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Matt Dralle
Site Admin
Joined: 08 Nov 2005
Posts: 26320
Location: Livermore CA USA
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 Posted: Mon Jan 10, 2011 9:32 am Post subject: Airfoil Drag Video... |
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This is a REALLY interesting video about drag. I had no idea...
http://www.youtube.com/watch?v=ftq8jTQ8ANE
Matt
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Matt Dralle
RV-8 #82880 N998RV
http://www.mattsrv8.com - Matt's RV-8 Construction Log
http://www.youtube.com/MattsRV8 - Matt's RV-8 HDTV YouTube Channel
Status: 132+ Hours TTSN - The Fun Never Stops...
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sportav8r(at)gmail.com
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| Posted: Mon Jan 10, 2011 11:39 am Post subject: Airfoil Drag Video... |
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Would like to see this repeated with the spiral-cut profile common on automotive AM/FM whip antennas now. Seems to eliminate the resonant vibrations - probably cuts drag by vortex generation, too.
-Bill B
On Mon, Jan 10, 2011 at 2:11 PM, Ralph Finch <ralphmariafinch(at)gmail.com (ralphmariafinch(at)gmail.com)> wrote:
[quote] --> RV-List message posted by: "Ralph Finch" <ralphmariafinch(at)gmail.com (ralphmariafinch(at)gmail.com)>
Not repeatable therefore not real useful for comparison. The guy should
rotate the airfoils to minimum drag each time, otherwise, he doesn't know if
they are in comparable positions. It's also a shame he didn't replace the
airfoil with an equal-flow-area rectangular shape. As a result he produces
confusing and misleading results, inferring that a round shape has more drag
than a rectangular shape!
--
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Doug Gray
Joined: 10 Jan 2006
Posts: 112
Location: Sydney, Australia
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| Posted: Mon Jan 10, 2011 12:23 pm Post subject: Airfoil Drag Video... |
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For a clear easily understood mathematical discussion see page 27 and
Appendix A of this document:
www.dsto.defence.gov.au/publications/3442/DSTO-TR-1622.pdf
After reading this I designed and manufactured my own gearleg fairings
with an accurate aerodynamic profile. Angled round whip antennas will
present an elliptical profile - this does reduce their drag coefficient
slightly.
Doug Gray
RV-6 flying
On Mon, 2011-01-10 at 09:29 -0800, Matt Dralle wrote:
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sportav8r(at)gmail.com
Guest
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| Posted: Mon Jan 10, 2011 1:25 pm Post subject: Airfoil Drag Video... |
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Does the article give actual formulae or coordinates for that streamline foil shape? So as to be able to construct one? How far off the ideal are the commercially available fairings from Van's and some of the aftermarket suppliers? Inquiring minds...!!!
I always wondered how much the spiraling propeller slipstream would affect ideal alignment of the gear leg fairings for minimum drag - and how to determine this experimentally. Remotely adjustable-incidence tufted gear leg fairings and remote cameras were the stuff of my pipe-dreams while my fairings were being finished, but I never got around to it. Has anyone done the work and posted results?
I know my RV is kinda slow for a 160hp FP 6A, but I always wondered how much room for improvement there still was.
Stormy
On Mon, Jan 10, 2011 at 3:14 PM, Doug Gray <dgra1233(at)bigpond.net.au (dgra1233(at)bigpond.net.au)> wrote:
[quote]--> RV-List message posted by: Doug Gray <dgra1233(at)bigpond.net.au (dgra1233(at)bigpond.net.au)>
For a clear easily understood mathematical discussion see page 27 and
Appendix A of this document:
www.dsto.defence.gov.au/publications/3442/DSTO-TR-1622.pdf
After reading this I designed and manufactured my own gearleg fairings
with an accurate aerodynamic profile. Angled round whip antennas will
present an elliptical profile - this does reduce their drag coefficient
slightly.
Doug Gray
RV-6 flying
On Mon, 2011-01-10 at 09:29 -0800, Matt Dralle wrote:
> --> RV-List message posted by: Matt Dralle <dralle(at)matronics.com (dralle(at)matronics.com)>
>
> This is a REALLY interesting video about drag. I had no idea...
>
>
> http://www.youtube.com/watch?v=ftq8jTQ8ANE
>
> Matt
>
> -
> Matt Dralle
> RV-8 #82880 N998RV
> http://www.mattsrv8.com - Matt's RV-8 Construction Log
> http://www.youtube.com/MattsRV8 - Matt's RV-8 HDTV YouTube Channel
> Status: 132+ Hours TTSN - The Fun Never Stops...
>
>
>
>
>
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get="_blank">http://www.matronics.com/Navigator?RV-List
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le, List Admin.
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[b]
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Doug Gray
Joined: 10 Jan 2006
Posts: 112
Location: Sydney, Australia
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| Posted: Mon Jan 10, 2011 4:34 pm Post subject: Airfoil Drag Video... |
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I used Javafoil to generate an NACA 63 airfoil plot and data points for a section that was approximately what I needed in terms of thickness ratio. I used 22% which gave me a wider fairing than most I have seen. These were used as patterns to build the parts.
Javafoil also gives drag co-efficients for the shapes. Plug these values in the equations given.
My guess is that the leading edge shape is critical, I cannot comment about the accuracy of Vans or other parts.
Doug
On Mon, 2011-01-10 at 16:16 -0500, Bill Boyd wrote:
[quote] Does the article give actual formulae or coordinates for that streamline foil shape? So as to be able to construct one? How far off the ideal are the commercially available fairings from Van's and some of the aftermarket suppliers? Inquiring minds...!!!
I always wondered how much the spiraling propeller slipstream would affect ideal alignment of the gear leg fairings for minimum drag - and how to determine this experimentally. Remotely adjustable-incidence tufted gear leg fairings and remote cameras were the stuff of my pipe-dreams while my fairings were being finished, but I never got around to it. Has anyone done the work and posted results?
I know my RV is kinda slow for a 160hp FP 6A, but I always wondered how much room for improvement there still was.
Stormy
On Mon, Jan 10, 2011 at 3:14 PM, Doug Gray <dgra1233(at)bigpond.net.au (dgra1233(at)bigpond.net.au)> wrote:
| Quote: | --> RV-List message posted by: Doug Gray <dgra1233(at)bigpond.net.au (dgra1233(at)bigpond.net.au)>
For a clear easily understood mathematical discussion see page 27 and
Appendix A of this document:
www.dsto.defence.gov.au/publications/3442/DSTO-TR-1622.pdf
After reading this I designed and manufactured my own gearleg fairings
with an accurate aerodynamic profile. Angled round whip antennas will
present an elliptical profile - this does reduce their drag coefficient
slightly.
Doug Gray
RV-6 flying |
[b]
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
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bjudge(at)gmail.com
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| Posted: Tue Jan 11, 2011 6:06 am Post subject: Airfoil Drag Video... |
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I don't have any authoritative source for saying this but I believe the spiral on your car antenna is to break up Karman Oscillations, not for drag reduction, they put these spirals on chimneys, cell towers and TV antennas so that the oscillations break up before the hardware does.
http://peterlynnhimself.com/Why_Kites_Dont_Fly2.php#vonkarmaneffects
Bill
N84WJ
rv-8.blogspot.com
On Mon, Jan 10, 2011 at 11:59 PM, RV-List Digest Server <rv-list(at)matronics.com (rv-list(at)matronics.com)> wrote:
[quote]*
=========================
Online Versions of Today's List Digest Archive
=========================
Today's complete RV-List Digest can also be found in either of the
two Web Links listed below. The .html file includes the Digest formatted
in HTML for viewing with a web browser and features Hyperlinked Indexes
and Message Navigation. The .txt file includes the plain ASCII version
of the RV-List Digest and can be viewed with a generic text editor
such as Notepad or with a web browser.
HTML Version:
http://www.matronics.com/digest/digestview.php?Style=82701&View=html&Chapter=2011-01-10&Archive=RV
Text Version:
http://www.matronics.com/digest/digestview.php?Style=82701&View=txt&Chapter=2011-01-10&Archive=RV
================================================
EMail Version of Today's List Digest Archive
================================================
----------------------------------------------------------
RV-List Digest Archive
---
Total Messages Posted Mon 01/10/11: 6
----------------------------------------------------------
Today's Message Index:
----------------------
1. 09:32 AM - Airfoil Drag Video... (Matt Dralle)
2. 11:25 AM - Re: Airfoil Drag Video... (Ralph Finch)
3. 11:39 AM - Re: Airfoil Drag Video... (Bill Boyd)
4. 12:23 PM - Re: Airfoil Drag Video... (Doug Gray)
5. 01:25 PM - Re: Airfoil Drag Video... (Bill Boyd)
6. 04:34 PM - Re: Airfoil Drag Video... (Doug Gray)
________________________________ Message 1 _____________________________________
Time: 09:32:20 AM PST US
From: Matt Dralle <dralle(at)matronics.com (dralle(at)matronics.com)>
Subject: Airfoil Drag Video...
This is a REALLY interesting video about drag. I had no idea...
http://www.youtube.com/watch?v=ftq8jTQ8ANE
Matt
-
Matt Dralle
RV-8 #82880 N998RV
http://www.mattsrv8.com - Matt's RV-8 Construction Log
http://www.youtube.com/MattsRV8 - Matt's RV-8 HDTV YouTube Channel
Status: 132+ Hours TTSN - The Fun Never Stops...
________________________________ Message 2 _____________________________________
Time: 11:25:32 AM PST US
From: "Ralph Finch" <ralphmariafinch(at)gmail.com (ralphmariafinch(at)gmail.com)>
Subject: RE: Airfoil Drag Video...
Not repeatable therefore not real useful for comparison. The guy should
rotate the airfoils to minimum drag each time, otherwise, he doesn't know if
they are in comparable positions. It's also a shame he didn't replace the
airfoil with an equal-flow-area rectangular shape. As a result he produces
confusing and misleading results, inferring that a round shape has more drag
than a rectangular shape!
--
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
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sportav8r(at)gmail.com
Guest
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| Posted: Tue Jan 11, 2011 9:05 am Post subject: Airfoil Drag Video... |
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I _knew_ it would have something to do with bad karman  After all, as the link explains, the turbulence is a case of 'what goes around, comes around' - until it separates from the cylinder and collides with the stream coming 'round the other way.
It would be interesting to know the actual drag of spiral-wrapped cylinders. We learned yesterday in the submarine hydrodynamics article that a cylinder has the same drag as a fat airfoil of chord sixty times (!) the diameter of the cylinder, so it would not surprise me if the automobile antenna with a spiral groove cut in it has less drag than a pure cylindrical wire. But the opposite could also be true; the result is not necessarily intuitive. I'd like to see data, just for grins.
-BB
On Tue, Jan 11, 2011 at 9:02 AM, Bill Judge <bjudge(at)gmail.com (bjudge(at)gmail.com)> wrote:
[quote] I don't have any authoritative source for saying this but I believe the spiral on your car antenna is to break up Karman Oscillations, not for drag reduction, they put these spirals on chimneys, cell towers and TV antennas so that the oscillations break up before the hardware does.
http://peterlynnhimself.com/Why_Kites_Dont_Fly2.php#vonkarmaneffects
rv-8.blogspot.com
On Mon, Jan 10, 2011 at 11:59 PM, RV-List Digest Server <rv-list(at)matronics.com (rv-list(at)matronics.com)> wrote:
[quote]*
=========================
Online Versions of Today's List Digest Archive
=========================
Today's complete RV-List Digest can also be found in either of the
two Web Links listed below. The .html file includes the Digest formatted
in HTML for viewing with a web browser and features Hyperlinked Indexes
and Message Navigation. The .txt file includes the plain ASCII version
of the RV-List Digest and can be viewed with a generic text editor
such as Notepad or with a web browser.
HTML Version:
http://www.matronics.com/digest/digestview.php?Style=82701&View=html&Chapter=2011-01-10&Archive=RV
Text Version:
http://www.matronics.com/digest/digestview.php?Style=82701&View=txt&Chapter=2011-01-10&Archive=RV
================================================
EMail Version of Today's List Digest Archive
================================================
----------------------------------------------------------
RV-List Digest Archive
---
Total Messages Posted Mon 01/10/11: 6
----------------------------------------------------------
Today's Message Index:
----------------------
1. 09:32 AM - Airfoil Drag Video... (Matt Dralle)
2. 11:25 AM - Re: Airfoil Drag Video... (Ralph Finch)
3. 11:39 AM - Re: Airfoil Drag Video... (Bill Boyd)
4. 12:23 PM - Re: Airfoil Drag Video... (Doug Gray)
5. 01:25 PM - Re: Airfoil Drag Video... (Bill Boyd)
6. 04:34 PM - Re: Airfoil Drag Video... (Doug Gray)
________________________________ Message 1 _____________________________________
Time: 09:32:20 AM PST US
From: Matt Dralle <dralle(at)matronics.com (dralle(at)matronics.com)>
Subject: Airfoil Drag Video...
This is a REALLY interesting video about drag. I had no idea...
http://www.youtube.com/watch?v=ftq8jTQ8ANE
Matt
-
Matt Dralle
RV-8 #82880 N998RV
http://www.mattsrv8.com - Matt's RV-8 Construction Log
http://www.youtube.com/MattsRV8 - Matt's RV-8 HDTV YouTube Channel
Status: 132+ Hours TTSN - The Fun Never Stops...
________________________________ Message 2 _____________________________________
Time: 11:25:32 AM PST US
From: "Ralph Finch" <ralphmariafinch(at)gmail.com (ralphmariafinch(at)gmail.com)>
Subject: RE: Airfoil Drag Video...
Not repeatable therefore not real useful for comparison. The guy should
rotate the airfoils to minimum drag each time, otherwise, he doesn't know if
they are in comparable positions. It's also a shame he didn't replace the
airfoil with an equal-flow-area rectangular shape. As a result he produces
confusing and misleading results, inferring that a round shape has more drag
than a rectangular shape!
--
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
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