Anchoring and mooring

Where there is a tide, the depth changes during your stay, so you need two depths. The maximum, at high water, decides how much cable to let out. The minimum, at low water, tells you whether you risk grounding. To find them you take the times and heights of the tide from the tables and add them to the charted depth: the depth of water is the charted depth plus the height of tide, for example 5 metres charted and a tide of 4.6 metres give 9.6 metres of water. For low water, on arrival you need at least the fall of tide until low water, plus your draught, plus a safety clearance under the keel.

The manoeuvre follows a fixed order, the six steps. Everything is prepared first: you choose the spot, turn on and test the windlass and fit the tripping line. Then you head into the wind or tide, whichever is stronger, and stop the boat, so the anchor goes down where you want it. You lower to the sea bed and, as the boat drifts back, you let out the chain: if needed, a touch astern helps. How much you let out is given by the scope: at least 4 times the maximum expected depth for all chain, 6 for mixed chain and line.

At the end you check that the anchor is holding. A boat at anchor always swings a little round the anchor, and that is normal; the anchor is dragging when the boat changes position over the ground: you see it from transits ashore, from the GPS position or from the distance to other boats. You set the anchor alarm, fit the snubber and show the signal: the black ball forward by day, the white all-round anchor light by night. Throughout, take care with the windlass: it is dangerous to fingers, lifejacket, harness line and remote.

When you moor alongside a wall, think first of all about the tide: the boat rises and falls against the quay, so the lines must be able to follow her. That is why stretchy nylon warps are used, at least 4 times the rise and fall of the tide, each one led through a fairlead and then onto a cleat. When a warp is attached to the bollard or ring, the rest is brought back on board and cleated: that way each warp can be adjusted from on board as the tide rises and falls.

Each line has its own task, and the name says which: bow line, bow or forespring, stern or back spring and stern line. For fenders you use peardrop and cylindrical fenders and, if needed, a fender board. When boats lie alongside each other they are rafted up, in a raft: breast ropes are attached between the vessels at bow and stern, together with springs, and the outside boat takes its own bow and stern lines ashore to minimise the strain on the inside boat's shore lines.

Mooring needs only a few knots, and each has its own job. The round turn and two half hitches is a multipurpose knot that can be untied under tension. The bowline makes a fixed eye, very secure, but it cannot be untied under tension: it is used for loops in mooring lines. The clove hitch is quick to tie and easy to adjust, and is ideal for securing fenders. To make fast to a cleat you lead the rope to the open side and take a full turn round the base, which takes the load; then one or two figures of eight over the horns and a final round turn, which adds friction (the steps are in the card Making fast to a cleat). In the figure you see the round turn and two half hitches; every step is in the Knots topic.

Before you slip the lines you go through a checklist. You have a free fender ready with an emergency line. You free the boat from the shore: tender and gangway hoisted and stowed, shore power disconnected, gas closed. You start the engine, with the 220 V disconnected, and check that water comes out of the exhaust, steadily, looking at the smoke too; you test the rudder, with the autopilot off, at plus 10 and minus 10 degrees. The unmooring is planned and communicated to the crew, so everyone knows what to do. When you arrive, at the end of the day, you check the position of the fenders and of the boat, and the moorings.