Cambridge Canvas & Sail Loft Inc

For new custom sails you may wish to follow all of the steps and be detailed and specific about your requirements. For used sails focus on the basics like; dimensions, cloth weight, and luff types on headsails. If you have some flexibility you will stand a much better shot at finding a used sail. Print this page then measure according to the instructions below and fill in the blanks. Measuring for Mainsails   Measuring for Headsails: Mainsail Diagram 1. LUFF Hook your tape measure up to the main halyard (along with the head of the old mainsail if available). Hoist it under normal luff tension. If your old sail is not available then hoist to the maximum height you want your mainsail to stretch up to. If there are bands on the mast, measure to the band. Then measure down to the top surface of the boom itself. (Not the tack pin on the boom). This will be the “LUFF” (or “P”). 2. LEECH While the tape measure is still hoisted, swing it back to the aft end of the boom and measure to the point where you want your clew ring to be located. This is the "LEECH". 3. FOOT Lower the tape and attach it to the out haul line along with the clew of your old mainsail if available. Pull the out haul to the maximum point of draw. Take the measurement from there to the aft face of the mast. (Not to the tack fitting on the boom). This will be the "FOOT" (or "E" dimension). If no old mainsail is available pull it out to where you want your clew to stop. (If there is a band on the boom, measure to it). 4. LUFF & FOOT HARDWARE Internal Slide Slugs and Slug boltrope External Slide Note the shape and size of the slides, slugs, or bolt rope and how they attach to the mast. These are easily changed on mainsails but it is helpful to know anyway. Flat internal and external slides are measured in width while cylindrical slugs and bolt rope are measured in diameter. 5. TACK PIN SETBACK Determine the location of the Tack Pin on your boom "gooseneck". This is measured in inches behind the mast and above the boom and is used to locate the tack ring on your mainsail in the right place so it doesn't pucker. This is not necessary for used sails since they are already fixed. You can add shackles if needed to smooth it out. This is called "TACK PIN SET BACK".   1. MAX. LUFF Hook a long tape measure up to your jib halyard (or top furling swivel on a furler) just as if it were the head ring of the sail. Hoist it all the way until it stops at the top. Measure down to whatever point you intend to attach the sails tack to. This will be your MAX. LUFF dimension or "MAX. HOIST". 2. "J" DIMENSION Measure the horizontal distance between the tack fitting and the mast. This is known as "J" dimension and will be the number the "L/P" is compared to for percent overlap. To Figure % Overlap Multiply the boat's "J" dimension times the headsail percent you want. That should be equal to the sail's "L/P." Luff Perpendicular is the length of a line drawn from the clew to the luff, intersecting the luff at 90 degrees.) If your "J" is 10 feet and you want a 150% the L/P must equal 15 ft. 3. FURLING SAILS If you have a furling unit, hook the tape measure up to the upper furling swivel (as if it were the head of the sail). Hoist the tape all the way up and measure down to the tack fitting on the furling drum. For both furlers and foil type headstays you will need to determine the diameter of the luff tape needed. (Luff tape is the small bead that feeds into the headfoil).This can be measured on an old sail with calipers or a fine scale ruler. The size is usually is provided with furling unit documentation too. We do have a chart that lists most manufacturers sizes. Measuring for Spinnakers: Two dimensions are needed. First the "J" dimension; the distance from the tack to the mast as pictured under measuring headsails. Second, the "I" dimension as measured from the upper intersection of the headstay vertically down to the deck at the chain plates (not the cabin top) also pictured on the diagram above under "Measuring For Headsails". The spinnaker luff should roughly equal "I" and foot should be roughly equal to "J" X 180%.       Measuring for Mainsails 1. Luff ("P") 2. Leech 3. Foot ("E") 4. Luff    Foot       (circle type & fill in size) 5. Above Boom          Behind Mast Measuring for Headsails 1. Max Luff 2. "J" Dimension 3. Furler Hoist

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