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Why don't wings have dimples?



 
 
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  #12  
Old June 12th 06, 05:05 PM posted to rec.aviation.homebuilt
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Default Why don't wings have dimples?

In article ,
Ron Wanttaja wrote:

On 12 Jun 2006 06:07:26 -0700, wrote:

if golf balls have
dimples, to help them sail further, why don't wings


Philippe Vessaire wrote:

because birds hav'nt....


Dang.

That's a lot of feathers for the fellow to have to glue to his wings.


"Fortunately, I keep my feathers numbered for just such an emergency."
- Daffy Duck


Foghorn Leghorn.


Ron Wanttaja

  #13  
Old June 12th 06, 05:14 PM posted to rec.aviation.homebuilt
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Default Why don't wings have dimples?


Capt. Geoffrey Thorpe wrote:

...

Dimples work on round things under a relativly narrow range of reynolds
numbers (a function of speed, size and properties of air) by helping keep
the boundry layer attached. Golf balls happen to fit into that range and
have the right shape. Gliders sometimes use "turbulator" tape to trip a
laminar boundry layer and make it turbulant so it will stay attached
longer - but the placement is critical (and only works if you have a very
laminar wing to begin with).

So, if you are having boundry layer seperation problems due to the shape of
your fairing aft of the maximum "thickness", then dimples or other boundry
layer devices may or may not help but most likely they will not.


So maybe you could use dimples on fairings, fuselage or struts,
especially
if the struts are circular tubing, eh?

--

FF

Lots of aviation stuff for sale cheap:

http://groups.google.com/group/rec.a...e=source&hl=en

  #14  
Old June 12th 06, 08:29 PM posted to rec.aviation.homebuilt
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Default Why don't wings have dimples?


Dancing Fingers wrote:
Hi all,
I always wanted to build my own airplane but the time and money has
eluded me. So I've decided to design and build my own recumbent trike,
with farings. This brings me to my question, if golf balls have
dimples, to help them sail further, why don't wings -- especially for
STOL aircraft? Would putting dimples in my faring reduce my wind
resistance?
Just curious.
Chris


I read a story about NASA research of wings with thousands of tiny
holes that suck air into them on the top of the wing. Apparently they
aid in laminar flow, but there were concerns with the holes clogging
too easily with dirt.

Dean

  #15  
Old June 12th 06, 09:49 PM posted to rec.aviation.homebuilt
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Default Why don't wings have dimples?


wrote in message
ups.com...

Capt. Geoffrey Thorpe wrote:

...
So maybe you could use dimples on fairings, fuselage or struts,
especially
if the struts are circular tubing, eh?

--

FF


Could be. Somewhere or another I saw some wind tunnel data on golf balls
that nicely showed how the flow remained attached further around the back
side (no spin was involved - just a reduction in the wake). But you would
have to find out what the range of Reynolds number this works for...

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.


  #16  
Old June 12th 06, 11:34 PM posted to rec.aviation.homebuilt
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Default Why don't wings have dimples?

Thanks everyone for the great answers vto my silly question.
Capt. Geoffrey Thorpe wrote:
wrote in message
ups.com...

Capt. Geoffrey Thorpe wrote:

...
So maybe you could use dimples on fairings, fuselage or struts,
especially
if the struts are circular tubing, eh?

--

FF


Could be. Somewhere or another I saw some wind tunnel data on golf balls
that nicely showed how the flow remained attached further around the back
side (no spin was involved - just a reduction in the wake). But you would
have to find out what the range of Reynolds number this works for...

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.


  #17  
Old June 13th 06, 06:11 PM posted to rec.aviation.homebuilt
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Default Why don't wings have dimples?

Does anyone know of a good simulation program where you could play with
dimples on a large hot dog shape, just to see what happens.
Just more curious.
Chris
Dancing Fingers wrote:
Thanks everyone for the great answers vto my silly question.
Capt. Geoffrey Thorpe wrote:
wrote in message
ups.com...

Capt. Geoffrey Thorpe wrote:

...
So maybe you could use dimples on fairings, fuselage or struts,
especially
if the struts are circular tubing, eh?

--

FF


Could be. Somewhere or another I saw some wind tunnel data on golf balls
that nicely showed how the flow remained attached further around the back
side (no spin was involved - just a reduction in the wake). But you would
have to find out what the range of Reynolds number this works for...

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.


  #18  
Old June 13th 06, 06:51 PM posted to rec.aviation.homebuilt
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Default Why don't wings have dimples?

("Alan Baker" wrote)
First of all, golf balls have dimples because in order to create lift they
need to influence the air passing by them with the golf ball's spin. The
dimples help to make the air slow down beneath the ball and speed up above
it; creating downward flow.

Wings produce that downward flow with their shape.



How about a dimpled spinner?

Your choice - slice or draw.


Montblack

  #19  
Old June 14th 06, 01:46 AM posted to rec.aviation.homebuilt
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Default Why don't wings have dimples?

"Capt. Geoffrey Thorpe" The Sea Hawk at wow way d0t com wrote in message
...

wrote in message
ups.com...

Capt. Geoffrey Thorpe wrote:

...
So maybe you could use dimples on fairings, fuselage or struts,
especially
if the struts are circular tubing, eh?

--

FF


Could be. Somewhere or another I saw some wind tunnel data on golf balls
that nicely showed how the flow remained attached further around the back
side (no spin was involved - just a reduction in the wake). But you would
have to find out what the range of Reynolds number this works for...

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.


I've seen a video of that, but don't recall where. However, I believe that
you have it backward--the flow detaches earlier (from the non-spinning golf
ball) and reduces the drag.

I am not quite sure how that might relate to wings and propellers; but I
suspect that they (wings and props) are two radically different, and
possibly opposite, phenomena.

Peter


  #20  
Old June 14th 06, 01:55 AM posted to rec.aviation.homebuilt
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Default Why don't wings have dimples?


"Alan Baker" wrote in message
...
In article . com,
"Dancing Fingers" wrote:

Hi all,
I always wanted to build my own airplane but the time and money has
eluded me. So I've decided to design and build my own recumbent trike,
with farings. This brings me to my question, if golf balls have
dimples, to help them sail further, why don't wings -- especially for
STOL aircraft? Would putting dimples in my faring reduce my wind
resistance?
Just curious.
Chris


First of all, golf balls have dimples because in order to create lift
they need to influence the air passing by them with the golf ball's
spin. The dimples help to make the air slow down beneath the ball and
speed up above it; creating downward flow.


I believe that you have the effect exactly backward. The spin, which should
only be significant using the more steeply pitched irons; slows the relative
speed over the "top" of the ball and causes it to remain attached longer,
while the air flowing under the bottom breaks away more quickly, which would
result in a slight net lift. It also explains why a "slice" curves as it
does--which is why a smooth ball would have improved my game. :-(

Wings produce that downward flow with their shape.


Exactly.

Peter


 




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