One of many key positions on a race team, the sail trimmer takes responsibility for optimizing sail performance. While the most important time to shine is during the race, a good trimmer knows that success starts before the boat leaves the dock. Read these tips from UK-based North Sails expert, Sam Richmond, who moonlights as trimmer on Maxi 72 Jethou and Fast40+ Ino, and learn why attention to detail makes the difference between “good” and “great” in every situation.

Guidelines for Good Sail Trim

Power from your sails comes down to three sources: Angle, shape, and twist. A trimmer’s job is to achieve the most amount of power, while keeping in mind the balance of trim between sails.

  1. Angles: Pull the sail in to add power and ease the sail out and to reduce power.  Heading up will also reduce the power, whereas if you trim on or bear away you increase this. This is a common technique for the starting line.
  2. Sail Shape: deeper sails generate more power. Flat sails generate less power and also create less drag. Depth is adjusted in a few different ways; sheet tension, forestay and backstay tension and lead/jib car position.
  3. Twist: A closed leech will generate more power where as a twisted, open leech spills power. Twist is controlled with lead/car position and sheet tension.


Always carry a wet notes pad to make notes onboard. Record everything from the conditions, rig tune, and sail trim, and be sure to include true wind speed and angle for reference. This will give you a foundation to base your decisions on, and provide a guide for making changes and improvements with your team.

Every line that can be adjusted needs a mark – use your marks to re-create settings that were fast. Aside from your sheets, think of your jib car position, in-hauler, outhaul, cunningham, halyards, traveller and backstay. These all affect the way your sails behave so try different settings until you find the sweet spot. Once you’ve found the groove, mark the line so you have a place to work from, and you know where to set it without hesitation.

When using an asymmetrical spinnaker, mark your sheet at the point where enough is pulled forward to prevent the windward sheet from going tight on the hoist. On a symmetrical chute, mark the guy so you know the foreguy/pole can still go up. Mark the inboard end of the pole on the mast so you can gybe as soon as possible if if you need to.

At the leeward mark, remind the pit person to hoist the jib and set the backstay to the mark you’ve made. This will allow for a smooth, clean mark rounding. Thinking about these things ahead of time allows the crew to focus on boat speed as soon as you round, while other competitors are struggling to get the set up correct for the next upwind.

Best Practices

The headsail trimmer should be constantly monitoring performance by using comparison tools onboard. Comparing your boat to other boats, target boat speeds and angles, how are “we” doing compared to just when we last made a change, and the feel of the boat. A good trimmer can feel a loss of power in the boat before it shows up as a loss of speed.

Take photos of your sails and send them to us so we can analyze the sail shape, compare them to new ones, and show you where improvements can be made.  It is much easier to do this in the pre-start routine and shouldn’t be done during the race.

Communication is key. Making constant trim adjustments to improve or maintain performance, the trimmer must also communicate the current state of performance to the crew, suggesting how to improve, and reporting progress as adjustments take hold. Constant communication will keep your team attentive and working together. For example, if you encounter a lull in pressure, it would be common for a trimmer to call for the backstay to be eased. The mainsheet trimmer knows he needs to ease the sheet and the jib trimmer will ease too, while the helm “falls off” [bow down] to help get the boat going again. Perhaps at the same time, the crew moves their weight to windward to help bear off.

Small efforts make a big difference in getting your boat back up to speed first. These constant changes or “transitions” in sail trim and crew weight placement can be the difference between the best and the rest.

Sail Changes

When conditions put you at a crossover between sails, a few extra factors come into play. Most notable are sea state, trending conditions, and past experience. In waves or chop you may opt to use the larger of two headsails for extra power when driving up and over waves. In flatter water a smaller sail can enable you to sheet harder and therefore point higher.

Consider the weather forecast and the conditions you have experienced up to the decision point. Are you anticipating the breeze to build up, drop off or shift? Also keep in mind that in a building breeze the sea state may remain flat, but in a dying breeze there will be leftover swell and power may still be needed.

As you gain experience with a specific boat and sail inventory, your notes on past performance will inform your decision on what sail to use. For example, in flatter water you may choose to use the J2 down to 8 knots, but as the chop builds, the J1 may be a bit faster with the slight increase in pressure. If time allows,  you can try both options before the race and choose based on how the boat feels when testing your straight line speed.

Never Relent

A trimmers job is never done. Don’t cleat it and certainly don’t hang out to leeward! The jib trimmer will be the last of the crew to the rail, so only stay to leeward if conditions allow.  Once the crew is fully hiked out, the trimmer should hike too, and take the tail of the sheet with you so you can ease quickly if you need to without leaving the rail. Keeping the boat flat in pressure allows the foils to do their job.

Source: NorthSails

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