How do I choose and set an anchor so my boat holds securely?

Choose an anchor suited to the seabed and your boat's loaded displacement, then pay out enough chain or rope to pull almost horizontally along the bottom. Set it by reversing progressively, check that the boat stops moving against fixed shore references, and leave room to swing as wind or tide changes.

Check the anchor and gear

Check the charted seabed first. Even a good anchor struggles if its fluke cannot penetrate. Sand and firm mud usually offer good holding; weed, rock and very soft mud call for more care or another spot.

For the sand, mud and clay common around Denmark, a modern scoop or concave-fluke anchor, such as a Rocna, Mantus or Spade, is a practical starting point. A Danforth or Fortress can hold particularly well in suitable sand or mud, but needs room to reset after a substantial change in pull. Older hinged CQR anchors can set less consistently in difficult ground.

Use the manufacturer's sizing table for both boat length and loaded displacement, and check its wind assumptions. For cruising with overnight stops, choose the next size up if the bow roller, locker and windlass can handle it. Extra weight helps within a suitable design, but cannot compensate for weed-clogged flukes or inadequate scope.

• Check the shackle, its pin securing arrangement, chain links and rope-to-chain splice for wear or corrosion.
• Match the chain's diameter and link dimensions to the windlass gypsy.
• Around 10 mm chain can suit a 12-metre, 10-tonne cruiser, but grade, working load and windage determine the final choice.
• Check that the bitter end is secured inside the locker with an attachment that can be released in an emergency.

Choose the spot and scope

Find shelter from the forecast wind and swell, allowing for overnight changes. Check depths throughout the expected swing circle against your draught and the lowest expected water level. Even in Danish waters, wind-driven changes can lower the water by 30 cm or more.

Scope is deployed rode length divided by the vertical distance from the bow roller to the seabed. Include bow height and the highest expected water level when calculating how much to deploy. Check under-keel clearance separately at low water.

For an overnight stop, aim for a scope of 7:1 to 8:1 where space permits. Treat 5:1 as a lower starting point for settled, sheltered conditions, with no guarantee of holding in all weather. In 5 metres of water with the roller 1 metre above the surface, 7:1 requires 42 metres of rode.

Allow approximately the deployed rode length plus the boat's length when checking clearance from fixed hazards. Check neighbouring boats' swing patterns too: boats on rope and boats on chain may move differently.