Correct width measurements of a mainsail with a partial pocket luff.

Question Details

Where a mainsail has a pocket luff over only a part of the luff, how are the luff perpendicular, quarter width, half width, three-quarter width and head width to be taken?


qa3The ERS G.1.4 (g) defines a double luff sail as “….a sail with more than one luff or a sail passing round a spar and attached back on itself.”

The sail does pass round the spar and attaches back on itself so it is a double luff sail and shall be measured as prescribed even where the double luff is not present. The class rule G.2.4 (b)(1) prescribes that the luff perpendicular and cross widths shall be taken to the luff, or to the fore edge of the spar, whichever gives the greater dimension.

The ERS G.4.2 shows how the head point of the mainsail is found at the intersection of the luff, extended as necessary, and the line through the highest point of the sail at 90 degrees to the luff. When the luff is extended in this way, the head point will be a point at the forward edge of the mast spar.

Where the sail has a series of short luff sleeves, each like a double luff, in total no more than 10% of the luff in length and no one of them more than twice as long as the shortest, then the sail ceases to be a pocket luff sail. The widths shall all be taken to the luff excluding the luff sleeves which are discontinuous attachments. Class rule G.2.4 (b)(5) refers.