Boyd Allen
Active member
Obviously they are talking about rising or falling relative to line of sight (LOS)...not so confusing to me.
Obviously they are talking about rising or falling relative to line of sight (LOS)...not so confusing to me.
hmmm
cool link.
One thing that bugs me though about the Sierra guys is that they use stuff like "rising arc" and "summit" and "falling arc" of trajectory when in reality a bullet just DROPS from the line of the bore. Later in their explanation they note that the yaw of repose is different on the "rising side" than the "falling side"....
?????
howso?
al
They are correct. The bullet's nose will never move as high above the trajectory curve as it was on the previous turn because of axis shifts and changes in pressure. The nose drops as does the trajectory curve. The spinning of the bullet is acutally in a small swinging arc. This cycloidal movement is more down and toward the direction of rotation as it takes it trip down range.
Rinker is my hero!
You'se guys are getting close but still figgering planes and not decellerating projectiles
Let's fuh'GEDDABOUT the part of the trajectory before the stream of crosswind at 500-600..... we just pick up the bullet crabbing across the stream, it's DEFINITELY on a downwind course and fairly crabbed over..... and sl o o w i n g as it goes....
Now, when it pops out into clear air on the other side it does NOT "resume course"....... it renegotiates a new velocity which retains some of it's divergence.... not ALL, but some of it.
I'll try to draw a picture since this is the ONE salient point which puts about three years argument into perspective!
This goes back to months ago with "you and me on two sides of the ribber" Gene
Let's Get 'Er Done Eh!!!!
LOL al
This is why I think that all of this discussion about whether a bullet turns into or away from the wind by less than a half degree is a bit silly.
http://www.nennstiel-ruprecht.de/bullfly/fig21.htm
This is why I think that all of this discussion about whether a bullet turns into or away from the wind by less than a half degree is a bit silly.
http://www.nennstiel-ruprecht.de/bullfly/fig21.htm
Al, in your first paragraph above, you stated,
"You'se guys are getting close but still figgering planes and not decellerating projectiles."
(GB) No, that's not true. If you will read again, my post #150, I made it clear, I was referring to a decellerating bullet, not an airplane.
In paragraph three above you stated,
"Now, when it pops out into clear air on the other side it does NOT "resume course"....... it renegotiates a new velocity which retains some of it's divergence.... not ALL, but some of it."
(GB) What do you mean by, "it renegotiates a new 'velocity? Do you mean a new heading? Ground track? What?
Al, you said you would try to draw a picture to explain what you're talking about. That would help.
Gene Beggs
Ever noticed that the flowfield is somewhat smaller (more gentle) on the bottom of the bullet in shadowgraphs like this one???
Al,
Did you look at the picture? In this thread much was made of whether the bullet tilts very slightly toward or away from the wind. I posted the drawing as a reminder that the model that has been discussed is evidently too simple, which has seems to have caused mountains to be made of molehills. I repeat, round balls are the worst case for wind drift, therefore it must not depend on slight angular variations in elongated bullets, especially since these slight variations would seem to disappear into the noise of the gyrations that the picture shows.
Boyd boyd BOYD..... the degrees don't MATTER! The question at hand is, WHAT DRIVES THE BULLET OVER....... and it ain't the wind blowing on it.
It IS the non-linear suctive force, the negative pressure present in the lee of the bullet as it tears a hole in the ambient
('AT oughtta' get 'er goin' ag'in!!)
LOLOL
al
This would be so much easier with a blackboard.
The scenario:
BIB 95gr FB BC=0.435
muzzle velocity=3000ft/sec
crosswind @ 3'oclock @ 10mi/hr (15ft/sec) from 500-600yd only
At 500yd the bullet is going 1964ft/sec. When it hits the 15ft/sec crosswind the bullet turns into the wind [the point turns to the right] by arctan(15/1964)=0.44degrees.
The nose angle continues to increase until the bullet has reached 600yd, at which time it is going 1783ft/sec and has a nose angle of 0.48degrees. It has been deflected downwind (left) about 1.2 inches between 500-600yd.
Upon entering the "calm" air past 600yd, the bullet's nose turns leftward into the relative wind by arctan(15/1783), which is 0.48degrees. So, the bullet is now pointing 0.04degrees to the left of the line upon which it entered the crosswind, and thus continues to diverge downwind from the original line of departure from the bore, which amounts to about 2.5 inches leftward displacement for every 100yd thereafter (3600inches/100yd*tan(0.04degrees)) for a grand total of about 11.2 inches at 1000yd (of which only a little over an inch happened during the "push").
Resolved: I will shoot more and do less typin' and figgerin'.
Toby Bradshaw
baywingdb@comcast.net