Tartan 3700, Owner'S Manual

Page: 39 / 72

TartTarta
Based upon the relationships described above, the more spreaders and shrouds used transversely,
and the more intermediate forestays and running backstays used longitudinally, the smaller the
allowable mast section may be. This can be advantageous as weight aloft and windage may be reduced
in addition to minimizing the undesirable aerodynamic effect of the mast on the mainsail. The smaller
the mast section, the less disturbed is the air flow across the main. However, a practical and
functional balance of rig complexity and aerodynamic efficiency has governed the design of the rig of
the Tartan 3700. The spar section and carbon fiber laminate schedule have been engineered to
provide a strong, stiff and safe mast while minimizing weight aloft.
Tuning involves adjusting the tension in these shrouds and stays so that the mast will remain straight
in most sailing conditions with an appropriate amount of rake for comfortable helm balance. Tuning
is carried out in two phases -­‐ tuning at the dock and tuning while under sail.
4.3 Tuning at the Dock
All turnbuckles are equipped with toggles at their base, which eliminates bending load on the swage
and turnbuckle threads. Toggles are fitted to both ends of the forestay. As the boat tacks and the
headsail loading varies from side to side, the forestay terminals are subject to extreme fatigue loading.
Start tuning the spar by ensuring that the mast is in the center of the boat, perpendicular to the
designed transverse water line. Your boat may not sit level at the dock due to distribution of gear,
stores and tankage levels, so check the water line position both sides. Then slacken the lower shrouds
completely by undoing their turnbuckles. Take the main halyard and lead the shackle end to a point
on the rail or chainplate. Adjust the halyard so that the shackles just touch the reference point on the
rail or chainplate with a given downward tension, and then cleat the halyard. Then take the halyard
to the same reference point on the other side of the deck. With the same amount of downward
tension, you will be able to just touch the shackle to the reference point if the mast is plumb
transversely. If not, let off one upper shroud turnbuckle and take up on the other in order to bring the
masthead closer to center line until the halyard shackle touches both reference points under the same
downward tension.
The particular part of the rail or deck you choose as your reference point is not important as long as it
is the same point on each side. Once the mast is centered transversely, tighten both upper shroud
turnbuckles uniformly, one full turn one side, then one full turn on the other. Repeat until the
turnbuckles become difficult to turn. Pin the turnbuckles.
Tighten the lower shroud turnbuckles so that almost all of the slack is removed; the center point of
each lower shroud should have about 1 inch of play in either direction. Sight up the aft side of the
mast to make sure that it is straight. The lower shrouds may require adjustment to straighten the
mast.
Now check the rake. Rake is the fore and aft angle of the spar. The Tartan 3700 spar is designed to
carry up to (approx.)
15 inches of rake . Rake effects the position of the center of effort of your sail
plan and, consequently, the balance of the helm. The effects are more pronounced in heavier winds.
The extent of rake on our boat should be determined by your particular sailing characteristics, the
typical local wind conditions and your sailmaker's suggestions.