Correct rig trim is a basic requirement for optimal sailing performance. The aim is, with a few exceptions, Tension on the forestay so that the luff of the Genu does not sag too much on upwind courses, which is almost always associated with a loss of height. At the same time, the curvature of the mast also affects the mainsail. A mast bending forward in the middle pulls the main shaft flatter in the middle, which reduces pressure when the wind increases and pushes the reefing point out. Likewise, a masthead bending aft and leeward can take pressure off the main, which opens the leech.
"When you walk through the harbors and look at different rigs, you can only be amazed that they are still standing" - trim and sailing expert Albert Schweizer
Correct rig trim is also an important safety aspect. Basically, the shrouds and stays are only there to keep the mast from falling over. This can be achieved with very little tension on the wires under static conditions, such as in the harbor without the sails set. Obviously, this leads many owners to leave their rig exactly as it is - with too little pre-tensioning. Good results can be achieved with the simple "folding rule" method - without any expensive precision tools. We explain them in detail on the fifth page.
A fallacy is that permanently tight shrouds put too much stress on the structure of the yacht. That is basically true. For example, a yacht changes its shape slightly over the season due to rig tension, but this should have been taken into account in the design and taken into account in the construction. Wooden boats are particularly affected. However, this does not mean that it is better to forego this tension, but rather to check the basic trim more often during the season and to trim it if necessary. In the winter season, the yacht should then return to its original shape relieved.