To get the best shape from the mainsail, we need to present it at the correct angle to the wind. Next, we usually need to adjust the camber so that it's about 35% to 40% aft of the cutting edge, or luff, of the sail, but with a large genoa this can be too far forward,
Then we need to put in the correct amount of twist, to allow for changes in the direction of the apparent wind at different heights. Finally, we need to adjust the fullness of the sail to match the force of the wind. And if we're close hauled, the helmsman needs to steer so that the yacht finds 'the groove' and starts really flying along.
I deliberately set the headsail first, even though most people's instinct is to do it the other way round. That's because the headsail greets the wind first, and its size and set has an impact on the set of the main. If the headsail is a big one, then you don't want to set the camber on the main too far forward, or you'll backwind it on anything approaching close hauled.
Staying on a close-hauled tack, first of all sheet in the main until the boom won't come in any further and the only effect of the sheet is to pull down on the boom, adding tension to the leech. Then adjust the camber by using the main halyard. If you need to move the camber forward, add tension to the main halyard to move the curve forward, or 'harden' the entry of the sail. If you need to move the curve aft, gently slacken off tension to soften its entry.
If you are blessed with an enormous genoa, you will probably want the maximum curve about 50% aft of the luff, and this probably means slackening the tension on the main halyard to move the camber aft a bit.
Next, pay attention to the twist in the main. When close hauled, the mainsheet won't pull the boom in any further. What it does now is control the tension on the leech, which in turn adjusts the amount of twist. Tightening the mainsheet pulls down on the boom and reduces twist; slackening it does the opposite.
You want to aim to have the top batten about in line with the boom. When it's properly set, the leech of the main will probably follow the same line as that of the headsail. If you let the kicker or boom vang right off, you can play with the twist. Letting the mainsheet go slack, you will probably see the boom lift and the top part of the sail twist excessively and start dumping wind to leeward. Tighten up, and it all starts to look good again.
Once you've got the twist right, you can then pay attention to the angle of attack. You do this by moving the mainsheet traveller so that the mainsail cuts the wind smoothly and you eliminate any tendency for the leech to beat, just as you did for the headsail.
So on a close-hauled tack, haul in the main as far as it will go, set the camber, then adjust the twist by tweaking the tension on the mainsheet. Then use the mainsheet traveller to adjust the angle of attack.
Finally, you can adjust the depth of the camber by tensioning the outhaul, depending on the wind strength. Tension it to flatten the sail, slacken it to fill the sail more. You will see that when close hauled, the mainsheet has no power to do anything other than adjust the twist: you adjust the angle of attack by the traveller.
Now it's finally down to the helmsman to present the whole rig at the correct angle to the wind. If you've done the trimming correctly, the helmsman can find the 'groove'. This is the point at which the whole thing comes together, and the yacht begins to fly. Steer so that the yacht is slightly too far on the wind, or 'pinching', and then steer slowly off the wind without touching the sail trim.
At a particular point, you should feel the accelerator kick in, the yacht will heel a tad, and you will experience that wonderful feeling of finding 'the groove'. Few experienced skippers or navigators will call a course when you're so close to the wind: usually, they will ask for 'best to windward', and then it's up to the helmsman and the sail trimmer to get the yacht flying along the groove.
Adjusting the course by a few degrees won't make that much difference to the final landfall, but finding the groove will give you maybe an extra knot or so, and will make all the difference in the world.
Anyone who finds the groove, or the angle of approach that is most efficient, for the first will be thrilled by the feel of it.
So what happens if you want to move off the wind onto a broad reach? Simply adjust the kicker so that you keep the right amount of tension on the boom to maintain twist, and then first ease the traveller to its midpoint, then the mainsheet and headsail sheets.
Don't be tempted to try to sail off the wind without easing sheets, because you will stall the sails and lose power. In the same way, if you are sailing on a broad reach, don't be tempted to haul in the sheets, because the same will happen. Always think aerofoil, rather than bed sheet.
Use the outhaul to adjust the fill of the mainsail as the wind speed changes. Slackening the outhaul is like deploying the flaps on an aircraft - it will give you more lift, but increase the drag, so you only want to do it as the wind speed drops.
Richard Thomas holds a Commercially Endorsed RYA Yachtmaster and Cruising Instructor (Sail) certificate. He runs his own delivery business, www.yachtmovers.co.uk
and is available for deliveries, assisted passages, own-yacht tuition, and yacht management.
