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Cathy,

The mast is initially straight from ISOMAT (early boats) or Charleston Spar (later boats).

From our Tech Tips on the main site:



"To optimize performance and minimize the chance of mast failure your mast should be tuned properly.

Note: To be rigged correctly, the Cap shroud must be led through the aft hole in the spreader tips.

Set mast at 0 degree rake to ensure proper performance of the raked spreaders. Increasing rake will allow the spreaders to fall aft of the chain plates & neutralize their proper function.

Determine rake by hanging a weight from the main halyard and adjust the headstay turnbuckle so that the weight falls just to the aft edge of the mast.

Make sure the boat is level and there is no bend in the mast.

You have a keel stepped mast with mast wedges; the wedges should be positioned after adjusting the rake.

Then tighten the backstay to give a slight aft bend in the mast (1" - 2"). Next, the shrouds should be adjusted. Using a tape measure, measure the distance from the first spreaders to the starboard and port chain plates. Tighten or loosen the lower shrouds at the turnbuckles until the distances are equal and the mast is straight. The intermediate or upper shrouds should be adjusted next and slightly less tight than the lower shrouds. Check for mast straightness by sighting up the sail track and adjust the shroud turnbuckles accordingly. The shrouds should be fine tuned while sailing to weather in a moderate breeze. Always adjust the shrouds starting with the lowers and progressing up and be sure to check for mast straightness on both tacks. It is normal for the leeward shrouds to slacken slightly."



When doing this, it helps you confidence to understand the mast is not a noodle trying to collapse, but a telephone pole that has enough inherent stiffness to stand just fine with the shrouds slack. The shrouds and stays support sailing loads.

This is probably a good all around setting for a boat with a very stiff rig such as ours. In race boats, rake is one of the things we adjust prior to the start based on wind conditions on the course (prebend using the shrouds is another). The we use mast bend as a dynamic adjustment (through a backstay adjuster and running backstays and checkstays depending on how much power, point and helm we're looking for.