Fig. 54.
Jib-headed Topsail.—K, measured from top of gaff close in to mast to pin of halyard sheave in topmast.
L, perpendicular to K, measured to pin of topsail sheet sheave in gaff; or to lacing-hole in jackyard.
To find the area of the Jib-header, multiply K by L and divide the product by two.
Head Sails.—I, measured from the main boom gooseneck to the shoulder of topmast, or in cases where no sails are attached to the topmast stay or pole stay, the measurement to be taken from the main boom gooseneck to the pin of the highest sheave in or on the topmast or pole, or to the pin of the sheave of any block secured to the topmast or pole, and used in either case for head sail or spinnaker.
J, measured from the foreside of the mast to top of cranse iron on bowsprit end where cut by line of topmast stay or pole stay; or, in cases where no sail or sails are attached to the stay, the measurement to be taken from the foreside of the mast to the pin of the sheave for jib outhaul.
In all cases, if the distance from the centre fore and aft line of the mast to the outer end of spinnaker boom (when shipped in its place and square to the keel) exceeds the distance from the fore side of the mast to the cranse iron on the bowsprit end (where cut by the line of topmast stay), or pin of sheave for jib outhaul as the case may be, the excess shall be added to the base of the triangle formed by the head sails; and the area of the head sail to be computed accordingly.
In the case of a yacht having no head sail, but carrying a spinnaker, the area for head sail shall be computed from the length of spinnaker boom and the height from main boom gooseneck to shoulder of topmast, or highest pin in sheave of polemast, as provided for in this rule.
The length of head-stick or head-yard to spinnaker shall not exceed one-twentieth the length of spinnaker boom. Foot yards not allowed on spinnakers.
To find the area of Head Sails, jib, topsail, or spinnaker, multiply I by J and divide by two.