The perfect sail trim is sometimes called the perfectionist gimmick dismissed by regatta sailors. The correct sail setting brings not only speed, but also comfort. Because if the sails generate too much pressure, they will heel too much - not a desirable condition for sailors. With the heel, the greediness also increases. The consequences are more rudder pressure and a overall restless driving condition. The right trim is by no means only interesting for ambitious regatta sailors.
For the success of all trim efforts while sailing, a proper basic trim of the rig is necessary. It is never too late for this - it can and should be readjusted at any time during the season as soon as it appears necessary. For sailors who tend to be lazy on the water, the correct basic trim is all the more important. For tips on setting up the rig, see this article.
First, let's focus on trimming the mainsail. The most important indicator is the leech of the sail. Small wind bands provide precise information about the flow of the sail at different heights. Even if the threads often break on furling mainsails, they should be re-glued as soon as possible.
That's how it should be: The wind threads on the leech should blow straight aft, only the top thread may occasionally fold away to leeward. If the lower threads also fold to leeward, the sheet is too tight and can be lowered slowly to the desired result.
In gusty winds, make sure that the sheet is laid in such a way that it can be quickly thrown away at any time - either to take pressure off the leech or to reduce the angle of attack. The reduces the heel in the gust and the risk of getting out of hand.
The profile depth of the sail describes the position of the "belly" in the sail. The following applies: the stronger the wind, the further aft the bulge forms in the sail. In order to move it as far forward as possible, the luff must be well enforced. This is not so easy, especially in the lower area.
If the mainsheet is driven loosely, the tree can rise (middle) and the sail twists, it twists in the upper area. The more sheet tension is exerted, the more the leech closes. The twist disappears and the rudder pressure also increases
The use of a cunningham can help. Most of the time, the eye required for this is already present in the sail about 30 centimeters above the large tree, all that remains is to shear a straightener. With this the luff can be enforced. The Cunningham is missing on roller sails due to the design, but they are cut flatter.
On these three graphics, the change in the profile with increasing wind and use of the Cunningham is clearly visible. The cutting edge becomes flatter, the greatest tread depth shifts aft. The effectiveness of the mainsail decreases. If the luff is pulled tight (below), the profile regenerates
Afraid of bending the mast? It doesn't have to be, to a certain extent it is indispensable for good trim. How much a mast can be bent depends on the type of rig and its setting. If swept spreaders are used, more bending is usually possible in the middle area, so when bending the mast is also compressed and so the upper shrouds get a little loose. Riggs with neutral spreaders bend more in the area above.
The change of the mainsail profile when pushing through the backstay takes place from two different angles. The leech opens, which means that pressure is lost, which is desirable when the wind increases. At the same time, the mast bends, the distance between the keep and leech is lengthened, the sail is stretched and the profile is flattened. This is also a desired effect with increasing winds, since excess pressure is released without having to reef. The backstay is too tight if there are diagonal folds from the clew.