Boat Propeller API

Boat-propeller maths as an API, computed locally and deterministically — the slip, RPM and pitch numbers that decide whether a boat hits its numbers or labours. The slip endpoint gives propeller slip from the pitch, the prop RPM and the actual boat speed: theoretical speed = pitch × prop RPM ÷ 1215, and slip = (theoretical − actual) ÷ theoretical — a 19-inch prop at 2000 RPM should make 31 knots in theory, so a real 26.6 knots is about 15 % slip, normal for a clean planing boat. The prop-rpm endpoint gives the propeller RPM from the engine RPM and the gear (reduction) ratio — a 2:1 gearbox spins the prop at half engine speed — and, with a pitch, the theoretical no-slip speed at that RPM. The pitch endpoint gives the pitch needed to reach a target speed at a prop RPM and expected slip, pitch = target × 1215 ÷ (prop RPM × (1 − slip)), so you can prop the boat to let the engine reach the top of its wide-open-throttle range instead of lugging. Everything is computed locally and deterministically, so it is instant and private. Ideal for boating and marine apps, repower and prop-shop tools, performance calculators, and seamanship study aids. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 compute endpoints. Estimates — hull, load and bottom condition shift real slip.