Making the Boat Go Faster — Your First Lesson in Sail Trim
One of the most common beginner sailing mistakes is assuming that pulling the sail in harder must make the boat go faster.
It seems perfectly logical.
You have a sail.
You have a rope attached to it.
The boat is moving.
So if you want more speed, surely you pull the rope harder?
Unfortunately, sailing boats have a rather inconvenient habit of refusing to obey this particular piece of beginner logic.
In fact, pulling the sail in too tightly can make the boat slower.
Your first lesson in sail trim therefore isn't really about learning a complicated set of rules. It is about learning to look at the sail, listen to what it is telling you, and make small adjustments.
And there is one wonderfully simple rule that can take you a surprisingly long way:
Ease the sail until it starts to complain, then pull it in just enough to make it happy.
That is sail trim at its most basic.
Later, we can worry about telltales, sail shape, twist, leech tension, outhauls, kicking straps and the finer points of aerodynamics.
For now, we just want to make the boat go.
The Mainsheet Is Not an Accelerator
One of the first things to understand is that the mainsheet is not like the accelerator pedal in a car.
Pulling harder does not automatically create more power.
The sheet primarily controls the angle of the sail relative to the boat and the wind.
If the sail is too far out, the wind cannot flow properly around it and the sail begins to flap.
If the sail is pulled too far in, the sail can also stop working efficiently.
Somewhere between those two extremes is the position where the sail works well.
The beginner's job is to find it.
And fortunately, the sail gives you a very obvious clue.
It starts flapping when you have eased it too far.
The Simplest Sail-Trim Exercise You Will Ever Learn
Imagine you are sailing along comfortably.
Try not to change course.
Keep the boat pointing approximately in the same direction and look at the mainsail.
Now slowly let the mainsheet out.
Not all at once.
Just a little at a time.
Watch the sail carefully.
Eventually, the front part of the sail will begin to flutter or flap.
Sailors call this luffing.
You have now eased the sail slightly too far.
So gently pull the mainsheet back in.
The moment the flapping disappears, stop.
You are now much closer to a useful sail setting.
That is the whole basic exercise.
1. Hold a steady course.
2. Slowly ease the sheet.
3. Watch for the sail beginning to luff.
4. Pull the sheet back in gently.
5. Stop when the sail just becomes smooth again.
Then give the boat a few seconds to respond.
Do not immediately start pulling and easing again.
Let the boat settle.
Don't Wait Until the Whole Sail Is Flapping
There is an important difference between a sail just beginning to luff and a sail flogging violently in the wind.
You are looking for the first small sign.
Often this will appear towards the front edge of the mainsail, near the mast.
The sail may tremble.
A small section may flutter.
The smooth curved shape may begin to collapse.
That is enough.
You do not need to let the sail flap wildly.
Once you see that first sign, gently sheet in until it disappears.
This teaches you something much more useful than simply being told:
"Pull the mainsheet in about this far."
Why?
Because the correct position keeps changing.
The Correct Sail Position Depends on Where You Are Going
This connects directly with the points of sail we introduced earlier.
A sailing boat doesn't keep its sails in the same position all the time.
As the boat changes direction relative to the wind, the sails must change position as well.
A useful beginner rule is:
Turn towards the wind - sheet in.
Turn away from the wind - ease out.
So if you are sailing close-hauled, with the boat travelling as close towards the wind as it comfortably can, the mainsail will normally be relatively well sheeted in.
Bear away onto a close reach and you can ease it slightly.
Move onto a beam reach and the sail comes further out.
Bear away onto a broad reach and it comes further out again.
Sail downwind and the sail may be a long way out.
That means there is no single "correct mainsheet position".
The correct position depends upon:
the direction you are travelling;
the direction of the wind;
the strength of the wind;
the sail;
and the boat.
This is why learning to look at the sail is so much more useful than memorising where the boom ought to be.
Try It Every Time You Change Direction
Suppose you are happily sailing on a beam reach.
The sail is set nicely.
The boat feels balanced.
Then you decide to head further away from the wind.
You move the tiller.
The boat turns.
But if you leave the sail exactly where it was, it may now be pulled in too tightly.
So ease the sheet.
Let the sail out until it just begins to complain.
Then bring it back in enough to stop the luffing.
Now suppose you turn back towards the wind.
The opposite happens.
As the boat turns towards the wind, you will normally need to pull the sail further in.
Course and sail trim therefore belong together.
Change one and you usually need to think about changing the other.
Why Doesn't Pulling the Sail In Harder Make the Boat Faster?
Here we need just a little sailing science.
A sail works because air flows around it.
You can think of it as an aerofoil - something related to the wing of an aircraft, although the complete physics of sails is more complicated than that simple comparison suggests.
The important point for the beginner is that the sail needs to meet the wind at an appropriate angle.
Too loose and it flaps.
Too tight and the airflow around it becomes less efficient.
The sail may still look beautifully tight.
It may not make any noise at all.
But that does not mean it is producing the best forward-driving force.
In fact, an over-sheeted sail can produce:
excessive heeling;
increased sideways force;
more rudder drag;
more resistance through the water;
and less useful forward drive.
The boat can feel very dramatic without actually being very fast.
This is an important sailing lesson:
Noise, heel and effort are not the same thing as speed.
A Flat Boat Can Be a Fast Boat
Beginners often associate excitement with performance.
The boat heels.
Water rushes past.
Everyone hangs onto something.
Surely we must be going quickly.
Not necessarily.
Particularly in a dinghy, excessive heel can be inefficient.
The rudder and centreboard are designed to work properly when the boat is reasonably balanced.
Heel the boat excessively and their relationship with the water changes.
You may find yourself pulling the tiller harder simply to keep the boat travelling where you want it to go.
That creates additional drag.
Sometimes, particularly when a gust arrives, easing the mainsheet slightly can actually help the boat accelerate.
The boat becomes flatter.
The helm becomes lighter.
The boat stops fighting you.
And more of the sail's force is turned into useful forward motion.
That can feel rather strange the first time you experience it.
You ease the sail...
...and the boat goes better.
What Are Telltales?
Once you have become comfortable watching for the sail beginning to luff, you may notice small pieces of wool, ribbon or lightweight material attached to the sail.
These are telltales.
They are wonderful little sailing instruments.
They show us something we cannot normally see:
the airflow around the sail.
When the airflow is behaving well, telltales generally stream smoothly backwards.
When the airflow begins to break down, one or more telltales may:
lift;
flick;
circle;
disappear behind the sail;
or flap around.
Don't become obsessed with them during your first few minutes of sailing.
You already have plenty to think about.
But once steering starts becoming automatic, telltales become extremely useful.
They help you refine the simple:
Ease until it flaps, then sheet in slightly
method.
If You Have Jib Telltales
Many training boats have telltales on the jib.
You may see one on each side of the sail.
In straightforward conditions, you are often trying to get both telltales flowing reasonably smoothly backwards.
If one starts lifting or behaving differently from the other, it can indicate that the angle between the sail and the wind needs adjusting.
That adjustment might come from:
steering slightly differently;
changing the sheet tension;
or a combination of both.
For the beginner, don't worry about interpreting every flick immediately.
Start simply.
Look for smooth airflow.
Make one small change.
Wait.
See what happens.
That last point matters enormously.
Make One Adjustment at a Time
A common beginner sequence goes something like this:
The sail flutters.
Pull the sheet.
The boat heels.
Ease the sheet.
Turn the boat.
Pull the sheet again.
Move across the boat.
Turn the tiller.
Ease the sheet.
Wonder why everything has suddenly gone wrong.
The problem isn't necessarily that any individual action was wrong.
The problem is that there were six actions in about three seconds.
Sailing becomes much easier when you slow the process down.
Make one adjustment.
Then observe.
If you ease the mainsheet, give the boat a moment to respond.
If you change course, stabilise the course and then look again at your sail trim.
You are trying to develop a cause-and-effect relationship:
I did this.
The boat did that.
That is how you begin learning to sail by feel rather than simply following instructions.
The Boat Is Constantly Giving You Feedback
Your sail is not your only instrument.
The whole boat tells you how well it is sailing.
Pay attention to:
The sound
A badly luffing sail is obvious.
But also listen to the water moving around the hull.
The amount of heel
Does the boat suddenly feel as though it is being pushed over unnecessarily?
The tiller
Does it feel light and balanced, or are you having to pull hard against it?
The wake
Look behind occasionally when it is safe to do so.
Is the boat moving cleanly through the water?
Your speed relative to other boats
If another similar boat seems to be effortlessly sailing away while yours feels extremely dramatic, it may be worth experimenting with the sail trim.
The feeling of acceleration
One of the most satisfying sailing experiences is making a small adjustment and feeling the boat immediately respond.
That is when sail trim begins to make sense.
A Brilliant Beginner Exercise: Deliberately Get It Wrong
One of the best ways to understand correct sail trim is to deliberately experience incorrect sail trim.
Choose an open stretch of water with plenty of room and appropriate supervision.
Settle onto a comfortable reach.
Get the boat moving.
Now deliberately ease the mainsheet too far.
Watch what happens.
The sail luffs.
The boat slows.
Now pull the sail back in until the luffing stops.
Feel the boat accelerate.
Then deliberately pull the mainsheet too far in.
What happens now?
Does the boat heel more?
Does the tiller feel different?
Does the boat actually go any faster?
Now ease the sheet again until the sail is just comfortably working.
This is much more powerful than somebody simply telling you where to put the mainsheet.
You have experienced the difference yourself.
Another Useful Exercise: Turn and Trim
Once basic steering feels comfortable, try this sequence.
Start on a beam reach.
Trim the sail using our simple method.
Now bear away slightly.
Ease the sail.
Bear away again.
Ease again.
Then gradually turn back towards the wind.
As you do so, progressively sheet in.
You begin to establish a relationship between:
boat direction -> wind direction -> sail position
That relationship is at the heart of sailing.
You don't need to calculate it.
You begin to recognise it.
Eventually, your hands start adjusting the mainsheet almost automatically as the boat changes course.
What Happens in a Gust?
Imagine you are sailing happily when a stronger puff of wind arrives.
Suddenly the boat heels.
A beginner's instinct can be to hold onto everything even more tightly.
Sometimes that includes holding the mainsheet firmly in position.
But if the boat is becoming excessively overpowered, a small ease of the mainsheet can spill some of that power.
The boat becomes flatter.
The helm becomes easier.
When the gust has passed, trim the sail again.
For now, the important principle is simply this:
The mainsheet is something you continually adjust.
It is not something you set once at the beginning of the sail and then forget.
Don't Cleat It and Forget It
Some boats have a mainsheet cleat.
They are extremely useful.
They can also encourage a bad beginner habit.
The sailor finds a mainsheet position that seems approximately correct, puts the sheet into the cleat and mentally crosses:
"Mainsheet"
off the list.
But the wind changes.
The boat changes course.
A gust arrives.
The boat slows.
And the mainsheet remains exactly where it was five minutes ago.
Learning to sail means developing the habit of continually asking:
Does this still feel right?
Your sail trim is never completely finished.
Common Beginner Sail-Trim Mistakes
1. Pulling everything in hard
It feels secure.
It looks tidy.
It is frequently slow.
2. Looking only at your hands
Don't stare at the mainsheet.
Look at what the mainsheet is controlling.
Watch the sail.
3. Never experimenting
If you think the sail is correct, ease it slightly and see what happens.
You can always pull it back in.
4. Making enormous adjustments
Sail trim is usually about small changes.
A few centimetres of sheet movement can make a noticeable difference.
5. Forgetting to retrim after turning
New direction.
New angle to the wind.
Probably a new sail position.
6. Trying to correct every tiny flutter
The wind is rarely perfectly steady, particularly on rivers and inland waters.
Trees, buildings, other boats and bends in the river can all create shifting and disturbed air.
Don't chase every tiny movement.
Look for the general pattern.
7. Pulling harder when the boat heels
Sometimes the answer is exactly the opposite.
Ease slightly.
Flatten the boat.
Then reassess.
Watch the Sail - But Keep Looking Where You Are Going
There is one small problem with telling beginners to watch their sail.
They can become so fascinated by it that they stop looking anywhere else.
You must still keep a proper lookout.
Look ahead.
Look around you.
Check for other boats.
Then glance at the sail.
Then look ahead again.
A good helm is constantly moving their attention between:
where the boat is going;
what the wind is doing;
what the sail is doing;
what other boats are doing;
and how the boat feels.
At first that seems like a lot.
Eventually it becomes normal.
The Science Can Come Later
There is a great deal more we can say about sail trim.
We can investigate:
angle of attack;
attached and separated airflow;
pressure differences;
sail camber;
twist;
mast bend;
vang or kicking strap tension;
Cunningham tension;
outhaul adjustment;
traveller position;
jib leads;
slot effects between mainsail and jib;
apparent wind;
and how trim changes in different wind strengths.
Racing sailors can spend years refining these things.
But you don't need any of them to begin understanding your sail.
For your first lesson, remember one thing:
Ease the sail until it starts to complain, then pull it in just enough to make it happy.
Your Sail-Trim Checklist
Next time you are sailing, try this:
Establish a steady course.
Look ahead and make sure you have room.
Look at the sail.
Ease the sheet slowly.
Watch for the first sign of luffing.
Sheet in just enough to remove it.
Let the boat settle.
Feel whether the boat accelerates.
Change course.
Retrim the sail.
If telltales are fitted, start watching them too.
Repeat.
That simple exercise begins developing one of sailing's most important skills:
feeling what the boat wants.
Sailing Is a Conversation, Not a Set of Fixed Instructions
Perhaps that is one of the most important lessons for anybody learning to sail.
There isn't always one fixed answer.
The wind moves.
The boat moves.
You move.
The water changes.
The sail changes shape.
And you constantly respond.
A beginner often wants the instructor to say:
"Put the mainsheet exactly here."
An experienced sailor is more likely to say:
"Try easing it."
Then:
"Watch the sail."
Then:
"Feel what happens."
Because eventually that is what sailing becomes.
Not a collection of instructions memorised on shore, but a continuous conversation between sailor, boat, wind and water.
So next time the boat feels slow, resist the temptation simply to pull everything in harder.
Ease the sheet.
Watch the sail.
Let it complain.
Then pull it in just enough to make it happy.
You may be surprised how much faster the boat becomes.
My name is Philip. I started sailing when I was 65.
I joined a club and because my son had already been part of a club for many years - borrowing all types of boat. He knew what we needed and the type of boat I would require.
So we did by an RS Toura - a virtually unsinkable dinghy which has given me the confidence to experiment and learn and take my RYA exams and become a competent sailor and then to move up to the boat of my dreams - the A-Rater.
Coming up Next
Lesson 11 in my beginner sailing series explains how to tack without turning too far, stopping head-to-wind… or meeting the boom unexpectedly.
Tacking looks complicated the first time you try it.
Turn towards the wind.
The sails flap.
The boom comes across.
Duck.
Change sides.
Straighten the rudder.
Sail away.
Easy — once you know the sequence.
Return to https://pmrsailing.uk/Lessons.html
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