https://matteocampagna.com/en/registry/equipment/arrow-spine-draw-weight Changes to this claim in Matteo Campagna's evidence registry: its status, its year-by-year history, revisions of the page. en-gb https://matteocampagna.com/en/registry/equipment/arrow-spine-draw-weightThe rule holds in every model that has looked at it, each reaching it by a different route; what is missing is the proof on the target. The first, from 1990, checked against high-speed films of a Polish national-team archer and against a shooting machine, finds that a shaft of suitable stiffness leaves the string with the nock almost still sideways, while one that is too weak or too stiff leaves it with a lateral velocity, and it derives a nomogram within which the equipment of eighteen of the twenty-two best Polish archers fell. In 1997 a second model, compared with the same films, confirms the rule in both directions, since the shaft that is too weak slaps against the button and the one that is too stiff leaves the string with a stronger lateral jolt on the nock, but it questions the explanation: even with the suitable shaft the nock does not stay still sideways for long before the arrow leaves, so the rule stands while the reason for it remains open. The models of 2001 and 2012 reach the same rule and measure its window: a more powerful bow takes a stiffer and heavier arrow, changing spine by one step calls for about eleven newtons of draw weight while a bow can only be adjusted within about ten per cent of its nominal weight, so at a given draw length only one or two spines can be tuned well, and ten millimetres of shaft are worth four and a half newtons. In 2025 come two further confirmations, still indirect: a new model rebuilds the manufacturers' charts at a finer half-inch step, and on the shooting machine, with a right-handed bow, the stiffer shafts land to the left. The part on archers is still the coincidence with the equipment of those twenty-two Poles, who had in all likelihood chosen their shafts from the manufacturers' charts, and nobody has yet measured the grouping of archers with suitable and unsuitable spine.claim:spine-libbraggio-lunghezza:revision:2026-10-12:3Mon, 12 Oct 2026 08:00:00 GMT https://matteocampagna.com/en/registry/equipment/arrow-spine-draw-weight#storiaA second model, compared with the same high-speed films, confirms the rule in both directions: on three shafts with the same wall, the softest slaps against the button and the stiffest clears the grip with more room but leaves the string with a stronger lateral jolt on the nock. It does, however, question the 1990 explanation, because even with the standard shaft the nock does not stay close to the plane of the bow for long before the arrow leaves the string. It is a model, with no archers compared: the status does not move.claim:spine-libbraggio-lunghezza:history_entry:2026-09-26:1997Sat, 26 Sep 2026 08:00:00 GMT https://matteocampagna.com/en/registry/equipment/arrow-spine-draw-weight#storiaTwo further confirmations arrive, independent but still indirect. A new numerical model rebuilds the charts from draw weight and length, with the recommended spine falling about threefold from a light bow with a short arrow to a heavy bow with a long one, and finds that the right size changes with as little as half an inch; it also gives the working definition of being tuned, that is no residual lateral rotation after the arrow leaves the string. On the shooting machine, with a right-handed bow, the stiffer shafts land to the left, and among World Cup archers those drawing more pounds use heavier arrows. No measurement of grouping in archers, so the status stays reported.claim:spine-libbraggio-lunghezza:history_entry:2026-09-07:2025Mon, 07 Sep 2026 08:00:00 GMT https://matteocampagna.com/en/registry/equipment/arrow-spine-draw-weight#storiaA recurve model calibrated against bench measurements puts figures on tuning: changing spine by one step calls for about eleven newtons of draw weight, and draw weight can only be adjusted by about ten per cent, so at a given draw length only one or two spines can be tuned well; lengthening the shaft by ten millimetres is worth four and a half newtons, that is a few pounds. Figures consistent with what is done on the field, but coming from a model on a single bow: the status does not change.claim:spine-libbraggio-lunghezza:history_entry:2026-09-07:2012Mon, 07 Sep 2026 08:00:00 GMT https://matteocampagna.com/en/registry/equipment/arrow-spine-draw-weight#storiaA new model, independent of those built on the Polish films, reaches the same rule: a more powerful bow takes a stiffer and heavier arrow, and for Olympic competition bows the useful range of draw weight, length, mass and stiffness is narrow, from 121 to 244 N, from 622 to 826 mm, from 16.6 to 23.8 g. It also adds that the lateral stiffness of string and limbs weighs more on the shaft's flexing than the bow's mass does. Two coherent lines of work, but neither measures grouping in archers with suitable and unsuitable spine, so the status holds.claim:spine-libbraggio-lunghezza:history_entry:2026-09-07:2001Mon, 07 Sep 2026 08:00:00 GMT https://matteocampagna.com/en/registry/equipment/arrow-spine-draw-weight#storiaA fuller model of the interaction between bow and arrow reproduces the flexing of the shaft and proposes simulation as a tuning tool. It does not compare shafts of different spine against each other in archers, so it reinforces the mechanism and nothing more: the status does not move.claim:spine-libbraggio-lunghezza:history_entry:2026-09-07:1998Mon, 07 Sep 2026 08:00:00 GMT https://matteocampagna.com/en/registry/equipment/arrow-spine-draw-weightclaim:spine-libbraggio-lunghezza:new_claim:2026-08-18:riportatoTue, 18 Aug 2026 08:00:00 GMT