Hydrostatics
How Boat Forge works
Shape: the hull is built from about 60 cross-sections. Length, beam and depth set the size; the shape sliders control how full the bow is, where the widest point sits, the transom width, the V of the bottom (deadrise), how much the bottom curves up at the ends (rocker), the rise of the deck line (sheer) and how far the sides lean out (flare).
Floating: it adds up the weight of the hull (from its surface area and material), deck, engine, fuel, crew, gear, cabin, rig and ballast, then sinks the hull until it displaces that weight of water (Archimedes), and tilts it until it is balanced. From that it works out draft, freeboard, the waterline, form coefficients and the metacentric height (GM).
Speed: planing hulls use Crouch’s formula; displacement hulls are limited by their hull speed (1.34 × √waterline length in feet, in knots). Sailboats get sail-area/displacement and displacement/length ratios. These are estimates for comparing designs — a real boat also needs a professional structural design and must meet your country’s rules (e.g. ISO 12217 stability, CE/RCD, USCG).