What passage planning is.
The systematic process of preparing for a voyage before you leave the dock. Under SOLAS, all vessels — from supertankers to small yachts — must plan their voyages. Beyond the legal requirement, it's simply how you avoid getting caught out: 30 minutes with a chart, tide tables, and a forecast can prevent hours of misery at sea.
The 4 IMO stages.
The IMO defines four stages of passage planning. For yacht sailors the same framework applies, scaled to your vessel.
1. Appraisal
Gather all the information before you start planning.
- ·Charts for the route — up to date, correct scale
- ·Pilot books and sailing directions
- ·Notices to Mariners for recent changes
- ·Weather forecasts for the passage window
- ·Tidal heights and streams
- ·TSS, restricted areas, military zones
- ·Crew experience and condition
2. Planning
Plot the route and make the decisions.
- ·Plot waypoints (paper or electronic)
- ·Course and distance for each leg
- ·Hazards and safe passing distances
- ·ETAs from expected speed
- ·Departure time to carry a fair tide
- ·Bolt holes — safe harbours en route
- ·Abort criteria (wind, sea state, visibility)
- ·Fuel with reserves
3. Execution
Put the plan into action — but stay flexible.
- ·Brief the crew before departure
- ·Follow the planned route and waypoints
- ·Log position fixes at regular intervals
- ·Maintain a proper lookout
- ·Be ready to deviate if conditions change
- ·Monitor weather throughout
4. Monitoring
Continuously check progress against the plan.
- ·Compare actual to planned position
- ·Are ETAs realistic — ahead or behind?
- ·Compare weather to forecast
- ·Watch for set and drift
- ·Decide early if you need a bolt hole
- ·Update the plan if conditions require
Weather assessment.
Weather is the single biggest variable. Check multiple sources and understand the models behind them.
48 hours before
Get the big picture — synoptic charts, fronts, the general pattern. Look at 5-day forecasts on Windy using ECMWF. Window opening or closing?
24 hours before
Narrow the focus — inshore waters forecast, shipping forecast, compare models. Check WindFinder for departure-point conditions.
Morning of departure
Final check — has anything changed? Compare station data with the forecast; if they already disagree, respect reality. Does the sky match the forecast?
Tidal planning.
In tidal waters, getting the tide right can halve your passage time or double it. Two aspects: heights and streams.
Tidal heights
How deep is the water at a given time? Calculate height at departure and arrival (twelfths rule for quick estimates). Check enough water under the keel at every stage, plus a safety margin (typically 0.5 m minimum).
Tidal streams
Which way and how fast? A 2-kn stream against you at 5 kn boat speed = 3 kn over the ground; behind you = 7 kn. Use stream atlases or Savvy Navvy to time departure for a fair tide.
Springs vs neaps
Springs (new/full moon) have bigger ranges and stronger streams; neaps (quarter moons) are gentler. For strong tidal gates — Alderney Race, the Swinge, Messina — timing around neaps makes the passage dramatically safer.
Fuel & range.
Even on a sailing yacht, fuel planning matters — motoring in calms, charging batteries, and the chance of motoring the whole passage if the wind dies.
The 30% reserve rule
Calculate the fuel you expect to use, then add 30% for:
- ·Unexpected calms
- ·Adverse current
- ·Diverting to a bolt hole
- ·Higher consumption in rough weather
Quick calculation
- 1Distance to cover (NM)
- 2Motoring speed (kn) — ~5–6 for a cruiser
- 3Hours = distance / speed
- 4Consumption at cruising RPM (l/hr)
- 5Total = hours × consumption × 1.3
Crew briefing.
Before departure, brief the crew. Everyone aboard should know:
The route
Where, which way, how long? Show it on the chart; point out course-change waypoints.
Weather expected
What wind, from where, forecast to change? What sea state?
Watch system
For passages over a few hours, set a rota — who's on when, where the off-watch rest, when meals are.
Emergency procedures
MOB drill, life-jacket and VHF locations, fire extinguishers. Review the safety brief if you have one.
Bolt holes
If things go wrong, where do we divert? Using Plan B is good seamanship, not failure.
Passage checklist.
Use this before every passage. A quick mental run-through for day sails; work through it properly for longer ones.
- Charts available and up to date
- Pilot books / sailing directions consulted
- Notices to Mariners checked
- Tide tables for departure and arrival
- Waypoints plotted with courses and distances
- Hazards identified with safe passing distances
- Bolt holes identified
- ETAs calculated for each waypoint
- Forecast checked (multiple sources)
- Tidal heights calculated — enough depth everywhere
- Tidal streams checked — departure optimised
- Abort criteria defined
- Fuel sufficient (30% reserve)
- Water and provisions adequate
- Safety equipment checked and accessible
- Crew briefed on plan, weather, watches, emergencies
- Shore contact informed of plan and ETA