Frame spacing

Frame spacing is the distance between adjacent transverse frames (or between longitudinals in a longitudinally framed structure), one of the basic inputs to local scantling formulas. Plate panel thickness scales with spacing: required thickness is roughly proportional to spacing times the square root of the design pressure, so closer spacing allows thinner plate but adds stiffener weight and welding. Class rules set a standard or reference spacing and adjust scantlings when the actual spacing departs from it. Typical merchant-ship spacing is 0.6 to 1.0 m, often tied to a round fraction of the plate width to limit offcut. Spacing also fixes the unsupported span used in buckling and panel bending checks.