A mainsail is cut to your rig, not to your boat's brochure. These are the exact values on our mainsail form (CS-MS-02), what each one means, and where to put the end of the tape. Everything is in centimetres.
Before you put a tape on anything
Attach the tape and a retrieval line to the headboard car — not the halyard shackle, because the car is where the sail's head will actually sit. Hoist to your selected upper datum and record Lp/P and Lw before lowering. If you have a sprayhood or bimini, leave it up: the sail has to clear it, so it belongs in the measurement.
The coded measurements
| Code | What it is, and where the tape goes | Where |
|---|---|---|
| Lp / PLuff | Selected upper datum down to the tack. Hoist the tape with the headboard car. | |
| LwLeech | Selected upper datum to the clew — with the sprayhood or bimini in place if you have one. | |
| Ld / EFoot | Main tack fitting to the clew connection, or to the boom black band. | |
| DBackstay clearance | Main tack fitting to the backstay, measured horizontally at boom level. This is what decides how much roach your leech can carry without fouling the backstay on a gybe. | |
| K1Boom to tack | Top of the boom up to the main tack fitting. | |
| K2Boom to gate | Top of the boom to the mast gate entry — where the slides feed in. | |
| K3Mast to tack | Aft face of the mast to the main tack fitting. |
The hardware page is not optional
Page 3 asks for your installed slide profile — length, height, width and thickness in millimetres — plus the mast make, model and extrusion reference, the number of batten cars and intermediates, and the thread size. Our rule is blunt and it is on the form: “Generic mast-section dimensions are not accepted.” A mast section number from a catalogue describes the mast as drawn; your mast has been sailed, repaired and re-fitted. Select the profile that matches what is actually installed and fill in only that row. If none matches, leave it blank and send square-ruler photographs.
The rule that runs through every form we print
If you aren’t sure of a bearing, leave it blank and tell us. Our forms say it on every page, and it isn’t politeness — it’s arithmetic. A blank is a question we can 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 sail that doesn’t fit. We would rather have four honest numbers and a note than five numbers where one is fiction.
Or don’t measure anything at all
The easiest measurement is the sail you already own. Bag it, send it, and we’ll do all of this on a flat loft floor with proper tension — then send you the production dimensions to approve before we cut.