Take a measurement
Press Measure, then click two points on the model. You get the true distance and its three components in millimetres. Every new pair of clicks adds a row.
X along the boat (0 = aft end of the deck), Y across (0 = boat centreline), Z up ().
Cross-section
Move the slider to cut a hull anywhere along its length. Press Section to see the cut in 3D too.
How deep does she float?
Add weight on board (crew, gear, water, food). The water level in the 3D view and in the cross-section moves to match.
load 0 kg
Calculated from the volume of the two hulls in sea water (1.025 kg/l), with the boat floating level. In reality the trim changes with where the weight sits. The Hydro tab shows trim and heel.
Heel and trim
Load the boat, move the weight fore and aft and heel her over. The 3D view tilts the boat and the water finds its level.
Centre of gravity height
Not given in the plans. 450 mm is an estimate for the loaded boat with crew sitting on deck. Higher = less stable.
Stability curve
Resistance and engine
Speed under sail
Speeds in knots. VMG = speed made good straight upwind or downwind. Angles from the true wind. R = reefed.
Calibration
How it is calculated
Heel, trim, draft, stability: exact geometry of the hull model, cut in 160 slices and balanced so that weight = buoyancy and the centre of buoyancy sits under the centre of gravity. Cabins and beams are not counted as buoyancy (matters only once a deck goes under).
Resistance: skin friction (ITTC-57 line) on the wetted surface × 1.15 form factor, plus wave resistance from Michell's thin-ship theory applied to the real hull shape, including the interference between the two hulls. Expect ±20–30%.
Sailing speeds: simplified velocity prediction. Generic sail coefficients for a gaff main and jib, windage, induced drag of the V hulls (no daggerboards), reefing to stay below the chosen share of the righting moment. Calibrated on one reported top speed. Use it to compare angles and wind strengths, not as a promise. Leeway is not shown in the angles.
Bulkheads
Width and height measured on the bulkhead shapes of the plywood cutting layout (Cutting Sheet 1), rescaled to real 2440×1220 mm sheets. Position X from the study-plan plan view.
Offsets (every 250 mm)
At each station X: keel height, deck height, half-breadth at deck, deck-to-keel depth and hull-side length in section.