Sail numbers

Slide a wire up the jib luff to make the jibstay.  Attach an uphaul (mine is non-adjustable) to the jib head, and to the jibstay at the hounds.  Because my jibstay is also non-adjustable, the mast instead has a number of holes, spaced to give 1 degree rake adjustment per hole.  A jibstay hook is fashioned to a length that, when inserted into the topmost hole, gives the mast zero rake.  In order to have the topping lift clear the jib leech, there should be at least 60mm between the jib head and the end of the jibstay.

Jib boom

The position of the jib boom pivot should ideally be adjustable.  I have two pivot positions on my jib boom at 80mm and 90mm from the tack.

The topping lift has a length of "roach pole" elastic attached, to keep it from floating in a high breeze and hooking up on the spreaders.  The elastic terminates in the boom with a small plastic ball, and a crimp.  The boom aft end fitting is screwed to the boom, and can be moved in or out.

UPDATE  I've reconsidered the legality of this arrangement for the topping lift restraint line, following the announcement of an official request to IOMICA for interpretation by the AUS IOM NCA.  Previously, I had thought that a restraint line was permitted to attach anywhere, but in fact its attachment to the boom is not explicitly permitted -- hence is prohibited.  What I show here is probably not legal!  Please don't copy it.

The topping lift goes to a sensitive adjuster with a 4:1 purchase by running up to an eye (fishing swivel) at the pivot attachment on the boom and back through a ring to a bowsie.  The bowsie position (ie topping lift position) is measured against a scale inked on the boom.  The major mark represents a "standard" twist setting of 10 degrees, while each minor mark yields a further 2 degrees of twist.  The minor marks are spaced at 2mm, and give a 0.5mm change in topping lift length -- really small, but that is the fineness of adjustment required.  The small plastic ball simply keeps the topping lift line inside the SailsEtc special section boom.  While the topping lift line is quite fine, 30kg BS Dyneema (Spectra), the lift adjustment line that runs through the bowsie is somewhat thicker, 50kg Dyneema.  This ensures the bowsie takes and keeps its position, since it can slip down the thinner line.

Finally, the jib boom is finished with a trio of sheet attachment shackles.  I like to be able to vary the jib sheeting radius depending upon pivot position and whether the race course is dominated by beating/running, or by reaching.  If reaching, I'll usually select a slightly larger radius to help with sailing by the lee on a broad reach.

The sheet adjustment holes and the sheet hook are similar to those used on the main boom, and are shown on the "Mast" page. 

Mainsail luffline

The luff line arrangement at the foot of the mainsail has been pulled away from the mast so it photographs well.  In practice, the luff line is -- must be -- snug up against the aft mast face.  In practice, the tack is also tied to the mast.  The photo shows the luff line tension adjustment line passing to the forward face of the mast, opposite the gooseneck.  This is fine if you have an open cockpit and easy access to the mast foot, but it doesn't work very well in my Ikon.  I'll have to try a different arrangement.

In fact, the luff line tension arrangement includes a length of elastic, visible as the orange line in the photo.  The tension line terminates at a hook screwed below the gooseneck, but you could as well use one of the gooseneck attachment screws.

The luff is pierced in three or four places with a fine tipped soldering iron so the luff line can be tied to the mast.  In order to obtain the right looseness of the tie, I make it with a 1.5mm rod placed against the mast, and then tie the luff line snugly.  When the rod is removed, there is a small gap between the luff and the mast which allows the sail to rotate easily on the reach or run, but still remain snug against the mast.

Mainsail boom

2005-12-18

©2024 Lester Gilbert