How Does Archery Work? Bows, Arrows and Why Accuracy Beats Strength
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An archer draws a bow with a force of around twenty kilograms over about half a second, and the arrow leaves at 60 metres a second in a few thousandths of one, which is the whole idea: the bow is a spring that stores slow work and returns it fast. The weapon that decided Agincourt and was carried by every army from the pharaohs to the Manchus is now a sport of stillness, in which the archer's task is to do exactly the same thing seventy-two times in a row at a target the size of a dinner plate seventy metres away, and the physics of why a flexible stick of wood or carbon sends an arrow where it is pointed is less obvious than it looks.
The spring
A bow's limbs bend as the string is drawn back and straighten when it is released, and the energy stored is the area under the force-draw curve, the pull multiplied by the distance over which it is pulled. A simple wooden bow, a self bow, has a curve that rises steadily, so that the last inches of the draw are the hardest; a recurve bow, whose tips curve away from the archer, stores more energy for the same peak draw because the recurved tips add leverage as the string leaves them; and a compound bow uses cams, eccentric wheels at the limb tips, so that the draw weight peaks in the middle and falls to a fraction at full draw, letting the archer hold seventy pounds of stored energy with twenty pounds of effort while aiming. About three quarters of the stored energy goes into the arrow; the rest goes into the limbs' own motion, the string and the air.
The paradox
The arrow does not sit in the line of the string's travel. On a traditional bow the arrow rests against the side of the handle, pointing slightly across the line of flight, and when the string is released it pushes the arrow's nock forward while the point is held off-line by the bow, so that the shaft bends around the handle, flexes back the other way as it leaves, and oscillates in the air, straightening out within a few metres. This is the archer's paradox, described in the 1930s with high-speed film: the arrow flies where it was aimed because it bends around the obstacle in its way, and a shaft of the wrong stiffness, the spine, for the bow's draw weight will bend too much or too little and fly off to one side. Modern bows cut a window through the handle so that the arrow sits nearer the centre, and the paradox is reduced but not gone.
The arrow and the sight
The parts of a modern competition setup:
- •The riser: a machined aluminium or carbon handle with the sight window, the arrow rest and the mounting for the limbs
- •The limbs: carbon and foam laminates in a recurve profile, detachable and sold by draw weight
- •The string: strands of a polyethylene fibre that barely stretches, with a nocking point and a serving where the fingers pull
- •The arrows: carbon or aluminium-carbon shafts matched in spine to the bow, with fletchings, vanes at the rear that spin the arrow and stabilise it, and points chosen for weight
- •The sight: a pin on an adjustable bracket, set for each distance, since the arrow drops about two metres over seventy
- •The stabilisers: rods projecting forward and back that add inertia and damp the bow's movement at release
- •The clicker: a thin blade that snaps off the arrow point at exactly the archer's full draw, so that every shot is loosed at the same length
What the archer does
Olympic archery is shot with a recurve at seventy metres, at a target 122 centimetres across whose ten-ring is 12.2 centimetres, and a top archer puts most arrows in that ring. The skill is repetition. The archer's stance, the placing of the fingers on the string, the anchor of the hand against the jaw, the alignment of the bow arm and the timing of the release are made identical shot after shot, and the release itself is not a decision but a reflex triggered by the clicker, since a hand that chooses when to let go flinches. Strength matters less than the ability to hold a forty-pound draw steady while the sight pin settles, and the mental game, shooting under a clock against an opponent in head-to-head sets, is what the training is mostly for; South Korea, whose archers have won most Olympic golds since 1984, trains them in stadiums full of noise.
From the field to the range
The bow is at least ten thousand years old, and the composite bow of horn, wood and sinew, made by the steppe peoples, was the weapon of the Scythians, the Huns and the Mongols, who shot from horseback at a gallop; the English longbow of yew, drawn to 150 pounds, was the weapon of Crecy and Agincourt, and its archers' skeletons show the twisted spines and enlarged shoulders of a lifetime's practice. Gunpowder ended the bow's military life by the seventeenth century, and archery became a pastime of the gentry, then a sport, in the Olympics in 1900 and continuously since 1972. The compound bow, invented in Missouri in 1966, made bowhunting the American mass sport that it is, and the recurve, the shape the Scythians carried, is what the Olympic archer draws.
The takeaway
Archery works by storing the slow work of the draw in the bent limbs of the bow and releasing it into the arrow in milliseconds, with recurve tips and compound cams storing more energy for the same effort; the arrow bends around the bow's handle as it leaves and flies straight because its stiffness is matched to the bow. The sport is the art of exact repetition, with sight, stabilisers and a clicker that fixes the draw, and its Olympic form, a recurve at seventy metres, descends from the composite bow of the steppe.