Long Range Hunting Online Magazine Question about wimd meters....
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#29
07-30-2006, 10:47 AM
 Bronze Member Join Date: Nov 2001 Location: Wyoming Posts: 92

I get the full wind value, plug that in, guestimate the angle, plug that in and then enter the correction in clicks as given to me by the 'ol laptop. It seems to work fairly well, but I'm working on a better way to gauge wind direction without buying a weather station.
Coyoter
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#30
07-31-2006, 01:49 AM
 Posts: n/a

[ QUOTE ]
Why can't I take a reading 90 degrees to my rifle and use that number? Isn't this the wind that my bullet will see? Why do i care what the full wind is unless that happens to be at 90 degrees?edge.

[/ QUOTE ]

I think you mean Zero degrees - you want the POS component of the wind. The question is, will keeping the wind meter parallel with my POS give me the POS component (ie, the COS(alpha) of true wind speed). It depends on the geometry of the wind meter. On a unit like my
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Skywatch Meteos that's Omnidirectional, you obviously can't get the POS component. I'm guessing most wind meters have too much turbulence and would read load in comparison to the cos(alpha).

I think I'll add the -

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Kestrel 2500NV Night Vision to my wind bag collection. I'll be adding the Speedtech Wind Tunnel

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( Meets NCAA Track and Field requirements and provides precise wind velocity in a specific direction for precision measurements. ) to test this conjecture.

BTW, the POS wind component at 45 degrees is not 1/2, but sqrt(2)/2 or aprox .707
#31
07-31-2006, 07:03 AM
 Platinum Member Join Date: Nov 2005 Posts: 1,088

My thinking is 90 degrees to the bullet flight since this is the wind velocity that effects the bullets flight. If the wind is along the bore centerline, either in my face or dead away then I can ignore it unless a Gale is blowing [img]/ubbthreads/images/graemlins/smile.gif[/img] .

I'm not sure if that was what you meant.

edge.

PS Obviously only with a directional wind meter!
#32
07-31-2006, 12:38 PM
 Platinum Member Join Date: Jun 2001 Location: Potomac River Posts: 5,070

[ QUOTE ]
1 inch diameter impeller with precision axle and sapphire bearings. Off-axis accuracy -1% @ 5º off-axis; -2% @ 10º; -3% @ 15º. Calibration drift &lt; 1% after 100 hours use at 16 MPH / 7 m/s. Sustained operation above 60
MPH / 27 m/s will wear impeller rapidly and may cause destruction of impeller

[/ QUOTE ]

They obviously believe no one will ever try to take a reading at 90 degrees but the error will grow greatly if you try.
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#33
07-31-2006, 07:02 PM
 Platinum Member Join Date: Dec 2001 Location: Mukilteo, WA Posts: 1,092

Well, cosine of 15 degrees rounds to .97 which accounts for 3% error--unless that .97 value is what you're trying to read in which case it might be doing exactly what you want.
#34
08-01-2006, 01:44 AM
 Posts: n/a

&gt;&gt;cosine of 15 degrees rounds to .97

Good point. You don't need be know the angle between POS and wind exactly. You don't have to align the wind meter exactly with the wind direction.
#35
08-01-2006, 06:10 AM
 Platinum Member Join Date: Jun 2001 Location: Potomac River Posts: 5,070

Jon

Yes I noticed that, but getting the right answer for the wrong reason doesn't hold up well.

You know very well what is happening to air flow and edge effects.

Now then if one of you fluid dynamics experts wants to take a wind meter and an electric fan and run the experiment that is a different thing. Even then, you will have gotten the right answer for the wrong reason. Engineers have known for a good while what makes an airplane fly.

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