The mainsail cover protects the lowered sail on the boom, so it has to follow the real bulk of the stowed sail, not the memory of an old cover. It has to be cut to the packed sail, the headboard, the mast with halyards and the boom body on this boat. The cover measurements are in centimetres; colour, closure, construction and logo notes belong in the specification fields.
Before you put a tape on anything
Before measuring, lower and stow the mainsail exactly as it is normally covered, then remove any existing cover. Wrap the tape round the packed sail and boom at the shown positions, pulling it taut without visibly changing the bulk. Measure the mast and boom where the cover will actually meet them, and photograph the tape position if the section varies. If the packed shape is uneven, send tape-position photographs rather than smoothing the sail into a nicer value.
The coded measurements
| Code | What to measure |
|---|---|
| A | Full wrap at packed-sail front, with boom and headboard |
| B | Full wrap 50 cm aft of the aft face of mast, with boom |
| C | Full wrap 30 cm forward of clew bearing, with boom |
| L | Aft face of mast to mainsail clew bearing on boom |
| M | Mast circumference including halyards |
| P | Boom circumference; photograph tape position if section varies |
Why the old cover comes off
This cover is cut round the sail as it lies on the boom. The form asks for the packed front, the stowed body, the mast with halyards and the boom body because those parts decide whether the closure reaches and the cloth sits cleanly. It also says to keep the tape taut without changing the packed bulk, and to photograph positions when the shape varies. Measure over the old cover or crush the sail smaller and the wrong answer looks just as official as a real measurement.
The rule that runs through every form we print
If you aren’t sure of a bearing, leave it blank and tell us. A blank is a question we answer with one phone call. A guess is indistinguishable from a measurement, so it survives all the way to the cutting floor and comes back as a cover that doesn’t fit. Four honest numbers and a note beat five where one is fiction.
The words on this page, explained
Not sure? Send a photo.
A few phone photos of your boom, frame or stowed sail answer half our questions. Send them with your enquiry and we’ll guide you through the rest — then confirm every dimension before we cut.