Twisting the bow with the hand moves the arrow on the target

The summary today

That twisting the grip moves the arrow is one of the few points where the mechanics are clear and the measurements on archers are thin. The models give striking figures: on a 166 N recurve bow, thirteen hundredths of a degree of difference from shot to shot is worth more than one ring at 70 m, and corresponds to under two millimetres of misalignment between arrow point and front stabiliser as seen at full draw. A test bench confirms it with no archer involved: on a mechanical launcher with a Japanese bow, varying torsion alone moves the point of impact at 28 m from one side of the target to the other. As early as 1990, on a shooting machine at 30 m, each degree of bow rotation moved the impact 15.8 cm in one direction and 21.9 cm in the other, a measurement the author used within his model. What is missing is the archer. High-speed video of sixteen world-class recurve archers shows that the bow does not rotate measurably until the arrow has gone, and that seven of them were probably holding it twisted while aiming: what matters is the twist set by the hand, and above all how much it changes from one arrow to the next, but nobody has measured it alongside the point of impact. The only measurement on people uses an instrumented kyudo bow: in nineteen practitioners the torsion exists, can be measured, grows with draw force and behaves differently in the last five hundredths of a second depending on how often the archer hits. Everything else concerns the Japanese bow or a model, and nobody has measured torsion and point of impact on the same shot of a recurve archer.

Also phrased as: "grip torsion"; "the bow hand turning"; "twisting the riser and arrows left or right"; "tenouchi"; "point and stabiliser alignment at full draw"; "bow torque at release"; "a bow turning in the hand moves the arrow"; "grip rotation and impact"; "bow twist"; "don't torque the bow"

Evidence

• 1987
  Context Equipment tests Published later

  One leading archer of the Italian national team, three stabilisation set-ups for fifteen shots each: between 22 and 26 milliseconds the button and the arrow spring back elastically, with a lateral force falling to zero at separation; between 26 and 30 milliseconds the lateral acceleration comes from the bow's own internal oscillations, triggered by the peak force on the button at about 22 milliseconds. It describes where the lateral movement comes from, not the effect of twisting with the hand.

  Reduction of Lateral Bow Displacement Using Different Torque Flight Compensators and Stabilizers in Archery · L. M. Leonardi, C. Gallozzi, A. Pace, A. Dal Monte

• 1990
  For Model Published later

  Mathematical model of arrow flight compared with high-speed footage at 1,000 to 2,500 frames per second and with a shooting machine at 30 m, using the equipment of 22 Polish archers. On the machine, with only the rotation of the bow about its vertical axis left free, each degree moves the impact 15.8 cm in one direction and 21.9 cm in the other, about 30 per cent more; for every arrow to land in the ten at 30 m the torsion angle therefore has to be repeated to within two tenths of a degree. The source is registered as a model, and counts as one here.

  Experimental and theoretical research in archery · Roman Pekalski

• 1997
  Context Equipment tests Published later

  A three-segment model of the Japanese bow, validated on a strain-gauged launching rig built, however, with a Western hunting bow made symmetrical, not with a Japanese bow: three torsion profiles adjusted so that the integral over the 26 milliseconds of the launch was identical give different trajectories, while arrow speed varies by less than one per cent. Change only the initial value by fifty per cent and the trajectory changes completely; with high initial torsion the arrow and bow touch early and the arrow goes right, with low torsion the deviation is larger still. Regional journal.

  Dynamics of Japanese Bows and Arrows : Analysis of "Tsunomi" with Link Model and Experiment · Koji Kobayashi, Keiji Kyogoku, Tsunamitsu Nakahara

• 2007
  For Kyudo archers Published later

  19 university kyudo practitioners, 8 shots each at 28 m, with strain gauges on the grip: a tenth of a second before the arrow leaves the right hand, torsion is proportional to the force on the bow in every participant, with typical values between 0.57 and 0.61 Nm. In the final five hundredths of a second, torsion rises in those who hit most often, falls in intermediate practitioners and varies erratically in the least accurate.

  B39 Quantification of TENOUCHI for Playing Kyudo · Sekiya Koike, Takuro Sugiura, Sakura Murata, Toshio Mori

• 2008
  For Equipment tests Published later

  A test on a mechanical launcher with Japanese bows of 13 and 15 kgf and a duralumin arrow, target at 28 m outdoors, two sets of data: varying grip torsion from zero to about 14 Nm, the horizontal deviation from the centre runs from about minus forty to plus eighty on the graph's scale, that is from one side of the target to the other. No archer involved, and that is what makes it a clean measurement.

  B4 Effect of Te-no-uchi in Japanese-style archery · Tetsuhiko Yamamoto, Hiroshi Kinjo, Motoki Tanaka

• 2011
  Context Equipment tests Published later

  A model of a single-cam compound bow, then checked by twisting the bow in a machine: one degree of torsion anticlockwise, seen from above on a right-handed bow, makes the arrow bend far more and sends it left; one degree clockwise makes it bend little but gives it an angle of attack of minus four tenths of a degree and sends it right. The two directions are not symmetrical, and the nocking-point shift caused by the archer's torsion is larger than the one caused by cable tension. The twist was reproduced in the machine by pulling or pushing the cable guard, with the angle measured shot by shot by comparing the shaft's line with the front stabiliser, and the measured angle of attack and flexing agree with the calculation. What does the damage is not constant twist but its variation from arrow to arrow, and the article adds that the string's contact with the face or the body is to be treated the same way, although it was not modelled.

  The Behaviour of An Arrow Shot from a Compound Archery Bow · J L Park

• 2012
  For Equipment tests Published later

  A model of a 166 N recurve bow with a right-handed archer: thirteen hundredths of a degree of difference in torsion from shot to shot moves the arrow more than a ring at 70 m, and the same difference corresponds to about 1.7 mm of misalignment between the arrow point and the front stabiliser as seen at full draw. This is the figure that makes the thing checkable by eye.

  Arrow behaviour in the lateral plane during and immediately following the power stroke of a recurve archery bow · James L Park

• 2012
  Context Equipment tests Published later

  The same recurve model adds two useful things. First, a diagnostic clue: the ratio between the nock's two lateral deflections is 3.1 with no torsion, 1.7 with three tenths of a degree one way and 7.9 with three tenths the other. Second, torsion required no change in draw weight to keep angular rotation at zero, but at seven tenths of a degree the part of the shaft just ahead of the vanes strikes the button shortly after separation from the string.

  Arrow behaviour in the lateral plane during and immediately following the power stroke of a recurve archery bow · James L Park

• 2012
  Context Archers Published later

  High-speed video of 16 recurve archers from national teams at the London Olympic test event in October 2011: in none of them does the bow move sideways or rotate measurably about its vertical axis before the arrow is in free flight, while seven of the sixteen were strongly suspected of holding it twisted with the hand. The authors note that as long as the action is repeated the same way on every arrow, the score can still be high.

  High-speed video analysis of arrow behaviour during the power stroke of a recurve archery bow · James L Park, Oliver Logan

Status history

1. 1987 Not studied The earliest test in the bibliography describes how the bow's lateral movement arises, on one archer of the Italian national team: once the arrow has loaded the button to its maximum, button and arrow spring back elastically and the lateral push falls to zero at separation, after which the bow moves sideways through its own internal oscillations. It explains the mechanics around the question but does not measure whether twisting with the hand moves the arrow on the target: on that there is still nothing.
2. 1990 Transferred The first figure on torsion comes from a mathematical model checked against a shooting machine: at 30 m each degree of bow rotation moves the impact 15.8 cm in one direction and 21.9 cm in the other, and to put every arrow in the ten the angle has to be repeated to within two tenths of a degree. The work is registered as a model, checked on a machine rather than on archers shooting, and a model alone does not take a claim beyond transferred.
3. 1997 Transferred A three-link model of the Japanese bow, calibrated on a launching rig, adds something nobody had said: for the same total torsion applied to the grip, it is the timing of that torsion that changes the trajectory, while arrow speed varies by less than one per cent. Change only the initial value by fifty per cent and the trajectory changes completely. It is still a simulation result and the status does not move.
4. 2007 Reported With an instrumented bow, nineteen kyudo practitioners show that the torsion applied to the grip exists and can be measured: it grows in proportion to the force on the bow in every participant and, in the five hundredths of a second before the arrow leaves the hand, it behaves differently depending on how often the archer hits. Torsion thus enters a measurement on archers and no longer lives only in a model, so there is evidence in favour, limited to one sample and one discipline.
5. 2008 Reported On a mechanical launcher, with no archer, varying grip torsion alone moves the point of impact at 28 m from one side of the target to the other, with a total spread of about one hundred and twenty units on the graph's scale. For a claim about equipment, a laboratory test without archers counts as direct evidence, so the status no longer rests on a model; it stays at limited evidence because there is only one such test and it concerns the Japanese bow.
6. 2011 Reported The first calculation on the compound bow comes from a model verified on a shooting machine: a single degree of torsion changes the arrow's bending, gives it an angle of attack of four tenths of a degree and moves its impact sideways, differently in the two directions. No archer involved, so it is context and the status holds.
7. 2012 Reported A model of a 166 N recurve bow quantifies the sensitivity: thirteen hundredths of a degree more torsion from shot to shot moves the arrow by more than a ring at 70 m, and corresponds to about 1.7 mm of misalignment between point and front stabiliser as seen at full draw. The same model shows that torsion does not call for any change in draw weight, but that at seven tenths of a degree the back of the arrow strikes the button. The figure is striking and still comes from a model, so the status does not change. The same year high-speed video of sixteen world-class archers shows that the bow does not rotate measurably until the arrow has gone, and that seven of them were probably holding it twisted while aiming: the twist that matters is the one set by the hand, but the video does not measure where the arrows land.

Related

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• The yumi through engineering: materials, asymmetric limbs, draw force and tenouchiHow the Japanese bow works according to the measurements: bamboo and core woods, animal glue, asymmetric limbs, the draw force curve and tenouchi twist.
• Why do your groups open up with distance?Double the distance and the group doubles, or a little more: what geometry and competition scores say, and how to use two distances to find what opens your group.
• Why do my arrows go left, right, high or low?Where your arrows land is a report: how to read impact patterns, and what the measurements say about the sight, the grip, bow torque and launch speed.

Research lines

• 17 studiesGrip pressure and bow torque: from 1971 to today
• 29 studiesThe archer's paradox in research: from 1987 to today

Other claims in this domain

• CorroboratedAlong its flight the arrow loses an appreciable part of its launch speed12 studiesStatus since 2011
• CorroboratedAs it leaves the bow, the arrow flexes and snakes around the riser instead of leaving straight19 studies · 47 archers measuredStatus since 2012
• ReportedA camera-based scoring system misreads some arrows: the ones barely sticking out and the ones that shift the target face7 studies · 2 archers measuredStatus since 2017
• ReportedA chest band with fibre optic sensors measures breathing and mean heart rate with small errors, and an archer can wear it while shooting2 studiesStatus since 2019
• ReportedA compound bow stores between 70 and 100 joules and sheds about two thirds of the force at full draw4 studiesStatus since 2015

See all claims on equipment and tuning