This article was first published on SailNet in August of 2000
Halyard and Cunningham After you’ve gotten the sail up, you’re ready to fine-tune your halyard. As you do this, make sure the boat is headed into the wind and all the mainsail controls are eased—mainsheet, vang, outhaul, and cunningham. Then, have a look at the luff of the sail and make sure that you’re not creating any unproductive wrinkles by over-tensioning the halyard. Conversely, if you’ve left the halyard too loose, you’ll see scallops along the boltrope or the extreme forward edge of the sail. Both situations can be quickly corrected by adjusting the halyard tension. When you’ve got the right setting for the conditions, many sailmakers recommend marking the halyard near the cleat or jammer (or whatever system your boat has) so that you have a future reference for that wind speed.
Now bear off and start filling the sail by sheeting in on the mainsheet. As you sail along, you can fine-tune the luff tension by using the cunningham. On most boats, the cunningham is a purchase system that is attached to a cringle or eyelet in the luff of the main, just a short distance up from the tack. If the breeze increases significantly and you find that the boat is beginning to be overpowered, you can flatten the entry of the mainsail and move the draft forward by tensioning the luff with the cunningham. Conversely, if you find that the wind is getting light and your luff is too tight, causing the mainsail to be too flat and therefore not powerful enough, you can ease the cunningham to give the sail more power.
Outhaul The outhaul is used to alter the tension along the foot of the sail. By pulling the outhaul on, the foot gets taut and the lower portion of the mainsail becomes more flat. By releasing the tension on the outhaul, the foot becomes slack and lower portion of the sail gets more full and consequently more powerful. On smaller boats, the outhaul is often rigged externally, but on most boats 20 feet and larger, the outhaul runs through the boom.
Most sailors understand that in general, you want the outhaul eased when sailing downwind, tensioned when sailing upwind, and slightly eased when on a reach. But there’s a lot more you can do with an outhaul. This control is an essential element for shifting gears in response to changes in wind strength. Say you’re sailing along upwind in 10 knots and you get a sustained puff that jacks the breeze up to 14 knots. More than likely your mainsail will be too full for the new breeze, a condition that will overpower the boat and create excessive weather helm for the person driving. There are several responses to this increase in wind, but essentially you want to depower the sail plan, and you can begin doing this by flattening the lower portion of the mainsail with additional tension on the outhaul.
Of course, nothing instructs like experience, so get out there and try these adjustments. If you pay attention to the impact they make, you'll begin to see how they work and they’ll soon become second nature for you. And using these controls in various situations will expedite your education on performance mainsail trim. So log off and get out sailing so you can give it a try.
For Part Two of Mainsail Controls for Performance, including a discussion of the backstay and the boom vang, click here.
Mainsail Trim for Racers Part I by Pete Colby
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