Sail-Shape Controls: What Does What

Erik Shampain covers the basics of sail controls and their respective cause and effects.
Etchells crew
The Etchells is hypersensitive to subtle control changes, requiring a top crew to constantly adjust and evaluate when switching between modes. Paul Todd/

After a successful day of one‑design racing, I’m often asked: “What base numbers do you use?” and “What were your rig settings today?”

These are common and valid inquiries, and like tuning guides, they’re a great place to start when initially setting up your boat. But at the end of the day, your better-than-average speed usually comes down to knowing how to adapt, on the fly, to changing conditions. It sounds pretty simple: First, identify the problem—inability to point, lack of speed—and then look critically at your setup to find a solution. But there’s a lot more to it than that.

Let’s start with a basic ­principle: A boat is either looking for power, in perfect power or overpowered. You must be able to recognize which is the case in order to figure out which changes to settings must be made to improve your speed and VMG. From there, you must understand cause and effect: “If I adjust this, then that happens.”


Make sure you’re clear about what each control does and how it affects the sails, the boat’s balance, and thus, VMG. Remember, for the most part, only slight adjustments are needed to make a change. Following the KISS (keep it simple, stupid) rule, here’s a quick guide we use on our Etchells, but much of it is applicable to other boats.

Better-than-average speed usually comes down to knowing how to adapt, on the fly, to changing conditions.

Traveler: Changes power by adding or reducing heel and changes weather helm. It can add drag to the sail plan if too high.

Mainsheet: Changes power by adding or reducing heel and weather helm. Also tightens the forestay because the mainsail’s leech shares some load with the backstay.


Cunningham: Depowers the mainsail as it pulls the draft forward, thus flattening the sail aft. Generally reduces drag and removes “overbend” wrinkles from excessive backstay.

Outhaul: Changes the mainsail camber down low. Increases or decreases power and drag.

Backstay: Changes the ­mainsail cambers more uniformly. It also changes the twist in the mainsail leech as the mast bends. It can rapidly affect power, which is helpful when increasing or reducing heel. It also tensions the headstay, which controls power in the jib.


Jib sheet: Changes leech ­tension while also slightly changing the cambers. Be careful not to ease the sheet too much, or you can make the top flatter with twist while keeping the bottom to full.

Jib lead: Changes depth and power in the jib, mostly in the bottom two-thirds. It changes twist, so make sure you check the jib leech after adjusting the leads.

Jib halyard: Similar to the ­cunningham, it changes the draft position and overall depth of the sail. Beware that as you tighten the jib halyard, the leech can get tighter, reducing twist.


Inhaul: Changes the proximity of the jib leech to the mainsail while also changing the angle of the jib to the wind, allowing you to point higher when used. If you are overpowered and the mainsail is depowered to the point that it luffs, let off the inhaul until the main settles down.

Jib tack (cunningham): Tightens luff by pulling draft forward, and flattens the back of the sail slightly. It can also ­create a small amount of twist.

Mast ram: Changes the ­cambers of both sails. It bends the mast down low. In the mainsail, it affects fullness in the lower sections, and in the jib, it affects headstay tension. Letting the mast bend farther causes the headstay to sag farther.

Let’s now take a look at these adjustments in action on the course. You’re going upwind shortly after the start in a tight lane, and you need to sail a little higher to hold that lane. Accept that you will go a little slower by sailing higher. If it’s windy and you are overpowered, you can generally sheet a little harder on both sails. That increases power, but by sailing higher to the wind, you are reducing power. Generally it will be a small net loss in VMG as you sail slightly higher and slightly slower, but you will hold your lane, which will ­net-gain you VMG later.

In some cases, such as in flat water where there is little chop or waves to slow you down, you can simply sail higher and flatter to achieve this mode without changing anything. While you decrease power in the sail plan by sailing higher into the wind, you also reduce leeway because the boat will be sailing flatter. If the power is perfect and the boat feels balanced, a tiny pinch in on the jib and either a tad of traveler up or mainsheet tension will do it. Pulling the traveler up or tightening the mainsheet adds power to the back of the sail plan, making it easier for the boat to head up.

In chop or waves, mainsheet on often works well, but when it starts to get bumpy, traveler up is better because you often need twist in the main to help reaccelerate after hitting a wave.

If the boat is underpowered, ease the backstay. This will round up the sail plan in both sails, creating more weather helm, making it easier to head up. As the backstay is eased, the main leach gets tighter and the sail gets fuller. It also adds sag to the headstay, which results in additional shape and power in the jib. Pro sailor, Steve Hunt, a four-time Etchells champion, cautions that the backstay and mainsheet always go hand in hand; if you adjust the backstay, immediately consider adjusting the mainsheet.

The backstay and mainsheet always go hand in hand; if you adjust the backstay, immediately consider adjusting the mainsheet.

Now that you’ve held your lane and are now free to go anywhere. The left side of the course is favored, so you need to sail “fast forward” to the left. This is accomplished by sailing slightly lower but faster through the water. It’s a similar VMG to the mark, but it gets you the positioning farther to the left side of the course. If overpowered, add backstay and let the traveler down. Just “lay” on the jib slightly, making the leeward telltales start to dance. Easing the traveler and pulling on the backstay will reduce power and drag in the back of the sail plan, allowing the boat to bear away slightly without healing over more. That results in a faster lower mode. If the power is perfect, just the smallest change is needed. Ideally, keep the same amount of heel. If the power is perfect, you likely don’t want to change the backstay and negatively affect the jib. In this situation, a little traveler down works well. Simply bear away and reduce the drag in the main ever so slightly.

If you’re underpowered, you can try simply bearing away slightly. Then the boat will heel somewhat and likely accelerate. Make sure that the jib isn’t sheeted too tightly or it might stall. A small ease of the mainsheet can also help; it will help increase headstay sag, thus powering the jib up even more.

Second Opinion

Andrew Palfrey, a two-time Etchells World Champion, Star Olympian and grand-prix coach, offers these tips for better upwind speed.

Balance and power, in harmony, are key. Keep in mind the vertical distribution of power, particularly when overpowered. For example, in higher true windspeeds, keep depth and driving force low in the sail plan to get through waves, while ensuring that the upper part of the sail plan is all about reducing drag.

Develop a tuning guide specific to your boat. Every boat will have a slightly different balance due to the slightest difference in the underwater foils.

Invest time (and even some money) on the basics of accurate foil and mast alignments. This is the building block of consistent performance. This is my primary focus when I am involved in a new build.

It is getting easier these days to quantify fast sails (and even rig to foil alignment) digitally. If you are high and fast, take a photo of both sails and the major controls, such as the backstay, traveler and inhaul. Simple apps to analyze sails such as the SailCloud are available for a fee. It is no longer the realm of only the sailmaker or pro coach. This will really help when you get your next new sail. Compare the two scans, and you are in a much more informed position to make any changes to mast setup or to discuss things with your sailmaker. Get facts and data before opinion.

When moding one way or the other, too often people overreact. If moding fast-forward in a boat like an Etchells, aim for only a 1 to 2 percent increase in forward speed. This is the slightest press into the jib, with the major controls sympathetic to the mode. Otherwise the resultant heel and change in balance will have a negative effect.

Keep asking questions—that is what the best sailors do.