Use of three-dimensional technology to construct ergonomic patterns for a well-fitting life jacket of heterogeneous thickness

To produce a life jacket that fits users both comfortably and stably, we developed a life jacket pattern based on the three-dimensional (3D) shape of the human body, with foam flotation material of different thicknesses used in different sections to achieve the required buoyancy and facilitate movement. We created a nonstandard life jacket for water sports that can adopt free design for canoeing and kayaking. Engineering design process and 3D technology were used to create the ergonomic 3D life jacket, which comprised an inner pattern, a polyethylene (PE) foam pattern for proper buoyancy in water, and the outer pattern. We developed a layering method for achieving the heterogeneous thickness of the life jacket and its outer pattern considering the ergonomic aspects of the 3D human body curvature and movability. The pattern expansion length was calculated to enlarge the outer pattern of each panel covering the varying thicknesses of life jacket and spacing for torso flexion. The calculation formula for this length was useful in increasing or decreasing the life jacket’s buoyancy, which was affected by the PE-foam thickness. Human-subject wear tests were performed in air and water to evaluate the developed life jacket. The developed life jacket had improved functionality. Significant differences (P ≤ 0.01) existed between the newly developed and conventional life jackets in air, in terms of the overall comfort, freedom of rowing movement, and fits in the chest and waist areas. Significant differences (P ≤ 0.05) also existed in water in terms of the overall fit and prevention of separation from the shoulder due to buoyancy.