Which Side of the River Has More Wind?

Sometimes crossing the river loses more distance than sailing in the “wrong” direction.

One of the first things we learn when sailing upwind is that the shortest route towards the windward mark is not necessarily a straight one. We tack backwards and forwards, trying to make the best progress towards our destination.

But river sailing adds another complication.

The wind is rarely the same across the whole width of the river.

One bank may have a useful breeze while the other appears almost completely becalmed. Fifty metres farther upstream the situation may reverse. A bend changes the angle of the banks. A line of tall trees suddenly shelters one side. A gap between buildings produces a surprisingly strong puff. A gust arriving from above may touch down in the middle of the river before spreading towards either bank.

This creates one of the most interesting tactical questions in river sailing:

Which side of the river should I sail on?

The frustrating answer is:

It depends — and the answer may change before you get there.

That is precisely what makes river sailing so fascinating.

A River Is Not a Wind Tunnel

When we talk about a forecast wind of, say, 10 knots from the west, it is tempting to imagine 10 knots of wind travelling uniformly across the landscape.

That isn't what happens.

The wind reaching our sails has already interacted with:

trees;
hedges;
buildings;
hills;
riverbanks;
gaps in vegetation;
other boats;
and the surface of the water itself.

On an open stretch of sea, the airflow may have travelled several miles across relatively unobstructed water.

On an inland river, it may have passed through or over a row of mature trees only seconds before reaching your boat.

The result can be a remarkably complicated patchwork of moving air.

One side of the river can therefore have considerably more useful wind than the other.

The Wind Shadow

Trees are particularly important.

Imagine the wind blowing across a line of tall trees before reaching the river.

The trees don't simply stop the wind and create perfectly still air behind them. Instead they disturb the airflow.

Immediately behind the trees there can be an area of reduced wind — a wind shadow.

But the effect extends much farther downwind than the height of the trees themselves.

The airflow can become turbulent, producing alternating patches of stronger and weaker wind.

This is why sailing close to a tree-lined bank can sometimes feel rather strange.

The boat accelerates.

Then stops.

Then heels suddenly.

Then stops again.

The wind direction may change at the same time.

What looks from a distance like a perfectly sensible route along the bank may actually be a succession of holes and turbulent gusts.

The Upwind Bank and the Downwind Bank

Suppose the wind is blowing approximately across the river.

One bank is therefore the windward bank and the other is the leeward bank.

At first sight it might seem obvious that the windward side should have more wind because it receives the breeze first.

Often it does.

But river sailing rarely rewards absolute rules.

If the windward bank has tall trees immediately beside the water, those trees may disturb the airflow before it reaches you.

Meanwhile, wind passing over buildings farther back from the opposite bank might descend towards the water and produce stronger patches elsewhere.

So instead of thinking:

“The windward bank is always better.”

Think:

“What has the wind travelled over before it reaches that part of the river?”

That is a much more useful question.

Look Upwind — But Look Beyond the River

This is one of the habits I increasingly find valuable when sailing on a river.

Don't just look at the water immediately ahead.

Look farther upwind.

Ask yourself:

Where has this air come from?

Perhaps there is:

a field;
a gap between trees;
a road;
a large building;
a valley;
a wooded bank;
or an opening between houses.

A large open field may allow relatively clean airflow towards the river.

A dense wood may produce considerable turbulence.

A gap between trees can occasionally act almost like a gateway through which stronger wind reaches the water.

Learning the geography around the river therefore becomes part of learning to sail it.

Experienced river sailors aren't merely sailing the boat.

They are gradually building a mental map of the wind.

Bends Change Everything

Now add a bend in the river.

Suddenly the relationship between the wind and the banks changes.

A bank that was providing relatively clean airflow may become sheltered.

The apparent wind angle changes relative to the river.

A line of trees that previously had little effect may suddenly lie directly upwind.

This is one reason why river sailing can demand so much concentration.

You may discover an excellent patch of wind and think:

“This is clearly the side to be on.”

Two hundred metres later that conclusion may be completely wrong.

Buildings Can Create Surprising Wind

Buildings add another complication.

Wind flowing around a building can accelerate around corners and through gaps.

It can also separate from the structure and create turbulent regions behind it.

That means a clubhouse, large house, industrial building or group of riverside properties can produce local wind patterns quite different from the general wind direction.

You may find a repeatable puff appearing in approximately the same place.

That isn't necessarily coincidence.

There may be a geographical reason for it.

This is where local knowledge becomes extremely valuable.

Someone who has sailed the same stretch of river for twenty years may know that:

“With a south-westerly, there's usually a useful puff just beyond those trees.”

That knowledge can be worth several boat lengths.

But even local knowledge needs to be treated cautiously.

Wind strength changes.

Wind direction changes.

Trees grow.

Buildings appear.

The atmosphere itself changes.

Yesterday's perfect route isn't automatically today's perfect route.

Pressure — Finding the Darker Water

Sailors often talk about pressure.

In this context we aren't normally talking about atmospheric pressure measured by a barometer.

We mean an area where there is more useful wind.

Learning to see these patches is one of the most useful skills a sailor can develop.

Look across the river.

Does one area of water look darker?

Is there more texture on its surface?

Are small ripples appearing?

Are moored boats beginning to move?

Are flags or burgees suddenly lifting?

Are the leaves on trees moving?

Most importantly:

What are the boats ahead doing?

A boat fifty metres ahead can be an excellent wind detector.

If it suddenly heels and accelerates, something has happened.

A gust may be heading towards you.

If three boats near one bank are moving while three boats on the opposite bank are almost stationary, that is useful information.

The river is showing you where the energy is.

Don't Just Look for More Wind — Look for Better Wind

There is an important distinction here.

The strongest wind isn't necessarily the best wind.

Imagine one side of the river has slightly stronger wind but it is extremely turbulent and frequently headed.

The opposite side has slightly less wind but it is steadier and provides a better angle towards the mark.

Which is better?

Probably the second — depending on the tactical situation.

What matters is not simply boat speed.

What matters is progress towards where you want to go.

That brings us back to velocity made good.

You can think of it simply as:

VMG = boat speed x cos(angle away from the desired direction)

You don't need to calculate it while racing.

The important principle is that speed in the wrong direction isn't necessarily useful speed.

But There Is Another Cost: Crossing the River

Suppose you are sailing up the right-hand side of the river.

You look across and notice slightly more wind on the left.

Should you tack and cross?

Perhaps.

But crossing has a cost.

You must tack.

You may lose speed during the manoeuvre.

You travel sideways across the river.

You may encounter other boats.

And by the time you reach the supposedly better wind, it may have disappeared.

This leads to one of the most important tactical ideas in river sailing:

A better patch of wind is only useful if the gain from reaching it is greater than the cost of getting there.

That is why the shortest-looking tactical decision isn't always the fastest one.

The Temptation to Chase Every Gust

This is particularly noticeable in light winds.

You see darker water twenty metres away.

You tack towards it.

The patch moves.

So you tack again.

Another gust appears somewhere else.

You change direction again.

Before long you have sailed an enormous distance while the apparently less active sailor beside you has simply continued steadily up the river.

And somehow they are ahead.

There is a lesson here.

Don't chase every gust.

Instead ask:

Is this a persistent advantage or merely a temporary patch of wind?

That distinction comes largely from experience.

Sometimes Sailing the “Wrong” Way Is Right

Imagine the windward mark lies slightly towards the left-hand side of the river.

The obvious strategy might be to favour the left.

But suppose the left bank is heavily sheltered by trees.

The right-hand side has clean breeze coming through an open field.

Sailing towards the right may initially appear to take you away from the mark.

Yet if you maintain 4 knots while boats on the left struggle at 2 knots, the apparent detour may produce a substantial advantage.

This is one of those situations where sailing teaches an important tactical principle:

Distance isn't the only thing that matters.

Speed matters.

Wind angle matters.

Current matters.

And what happens next matters.

Current Makes the Decision Even More Interesting

On a river we also have to consider the movement of the water.

Suppose the stronger wind is on one side but the favourable current is on the other.

Now the tactical problem becomes:

Wind versus current.

In light winds, current can dominate.

In stronger winds, the additional boat speed available from better pressure may be more important.

Again, there isn't a universal answer.

That is why good river sailing involves constant observation rather than memorising rules.

Watch the Fleet

One of the simplest experiments you can try during a race or training session requires no equipment whatsoever.

Instead of concentrating only on your own boat, deliberately spend a few seconds looking across the entire river.

Ask:

Who is moving fastest?

Then ask:

Why?

Perhaps they have:

more wind;
a better angle;
favourable current;
cleaner air;
fewer obstructions;
or simply better sail trim.

Over time you begin to recognise patterns.

This is particularly useful when boats ahead split onto different sides of the river.

They have accidentally created an experiment for you.

Watch what happens.

One group may reveal which side currently has the advantage.

Use Champagne as a Wind Detector

Sailing Champagne, our A-Rater, makes this particularly interesting.

A long, powerful boat with a large sail area reacts very visibly to changes in pressure.

A patch of extra wind can produce a noticeable increase in heel and speed.

That means photographs or video taken from another boat can become surprisingly useful afterwards.

Look at the water around Champagne.

Look at the heel angle.

Look at the sail shape.

Look at nearby boats.

Then compare those observations with what happened next.

Video can turn an instinctive sailing experience into something that can actually be studied.

It is one reason I increasingly think that filming sailing isn't simply about producing attractive pictures.

It can become a coaching tool.

A Simple Training Exercise

Next time you are sailing on a river, try this.

Choose a reasonably open section and, before making a tactical decision, identify three zones:

Left — Middle — Right

For each zone ask:

How much wind can I see?
What direction does it appear to be coming from?
What lies upwind of it?
What are other boats doing there?
What is the current doing?
How much would it cost me to reach it?

Then make your decision.

A minute later, look again.

Was your prediction correct?

If not, don't regard that as failure.

Ask why it was wrong.

That is how tactical judgement develops.

The Most Important Lesson: Keep Looking

Perhaps the biggest mistake is finding the good side of the river and assuming it will remain the good side.

It won't necessarily.

The wind shifts.

Gusts move.

Clouds alter heating.

Bends change the geography.

Trees shelter different areas.