Tensioning a Masthead Rig
Adjust the cap shrouds, backstay and forestay to a moderate tension, ensuring that the amount of adjustment is equal on the cap shrouds in order to prevent the mast from leaning over one side. Take up the adjustment on the forward lower shrouds until the mast at the spreaders is bowed forward 2-3cms. Ensuring that there is no sideways bend, just fore and aft. Then just take up the slack on the aft lower shrouds. The tension on these should not be enough to pull the mast back straight. The rigging screws may then be locked and preferably taped for security. When sailing to windward, the mast should appear more or less straight. If it seems that the mast is bowed aft at the hounds, the backstay should be tensioned.
In heavy weather, a tendency for the mast to bend the wrong way will become more pronounced and the backstay should be tensioned further in these circumstances. In light airs, very little tension will be needed on the backstay, so for the best performance, it is a good idea to have a system where the tension can be readily adjusted. The racing skipper would opt for a tackle or a lever to give the fine adjustment needed.
Since not all the shrouds are required to work all the time, it is not imperative that they are all tight all the time. It is the relative tensions that are important so that each of the shrouds does its job of keeping the mast in column. The pre-bend suggested earlier is to allow for the masthead being pulled forward by the headsail deflecting the forestay from a straight line in moderate weather on the wind.
The setting up of the mast is something that need be done only when the boat is launched at the beginning of the season. There should be no reason to continue adjustment and all that is needed is to adjust the backstay tension for the condition on the day. The basic rigging tension should not be increased repeatedly, otherwise unnecessarily large loads could be imposed to the mast support structure.
© Rydgeway Marine Ltd
