Question about wimd meters....

[Coyoter]

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

 

[Guest]

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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.

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I think you mean Zero degrees - you want the *** component of the wind. The question is, will keeping the wind meter parallel with my *** give me the *** 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 *** 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 *** wind component at 45 degrees is not 1/2, but sqrt(2)/2 or aprox .707

 

[edge]

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 /ubbthreads/images/graemlins/smile.gif .

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

edge.

PS Obviously only with a directional wind meter!

 

[Buffalobob]

Here is Kestrel's answer to your question about "off axis reading and the amount of error:

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1 inch diameter impeller with precision axle and sapphire bearings. Off-axis accuracy -1% @ 5º off-axis; -2% @ 10º; -3% @ 15º. Calibration drift < 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

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They obviously believe no one will ever try to take a reading at 90 degrees but the error will grow greatly if you try.

 

[Jon A]

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.

 

[Guest]

>>cosine of 15 degrees rounds to .97

Good point. You don't need be know the angle between *** and wind exactly. You don't have to align the wind meter exactly with the wind direction.

 

[Buffalobob]

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.

Try to remember that "Edge" is asking a question and plans on using the answer. A bad answer causes a bad bullet placement.

 

[edge]

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SNIP

Try to remember that "Edge" is asking a question and plans on using the answer. A bad answer causes a bad bullet placement.

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Thanks buffalobob, I just want to know if I take a wind reading @ 45 degrees to the wind will it read .707 of the full wind.

I always know EXACTLY the direction that I am pointing the muzzle, but I don't always know the exact angle to the wind!

Those attachments for "track& field" seem to indicate that that is exactly what they do.

If they work, then no more take a reading, guess the angle, calculate percentage of full wind, adjust for partial wind. Instead take partial reading directly and adjust...bang /ubbthreads/images/graemlins/smile.gif

edge.

 

[Jon A]

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

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It either measures the cosine component when used this way with reasonable accuracy or it doesn't. If it does, there's nothing wrong about it. It would be precisely the right way to do it.

I haven't conducted scientific enough experiments to determine its accuracy when used in such a way, but trying it both ways it has seemed to do very well until the wind gets to a really steep angle (head/tail wind).

Yes, I use mine this way quite a bit. I never excpected it to be 100% perfectly precise (I think adding the tunnels probably will help quite a bit)...but what is when you're dealing with wind? What's the point of being able to measure the speed down to the last .001 MPH when it changes by a couple MPH every second or so anyway? Same with direction. And of course the wind where you're standing is only a small part of the big picture anyway.

Those are just my feelings and what I do. Then again, I suck in the wind anyway so follow my advice on this subject at your own peril. /ubbthreads/images/graemlins/laugh.gif The only advice I know to be 100% good is use a high BC bullet! Cheat as much as possible! /ubbthreads/images/graemlins/laugh.gif

 

[Buffalobob]

Jon

I Set up the big fan and ran the meter in about 5-10 mph wind. Your feelings are what I found. Once the angle of incidence gets past about 60 degrees the readings stay way high and at exactly perpindicular it is goofy because even a small angle creates flow.

One of the problems with the set up is that even indoors the fan creates turbulent flow with velocities varying about 20%.

I don't have the tunnel but I would expect the tunnel to do the same or even worse.


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I haven't conducted scientific enough experiments to determine its accuracy when used in such a way, but trying it both ways it has seemed to do very well until the wind gets to a really steep angle (head/tail wind).


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That is what I came up with is that the most inaccurate reading will be in a near headwind or tailwind.

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Those are just my feelings and what I do. Then again, I suck in the wind anyway so follow my advice on this subject at your own peril. The only advice I know to be 100% good is use a high BC bullet! Cheat as much as possible!

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That pretty well sums up shooting in the wind for most of us.