Tartan 4000, Owner'S Manual, Page: 32 / 80

T4000 OM
concerning the steering system.
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.