Currents - Part 2: How to Route with Currents

By far, the biggest mental adjustment in routing with currents in FW, QTVLM or Expedition is to understand one thing - the route 'line' is NOT your heading anymore. It's the optimal path that your boat should take over ground to get where you want to go.

The Critical Mental Shift

Route Line ≠ Heading

The route line shows the optimal path over ground, not your compass heading.

When currents are involved, your boat must point in a different direction than the route line to compensate for the current pushing you sideways.

Step 1: Generate Your Route

You generate this route by loading both the wind AND the current GRIB for the time period and then running a route as usual.

Where to Get Currents

The currents are found on the same wind page:

https://fairwinds.world/wind

Process

1. Download the wind GRIB for your race period
2. Download the current GRIB for the same region/period
3. Load both into your router (FW, QTVLM, or Expedition)
4. Run your route as normal

The router will calculate the optimal path considering both wind and current vectors.

Step 2: Steering Your Boat

Once you have the route, the next problem is... how do I steer my boat so that it 'stays on the line'?

There are two main approaches:

The Easy Way: Let FairWinds Do It

Compensated Heading

FairWinds has the concept of a wind+current reckoning line and a 'compensated heading'.

How It Works

1. Activate your route in FairWinds
2. FW will figure out the 'compensated heading' for you
3. This positions your point of sail so that your wind+current reckoning line moves you along the route to the next waypoint
4. It essentially reverse engineers the calculations that the router does to produce the route

Performance

It's pretty good unless you go head to wind in your route. Don't do that.

The Medium Way: Scheduled Waypoints

Full Control Method

1. Import your route as a reference
2. Create a scheduled set of waypoints over that route based on the current+wind reckoning path
3. This gives you total control and predictability

When to Use This

If you want total control and predictability, this is the way.

This method requires more manual work but gives you complete oversight of your navigation plan.

⚠️ Important Warnings

Rule #1: Avoid Head-to-Wind Routes

Don't make routes where the compensated heading goes head to wind, especially in strong currents.

Why This Matters

• In strong currents, the compensated heading can become extreme
• If the route requires you to point into the wind to compensate for current, your boat will stall
• The router may suggest an "optimal" path that's physically impossible to sail

Be Patient

It will take time to learn how to create and read new routes with currents.

Expect a learning curve as you develop intuition for:

• How currents affect your heading
• When compensated headings become impractical
• How to read the difference between route lines and reckoning lines

Visual Indicators in FairWinds

Route Line (Blue)

The optimal path over ground calculated by the router

Reckoning Line (Orange/Red)

Your actual projected path considering:

• Current heading
• Wind speed and direction
• Current speed and direction
• Boat polars

Compensated Heading

When a route is activated, FW adjusts your heading so the reckoning line follows the route line

Tips for Success

Start Simple

• Begin with races in moderate current regions
• Practice with the English Channel before tackling the Gulf Stream

Check Your Compensated Heading

• After activating a route, verify your heading makes sense
• If you're pointing more than 60° from your destination, investigate

Use Reference Routes

• Keep your router-generated route as a reference
• Create manual waypoints based on what you learn

Monitor Grib Cutovers

• Remember: forecasts update every 6 hours (00, 06, 12, 18z)
• Currents can change significantly with new data
• Your compensated heading may need adjustment

Common Mistakes

1. Ignoring the Reckoning Line

Problem: Following the route line with your heading instead of letting FW compensate

Solution: Activate the route and trust the compensated heading

2. Head-to-Wind Routes

Problem: Router suggests a path that requires pointing into the wind

Solution: Add intermediate waypoints or adjust your route strategy

3. Not Loading Currents

Problem: Routing with wind only in a current region

Solution: Always load both wind AND current GRIBs for current regions

4. Forgetting Forecast Updates

Problem: Currents change at grib cutover but route isn't updated

Solution: Re-run your route after major forecast updates

Next Steps

• Part 3: Advanced current strategies and tactics
• Practice in the English Channel practice races
• Join the FairWinds community to share current routing tips

Key Takeaways

1. Route line = path over ground, not your heading
2. Load both wind AND current GRIBs from fairwinds.world/wind
3. Easy mode: Let FW calculate compensated heading automatically
4. Medium mode: Use scheduled waypoints for full control
5. Never route head-to-wind in strong currents
6. Be patient - currents add significant complexity!