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**Novice Sail Trim**
Published 2023-06-03; Updated 2024-06-24
This sail trim guide is for novice sailors in less than 15 knots of wind. As a skipper, novice means that you're comfortable sailing a dinghy or small keelboat on your own as described in the 10 Easy Steps guide and are familiar with the Essential Line Handling Techniques. Now, you want to improve your sail handling beyond intuition for more speed and control.
As crew, novice means that you are comfortable on the boat and engaged as an active participant, having been briefed by your skipper on terminology and expectations. That could be as soon as your first day on a boat, or take a few trips to build the comfort level. For crew, this guide is good for moving beyond blindly following the skipper's instructions to have autonomy and understanding in sail adjustment.
If already you've mastered the techniques in this article, then my Intermediate Trim guide may be more appropriate.
There's a lot more to effective sailing than sail handling. Steering, navigation, ballast management, mooring, rig adjustment, race strategy, and boat maintenance are all key skills. However, if you're day sailing in a small boat, or crewing for someone else, then sail handling is one of the first skills you'll want independent ability in.
Furthermore, it may be surprising that this article is the equivalent of 11 pages almost exclusively on how to adjust a mainsheet in moderate wind. This should underscore how important it is. Optimal mainsail angle of attack is the base learning for all other sail trim. It is also the most significant area of potential improvement for most sailors.
Look at the sail while sailing. That's how you know when it needs to be adjusted and learn how it reacts to different conditions.
Look at the sail when adjusting it. Do not look at the control line or other boats while adjusting a sail. The primary feedback all comes from the sail. This includes while raising a sail with a halyard.
When performance day sailing and racing, I spend about one third of my time looking at the sail. That's usually looking at the sail for four seconds and then spending about eight seconds looking at other boats, the horizon, and water. I occasionally glance around checking on systems and people in the boat. I only ever look at lines to verify that they are untangled, cleated or uncleated properly, and not chafing. I always look at the sail and never at lines while adjusting them unless they are jammed, or in the special cases described below.
(There are a few exceptions for experienced sailors who are racing. In a dinghy, racers can feel the impact of their adjustments. They will depend more on feel than vision to use their eyes for watching other boats and the marks in close quarters at a start line or mark rounding. For very large adjustments, including changing points of sail and switching to a spinnaker, they will also use marks drawn or taped on the lines help them consistently hit their same base trim before making fine adjustments. By definition, none of this applies to novices, but it is something to look forward to!)
When sailing with the wind coming from front or mostly beside the boat, the sail acts as a vertical airfoil. Adjust the sail's angle of attack using the sheet until the sail is about 5 degrees trimmed in from the barely luffing point. Most new sailors overtrim, especially when sailing upwind and heeling. Just ease the sail until the luff point and then bring it back a bit.
When the wind is coming from behind the boat, the sail is a big drag parachute. Downwind, ease the sheet to catch as much wind as possible. The jib does very little downwind, which is why more experienced sailors may fly a spinnaker.
Bits of yarn or ribbon called tell tales that are taped to the sails can help be an early warning system for trim adjustments. They are taped in both sides of the sail with a slight offset. The inside tell tale is the one that you can see directly, on the windward side of the sail. The outside tell tale is the one that you can only see dimmly through the sail, on the leeward side of the sail.
These are like flags, so they should stream backwards along the sail when both sides are receiving correct amounts of wind. If one of them "breaks" and is not flying straight backwards, then move the sail in the direction of the broken tell tale to give that side of the sail more wind. When the wind is light, tell tales may not be reliable. The yarn ones especially tend to get stuck to the sail.
There are various mneumonics for sail trim, all of which are a bad idea to fuss with. The tell tales are showing you the wind pressure directly--just move the sail into it--and the sail luffing lets you know when something is really wrong.
Always hold a sheet like a microphone, with the working end towards the sail coming out of your fist by your pinkie and the tail end coming out by your thumb. This lets you use your bicep to do most of the work (instead of lower back) and gives a large range of motion. It also avoids the risk of index finger and thumb being caught in a block or winch.
Try to hold the a sheet with just enough pressure that it does not slip from your hand. (The same advice applies to a tiller or wheel.) A tight deathgrip is fatiguing, but also reduces your ability to sense a change in pressure that is valuable feedback.
Never wrap a sheet around your hand to get more purchase. It can be hard to release in a dangerous situation, risks rope burn, and can pull your hand into a dangerous position or trap you if falling overboard.
Consider wearing fingerless sailing or biking gloves to reduce chafing on your hand and improve grip when wet.
Keep your hand well back from a cleat, winch, or block. Especially when releasing a cleat, the line can jump forward.
 A cam cleat has two rotating jaws that the line is pulled down (or for some mainsheets, up) between to lock in place. These are frequently used to reduce the strain and free up a hand for a sailor on sheets. When releasing, you must both pull in and up (or down) from the cleat. This can be difficult when sitting on the rail/gunnel. With a little practices, you can learn to flick slack in the line down so that it releases when it hits the cleat and does not require leaning in over the cleat.
For more information about winch operation and preparing sheets, see the rope skills guide.
I discuss more sail controls for shape in the the intermediate sail trim article. These controls are essential for high performance and stronger wind conditions, but can be neglected as a novice focusing on the sheets. For a novice level, reasonable settings and amount of understanding are as follows.
The cunningham (mainsail downhaul) adjusts luff (front edge) tension. Leave it off in light wind and progressively tighten it for stronger wind to help the boat point higher upwind.
The halyard also adjusts luff tension, and is used in the absence of a cunningham. Raise your halyard all of the way on any sails as a novice. Be careful to not overtension once the sail is at the top; you're just straining the part of the line after the top block and potentially jamming your sail at that point.
The vang adjusts leech (back edge) tension and flattens the mainsail to reduce power in higher wind. Keep it only just tighter than sagging to prevent the boom from riding up in gusts downwind and provide some shape upwind. On a dinghy, tighten more upwind in strong conditions.
The outhaul adjusts foot (bottom edge) tension and flattens the mainsail. In a keelboat, bring it back to the marked line. In a dinghy, seek about 20cm of space between the mainsail and boom when upwind. Loosen in light wind and when sailing downwind. Tighten to 10cm in stronger wind, but do not flatten all of the way or you won't have good acceleration and control upwind.
The traveler allows independent control of the angle of attack and leech tension with the mainsheet. Leave it centered as a novice.
Jib cars control the leech of the jib upwind. Leave them centered as a novice, although bring them forward when reefing (which is not really a novice situation!)
Leech lines control the leech of the sails and are typically set just after raising sails. They are also convenient for helping keep shape in older sails. Ignore them as a novice and just ensure that they aren't loose and able to catch in anything.
Stay tension and mast rake are very advanced controls. If your boat has stays, have someone else adjust these for you once to a level that is safe for the rig, and then ignore them until you've mastered the other elements. The exceptions are dinghy forestays (which in a boat like a 420 is the wire through the jib luff, not the wire used to retain the mast on shore). In many boats these must be set every time it is sailed. Refer to the manual and trim guide for your boat to determine appropriate tension in this case.
If you want to begin experimenting more, start with the traveler as it is the easiest control to understand. The traveler lets you separate the downward and inward pull of the mainsheet when sailing upwind. Adjust it to keep the mainsheet roughly vertical until it goes beyond the traveler track, at which point the traveler will be released nearly to the end on that side. Avoid pulling the traveler past halfway when close hauled.
When the boat passes from close hauled on one tack through head to wind to close hauled on another tack, the sail switches sides after luffing and the maneuver is called tacking.
Tacking is potentially difficult to achieve if there is very strong or very light wind, in which case the boat may not make it through the tack and can become stuck in irons. It is generally considered safe because the sail naturally loses power in the middle of the maneuver, so the forces are minimized and easy to control.
To avoid being stuck in irons when tacking, tack decisively and with some speed on. If pinching into strong wind or while racing, you may even need to turn away from the wind a bit to accelerate enough to make a clean tack.
Move the rudder significantly, but not all of the way to the stops because it will add too much drag. Hold the rudder in place until the boat is nearly pointed to the new tack, and then ease it back towards the center. Larger and heavier boats take some time to respond to rudder inputs both entering and leaving the tack, so anticipate to avoid overcorrecting on each end.
The mainsheet does not need to be adjusted during a typical tack from close-hauled on one side to the other side, because the trim will be the same.
The sheet of a self-tacking jib does not need to be adjusted during a tack. This is the point of a self-tacking jib.
A traditional jib with separate sheets needs to be brought across. The new trim will be the same as the previous one, but on the other side. For a basic tacking maneuver, wait until the jib luffs. Release the previous working jibsheet, and then pull the jib around as the wind blows it through and trim in quickly, before it fills with wind and gets difficult. In less than 15 knots of wind on any boat less than 40', anyone should be able to get the new working jibsheet mostly trimmed without using a winch. Pulling directly without cranking is much faster and easier. As the jib loads up with wind on the new tack a winch is then required on most keelboats to finish the trim.
If the jibsheets catch on the mast, do not immediately go forward to clear them. Leaving the cockpit suddenly can be dangerous, especially during a maneuver. Instead:
- Wait a second to see if it blows free by itself.
- Try flicking one or both sheets to move a hump of slack towards the obstruction.
- Try pulling on the old working sheet to bring the clew back past the obstruction and release it.
- Notify the skipper of the problem. They may choose to turn the rudder back instead.
- If still stuck, discuss the situation with the skipper instead of taking action without coordination. They may direct you to go forward, or have a safer solution.
Clearing a line that is jammed under tension can be dangerous. It will move suddenly with potentially great force when released, possibly hitting the person who cleared it or catching and dragging them. Fingers can get trapped between the line and the obstruction. Treat these situations with the gravity that they deserve.
If the boat loses too much speed during the tack, it will "miss stays" and end up "in irons," with the sails luffing and no steerage. The most reliable way to recover in this situation is to backwind the sails.
Holding the mainsail out on the new side and steering backwards will help the boat complete the tack. If a headsail is available, it can be backwinded on the same side it was previously on to help push the bow around.
On some boats, holding the jib backwinded for a moment on every tack can help them pull through the tack faster even if they are going to succeed without it.
When a boat is stalled within the no sailing zone but has successfully passed head to wind, sculling with the rudder or rocking the boat may help it complete the tack. Even in racing, sculling is permitted if stuck above close hauled to get back onto a close hauled point of sail.
A boat generally loses speed during a tack. The better it tacks, the less speed lost. Sail handling techniques can improve performance.
Headsails apply their force ahead of the mast and turn the boat off the wind. The mainsail applies force behind the mast and turns the boat into the wind. To sail straight, these must be roughly balanced, with the rudder compensating for the remaining weather helm. To turn into the wind quickly, ease (but do not luff) headsails and slightly overtrim the main to intentionally unbalance the sail plan without creating excess rudder drag.
Overtrimming the main on a catboat or a boat with headsails will also increase heel. Except for skiffs, allow the boat to heel for a tack by bringing crew weight in. This changes the hull shape relative to the water. The asymmetry causes the boat to head up into the wind faster. Once through head to wind, keep the boat flat so that the hull isn't fighting the rotation of now falling off the wind.
On a very broad tack when moving to or from a point of sail other than closehauled, continue trimming the sails throughout the tack. This keeps the lift forces active and reduces the drag forces of a luffing sail. A sailboat can't turn unless it is also moving forward relative to the water.
Dinghies can roll tack by greatly exaggerating the ballast movement and heeling to maintain speed through a tack:
- Initiate the tack by creating excess heel. Slightly overtighten the main and shift ceew weight leeward, probably to the center of the boat as it will already want to heel without crew hiking. Bury the leeward gunnel in the water.
- Remain/return to the original windward side until the boat has passed head to wind so that the heel angle pulls the luffing boom down over the crew's heads (whose seats may get wet).
- Stand up and quickly cross the nearly vertical cockpit to the the new windward rail and hike hard. This will rapidly bringing the mast up through the air and fill the sail. Do not create windward heel; the goal is to flatten the boat and the mast should never move beyond vertical.
If done correctly, the boat will exit the tack with the same speed that it entered. It is possible to exit faster than entering because that final roll can accelerate the boat with the strong apparent wind from the mast rising. Leaving a tack or gybe faster than it was entered in a race is illegal under rule 42.
For lightweight boats with relatively flat hulls, roll tacking loses its advantages in stronger wind. When racing, I generally don't roll tack a Laser above 10 kts of wind. Keeping on a plane right into the tack and maintaining good control is more important than that burst of apparent wind. In an RS Aero I don't roll above 5 kts, and in a skiff one never rolls.
When the boat passes from running on one tack to running on the other tack, that is called a gybe (also spelled "jibe"). The sail never luffs in this case. It is powered on one side and then suddenly powered on the other side.
Gybing is easy to accomplish because there is never any loss of power. In fact, it is too easy. It is potentially dangerous because there is never a natural reduction of force and the sail and boom can come across the boat very fast and when the crew is unprepared.
To maintain control during a gybe, bring the mainsail into the center of the boat just before turning the rudder. Then, ease it back out on the new side, rather than letting it crash on its own. In light wind, you can instead grab the mainsheet directly on the way to the boom and move it from one side to the other to force the sail to gybe. When gybing, the boat generally maintains speed.
Avoid a surprising crash gybe through vigilance when sailing downwind. Attend to incoming changes of wind direction and continuously watch the back edge of the sail to see if it is curling and about to move. In very strong and changeable winds, avoid sailing directly downwind entirely.
Dinghies can roll gybe, using similar tactics for the roll tack. The critical issue on the gybe is to ensure that the boom does not hit the water when it crosses, which can broach the boat.
There is no need to be afraid of gybing. Control the main and only sail in conditions that you can handle. Bring the main across intentionally by throwing it in light wind and centering it in heavy wind. The forces will never be overstrong and you will always have control of the boat.
Accidental gybes on large keelboats are prevented with boom brakes or preventers, and on smaller keelboats and dinghies with vigilance. Most boats sail slowly dead downwind and will spend most of their downwind time on deep reaches instead of directly running, in the case where gybes might occur. On a small boat, if you're looking at the incoming wind on the water and at the sail, and attending to the feel of the boat and the helm, then an accidental gybe is unlikely.
In a small boat, if the conditions make you afraid to gybe then you should return to shore. The maneuver should never be uncontrolled and thus hard and dangerous. If it isn't safe to gybe, then it isn't safe to sail.
If you're concerned about gybing in a large boat, that is one sign that you need to reduce sail by reefing. Only in storm conditions with exceptional wind and strong waves should it be necessary to fall back on a "chicken gybe" by tacking around 270 degrees instead of gybing.
Moreover, I've sailed some boats that are hard to tack in very high or very low wind. Gybing is a way to maintain speed and control of the turn and avoid getting stuck in irons. While we rightly fear a strike from the boom during a gybe, in high wind a controlled boom during gybe may be safer than an uncontrolled boom swinging wildly in wind and waves when stuck in irons during a failed tack.
The wind in the absence of a boat is the true wind, as distinguished by the apparent wind that the boat perceives in its own reference frame.
Wind is described by the direction it comes from. An East wind blows from East to West. If it is a due East wind, then facing at 90 degrees on a compass is facing into the wind.
Wind speed is measured in knots, abbreviated kt or kts. 1 knot is one nautical mile per hour, where a nautical mile is one degree of latitude. That's about 1/24000 the circumference of the Earth.
10 kts is about 11.5 mph and 18.5 kph. So, the speed in knots is slightly higher than in mph and a little less than double the speed in kph. This is important to know because your forecast may be in different units.
The power of wind rises with the cube of wind speed. For example, the difference between 5 and 10 kts is about the same as the difference between 20 and 21 kts. This means that the exact wind speed is more important to attend to in strong conditions.
A moving boat experiences apparent wind. Because the boat is moving, the wind always seems to be coming from a direction slightly more rotated towards the boat's own course. When sailing upwind, this makes the wind seem stronger, and when sailing downwind it makes it seem weaker. The presence of headsails also redirects the wind experienced by the mainsail.
There are two important and common implications of apparent wind. First, as a boat accelerates upwind or on a reach, the sails must be adjusted (by trimming them in) to account for the new relative direction of the wind. Second, it is easy to underestimate the wind strength when sailing downwind. Sailors must be aware of this in moderate to high wind to stay within a safe and controllable margin downwind, and also to avoid being surprised when later turning upwind.
There are also some interesting uncommon implications for very high performance boats such as racing catmarans and foilers. These include limitations on downwind sailing speed and effectively sailing upwind when on a deep reach relative to the true wind.
Wind is not constant. It changes direction and strength continuously throughout the day in predictable ways, and shifts on a scale of every few minutes in many areas in unpredictable ways. If there are large landforms or buildings--or other boats--nearby, they will also block or redirect wind.
Wind is created by temperature and pressure differences. Near the surface it is slowed by land features such as trees and hills, and funneled to greater strength by large features such as rows of buildings and mountain passes. Over large flat farmland or meadows, and large bodies of water, it proceeds unimpeded and can build to greater strength.
Good sailors always look at a forecast before sailing to know the approximate conditions and general way that they will change while sailing. Then, while sailing, they continuously attend to wind strength, direction, and incoming weather visible in the sky.
You can tell which way the wind is blowing by looking at flags, loose hair, windvanes, and trees. If you are ever very confused, simply ease your mainsheet and the front of the boom will point into the wind. Many boats have a wind indicator (windvane) on the top of the mast, or pieces of yarn tied to the stays to help visualize the local wind direction.
Look for signs of small changes in the wind strength and direction. You can see these by watching the movement of dark patches on the surface of the water, as well as by watching other sailboats. The patches are easier to notice when wearing polarized sunglasses that cut the glare. If there is a large glassy patch of water, that is smooth and has little wind. If sailing near buildings or cliffs, beware of ways that wind may bend significantly near them.
A gust of wind is a sudden, short-lived increase in wind strength. It often comes from a different direction than the average wind. A puff is a small gust, shorter and weaker. A lull is a time where the wind is reduced. A hole is the area where the lull is occuring. To sail fast, link together puffs and avoid holes, focusing on where you can sail effectively near your desired direction rather than sticking to a specific straight line course.
On a day with large scattered clouds, the shadows of clouds traveling across the water correspond to areas of slightly different temperature and can sometimes be used to predict puffs and lulls.
Periodically check the sky at the horizon in the average direction of the wind. That's where new weather will come from, including rainstorms that you should keep an eye out for. When a rainstorm arrives, it will usually be extremely windy right before it hits, and then the wind will die within the rain and remain light afterwards. Large towering clouds are thunderstorms. Day sailors seek to get off the water before storms arrive and create the danger of lightning.
In shore areas on the ocean (and great lakes), the wind will reverse direction during the day between sea breeze and land breeze due to their relative temperatures.
Here's a rough guide to the implications of various steady windspeeds for 25 degrees C air, average humidity, on bay or inland waters for sailboats under 35', and in moderate current and low traffic situations. Those details are important because changes to them can affect how much wind a boat and crew can handle. Cold air is denser and thus more powerful at the same speed than warm air. Larger and heavier boats need more wind to accelerate them. Areas with unprotected ocean sailing, strong current, heavy marine traffic, and cold water require more caution than described here because of their inherent risks. The nature of the wind greatly affects navigation: is it steady, gusting from the same direction, variable and gusting from multiple directions, or blowing with or against the current? So, what is reasonable at 15 kts of wind on one body of water and boat may only be appropriate for 7 kts in another situation.
Less than 5 kts of wind can be hard to sail in because it is too light to move even small boats well.
5-10 kts is a great windspeed range for beginner sailing.
10-15 kts is where things become interesting for more experienced sailors. In particular, this is the range where full sails can be used without being overpowered, so most boats are sailing at their best. It is also planing wind for most dinghies and single hull wind for racing catamarans.
Above ten knots in the summer becomes a "must sail" day for most of my sailing friends. With preparation, these conditions can be safe even on someone's first day of a sailing class, but are usually challenging for beginners in dinghies. The sailing in a keelboat in this range is ideal for a beginner, but the docking may be challenging for a beginner or novice skipper.
As a novice at sail trim, 10-15 kts is the highest range that you should be concerned with and expect to be comfortable within. For context and to suggest some goals for your development as a sailor, I'll describe some higher ranges.
15-20 kts is too much for most beginners in any sailboat. It will be at best unpleasant even with enough supervision for them to otherwise remain safe. This range can be an enjoyable challenge for intermediate sailors in boats of all sizes, and I'd certainly rather race in 15 kts than 10 kts of wind. The vang and cunningham are key controls one needs to operate in this range, and controlling tacks and gybes becomes critical because the forces involved even on a dinghy are substantial.
Above 20 kts is advanced sailing in a dinghy and the high end of intermediate in a keelboat. It requires effective handling of all sail controls (outhaul, cunningham, vang, traveler, halyard tension, jib cars), as well as reefing in a keelboat or downsizing the rig in a dinghy. In a dinghy, good hiking form, weight shifts, and board adjustments are also required to make progress upwind in these conditions and knockdowns are to be expected. In a keelboat steering becomes a key skill in these high wind situations. Note that in this windspeed range the focus has moved from trying solely trying to maximize speed to instead trying to maintain effective control while overpowered.
30-35 kts is challenging to handle in sailboats of all sizes. It should not be attempted without significant experience. This is somewhat misleadingly referred to as "survival conditions" in most sail trim guides and boat manuals. However, for an expert sailor with a reasonable boat, I'd consider it more of a misery condition than a survival one unless in large waves or on a lee shore. I've voluntarily sailed in these conditions only when they grew slightly beyond what I anticipated for the day or when on a deadline.
Above 35 kts enters the tropical storm category. Keelboats can survive conditions of 35-60 kts with extreme tactics (and some luck) but their skippers do everything possible to avoid these situations. This is well beyond day sailing and something that one handles on a blue water passage when there is no other option. I've only involuntarily sailed in these conditions, when caught by storms. For myself, this is the range that I want to be prepared to sail in but hopefully almost never encounter.
For dinghies, there are several risks in high wind. The boom moves with great force and can strike the sailor, and the lines are under high tension and can pinch body parts when caught, or cause rope burns when running fast. Depending on the weight and experience of the sailor, they may be unable to recover from a capsize. It is harder to make progress upwind, which can make it difficult or impossible to return to shore (or the desired part of shore on a lake or river).
With enough experience, inland sailing in a dinghy in high wind primarily caries the risk of damaging or losing the boat. One can usually swim to shore, but may not be able to recover a boat that has a critical failure such as losing the rig or cracking the hull. The sailor being struck and losing consciousness or held underwater is a risk in any boat and any conditions and is of course a higher risk in more extreme conditions.
On the ocean (or unswimmably large lakes or rivers) or with other boat traffic present, dinghy sailors must be much more conservative than when on protected water. In those cases it is not prudent to push beyond conditions where one can easily navigate and recover from capsize as there is less margin for error.
For large keelboats in high wind, the same risks of large forces on the lines apply. A crash gybe is particularly dangerous as it can break the gooseneck and leave the boom flying or sweep the cockpit with the sheet and hit sailors or knock them overboard. A crew overboard situation on a keelboat is always serious, and in high wind maneuvering the boat to safely recover the crew is more difficult.
However, it isn't generally the wind itself but the waves created that are dangerous for keelboats in very high wind. Keelboats are generally safer from capsize due to wind and less prone to critical gear failures than dinghies, but can be swamped, rolled, or pitch poled by large waves. They also lose steerage when severely heeled or pitched, which can lead to a broach or accidental gybe.
An overpowered sailboat is not just hard to control and uncomfortable to be on. It is also slow. There is no reason to sail overpowered. When overpowered, there will be too much windward helm upwind. The boat will heel far over, especially in gusts. (It will also heel too much if the angle of attack is too steep because the sheet is too tight; that isn't overpowered, that is just bad trim.)
When overpowered, the easiest control for depowering is to decrease the angle of attack of the sails. Ease the sheet and intentionally luff a little. Although the sail will lose its beautiful curve, you will have more control and actually move faster.
You can also achieve the same effect when close hauled by pinching and pointing slightly higher than close hauled. The combination of easing and pinching allows you to navigate gusts and higher winds.
Of course, trimming the sail too tightly also depowers the sail. But it is generally not a good tactic because it causes excess heel, puts more strain on all parts of the system (including your arm), and makes it hard to know how depowered you are.
There are many ways to depower the sail without luffing it using the advanced sailing controls. I've noted at the start of this guide that tightening the outhaul, vang, and cunningham can be helpful in high wind without explaining why. Once you are confident in your use of the sheets for trim, move on to the intermediate guide to learn how to use more controls for better sail shape in all conditions.
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