Measuring your Mainsail

The mainsail is generally easier to measure because its size is largely determined by the luff and foot dimensions.

However, there are still a few important details that affect the final design.

Backstay Clearance

Measure the distance between the aft end of the boom and the backstay, or between the mast and the backstay. This measurement helps determine how much roach can be built into the sail without interfering with the rig. More roach can provide additional sail area and performance, but only if there is adequate clearance.

Reefing System Details

Take a close look at your reefing hardware. If your reefing line attachment points are fixed in position on the boom, measure the distance from the tack to each attachment point. This allows the reef points in your new mainsail to be positioned correctly so they line up with your existing reefing system.