Page 161 - The Complete Rigger’s Apprentice

extend diagonally out and down to provide guying boat, and might be completely inappropriate. Most
in both vertical and lateral planes. Because the stem multihulls, for instance, have “three-point rigs,”
is relatively beamy, a healthy staying angle isn’t with only the jibstay and upper shrouds coming
hard to come by. to deck, the latter without benefit of spreaders.
Remember, this is just one possible rig layout Very long unsupported mast lengths result, and
for one boat. It is an attempt to make the best use this vulnerability is dealt with using jumper struts
of basic mechanical principles for that particular and stays

The Pardey Tie-Rod
SHROUD LOADS
Rigging extends past the tangs and chainplates;
the entire hull is a member of the rigging system, The exact layout of any rig is part mechanical neces-
absorbing the power of the sails and transforming
that power into vessel motion. The weather side sity, part intended vessel use, and part designer pref-
of the hull is in tension right down to the keel erence. But no matter what form the design takes,
from the upward pull of the shrouds. The shrouds the time comes to translate it into reality, and that
also pull in, because they connect to the hull at
an angle. This means that the deck is a set of means figuring out how much strain comes where.
spreaders. With a keel-stepped mast, even if the The trouble is, nobody knows with precision. By
vessel’s deck is heavily reinforced, it can slowly observing and keeping track of enough successes
buckle upward from the pressure of the shrouds. and failures, designers have developed an empirical
That’s why a vertical tie-rod in front of or behind
the mast, to hold the deck down in the middle, is a data base, and translated that into workable formu-
good idea. las. By conducting strain-gauge and inclining tests
Veteran cruisers Lin and Larry Pardey planned while sailing particular boats under a variety of con-
to install such a rod on their 30-foot cutter
Taleisin, but found that it was going to be in the ditions, we can check our general data, more closely
way whether they put it ahead of or behind the determine what happens on those particular boats,
mast. Their solution was a mini-rod attached to and modify the formulas accordingly. But different
a tang on the mast face and running diagonally
up to a deck beam. The rod is tensioned, like a weather and sea conditions, the habits and skills
turnbuckle, by a barrel in its middle (see “Turn-
buckles [The Inclined Plane]” in Chapter 2). It’s Lucy Belle’s Bobstay
completely out of traffic, provides a convenient
handhold or towel hanger, and is easily detached For vessels with twin bobstays, the usual procedure
if the mast needs to come out. You’ll see variations is to install a separate fitting for each on the stem.
on this theme on many vessels. Sometimes there Instead, consider the configuration used on the
is a rod on either side of the mast, sometimes one Friendship sloop Lucy Belle: a single piece of wire
in front. In every case, the pull is upward on the is seized around a thimble, the two legs measured
mast, rather than upward on the keel. to suit. Advantages: One fitting instead of two; two
splices and a seizing instead of four splices; and a
more easily sealed and maintained lower eye, par-
ticularly when the bobstay is galvanized wire.
Of course, the seizing must be of excellent
quality, since it must hold if either leg fails.

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