Page 307 - The Complete Rigger’s Apprentice

Dockside Tune The fore-and-aft rake of the mast is largely an
For rough tuning at the dock, start by using the aesthetic consideration. Yes, it can affect the center
shrouds and stays to plumb the mast athwartships, of effort, and therefore helm balance, but sail and
and to induce any desired rake in the fore-and-aft hull trim are usually far more powerful and simple
plane. Most riggers accomplish the lateral measure- ways to affect this. What is more, significant mast
ment by running the end of a long tape measure to rake throws off things like boom height and staysail
the masthead on a halyard. Then they triangulate shape. In any event, rake is constrained by the size
by measuring down to corresponding chainplates on and location of partners on keel-stepped rigs, and
either side. This sounds logical, but there are some the angle of the mast base platform on those that
problems with it: The halyard is measurably elas- are deck stepped. In general, I find it most effective
tic, so pulling the tape tight must be done exactly to set rake according to the designer’s intent, and
the same on both sides, or you get skewed readings; deal with the helm by other means.
the halyard is usually in a sheave that is set off-cen- When making initial adjustments, take up a lit-
ter, which also skews the results; you have to fight tle bit at a time on each turnbuckle, and when you
your way around boom and topping lift to get the think things are about right, take a look from some
tape from one side to the other; and even if you get distance away for perspective.
good measurements, the results tell you only where When you’re satisfied, you can begin the
the top of the mast is, when you want to center the actual tuning. What you’re after is a mast which is
whole thing. straight laterally, is either straight or has a desired
Instead, stand in front of the mast and make a bend fore-and-aft, and which retains its shape
mark with a China marker on the center of the front, under way. Wire stretches under load, and stretches
as high as you can readily reach. If there is a spin- further the longer it is and the more heavily it is
naker track there, choose the center of a fastener at loaded. So you have to compensate for that stretch,
that height. Measure down to the chainplates from now, by pretensioning each wire a specific amount,
there. You are still triangulating, just with a much so that it won’t stretch too much or too little. That’s
shorter triangle. No halyard elasticity, no offset, no tuning.
struggle, and you now know where the bottom of You want the longest wires to be the tight-
the mast is, so you can use it as a reference point, est, because they would otherwise stretch too far.
sighting up the luff to center the mast above. But Shorter wire will be less tight, but no wire should
wait, there’s more. What if the mast is not leaning, ever be slack. In terms of a percentage of maximum
but actually offset to one side? The step or the part- wire strength, you’ll want 10 to 12 percent load on
ners might be off center, or the chainplates might be the lowers, 12 to 15 percent on the intermediates,
asymmetrically placed. If this is so, there will be a if any, and 15 to 20 percent on the uppers. You can
different angle of shrouds on one side than the other. use any of a variety of tension gauges for measur-
So measure from a chest-high point on the center ing these loads, but in the absence of one, start by
of the face of the mast out to the upper shrouds. tightening the lowers, a little bit at a time, until you
If the numbers are different, you have an offset. If can strum a low musical note on them. Not just a
it is the partners that are off-center, you might be vibration, a musical note. That’s about 10 percent
able to get the mast on center by changing the size load. Make any intermediates a little tighter, and
of the wedges on either side. If the problem is with the uppers tighter still.
the step or the chainplates, things will be harder to Don’t go to the next wires until the slack is gone
fix, but you can at least use the knowledge of the from the ones you’re working on and the related
problem when you tune, going a little tighter on the section of mast has the desired shape in both
steeper-angled side, to compensate for the difference planes. Otherwise, it is easy to put assorted bows
in lateral pull. into the stick without knowing which wires have

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