Lofting

Lofting is the process of translating a ship's or boat's design from scaled plans into full-size drawings or patterns used in construction. Traditionally, lofting was a craft performed in the loft, the drafting room of a shipyard, by a skilled loftsman who laid off curves and lines on large sheets of paper or sailcloth to guide the shaping of frames, stems, and hull surfaces.

Historically, lofting ensured hull forms remained true to the designer's lines when scaled up to actual size. The practice was central to shipbuilding for centuries and gave its name to the loft area of a yard where draftsmen worked.

The method starts with the lines plan, including stations, waterlines, and buttock lines. A baseline is established and the plan scaled to full size. Using straightedge, battens, compasses, French curves, and markers, the loftsman transfers points from the scaled plan to the full-size sheet and draws the hull curves. Where necessary, molds or frames are cut from the patterns to guide the construction of the hull. There are two main types: line lofting, which produces the true hull lines, and mold lofting, which produces patterns for the individual frames.

In modern practice, computer-aided design and digital lofting have largely replaced manual methods, but the term remains in use to describe the transition from design to construction and the traditional skills still practiced in some yards.