Tartan 3700, Owner'S Manual

Page: 38 / 72

TartTarta
3.5 Ballast
The keel of your Tartan Yacht is of lead alloyed with antimony for added strength and cast to exacting
tolerances. In addition to providing the yacht's stability, the foil shape of the keel produces
hydrodynamic lift while sailing to weather, enhancing upwind performance.
The keel is fastened to the hull by means of stainless steel bolts, which are cast into the lead. These
bolts project through the bottom of the boat and are bedded with sealing material to prevent water
leaks. The bolts are secured by stainless steel nuts and washers, which are visible in the bilge.
4.0 RIGGING
4.1 General Description
In order to tune your mast effectively, it is important that you are familiar with the basic associated
principles. Some definitions and explanations follow: The term 'standing rigging' refers to fixed
pieces of stainless steel rod or wire supporting the mast. Those, which offer fore and aft support, are
called 'stays' (backstay, forestay, etc.). Those, which provide transverse support, are called 'shrouds'.
The shroud running from the masthead to a chainplate on the deck near the rail is called the main or
upper shroud. If it were to travel this route directly, the angle of support would be so fine as to induce
extremely large tensile forces in the shroud and equally large compressive forces in the mast. To
increase this angle of support, a spreader is positioned according to load requirements. This spreader
should be angled upwards to bisect the angle formed by the shroud as it bends over the spreader tip.
A horizontal spreader, or worse still a spreader angled downwards, is dangerous. The spreader may
be forced to slip further down the shroud resulting in the loss of the spreader and possible collapse of
the mast.
The spreader becomes a compressive member, and when properly loaded tends to push the middle of
the mast to leeward. To eliminate such a leeward bow, a lower shroud is installed running from the
mast at the base of the spreader down to the deck near the upper shroud chainplate. The primary
purpose of the lower shroud is to provide athwartship support. The addition of the spreader and the
lower shroud means that the mast is supported at more places transversely than fore and aft.
Therefore, the mast itself need not be as strong transversely as fore and aft. The mast then may have
a lesser (more aerodynamically advantageous) transverse dimension than fore and aft dimension.
4.2 Spars