Coastal timing desk
Read the tide before you commit to the leg.
Slack windows, drift triangles and printable deck cards for skippers working short coastal passages without a full navigation suite.
Featured toolSlack Window FinderEstimate the usable slack period around high or low water.Calculators
All calculatorsCalculatorSecondary Port Tide OffsetMove a standard-port high water time and height to a secondary port.Calculate CalculatorDrift TriangleSolve the heading that holds a chosen track through a cross current.Calculate CalculatorTrim BalanceScore a loaded kayak for fore-and-aft balance before launch.Calculate
Every tool
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PREDICTSlack Window FinderEstimate the usable slack period around high or low water.
PREDICTHeight InterpolationRead a height between two tide-table entries using the sine rule.
PREDICTChart Datum ShiftTranslate heights between chart datum, mean sea level and a local gauge.
PREDICTCurrent Turn TableFind the hour of current turn from a tidal gate or a headland.
PLANPassage ETABuild a leg ETA that already contains the current and a stop.
PLANDrift CorrectionSteer the heading that produces the track you actually want.
PLANBailout WindowDecide in advance when and where the leg can be abandoned.
PLANNight Leg ChecklistA short, ordered checklist for legs that finish after dusk.
CONVERTKnots to PaceTurn a current or boat speed into minutes per nautical mile.
CONVERTDepth SwitchConvert metres, feet and fathoms without losing the draft margin.
CONVERTChart Scale ReaderRead a chart scale as centimetres per nautical mile.
CONVERTBearing ConvertMove between true, magnetic and compass bearings cleanly.
ABOARDAnchor ScopeSet rode length from depth, conditions and holding ground.
ABOARDKayak TrimBalance a loaded kayak before the first headland.
ABOARDLoad PlanDecide where every dry bag lives before the boat is packed.
ABOARDDry Bag PackGroup gear into bags that survive a capsize.
REFERENCEPort IndexOne index card per port: reference port, offsets and hazards.
REFERENCEBeaufort ScaleTranslate a wind forecast into sea state for small craft.
REFERENCESignal CardsAgree hand signals before the group separates.
REFERENCELog TemplateA one-page deck log that takes ninety seconds to fill.Categories
Browse by categoryTide & CurrentRead the water before you commit to a departure.Passage PlanningTurn a departure time into a leg with a known finish.ConversionsMove between knots, paces, units and bearings without a mistake.AboardLoad, trim and ground tackle decisions made on deck.ReferencePrintable tables and index cards for the cockpit.
Field notes
All field notesThe slack window is not an instantA tide table gives you a time. The water gives you a period, and the two do not match.Read Reading a tide curve without a plotterSix-hour interpolation is the most common silent error in small-craft planning.Read Drift correction in three numbersSpeed, set and rate are enough to hold a track, if you recompute at every headland.Read A night leg checklist you will actually runOrder the items by when they must be true, not by how important they sound.Read Chart datum is not sea levelThree datums appear on one small chart, and mixing them is a quiet way to run aground.Read When to abort, written before you launchAn abort decision made on the water is usually late.Read
Quick reference
Reference indexValues assume a semi-diurnal coast and a calm sea. Re-read the card before a shallow entry.
| Item | Value | Note |
|---|---|---|
| One nautical mile | 1,852 m | 1852 metres exactly; do not round to 1,850 for a measured leg |
| One knot | 1.852 km/h | A pace of 32 min per mile is about 1.9 knots |
| One fathom | 1.83 m | Six feet; convert in one step, not two |
| Spring range | 2.0 to 5.5 m | Window length scales with range, not with printed time |
| Neap range | 0.8 to 2.4 m | Slack periods shorten; margins must grow |
| Current turn | site specific | Offset is published against a named reference port |
| Drift angle | tan(set, rate) | Above 20 degrees, re-time the leg |
| Chart datum | below MSL | Roughly half the local spring range below mean sea level |