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rcmutz
Joined: 12 Sep 2010
Posts: 12
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 Posted: Fri Jun 22, 2012 7:57 am Post subject: Wing friction and speed... |
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All:
The visousity of the fluid, the velocity of that fluid over the surface, and the length of the surface (ie Reynolds Number) are a major players here in how the boundry layer behaves. Before sanding or dimpling your wings, I would recommend you do some serious reading on boundary layer theory for compressible fluids.
PS- I know Roger's response is somewhat tongue and cheek we applied to airplane wings.
Richard Mutzman
BSAE, MSAE
N399RM
Message: 5
Date: Mon, 18 Jun 2012 10:55:04 -0400
From: Roger Rowlett <rrowlett(at)colgate.edu>
To: grumman-gang(at)mailman.xmission.com
Subject: Wing friction and speed...
Message-ID: <4FDF4148.3050407(at)colgate.edu>
Content-Type: text/plain; charset="us-ascii"
OK, I was intrigued by the recent discussion about the influence of hull
roughness on flying speed. In particular, I was curious about the theory
of sanding boat hulls to gain speed, so I decided to ask a championship
small-boat sailor I know about it. Here is is response for improving the
speed of your favorite Grumman:
"By all means sand your wings [to get more speed]. Use 100 grit
paper and work down to 60 grit. Then pound the wings with a large
ball peen hammer with extra attention to the leading edges. Then
down a bottle of Jack Daniels and go flying and you will notice the
difference. Seriously, "wet sanding" with up to 600 grit wet or dry
sandpaper used wet is a common "go fast" treatment for sailboat
hulls and I have done it on painted wood boats I have raced."
I wouldn't recommend altering your Grumman's wings according to my
colleague's instructions, but in the sailing community some appropriate
application of the boundary effect is known and used. Based on the
deteriorating condition of the paint on my AA-5 upper wing surface, I
should have the fastest model around. 
Cheers,
_______________________________________
Roger Rowlett
AA-5 N7159L
KVGC
[quote][b]
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teamgrumman(at)yahoo.com
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| Posted: Fri Jun 22, 2012 10:15 am Post subject: Wing friction and speed... |
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A few years ago, many probably, Hot Rod magazine did an article on skin friction and how it affected drag cars and Indy cars. Their conclusion: under 100 mph, the surface smoothness has a negligible effect. Between 100 and 150 mph, it had some effect, i.e., the smoother the better. Over 150 mph, aerodynamics really are the primary factors and controlling flow direction and separation had a big effect.
Bottom line is, the brake fairing fit to the wheel pant has a bigger influence than a waxed wing at top speed. Hell, the VOR antennas create more drag than an unwaxed wing.
From: Richard Mutzman <rcmutz(at)msn.com>
To: Team Grumman <teamgrumman-list(at)matronics.com>
Sent: Friday, June 22, 2012 8:57 AM
Subject: TeamGrumman-List: Re: Wing friction and speed...
All:
The visousity of the fluid, the velocity of that fluid over the surface, and the length of the surface (ie Reynolds Number) are a major players here in how the boundry layer behaves. Before sanding or dimpling your wings, I would recommend you do some serious reading on boundary layer theory for compressible fluids.
PS- I know Roger's response is somewhat tongue and cheek we applied to airplane wings.
Richard Mutzman
BSAE, MSAE
N399RM
Message: 5
Date: Mon, 18 Jun 2012 10:55:04 -0400
From: Roger Rowlett <rrowlett(at)colgate.edu>
To: grumman-gang(at)mailman.xmission.com
Subject: Wing friction and speed...
Message-ID: <4FDF4148.3050407(at)colgate.edu>
Content-Type: text/plain; charset="us-ascii"
OK, I was intrigued by the recent discussion about the influence of hull
roughness on flying speed. In particular, I was curious about the theory
of sanding boat hulls to gain speed, so I decided to ask a championship
small-boat sailor I know about it. Here is is response for improving the
speed of your favorite Grumman:
"By all means sand your wings [to get more speed]. Use 100 grit
paper and work down to 60 grit. Then pound the wings with a large
ball peen hammer with extra attention to the leading edges. Then
down a bottle of Jack Daniels and go flying and you will notice the
difference. Seriously, "wet sanding" with up to 600 grit wet or dry
sandpaper used wet is a common "go fast" treatment for sailboat
hulls and I have done it on painted wood boats I have raced."
I wouldn't recommend altering your Grumman's wings according to my
colleague's instructions, but in the sailing community some appropriate
application of the boundary effect is known and used. Based on the
deteriorating condition of the paint on my AA-5 upper wing surface, I
should have the fastest model around.
Cheers,
_______________________________________
Roger Rowlett
AA-5 N7159L
KVGC
| Quote: | http://www.matronics.com/Navigator?TeamGrumman-L-============================================
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[quote][b]
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BARRY CHECK 6
Joined: 15 Mar 2011
Posts: 738
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| Posted: Fri Jun 22, 2012 11:55 am Post subject: Wing friction and speed... |
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Richard:
"Somewhat"!!! I posted the original on how dirt and sanding would lower the COF and improve the boundary layer. But Roger is total Tong In Cheek. Busting grains of sand a bit... Come on 100 Grit and 600 Grit.
Our planes are so unbelievably dirty (as most planes are) you would not believe it. I have flow my plane without the rubber wing seat seal and without the sump covers (all at the same time) and there was NO noticeable difference in speed. There is so much drag created by every sharp corner - Such as between the fuselage and the wing or the fuselage and the Horz Stab and the Vert Stab and the turtle deck and the dorsal fin and the turtle deck and how about the gaping hole and its counterbalance weight. Want to reduce drag? Work on those! And every round object such as Gary mentioned (VOR ANT) produces four (4) times the drag as the same size FLAT object would. So, if you want your plane to look pretty - Go wash & wax it, we'll all go Oooo and Ahhhhh after you park. But, forget the Pilot Induced Ballistic Speed (BS) about gains. Oh, one more speed area - Reduce your vertical step length by 3" and that will take the step out of the clean air and into the dirty air around the body.
"A 1/4 of a MPH here and a 1/4 of a MPH there and sooner or later you are Super Sonic" Bob Gibson
Barry
On Fri, Jun 22, 2012 at 11:57 AM, Richard Mutzman <rcmutz(at)msn.com (rcmutz(at)msn.com)> wrote:
[quote] All:
The visousity of the fluid, the velocity of that fluid over the surface, and the length of the surface (ie Reynolds Number) are a major players here in how the boundry layer behaves. Before sanding or dimpling your wings, I would recommend you do some serious reading on boundary layer theory for compressible fluids.
PS- I know Roger's response is somewhat tongue and cheek we applied to airplane wings.
Richard Mutzman
BSAE, MSAE
N399RM
Message: 5
Date: Mon, 18 Jun 2012 10:55:04 -0400
From: Roger Rowlett <rrowlett(at)colgate.edu (rrowlett(at)colgate.edu)>
To: grumman-gang(at)mailman.xmission.com (grumman-gang(at)mailman.xmission.com)
Subject: Wing friction and speed...
Message-ID: <4FDF4148.3050407(at)colgate.edu (4FDF4148.3050407(at)colgate.edu)>
Content-Type: text/plain; charset="us-ascii"
OK, I was intrigued by the recent discussion about the influence of hull
roughness on flying speed. In particular, I was curious about the theory
of sanding boat hulls to gain speed, so I decided to ask a championship
small-boat sailor I know about it. Here is is response for improving the
speed of your favorite Grumman:
"By all means sand your wings [to get more speed]. Use 100 grit
paper and work down to 60 grit. Then pound the wings with a large
ball peen hammer with extra attention to the leading edges. Then
down a bottle of Jack Daniels and go flying and you will notice the
difference. Seriously, "wet sanding" with up to 600 grit wet or dry
sandpaper used wet is a common "go fast" treatment for sailboat
hulls and I have done it on painted wood boats I have raced."
I wouldn't recommend altering your Grumman's wings according to my
colleague's instructions, but in the sailing community some appropriate
application of the boundary effect is known and used. Based on the
deteriorating condition of the paint on my AA-5 upper wing surface, I
should have the fastest model around.
Cheers,
_______________________________________
Roger Rowlett
AA-5 N7159L
KVGC
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tp://forums.matronics.com
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