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A Scientific Basis For Evaluating Variable Crosswinds

 
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  #1  
Old 09-17-2011, 03:28 PM
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A Scientific Basis For Evaluating Variable Crosswinds

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Although we frequently discuss wind as if it is constant in both magnitude and direction, that's seldom true in the real shooting world, where features of terrain make accurate wind doping much more challenging. For instance, it's possible that a significant wind experienced at the shooter's location may be completely blocked somewhere downrange by a hill or other physical entity. Of course, the converse can be true, also. In that event, the bullet's flight could be influenced by a wind which is present closer to the target but absent at the shooting location.
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This is a thread for discussion of the article, A Scientific Basis For Evaluating Variable Crosswinds, By Paul Carter. Here you can ask questions or make comments about the article.
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  #2  
Old 09-17-2011, 06:17 PM
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Re: A Scientific Basis For Evaluating Variable Crosswinds

I agree in a general sense with this illustration and results of near-vs-far wind.
But it can be taken further.

Wind drift is not really about TOF, but of T-LAG and drift angles.
And that's where the boat scenario is better explained. It's only while the boat is deccelerating (lagging) that drift occurs, and the higher that decceleration the higher the drift angle that is set.

It often appears that a very fast bullet drifts less in wind. But this seems otherwise after observing a very heavy(high BC), yet slower bullet, produce less downrange drift.
If you took a very low BC bullet/going fast -vs- a very high BC bullet/going slow, both with the same TOF by 1kyd, and both exposed to the same near wind, the high BC bullet would win over the low BC bullet -by 1kyd.
This, even though the fast bullet had lower TOF while exposed to near wind.
It drifts more because it is deccelerating more.
Also both bullets deccelerate the most nearer the muzzle than the target, and that's why the drift angles are influenced most up close -vs- far downrange(where TOF constantly increases).

Just sayin
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Old 09-20-2011, 05:32 PM
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Re: A Scientific Basis For Evaluating Variable Crosswinds

Quote:
Originally Posted by Mikecr View Post
I agree in a general sense with this illustration and results of near-vs-far wind.
But it can be taken further.

Wind drift is not really about TOF, but of T-LAG and drift angles.
And that's where the boat scenario is better explained. It's only while the boat is deccelerating (lagging) that drift occurs, and the higher that decceleration the higher the drift angle that is set.

It often appears that a very fast bullet drifts less in wind. But this seems otherwise after observing a very heavy(high BC), yet slower bullet, produce less downrange drift.
If you took a very low BC bullet/going fast -vs- a very high BC bullet/going slow, both with the same TOF by 1kyd, and both exposed to the same near wind, the high BC bullet would win over the low BC bullet -by 1kyd.
This, even though the fast bullet had lower TOF while exposed to near wind.
It drifts more because it is deccelerating more.
Also both bullets deccelerate the most nearer the muzzle than the target, and that's why the drift angles are influenced most up close -vs- far downrange(where TOF constantly increases).

Just sayin
the argument of low velocity/ high bc vs. high velocity/low bc is not a scientific argument. you are changing two variables at one time.
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Old 09-20-2011, 07:48 PM
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Re: A Scientific Basis For Evaluating Variable Crosswinds

It was just a general example to illustrate my contention that wind drift is more about TLag than TOF.

TOF is only a factor in determining TLag, and it's TLag that actually is a factor in wind drift.
The decceleration that occurs due to drag causes the time lag which wind speed is applied to.
Wind drift(in inches) is: 17.6*CrossWindSpeed(mph)*TLag(sec)
TLag = TOF-TOFvac
A higher BC bullet deccelerates at a lower rate than a lower BC bullet regardless of velocity(provided the BC relationships hold).
So at any two points in flight, the higher BC bullet produces lower TLag, and is therefore less affected by crosswind between those points.

It's a perspective that readers need to consider before concluding that they could reduce wind drift by going with lighter bullets at higher speeds.
While they would reduce TOF, they could in the same move -increase TLag(due to higher drag) -increasing wind drift sensitivity.

When wind drift is truly the focus of concern, so is TLag.
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  #5  
Old 09-22-2011, 12:29 AM
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Re: A Scientific Basis For Evaluating Variable Crosswinds

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Originally Posted by vendetta333 View Post
the argument of low velocity/ high bc vs. high velocity/low bc is not a scientific argument. you are changing two variables at one time.
yup he is right both variables are quite different to each other.......
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  #6  
Old 09-22-2011, 04:14 PM
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Re: A Scientific Basis For Evaluating Variable Crosswinds

What's your point?
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  #7  
Old 09-30-2011, 11:52 PM
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Re: A Scientific Basis For Evaluating Variable Crosswinds

i just feel that people in general make many claims based on "experiments" that aren't experiments due to changing more than one variable at a time. the reply you posted cleared everything up, was just wanting to check with you. not trying to be a smartass, just a major pet peev of mine. thanx for the info. much helped me.
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