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The Effect of Variance of Arrow Velocity on Score

As was highlighted in Total Archery under "Time Interval Between Shots" an incredible consistency in arrow velocity was demonstrated in experiments by reducing the time to shoot three arrows from 120 seconds to between 30-50 seconds. The initial experiment over 120 seconds showed a general variance of between 5-7 fps (1.5-2.1m/s) and the 30-50 seconds experiment showed a variance of only 1-2 fps (0.3-0.6m/s); results which we feel should not easily be ignored.

Below is a table listing the impact on scores that varying arrow velocities could have at varying distances. Obviously, the greater the distance the greater the effect on score, with 90m, of course, showing the greatest impact. Also when we look at 70M, the Olympic Round distance, we find that a variance of 1fps could mean a 9 instead of a 10 and 2 fps an 8, which could mean winning or losing a match.

Variance in arrow velocity, besides being due to time interval, could also indicate technical flaws in form.

A greater variance in velocity becomes also more evident by archers, who use a "continuous" drawing process, i.e. who continue to draw uninterruptedly and as such would pass the "Holding" position (Refer KSL Shot Cycle) and as such no transfer of excessive tension in the bow hand, fingers and forearm to the back muscles can take place.

We would suggest you try to get hold of a chronograph and shoot some 6 arrows through it at the start of practice (after warm-up); again half way through your practice and again at the conclusion of your practice. Different variances at the different stages of your practice could possibly also indicate match fitness or lack there off.

Speed Variance Effect Tables

DISTANCE: 90M
FACE SIZE: 122CM
1 2 3 4
Speed M/S (~FPS) Drop over distance
in Meters
Vertical Drop Variance
in MM
Score
61.0 (200) 10.674 0 10
60.7 (199) 10.780 106 9
60.4 (198) 10.887 213 7
60.1 (197) 10.996 322 5
59.8 (196) 11.107 433 3
59.5 (195) 11.219 545 2

DISTANCE: 70M
FACE SIZE: 122CM
Speed M/S (~FPS) Drop over distance
in Meters
Vertical Drop Variance
in MM
Score
61.0 (200) 6.457 0 10
60.7 (199) 6.521 64 9
60.4 (198) 6.586 129 8
60.1 (197) 6.652 195 7
59.8 (196) 6.719 262 6
59.5 (195) 6.787 330 5

DISTANCE: 50M
FACE SIZE: 80CM
Speed M/S (~FPS) Drop over distance
in Meters
Vertical Drop Variance
in MM
Score
61.0 (200) 3.294 0 10
60.7 (199) 3.327 33 10
60.4 (198) 3.360 66 9
60.1 (197) 3.394 99 8
59.8 (196) 3.428 134 7
59.5 (195) 3.463 168 6

DISTANCE: 30M
FACE SIZE: 80CM
Speed M/S (~FPS) Drop over distance
in Meters
Vertical Drop Variance
in MM
Score
61.0 (200) 1.186 0 10
60.7 (199) 1.198 12 10
60.4 (198) 1.210 24 10
60.1 (197) 1.222 36 10
59.8 (196) 1.234 48 9
59.5 (195) 1.247 61 9

DISTANCE: 18M
FACE SIZE: 40CM
Speed M/S (~FPS) Drop over distance
in Meters
Vertical Drop Variance
in MM
Score
61.0 (200) 0.427 0 10
60.7 (199) 0.431 4 10
60.4 (198) 0.435 9 10
60.1 (197) 0.440 13 10
59.8 (196) 0.444 17 10
59.5 (195) 0.449 22 9

Additional notes to Speed Table:
  1. Column 1 - At the highest speed the arrow has been assumed to hit dead center.
  2. Column 2, shows the elevation above dead center of the target. E.g. at 90m and at 61m/s (200fps) the elevation of the arrow would be 10.674m + 1.3m(target center from ground level) or approximately 12m or 39 feet above ground level.
  3. No effects of wind, friction or other factors that may affect arrow speed has been taken into account, as the purpose of this table is only to make obvious and highlight the effect of differing arrow velocities on potential scores and to demonstrate the importance that correct technique is required to achieve consistent arrow velocities.
  4. The arrow velocity of 61m/s(200fps) has been based on a draw weight of approximately 42lbs. Some of the top archers could be shooting draw weights in excess of 50lbs. Approximately every additional pound of draw weight roughly translates to 0.6m/s (2fps), therefore the velocity for an archer shooting 52lbs should be in the order of about 67m/s(220fps). However, over 90m this would be a drop difference of 70mm for each 1fps in lieu of 106mm, so still a 9 instead of a 10. However, at 70m the drop difference would be 49mm instead of 64mm, so everything being equal it would be a 10 instead of a 9. However, we should not be "blinded" by speed, as too heavy a draw weight for a particular archer will affect his/her stamina, form and eventual score more than anything else.


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