How to anchor a boat properly

Anchoring looks like dropping a heavy thing overboard. It is actually a technique, and the difference between people who anchor well and people who drag is almost entirely in two habits: enough scope, and setting the anchor deliberately instead of hoping.

The one number to remember: scope

Scope is the ratio between the length of rode you let out and the depth of water — measured from the bow roller, not the waterline, and calculated at high tide, not at the moment you arrive.

• 7:1 for overnight or any wind — the standard for a rope rode.
• 5:1 as a working minimum in calm, settled conditions.
• 3:1 only for a lunch stop with someone aboard and awake.

An all-chain rode can work at slightly less scope because its weight keeps the pull horizontal — and that is the whole point of scope. An anchor holds when it is pulled sideways; when it is pulled upwards, it lets go.

The sequence that works

1. Choose the spot. Check the chart for bottom type — sand and mud hold well, weed and rock do not — and for shelter from the wind you will have overnight, not the wind you have now.
2. Check your swing. You will move in a circle with a radius of your rode plus your boat. Look at what is inside that circle, including other boats, and remember that boats on different rodes swing differently.
3. Approach into the wind or current, whichever is stronger, and come to a stop over your chosen spot.
4. Lower — do not throw. Pay the anchor down under control while the boat drifts slowly astern. Dumping it all in one place gives you a pile of chain on top of an anchor that never digs in.
5. Set it. With the full scope out and the rode made fast, put the engine gently astern and increase the load. Watch a landmark abeam: if it stays put, you are set. If it moves, you are dragging.
6. Take bearings. Two objects ashore, or a GPS anchor alarm. This is what tells you at 3 am whether you have moved.

Different situations

Shallow water. Scope is calculated on depth plus bow height, so in 6 feet of water with a 3-foot bow you need scope for 9 feet, not 6. Shallow anchoring needs proportionally more rode than people expect.

At a beach or sandbar. Beware of a falling tide: a boat that is afloat when you arrive can be aground two hours later. Check the tide table before, not after.

Overnight. Full scope, an anchor light, an anchor alarm, and a plan for what you do if the wind shifts at two in the morning.

Alone. Prepare everything before you approach — anchor ready, rode flaked, cleat clear — because you cannot be on the bow and at the helm at the same time.

Retrieving without breaking anything

Motor slowly towards the anchor while someone takes in the slack. When the rode is vertical, make it fast and let the boat's buoyancy break the anchor out. Do not try to pull it out by hand and never use the engine to yank a stuck anchor: you will damage the boat before you free the anchor.

If it is genuinely stuck, try motoring slowly in the opposite direction from which it was set — most fouled anchors come out backwards.

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