The short version
- The big three
- Mainsheet (how hard the sail is pulled in, and how tight its back edge is), vang (holds the boom down), cunningham and outhaul (how deep or flat the sail is).
- Light air
- A fuller sail with a slightly open back edge: outhaul and cunningham eased, vang just slack, sheet eased a touch.
- Medium air
- Full power: sheet in hard, vang snug, outhaul moderate, cunningham just taking the wrinkles out.
- Heavy air
- Depower: everything tight — cunningham, outhaul and vang hard on — and ease the sheet in gusts rather than letting the boat heel.
A word about "wind" in this guide. Your sails, and every telltale on the boat, respond to the apparent wind — the wind you feel on a moving boat, which is stronger and further forward than the true wind upwind, and moves with every puff and lull. See true wind vs apparent wind.
A singlehanded dinghy — a Laser/ILCA, an Optimist, a Finn, a Sunfish or something like them — has one sail doing everything a jib and main share on a bigger boat. That makes the mainsail controls the whole game. This guide is about upwind trim, where most of the difference between boats shows. It describes what each control does in general; your class's own tuning guide will have the exact numbers.
Classes differ. Not every boat has every control below, and some classes limit what you can fit or adjust. Check your class rules and your class association's tuning guide before you change your rig.
What each control does
| Control | What it changes | Pull on to | Ease to |
|---|---|---|---|
| Mainsheet | Boom angle and, upwind, how tight the leech (back edge) is | Point higher, close the leech | Open the leech, spill power, foot faster |
| Vang (kicker) | Holds the boom down so the leech stays tight when the sheet is eased | Keep leech tension in a breeze; bend the mast on some rigs | Let the sail twist and the boom rise in light air |
| Cunningham | Tension along the luff (front edge) | Pull the deepest part of the sail forward, flatten it, open the top | Let the sail be fuller with the depth further aft |
| Outhaul | Tension along the foot (bottom edge) | Flatten the lower sail — less power, less drag | Make the lower sail fuller — more power |
| Traveler, where fitted | Where the boom sits side to side without changing leech tension | Bring the boom toward the centerline | Let the boom out to depower without twisting the sail open |
Leech: the back edge of the sail. Luff: the front edge, along the mast. Foot: the bottom edge, along the boom.
Twist: the idea behind all of it
Look up the sail from the boom and you'll see that the top usually angles further out than the bottom. That's twist. More twist spills wind from the top of the sail, which is where it heels the boat most; less twist makes the whole sail work hard and lets you point.
On a boat with no traveler, the mainsheet does two jobs upwind: it pulls the boom in and pulls it down. Once the boom is as close to the centerline as it will go, more sheet just tightens the leech and reduces twist. That's why heavy-air technique leans on the vang: with the vang holding the boom down, you can ease the sheet in a gust and the boom goes out instead of up, so the sail depowers without flopping open.
The mainsail leech telltales are your twist gauge. In medium air, aim for the top one streaming most of the time and folding behind the sail now and then. See how to use telltales.
Light, medium and heavy air
Light air — build power and keep the flow
- Outhaul eased a little for a fuller lower sail, more in waves, less in flat water.
- Cunningham off — small wrinkles along the luff are fine.
- Vang just slack, so the sail can twist open and the air doesn't stall leaving the top.
- Sheet eased slightly from where you'd have it in medium air. Over-sheeting is the classic light-air mistake: the boat looks pointed but stops.
- Sit forward and keep movement smooth. Heel the boat slightly to leeward so gravity holds the sail in shape.
Medium air — full power
- Sheet in hard, so the boom is close to the centerline and the top telltale only folds behind the sail occasionally.
- Vang snug, taking up the slack once you're sheeted in, so the leech holds when you ease in a puff.
- Outhaul moderate, cunningham just enough to remove the luff wrinkles.
- Hike to keep the boat flat. This is the wind range where the boat is fastest with everything working.
Heavy air — depower and stay flat
- Cunningham hard on. It pulls the depth forward and opens the top of the sail.
- Outhaul tight, for a flat lower sail.
- Vang tight, so you can work the sheet in gusts without the boom lifting.
- Play the sheet: ease a little as a gust hits, sheet back in as it passes. Keeping the boat flat is faster than holding the sheet and heeling.
Depowering in the right order
As the wind builds, the order most coaches teach is: hike harder first, then flatten the sail, then twist it, and only then ease. In practice that means cunningham and outhaul before you start easing the sheet a lot, and the vang tight before you need to play the sheet in every gust. If you're easing the sheet so far that the sail is flapping half its depth, the sail is too full for the wind — pull on more cunningham and outhaul.
Class by class
These notes cover the controls each type of boat usually has. Exact settings — outhaul marks, mast rake, vang tension — belong to your class tuning guide and change between rig sizes.
- Laser / ILCA. No traveler adjustment while sailing: a rope traveler under the boom is set tight. Upwind in medium and heavy air sailors usually sheet until the blocks are close together and use a lot of vang in a breeze, sometimes called vang sheeting. The cunningham does a lot of the depowering, and the outhaul changes the lower sail a great deal.
- Optimist. A spritsail: the sprit pole sets the tension from the peak of the sail to the mast, and the luff ties set the luff's shape along the mast. Vang, outhaul and sheet work much as above. Diagonal wrinkles across the sail usually mean the sprit tension is wrong.
- Finn. A flexible, unstayed mast, so the vang and mainsheet bend the mast and flatten the sail as well as controlling the leech. Mast setup matters more than on most dinghies.
- Sunfish and lateen rigs. A different shape of rig: two spars, the sail laced to both. The outhaul, the position of the gooseneck along the boom and where the halyard is tied on the upper spar change the sail's shape. Many boats have no vang as standard.
Doing it with Sail Tactician
Trim is something you feel, but you can check it with numbers — as long as you change one thing at a time.
Questions
What does the vang do on a dinghy?
It pulls the boom down, which keeps the back edge of the sail tight when you ease the mainsheet. That lets you let the boom out in a gust to depower without the sail twisting wide open.
When should I use the cunningham?
When the wind is strong enough that you're struggling to keep the boat flat. Pulling it on moves the sail's depth forward, flattens it and opens the top, all of which reduce power. In light air leave it off.
Should the outhaul be tight or loose?
Loose for power in light air and waves, tight to flatten the sail in strong wind. In between is a medium setting your class tuning guide will give as a measurement.
How do I stop a Laser or ILCA heeling in a gust?
Hike hard, have the cunningham and vang on before the gust arrives, and ease the mainsheet a little as it hits so the boom goes out rather than the boat going over. Sheet back in as the gust passes.
Sources
Standard singlehanded-dinghy trim as taught in club and youth racing, in general terms only — class association tuning guides give the exact settings for each rig. Sail Tactician behavior from the in-app User Guide and training guide, version 3.2.
What changed
- First published.
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