Page 189 - The Complete Rigger’s Apprentice

Monohull sailors commonly deride provisions, in as they are characterized by failure, then lack of
seagoing multihulls, for living in the hull with the failure. As long as no novel parameters or designs
hull upside down. “Why,” the complaint goes, “don’t are introduced, it should be possible to approach
they just get a boat that won’t capsize?” But well-de- ideal specs. But design is often about novelty, about
signed multihulls are very, very difficult to capsize new scale, new ideas, new materials. And everything
(see “The Transverse Righting Moment Curve,” later is skewed and qualified by human error, neglect,
in this chapter); these provisions are just “sneaker and abuse, by human ingenuity at introducing
bulwark” prudence. They are seaworthy. unexpected factors into the execution of a design,
Contrast that with the experience of a friend or human inability to predict Nature’s introduction
who’d been foredeck crew in a racing monohull of such factors, and of course human obstinacy, pre-
one day. His boat won, and he began jumping up venting quality even when it is available.
and down for joy. “Stop,” shouted the afterguard, In sailing, we seem to have gone from an over-
“you’ll go through the deck!” Obsessive paring built-but-unimaginative period (traditional) to an
away of weight is a hallmark of racing craft, and underbuilt-but-novel design state. We have found
this vessel’s foredeck, where people had to work in improved performance in some cases, and drastically
often strenuous circumstances, was deemed strong reduced safety factors in nearly all. In this phase,
enough if it could just support a cautious sailor. even seemingly overbuilt items can fail; their nov-
That is not seaworthy. elty mandates that not all consequences have been
Seaworthiness is very difficult to define. Sea- anticipated. For example, I had a client who, in the
worthy vessels are strong, but how strong? Easy to interest of “better performance,” invested in carbon
steer, but how easy? Have a gentle motion, but how fiber masts for his ketch. These were excellent masts,
to quantify gentleness? To compound things, the built to hefty cruising standards as these things go.
popular perception is that the more “seaworthy” a He went ocean racing, and all was well until a spin-
vessel is, the slower and more sluggish it is. Is this naker halyard block parted in a breeze. The halyard
true? To what extent? And why? To answer these led from the head of the sail, through the block, then
questions we must start with: into the mast a few feet below the block. So when
the block broke, the load of the sail came on the
Effects of Engineering entry hole in the mast. It was an immensely strong
In terms of rigging, there’s essentially just one ques- mast, but its fibers were oriented vertically, to take
tion: Is it strong enough? That is, regardless of the expected loads. The halyard imposed an unexpected
seaworthiness of the hull, is the rigging likely to hold load, ripping a 7-foot gash in the face of the mast,
together under the loads the hull will put on it? But right down between the fibers. Builders of carbon
an appropriate rig is intimately wedded to its hull; masts have learned from incidents like this, and as a
in order to answer our single question, we must look result their masts have become more seaworthy. Or
at many others, like the ones in the preceding para- at least some of them have; remember, the biggest
graph. The formulas earlier in this chapter gave us reason to invest in a carbon fiber mast is to improve
basic integrity, but now we will be looking for sub- performance, and this isn't always compatible with
tler, more elusive harmony. durability and safety.
When engineers design a structure, they must
determine not only whether it is strong enough, but Effects of Attitude
for how long it will be strong enough. They consider A boat grows, bit by bit, out of the attitude of the
a structure overdesigned if it does not break within designer and builder. The client with the sneaker
predicted and/or acceptable time, for a particular bulwarks is also likely to pay similar attention to
use, at a particular intensity. But they do not always, handholds, engine access, navigation—he’ll build
or even usually, know what constitutes perfect himself a livable world. And the multihuller who
design. Thus, structures tend to oscillate in quality makes careful provision for being upside down will
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