Six Factors of Perfect Upwind Headsail Trim

It’s not news that headsail trim is about more than just pulling on sheets. Quantum’s experts outline six factors for mastering perfect headsail trim—no matter the conditions or the type of sailing—for both a better all-around cruising experience and a faster, more efficient boat on the racecourse.

The six main factors to consider when trimming the headsail are sail choice, sheet tension, lead height, sheet angle, headstay tension, and sail cloth tension. Balancing these considerations correctly will help both cruisers and racers perform and make your boat sing.

1. Sail Choice

Selecting the correct headsail is typically the first decision you need to make, often before you leave the dock and especially if you don’t carry your inventory with you. Depending on your type of sailing, you may not have a lot of sail options; however, sail choice is still important to consider. If you find you’re often leaving the dock without the proper sail, you might want to look into adjusting your sail plan and inventory. For many, particularly those on the high-performance side, you were either too conservative or made a bad call if you raced all day and carried a sail you didn’t use. It may seem like a small thing, but on boats such as Melges 32s, Fast 40s, or TP52s, an extra jib will cost at least one boat length per run. When cruising, unnecessary sails can take up valuable space and get in the way. Talk with your crew and make sure you have buy-in on the sails you’re taking; once you leave the dock, you have to live with your choices for the whole day or trip.

A bit of pre-planning can help you confidently judge the likely conditions you’ll encounter during your sail. If you’re racing, check the weather every morning instead of relying on a weather report or dock talk among the crew. Most apps or sources provide short-term forecasts and give a fairly accurate forecast based on current/recent observations. But always double-check the forecast the morning of your regatta or trip as it can change, even overnight!

If you don’t already have a crossover chart or an understanding of the ideal conditions for each sail, call a Quantum loft, and we’ll gladly walk through your inventory with you. There isn’t a one-size-fits-all rule for choosing the right headsail for your boat, so an expert’s guidance can help. For example, some boats prefer deeper headsails and some prefer flatter headsails. While a TP52 and Fast 40 look like similar boats, they are completely unlike in how they perform with different headsails. Err on the powerful side of headsails for a TP52, but with a Fast 40, you should pick a flatter jib if you’re not sure.

2. Sheet Tension

How hard you trim a jib depends on the shape of the sail, the amount of power the boat needs for the conditions, and the tactical mode you’re looking for. In lighter winds, you are generally looking for as much power as possible, and you can get this with a reasonably tight trim. A good rule of thumb is to trim the jib so that the top batten telltale is stalled about 10 percent to 20 percent of the time. In race mode, once the crew starts hiking, you want the leech telltales flying 100 percent of the time. As the boat becomes overpowered and the main trimmer starts to lower the traveler and twist the mainsail, you must start twisting the jib. Wait until the mainsail starts showing signs of backwinding and then start easing the sail.

Jib sheet tension has a huge effect on boat speed. If you’re not in VMG mode upwind, you may want some slight ease in the jib. There are a few ways to do this. One way is to ease the inhauler by moving the lead to an outboard position, generally a fixed pad-eye for racers and a toe rail for cruisers. If your boat doesn’t have these options, ease the jib sheet, but don’t ease it so much that it starts to luff in the top half of the sail.

3. Lead Height and Position

More often than not, trimmers will err toward having the lead too far forward or too far back, meaning the jib foot is too round or too flat. However, the lead position is actually dependent on the sail’s shape and age. If the jib is old and round in the back (Psst…a red flag that you need a new sail!), you have to be careful setting up the foot too far forward or too deep. This will cause the sail to carry more of the exit angle higher on the sail and you won’t be able to sheet the sail as hard. At the bottom of a jib’s range, you can power up the foot by easing, and at the top of the jib’s range, you flatten the foot and trim the sail a little tighter. Play around with lead position and sheeting angle, and try to make the telltales match from top to bottom. In windy conditions, it’s okay to have the top half of the sail luffing before the bottom of the jib.

Wave conditions also affect how you set up the sail plan. If the sea state is choppy, it’s best to power up the bottom of the sails and set up with a little more twist than normal. This provides a larger groove and the ability to foot off to maintain speed.

In puffy race conditions, it’s sometimes best to play the inhauler from the rail rather than coming off the rail to ease and trim the jib. If you’re in race mode and not hiking, you’re slowing down the boat! Don’t sit high side with your legs out, thinking about the next adjustment or waiting to make the next change. Always be actively trimming.

4. Inhaul and Sheet Angle

A general rule of thumb is to carry the tightest sheet angle in lighter winds and open it up in stronger conditions. There are no magic numbers on sheeting angles; just think about trying to match the twist profiles of the jib and mainsail as closely as possible. Larger boats can generally get away with tighter sheeting angles than smaller boats can. But just because you see photos of TP52s racing with two-degree sheeting angles, it doesn’t mean it will work on your boat. Some boats need to start out wide after a tack and then slowly work the lead angle in. Try different sheet angles and learn the limits of the sheeting angles your boat can handle.

Consider carrying a tighter sheeting angle when you’re off a start line, especially if there is a boat to leeward. In flat water, you can always get away with a tighter sheeting angle than in normal choppy conditions.

Keep in mind that the sheet angle is one of the biggest throttles on the boat. If you need to go into fast forward mode or true upwind, VMG is less important than boat speed. Just as dropping the mainsail traveler makes the boat go faster, the jib lead outboard speeds up the boat.

5. Headstay Tension

Proper headstay tension is dictated primarily by the mainsail shape. However, if your jibs are designed with a proper luff curve and the mainsail is set up to a target depth, a tighter headstay is almost always faster. Anytime you sag the headstay, you need to ease the leech to maintain the same twist angles in the jib. The tighter the headstay, the tighter you can trim the jib and maintain acceptable twist and less return on the exit angles. Work with the mainsail trimmer to carry the tightest headstay possible while maintaining the appropriate depth and twist in the mainsail.

6. Jib Cloth Tension (Luff tension, halyard tension, jib Cunningham)

The cloth along the length of the luff controls both depth and draft position. Some boats adjust the cloth through halyard tension, while others use a jib cunningham (tack) control. Trimmers often don’t use enough cloth tension, especially as sails age and become stretched out, and assume the best set up with a new sail is to leave some wrinkles in the luff. That may be true if the designer nailed the shape of the sail perfectly (such as a highly refined one-design sail), but for most rigs you have to look carefully to make sure you’re setting up the draft in the correct location. It never hurts to take a look at the jib from the foredeck to make sure your eyes are calibrated and the draft is appropriately placed. In general, you want the draft at about 30 percent in the bottom of the jib and between 35 percent and 40 percent forward in the top half of the jib.

As sails age, you need to carry more cloth tension to keep the draft forward. On modern keelboats with plenty of righting moment, the sail plan creates upwash (lifting or bending the apparent wind angle of the onset flow of wind) that allows entry angles of about 55 degrees relative to the centerline, even though the apparent wind angle in the middle of the sail plan is likely 20 degrees to 22 degrees. There is little relationship between the angle of the jib entry and the angle the boat sails upwind. The more lift a sail plan creates, the more upwash. To sail higher, pull the traveler up high, sheet the mainsail on, and create as much power as possible without slowing down the boat too much.

Trimming the headsail can be rewarding. It challenges you to get creative and continually evaluate how to sail the boat at top performance. That doesn’t mean only sailing fast as a racer; it also means sailing comfortably during that peaceful sunset cruise. Working closely with the mainsail trimmer and understanding and correctly balancing these six variables should result in a boat that’s easy to sail fast and a better experience all around.

Other helpful resources for optimizing trim:

The Lowdown on Headsail Options

What You Need to Know About Rig Tune & Performance

System Sailing Collection

Trim Guides for Cruisers: Mainsail & Headsail

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The Discussion

Ted Drossos
Ted Drossos

On Feb 15, 2019, Quantum’s Chris Williams wrote an article detailing the six important factors needed to get perfect headsail trim for the conditions. There is a portion in the second section about sheet tension where he discusses telltales on the leech of the jib. "I try to trim the jib so that the top battens’ leech telltale is stalled about 10 to 20 percent of the time. In race mode, once the crew starts hiking, you generally want the leech telltales flying 100 percent of the time." The example describes a jib with battens which leads me to believe that he is referring to a non overlapping headsail. I race a masthead rigged boat (C&C 110) with overlapping headsails. I don't have leech telltales on my headsails and was wondering if they would be as useful on overlapping masthead genoas as they are on a non overlapping fractional jib?

Hi Ted, there are more factors with a genoa due to the spreader lengths. I think they maybe useful, but you may also find that the shrouds rip the tell tales off pretty quickly when tacking. Generally the wider the spreaders the more your tell tales will likely fly often and the narrower your spreaders the easier the tell tales will be to stall. Similarly, on some yachts, you trim the genoa very hard against the top spreader and keep trimming to pull the middle of the sail into the rig. If this is the case having a tell tale in the top will not indicate how hard you need to stretch the genoa around the rig. I imagine on a C&C 110 you don't need to sheet this tight- so it maybe worth experimenting with.

Ted Drossos
Ted Drossos

Thanks for the reply Chris. I'll try experimenting with some leech telltales this season. Maybe the rod rigging won't rip them off so quickly.