A Stability Witness for Small Fishing Boats: Paint, a Plumb Line, and a Number the Crew Can Check Before Leaving the Beach

Design of a zero/low-cost loading witness set for artisanal fishing boats: painted load marks tied to a computed safe-load table, a dockside heel test (150 kg at 0.65 m offset, plumb-line readout) estimating GM against a printed pass limit, and freeboard checks for the flooded-bilge case. SIMULATED, NOT MEASURED; nothing was built or field-tested. For the reference 9.0 m boat (safe payload 850 kg, GM 1.382 m) the set costs USD 16.00 per boat. Load marks detect a 25 percent centred overload with probability 0.997; the heel test detects 300 kg stowed 0.6 m off centreline with false-pass rate 0.000 but does not detect centred overload (false-pass 0.99-1.00). Bilge water of 100 L cuts effective GM to 0.939 m. The witness certifies only the loading state at departure.