Mainsail Trim: Main halyard.

Let’s take a look at these photos of my new main sail during first outing after the new sail was installed.

Approx 35-40 degrees off wind of 9 kn with boat speed of 3 kn. The main sail is billowed and to the left of the photograph.

What do you notice? I didn’t spot it when sailing but knew something was not right. The sailmaker saw it right away. Subsequent to his instruction I’ve spent some time educating myself about sail controls and when to implement them.

In the examples provided the draft is too far forward in the sail. I had figured that much out when sailing. I tried to relocate the draft to no avail…..because I didn’t recognize the problem and hadn’t yet learned to read the sail and to make adjustments.

The vertical folds in the head of the sail (top) occur when the halyard is too tight. It turns out that the main halyard controls the location of the draft. Tension in the halyard, as is the case here, moves the draft forward. To move it back to where it should be, 40-60 percent along the chord of the sail, one should loosen the halyard.

If my vessel had a Cunningham it would do the same.

All of the main sail controls work in unison. One is often required to adjust two or more controls at a time to achieve a desired effect when sailing.

In general, the mainsail halyard should be tensioned in heavier winds to depower the sail in conjunction with other adjustments. This will move the draft forward. It should be detensioned in lighter winds and when sailing downwind for long periods. This will move the draft backwards. It is used to adjust the position of the draft after adjustments of an adjustable backstay and outhaul intended to depower or power up the main sail. These are the basics. There’s much more to learn!

I would have probably achieved a faster boat speed and an ability to point higher had I adjusted that halyard.

The main halyard and it’s clutch on the mast. The winch is below the lower edge of the photo and thus not depicted here.

Adjusting sail controls is all about orienting the sails interaction with the wind and the vessel to ensure that speed, efficiency and comfort are optimal. In the future, as I collect illustrative photographs, I’ll review sail controls in a way to take you beyond introductory sailing classes.

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