The stack pack is a mainsail cover with integral lazy-jacks, so the sail flakes straight into the cover on the boom. It has to be cut to the packed shape of your mainsail, the mast, the boom body and the boom groove on this boat, not to a brochure size. The main measurements are in centimetres; groove details are marked separately on the form.
Before you put a tape on anything
Before measuring, flake and pack the mainsail exactly as it will sit in service. The easy mistake is wrapping the tape round the boom as well as the sail: the form asks for the packed-sail wraps only, with the boom left out. Measure the mast and boom separately, photograph the tape positions, and leave uncertainty as a note rather than turning it into a tidy value.
The coded measurements
| Code | What to measure |
|---|---|
| A | Front packed-sail and headboard circumference; no boom |
| B | Packed-sail circumference at fixed 50 cm station; no boom |
| C | Packed-sail circumference at fixed 30 cm station; no boom |
| L | Aft mast face to mainsail clew bearing on boom |
| M | Complete mast circumference |
| P | Complete boom circumference, not groove perimeter |
| Y | Boom-groove mouth width |
| X | Boom-groove cavity width / diameter |
Why we ask for the boom, not just the sail
This stack pack is not a loose bag with a logo on it. The form asks for the packed sail, the mast, the boom body and the boom groove because those parts decide whether the cover closes cleanly and sits where it should. It also says the mast height and boom station are not universal, so we review the values against annotated tape photographs before cutting. Guess the boom shape or measure over the wrong thing and the error 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.