Vivant, Escapee, Etcetera... "...as we know, there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns - the ones we don't know we don't know." D. Rumsfeld -------------------------------1070995645 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable
In a message dated 12/4/2003 5:25:30 PM Central Standard Time,=20 dfs155@earthlink.net writes:
<= FONT=20 face=3DArial>I've related here before an episode wherein I encountered a r= eally=20 big cloud
of bugs that apparently had glue for guts. I found that upon=20 leveling out
for cruise, I couldn't seem to get up to my normal IAS (I=20 thought maybe the
nose gear had been trapped, partly extended, by the n= ose=20 gear door - a
problem I had for a while early on). Tried recycling the=20= gear=20 but didn't
help. Landed and found the leading edges coated with what fe= lt=20 like sand
paper (Billions and Billions of squashed bugs). Once cleaned=20= off,=20 the
problem went away. Don't remember the exact loss of IAS (maybe 20 k= ts)=20 but
was enough to get one's attention. I can only assume it was caused=20= by=20 loss
of laminar flow.
Dan and Cy,
 
One of the design characteristics of the 235/320/360 wing=20 (NLF-0215F) is that loss of laminar flow should only cause a rise in dr= ag=20 and little or no loss of lift. 
 
In the 2003 Kittyhawk to OSH x-ctry race, the descent into ARR (Chicago= =20 check point) resulted in the pickup of billions and billions of bilious gree= n=20 splats on any surface exposed to the air.  I lost about 6 Kts IAS on th= e=20 remaining leg to OSH and Mark Ravinski, in close trail of Larry Henney (a fe= w=20 minutes in front of me), called off their formation flight race since M= ark=20 couldn't see much thru the bug-goo covered canopy. I think your wing=20 contamination was worse than ours.
 
On one of my trips to the annual Labor Day Lancair fly-in, I encountere= d=20 smoke from the usual seasonal forest fires (smoke was present up to 15,000 f= eet)=20 as I flew over South Dakota and Monanta and made an overnight stop at=20 Bozeman.  Parking to the South, I had a good view down the wing into th= e=20 setting sun.  I saw overlapping v-marks, left by the smokey air,=20 emanating from the bugs picked up leaving an Iowa refueling stop. The=20 included angle of each vee was about 60 degrees and the smoke trai= ls=20 extended over what appeared to be 50% of the chord.  If only I had= =20 taken a picture of the wing.
 
The Navy performed laminar flow tests and found that leading edge=20 contaminations closer than 1 inch apart destroyed the laminar flow.
 
----
 
Jarret and Jack,
 
Jarret wrote:
<<
<= FONT=20 face=3DArial>We all know that Lance designed our Lnc2's w/
the NLF-0215= =20 airfoil, which is a natural laminar airfoil. The problem arises
when we= as=20 the builders built this a/c w/ this airfoil. There is no way that
we ar= e=20 all getting our outter skins to form this airfoil exactly. If memory
se= rves=20 correct the 0215 has NLF [natural laminar flow] out to about 55%
chord=20 --> In best case wind tunnel conditions <--  and I think that i= s=20 the
key. In the real world we are probably only getting 35-40% NLF so i= f=20 a
person was to put their VG's at 25-30% chord there would be little ef= fect=20 to
the laminar flow characteristics. The reason I feel we are only gett= ing=20 the
little NLF that we are is because of the variables in leading edge=20 shape as
well as skin waviness and ruffness[not to mention bugs, rain o= r=20 paint
chips]. Not to sound like the total pessimist, the 0215 is a grea= t=20 airfoil
and even though it is being used in the higher end of its inten= ded=20 Re#
[remember this airframe/wing was originally intended to be flown w/= =20 an
0-200]. Another point which I can't remember what the effect was, is= =20 the
reflexing of the flaps, this enables us to fly at a different AOA=20 than
optimum and which I believe [don't quote me] isn't helping our NLF= =20 situation
either.>>
If you are interested, our wing is based on the following research:
 
http:/= /techreports.larc.nasa.gov/ltrs/PDF/NASA-81-tp1865.pdf
 
Some of the design characteristics are to achieve about 40%=20 chord laminar flow (LF) on the upper surface and 60% on the lower (yes,= the=20 bottom of the wing is important). The airfoil (NLF-0215F) uses the reflexed=20= flap=20 for for several things. Control of the pitching moment of the high camb= er=20 airfoil and re-attachment of the turbulent air flow to reduce profile d= rag.=20 Care must be taken in the corner formed at the intersection to the flap and=20= wing=20 trailing edge so that separation does not occur there.  The wing was al= so=20 designed for an efficient transition area from LF to turbulent boundary laye= r.=20 Note that there are low drag turbulent boundary layer wings with "interestin= g"=20 characteristics.  The minimum profile drag occurs at an AOA of 1.52*=20 (experimental wing).  Yada...Yada...Yada....
 
Conclusion:
 
Put some oil on your wing, go fly, interpret the results - much like=20 reading tea leaves.  You will be impressed.
 
Scott=20 Krueger
MotorMouth, Charlatan, Bon Vivant, Escapee, Etcetera...

".= ..as=20 we know, there are known knowns; there are things we know we know. We also k= now=20 there are known unknowns; that is to say we know there are some things we do= not=20 know. But there are also unknown unknowns - the ones we don't know we don't=20 know." D. Rumsfeld
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