Page 208 - The Complete Rigger’s Apprentice

If the mast rakes, do not use it for the vertical to establish the distance (Figure 6-14). Add the
leg of the triangle. Draw a true vertical line from the distance from chainplate to intersection “A” to
upper point of attachment to the deck. the height of the mast. If the chainplates do not
If plans are unavailable, measure directly project far above the rail, deck camber alone can
from the actual mast and deck. Be sure to necessitate this procedure.
account for rake. If a house or other obstruc- To measure the length of wires that pass over
tion prevents you from measuring a straight line spreaders, proceed in two steps. First, find the
from mast base to chainplate, first measure out point on deck directly below the spreader tip. To do
to the rail, then aft or forward to the chainplate this draw a vertical line on the sail plan from the
(Figure 6-13). The squares of these two figures spreader tip to intersect the deck, then measure how
plus the square of the height is also the square far aft of the stem this intersection is. Turn to the
of the hypotenuse. If the mast is stepped through deck plan and measure from the stem aft the same
a house, or if some other impediment makes a distance, then measure out from the hull centerline
direct horizontal measurement from mast to the length of the spreader plus one-half the diameter
chainplate impossible, use plumb bobs and level of the mast at spreader height (Figure 6-15). Mea-

Figure 6-15. To determine length from chainplate
to spreader: Draw a vertical line on sail plan from
spreader tip to deck. Measure aft from stem to this
point. Turn to deck plan and measure aft the same
distance (assuming the scale is the same) and mark
this point on the midline. Measure outward one
spreader length plus one-half the mast diameter and
mark this point. (Take any aft swing of the spreader
into account.) Square the horizontal distance from
the latter point to the chainplate and add the square
of the vertical distance. The square root of the sum is
the desired length.

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