5 Expert Tips: Your complete guide to mainsail trimming

As a mainsheet trimmer you are the engine of the boat, so good mainsail trimming is vital as Alain Sign explains to Andy Rice

Experienced sailor though he may be, Alain Sign has had his hands full getting to grips with the role of mainsheet trimmer in a fleet as competitive as the Cape 31. Alain sees the mainsheet trimmer’s role as the hub, the central nervous system which is connected to every other role on the boat. “I’m having a conversation with pretty much everyone else on board,” he says.

“With the trim you’re looking to guide the helm to where they’re going, and I’m taking my cue from what the tactician is saying. Then I’m talking with the runner trimmer looking for power-on or power-off.

“And then there’s maintaining the right relationship between main and jib trim, working together through the gusts, lulls and shifts.”

Data analysis is another trend creeping into Cape 31 racing, with an analyst back on shore looking at when the boat was fast or slow and feeding the details back to the team before the next day’s racing.

Through the wind range, different elements of the multiple array of sail controls take on different levels of importance. Here are Alain’s five best tips for keeping your mainsail – and the overall boat speed – at the highest level of performance through different wind speeds.

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Mode priorities

All the time you need to be asking yourself, ‘What am I trying to achieve with the setup?’. I’m listening very carefully to the tactician’s priorities at any given moment as you need to mode the rig to what they need. Is it a fast-forward mode, or a high VMG mode, for example?

On a stable day I’m looking to control the heel angle so will be constantly playing around with the traveller. I’m also looking at boat speed and true wind angle, checking how close we’re sailing to the breeze.

With the helmsman I’m moving between sailing not too high and not too low, working to find the VMG sweet spot, managing the relationship between traveller position and mainsheet tension as my two primary controls.

Ease for speed

In sub-powered light wind conditions, if you’re struggling to get the boat moving, ease for speed. Make sure you ease the mainsheet and the jib to create really open leeches for the air to move past. Ensure lots of twist and don’t steer too close to the breeze, not until you’ve built the speed and momentum.

As soon as you get over 6 knots of breeze it’s good to bring the traveller all the way to windward, even to the point where the boom is two or three degrees above the centreline of the boat. This creates ‘false load’, creating a bit more weather helm and feel for the helmsman to work off.

Harden that leech

As you begin to progress into full power conditions, start closing off the mainsail leech. Now you’re starting to drop the traveller further to leeward, maintaining your target heel angle. You’re also working with the fine-tune on the mainsheet, and with the runners to straighten the mast for a lull or letting it bend in a gust.

In an ideal world, when the runner and the jib are set up nicely, they kind of do the work for you and there’s not much trimming or adjustment to be done with the mainsail. That’s when you know you’re getting close to the sweet spot of optimum rig tune.

Big breeze

The windier it gets, the more tension you want to put into the shrouds. On a Cape 31 you’re only allowed to adjust it before the race, so don’t go too extreme on these adjustments if the breeze is looking variable.

Once it’s getting windy enough for the mainsail to start ragging, you want to max out on your runners, pulling on lots of vang and Cunningham, and let the traveller to leeward. You also want the jib sheeted further out to leeward to keep the slot open.

On the Cape 31 the jib up-and-down is led to the main trimmer while the jib trimmer tends to be hiking off the side of the boat. This means you can ease the jib leech through the gust and pull it tighter again through the lull, maintaining the right balance of power between mainsail and jib.

If you’re getting really overpowered it’s sometimes worth easing off again on the vang, making sure the bottom of the mainsail keeps driving the boat forward while letting the top of the sail twist off and spill the excess power. It’s also possible to pull on too much Cunningham which you can see when the entry to the sail goes too flat, so make sure you don’t overdo it.

Use the runners

If the runner trimmer is looking around and anticipating the gusts and lulls, easing and tightening the runners accordingly, the mainsheet trimmer doesn’t have to do an awful lot.

When you’re in that light wind mode, where you’re going from 6 knots to 8 knots of breeze and you’re looking to find power, that’s when accurate runner trimming becomes really important. When the gust comes in, you want the boat to accelerate, getting those turns on the runner. Then if it’s slowly dying off, you need to be putting power back into the mainsail again.

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