https://matteocampagna.com/en/registry/equipment/compound-bow-energy-let-off 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/compound-bow-energy-let-offThere are three measurements, each on a single bow, and only one of them gives the let-off. In 2015 a physicist measured the force-draw curve of a production compound, a Hoyt Contender, in the laboratory: the force rises to about 200 newtons, stays almost constant over much of the draw and then drops sharply, with a let-off of about 65 per cent at full draw; integrating the curve, the bow stores 73.7 joules, returns 71 at the release and 57 end up in the arrow. In 2016 another study measured the curve of a production twin-cam compound and, with a model that reproduces it well, derived 96.5 joules up to full draw. In 2020 a third compound, a target model of 53.5 pounds and measured as a starting input in a study on wind, stores 92.8 joules, about twice the recurve tested alongside, but the paper does not report the let-off. A 2017 model adds that the two figures are design choices rather than constants: in compounds with eccentric wheels the holding force is usually about a third of the peak, but changing the eccentrics moves the let-off from under 50 to about 80 per cent, and at the same peak and draw, with different eccentrics and limbs, one virtual bow stores 18.5 per cent more energy with a let-off of about 61 per cent instead of 67, while another gains 6 per cent with almost the same let-off. The energy also depends on draw weight and draw length, which differ across the four works. Nobody has measured more than one specimen, so the figures describe single bows, not the compound in general.claim:compound-energia-letoff:revision:2026-10-07:3Wed, 07 Oct 2026 08:00:00 GMT https://matteocampagna.com/en/registry/equipment/compound-bow-energy-let-offclaim:compound-energia-letoff:new_claim:2026-10-01:riportatoThu, 01 Oct 2026 08:00:00 GMT