Getting Back Aboard Alone: A Self-Recovery Aid Design Study for Single-Handed Small-Boat Fishers, with Grip, Strength and Freeboard Budgets

A fisher who falls overboard alone beside a small boat may be unable to reboard over the freeboard, even in calm water, and may die alongside a floating boat. This paper designs a concrete self-recovery aid and calculates whether a cold, exhausted person in the water could use it. The aid is a hull-side rope ladder with wide rigid rungs at three stations, a submerged stirrup loop as its lowest step, paired recessed gunwale handholds, and a short waist tether clipped to a rung before moving a hand. In a simple biomechanical model, reboarding without an aid at 0.60 m freeboard requires 578.8 N for the weakest class against a cold arm capacity of 176.0 N. With the aid, leg extension supplies 75% of effective weight, residual arm load falls to 144.7 N, work is 549.9 J, and tethered grip falls to 36.2 N from an infeasible 166.4 N untethered. The maximum freeboard for the weakest class is 1.15 m, set by geometry. Simulated overall reach-and-deploy probability for the weakest class is 0.519 at 0.5 m/s drift and 0.399 at 0.8 m/s. Three-station cost is GBP 445.50. The aid does not help an unconscious person, and cold shock can defeat grip before strength matters; flotation remains primary. SIMULATED, NOT MEASURED.