SAILING GUIDE / WIND & WAVES

Read the weather. Prepare for your sail.

Explore how wind, waves and life aboard fit together. Change the conditions and see what needs your attention.

A learning simulator

01 / Explore

Your conditions

Start with an example, or make a scenario of your own.

WIND, WAVES & FEEL
Longer swellWaves from ahead
Schematic side view. Motion and waves are exaggerated to show the difference.
Gentle outing
3m/s

True wind in this weather scenario. The trim guide shows apparent wind aboard.

0.2m

A measure of the sea state. Individual waves can be higher.

Gusts and sea characterWind gusts: 4 m/s
4 m/s

Gust speed is at least as high as mean wind speed.

Sea character
Waves arrive

Wind and waves change independently. Light wind can still mean a lively sea.

How the demands change

Broad teaching levels for this scenario. Read the explanation beside each bar.

Comfort

5 of 5
Calm and comfortable

Small waves produce limited motion in this illustration.

More filled = greater comfort

Experience needed

1 of 5
Basic boat handling

A lookout, navigation and basic manoeuvres still matter in calm conditions.

More filled = greater demands

Safety demands

1 of 5
Basic routines

Lifejackets, a way to call for help, working equipment and a passage plan belong on every trip.

More filled = greater demands

Comfort: 5 of 5, Calm and comfortable. Experience needed: 1 of 5, Basic boat handling. Safety demands: 1 of 5, Basic routines

WHAT YOU NOTICE ABOARD

Time to find your feel

Light wind puts little load on the sails, but the boat may have limited steerage way. Small waves produce limited motion in this illustration.

Focus your attention here

  • Practise steering and sail handling with a lookout and plenty of room.
  • Share out tasks and make clothing, water and equipment easy to reach.
  • Follow the forecast for the whole trip and keep alternatives with good margins.

02 / Prepare

A calmer trip starts ashore.

The basics always stay in view. The bars highlight what needs extra attention in your scenario.

0 / 7 marked as done

Do & prepare

Basic routine

Stow and secure loose items before departure. A wake or manoeuvre can move things even in calm weather.

Basic routine

Know the reefing lines and routine before you need them. A calm moment is a good time to review the system together.

Basic routine

Decide who steers, keeps watch and navigates. Everyone needs to know how to call for help.

Basic routine

Read the forecast for the whole trip, plan alternatives and tell someone ashore about your passage plan.

Bring & check

Basic routine

A working lifejacket with the right fit matters in calm weather too. Review how to recover a person from the water.

Basic routine

Keep charts and charged communications equipment accessible, protected from water, with a navigation backup.

Basic routine

Keep water, food and a dry, warm layer within reach; conditions may change during the trip.

Checkmarks apply to this scenario and reset when conditions change. They are a memory aid, not an assessment of whether the trip is safe.

03 / Weather

More than just wind speed.

Visibility, temperature and sudden changes also shape a day afloat. These conditions are explained separately from the simulator’s bars.

01

Rain and cold

Even a light breeze can make for a demanding day if the crew gets wet and cold.

What changes
Cold makes it harder to work and stay focused. Rain and spray can reduce visibility and make the deck slippery.
Prepare for it
Bring layers, windproof and waterproof clothing, and dry spares. Keep food and drinks accessible and share the work before anyone gets tired and cold.

Sources: RYA · Winter on the waterSjöräddningssällskapet · Inför båtturen

02

Fog and poor visibility

Calm water can hide a difficult navigation situation.

What changes
Other boats and landmarks appear later. Looking out, listening and checking your position need more attention.
Prepare for it
Check visibility forecasts and consider waiting. Adjust speed and keep a careful lookout. Knowing your navigation equipment and sound signals is part of preparation; a screen cannot replace a lookout.

Sources: RYA · Safe speed and proper look outTransportstyrelsen · Utrustning inför båtturen

03

Thunderstorms and rapid changes

A thunderstorm can change conditions far faster than these controls suggest.

What changes
Lightning, strong gusts and heavy rain can arrive together. A moderate average wind does not describe the whole situation.
Prepare for it
Follow forecasts and warnings. Plan to stay in port or finish well before the storm. Seek suitable shelter ashore before thunder arrives; neither a boat nor its mast guarantees protection from lightning.

Sources: SMHI · ÅskaSMHI · Skydd mot blixtenRYA · Weather and tides

04

Sun and heat

A pleasant breeze can make it easy to forget how long you have been in the sun.

What changes
Long exposure to sun and heat can drain energy and concentration, even when the sailing feels easy.
Prepare for it
Keep water within reach and bring sun protection, a hat and covering clothing. Arrange shade and shared duties where possible. Keep spare clothes and warm layers for the evening.

Sources: RYA · Look after yourselfSjöräddningssällskapet · Inför båtturen

04 / Understand the sea

Read the whole picture.

Wind speed tells only part of the story. Explore the wind in the sails, wave height and sea character, then review the common mistakes.

Average wind and the wind in the sails

Here you choose true average wind, as in a weather forecast. Gusts are temporary increases. The sails meet apparent wind: the wind felt aboard once boat speed and course are included. The same forecast wind can feel different on different points of sail.

Wave height is not a maximum

The control uses significant wave height: roughly the average height of the highest third of waves. Height is measured from trough to crest. Individual waves can be much higher, sometimes around twice as high. The illustration shows the principle rather than every wave.

Sources: Meteorologiska institutet · Signifikanta våghöjden

Same height, different seas

Short, steep waves and long swell can affect the boat differently at the same height. Their direction relative to the boat changes its motion. Depth, coast and current also matter; wind against current can steepen the sea. These local effects are not calculated here.

Sources: SMHI · VågorRNLI · Weather and tidesRYA · Weather and tides

Common mistakes

01

Reading only the average wind

Why it mattersGusts and approaching changes can demand much more work than the average suggests.

What to doCompare the average, gusts and expected changes for the whole trip, including the return leg.

02

Assuming light wind means calm seas

Why it mattersSwell can remain after the wind drops or arrive from a windier area.

What to doRead the wave forecast separately. Check height, period and direction, and watch how the sea develops.

03

Preparing only when things get difficult

Why it mattersStowing gear and handling sails become harder when the boat is moving and the crew is busy.

What to doSecure loose items, check hatches and discuss reefing and crew roles while conditions are manageable.

04

Letting the checklist decide whether to sail

Why it mattersEquipment and ticked boxes cannot tell you whether the boat, crew and passage suit the conditions.

What to doConsider the whole picture using current marine weather, local knowledge and your boat's capabilities. Keep the option to change plans or stay in port.

Sources & further reading

The practical guidance draws on these sources. Bar levels are our simplified teaching examples, not official thresholds.

And what about the sails?

Explore wind angle, basic sail trim and telltales together in the trim guide.

Open the trim guide