18 ST FS Self-Tailing Manual Single Speed Winch - Full StainlessPower Rib™ANDERSEN Winches feature the Power Rib™. Unlike other winches with abrasive drum surfaces, ANDERSEN winch drums have vertical ribs running up the surface. This combined with the smooth polished stainless steel gives a maximum grip and minimum wear on ropes, reducing the replacements costs of sheets and halyards. What’s more, the Power Rib principle simply makes sailing more pleasurable. Fewer turns on the winch make tacking easier. Sheets can be gently eased out without harsh snatching and the risks of overrides and jammed sheets are significantly reduced. The grip provided by the ribs will remain the same year after year, unlike many other winches with an abrasive or sandpaper-like surface. Such surfaces have a tendency to wear down both ropes and themselves.Power RatioPower Ratio is the mechanical advantage of the winch and is calculated as follows:length of handle x gear ratio           radius of drumThe pull of the winch is based on the Power Ratio and not just on the physical size of the winch or the diameter of the drum. The Power Ratio is used to determine the load the winch may handle as follows: pull of handle (kg x Power Ratio = pull of winch (kg).This means that by applying a load of 10kg, using a 10" standard handle, on a Power Ratio 40:1 winch, the winch can pull 400kg, assuming that the winch is 100% efficient. This is not possible in practice as the efficiency is reduced by internal mechanical friction losses.Specifications:Drum Ø D: 2-3/4"Base Ø B: 4-3/4"Height H: 5-1/4"Line Entry L: 1-15/16"Line Size: 1/8-11/16"Weight: 7.0lbGear ratio 1st speed: 2.6 : 1Power ratio 1st speed: 18.8 :1