#naval-architecture

Sailing and naval-architecture maths as an API, computed locally and deterministically — the hull-speed and design-ratio numbers a sailor, boat-shopper or yacht designer sizes a boat with. The hullspeed endpoint gives the theoretical displacement speed limit from the waterline: hull speed = 1.34 × √LWL (feet) in knots, so a 25-foot waterline tops out around 6.7 knots (7.7 mph, 12.4 km/h) — with a tunable coefficient up to about 1.5 for light, easily-driven hulls, since planing boats leave the formula behind entirely. The ratios endpoint computes the two classic performance numbers: the Sail Area/Displacement ratio, SA/D = sail area ÷ (displaced volume in ft³)^⅔ using displaced volume = displacement ÷ 64 lb/ft³ for seawater — around 16–18 is a typical cruiser and 20-plus is sporty — and the Displacement/Length ratio, DLR = (displacement in long tons) ÷ (0.01 × LWL)³, where under 200 is light and over 300 is heavy, each returned with a class label. The ballast endpoint gives the ballast ratio = ballast ÷ displacement × 100, a rough proxy for stiffness and sail-carrying power that most cruisers hit near 35–45 %. Everything is computed locally and deterministically, so it is instant and private. Ideal for sailing, boating, marine, yacht-brokerage and boat-design app developers, boat-comparison and rig-sizing tools, and naval-architecture calculators. Pure local computation — no key, no third-party service, instant. Imperial units. Live, nothing stored. 3 compute endpoints. Design-ratio estimates, not a velocity prediction program.

api.oanor.com/sailing-api

Froude-number hydrodynamics as an API, computed locally and deterministically. The number endpoint computes the Froude number Fr = v/√(g·L) — the dimensionless ratio of inertial to gravitational forces — from a velocity and a characteristic length, classifies the flow as subcritical (Fr<1, tranquil), critical (Fr=1) or supercritical (Fr>1, rapid), and returns the critical velocity √(g·L) at which Fr=1; the velocity endpoint inverts it to v = Fr·√(g·L). The channel endpoint gives the open-channel Froude number from a flow velocity and depth, the flow regime, and the critical depth y_c = (q²/g)^(1/3) for the unit discharge q = v·y — the boundary between tranquil and shooting flow used in spillway and weir design. The hull-speed endpoint computes the displacement hull speed of a boat from its waterline length, v = 1.34·√(L_wl in ft) knots, the wave-making speed limit where the bow and stern waves equal the hull length, returned in knots, m/s and km/h with the corresponding Froude number — a 10 m waterline gives about 7.7 knots. Gravity defaults to 9.80665 m/s². Everything is computed locally and deterministically, so it is instant and private. Ideal for naval-architecture, marine, hydraulics, civil-engineering, river-modelling and fluid-mechanics-education app developers, spillway, weir and hull-design tools, and simulation software. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 4 endpoints. This is the Froude number and flow regime; for Manning open-channel discharge use a Manning API.

api.oanor.com/froude-api