Selden Winch Dimensioning Guide

Using the Dimensioning Guides

• Dynamic applications (sheets): the winch must give enough mechanical advantage to trim the sheet at the maximum calculated sheet load, based on the effort at a 10" winch handle. A larger winch means less effort; a smaller winch needs more effort but retrieves line faster.
• Static applications (halyards, outhauls, spinnaker guys): the winch should generate 75% of the calculated line load with the available mechanical advantage and a reasonable handle effort, and its Safe Working Load (SWL) must be equal to or greater than 100% of the calculated line load.
• The guides are based on sheet load, winch gearing and handle effort, not on SWL; check SWL separately, particularly for static applications.
• Under electric power an E-winch can generate higher line loads than a manual S-winch of the same size, so the E-winch guide may recommend a smaller size.

• Find your boat's RM 30° (kNm) on the X-axis of the chart for the job (e.g. main halyard, fractional rig), draw a vertical line and read which winch bars it crosses.
• Every winch whose bar the line crosses is suitable; choose by the balance you want between trimming speed and handle effort.
• Main sheet charts assume a 2:1 sheet with S>90% of E (end sheeted) or a 4:1 sheet with S>50% of E (mid sheeted); the Code 0 halyard chart assumes a 2:1 halyard; spinnaker sheet load is approximately 50-35% of guy load.

Example: S-winch for a jib/genoa sheet on a fractional rig with RM30° = 73 kNm. Draw a vertical line at 73 kNm: it crosses the ranges for S46, S52 and S60, so all three suit. S46 (RM close to the top of its range) needs more effort near maximum sheet load but retrieves line faster; S60 gives more mechanical advantage and less effort; S52 is the compromise.

Example: jib/genoa sheet, fractional rig, S-winch

Read the bars directly on the charts; no values are transcribed from them.

E-Series (E40i, E40-E66, E rev)

E-series, mainsail: main halyard and main sheet (end and mid sheeted), fractional rig

E-series, mainsail: outhaul (fractional), halyard, main sheet and outhaul (masthead rig)

E-series, flying sails: Code 0 halyard and sheet, spinnaker/gennaker halyard, gennaker sheet, spinnaker sheet and guy

E-series, jib and genoa: halyard and sheet, fractional and masthead rig

S-Series (S30-S66)

S-series, mainsail: main halyard, main sheet (end and mid sheeted) and outhaul, fractional rig

S-series, mainsail: main halyard, main sheet (end and mid sheeted) and outhaul, masthead rig

S-series, flying sails: Code 0 halyard and sheet, spinnaker/gennaker halyard, gennaker sheet, spinnaker sheet and guy

S-series, jib and genoa: halyard and sheet, fractional and masthead rig