Archery & Arrow API

Archery and arrow maths as an API, computed locally and deterministically — the FOC, energy and arrow-weight numbers an archer or bowhunter tunes a setup with. The FOC endpoint finds the front-of-center balance, the share of an arrow’s weight that sits forward of the middle: FOC = ((balance point − length ÷ 2) ÷ length) × 100 measured from the throat of the nock, so a 28-inch arrow balancing at 16 inches is 7.1 % — and it bands the result, since target archers run about 7–12 % while hunters push 12–19 % for penetration and forgiveness. The energy endpoint turns arrow weight and speed into terminal performance: kinetic energy (ft-lb) = grains × fps² ÷ 450,240 and momentum (slug-fps) = grains × fps ÷ 225,218, so a 400-grain arrow at 280 fps carries about 69.7 ft-lb and 0.50 slug-fps, with a suggested game class — momentum, not KE, is the better penetration predictor for heavy arrows. The weight endpoint totals a finished arrow from its parts — shaft (grains-per-inch × length) plus point, insert, nock and fletching — and divides by draw weight for grains-per-pound, flagging the 5-GPP minimum that protects the bow. Everything is computed locally and deterministically, so it is instant and private. Ideal for archery, bowhunting, traditional-archery and outdoor-sports app developers, arrow-builder and bow-tuning tools, and pro-shop calculators. Pure local computation — no key, no third-party service, instant. Imperial archery units. Live, nothing stored. 3 compute endpoints. For sight marks or bow tuning use a different API.