Tartan 3500 Owner’s Manual
T3500OM
15
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 a flexible
Thiokol
compound which allows for the divergent expansion and
contraction rates of lead and fiberglass 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.
