Estimate each genoa sheet from clew-to-winch route, genoa foot, winch wraps, drum diameter, and spare tail. Path geometry — not a sheet working-load or hardware selector.
Use when replacing genoa sheets and you can measure (or tape) the lead from clew through the car to the winch with the sail eased for tacking.
Enter route, foot, wraps, drum OD, and spare.
Not a substitute for measuring the old sheets end-to-end or maker load tables.
Forum practice sums the eased lead, often a foot-length allowance for tacking the clew, winch circumference × wraps, and spare.
wrap_ft = wraps × π × (drum_od_in / 12)
sheet_ft = route + foot + wrap_ft + spare
LOA×1.5 rules of thumb exist; this calculator uses measured segments. Not a load calculator.
Defaults: route 28, foot 16, wraps 3, drum 3.5 in, spare 6 → wrap ≈ 2.75 → sheet ≈ 52.75 ft each.
Route 22, foot 12, wraps 2, drum 3, spare 4 → ≈ 39.57 ft.
Assumptions: one continuous sheet per side; foot allowance helps when the clew crosses; drum OD is the winding diameter.
Limits: continuous-line systems, barber haulers, and inside/outside leads need a messenger measure.
Responsibility: planning aid only — buy matched pairs.
When you tack, the old sheet must reach until the new sheet takes over. Foot is a common planning allowance; measure your worst-case lead if you can.
Some guides use that. Prefer route + foot + wraps when you can tape the path.
Furling line rolls the sail. Sheets trim the clew — different path and calculator.
LP sizes sail overlap. This page sizes sheet length only.