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>>Boat Anchoring

Boat Anchoring

A good skipper not only must be able to handle a vessel in full flow, but also keep it in one place when necessary. A good anchor and good anchoring skills are therefore important strings to a sailor’s bow.

A Good Anchor

The key skill of a good anchor is not its gross weight, but its ability to lock into the ground. A heavy anchor may drop easily but it takes a lot to raise it back up to the deck. A well-designed anchor will grab hold of the earth and instead use the formidable weight of the wet mud and sand to secure the vessel.

A good anchor will also need to be strong. Although in a typical situation the strength of an anchor will not be tested because the boat will not pull particularly hard on the line, there are instances, such as when caught in a severe storm or when the anchor gets stuck on a rock, when the strength of the anchor will be critical.

The strength or holding power of an anchor refers to a measure in weight of the amount of pull an anchor can sustain without breaking free. The weight of anchor needed will vary according to the length of the boat and its working load.

Anchor Types

There are a wide variety of anchors available, and which is the most effective for any given craft is dependent on the two main factors of the load placed on the anchor and the type of seabed. The main types of anchor include the Fisherman’s, Danforth, Plough or CQR, Mushroom, Bruce and Grapnel.

  • Fisherman’s – This is the traditional shank with two arms anchor most people think of when imagining an anchor. They hold well in rock or weed, but will drag on any other bottom. It is mostly used by small fishing crafts where a bit of drag is not the end of the world, as they are likely to anchor over reefs and rocky outcrops, but their weight makes them unpopular for larger recreational crafts.
  • Danforth – This can be adapted for use with large and small vessels, but is particularly popular with small boats because of its strong holding power in sand or hard-mud bottoms, as well as clay, shell, or rock. However, it is not an ideal anchor for grass, deep mud, or silt, where it may pull free. It may also false-set on rocky or debris-strewn bottoms.
  • Plough or CQR – This English anchor is one of the most popular and oldest designs. It is reliable on most bottoms and responds well to wind and tide changes compared with other anchors, but it struggles on rock and can be difficult to stow because of its hinged design and frequently heavy weight.
  • Mushroom – This anchor is so named because it looks like an upside-down mushroom. It is the anchor mostly used by permanent mooring buoys. As silt and sand builds up over the anchor it can result in a holding power 10x its starting weight. While this is an excellent anchor choice in permanent mooring situations, it is ineffective for temporary mooring, and only excels on a sand, mud and silt bottom.
  • Bruce – Heavier than the Danforth type, the Bruce anchor is a recent versatile design that specialises in holding in sand, mud, clay, and holds its own in rocky terrain. Its ability to turn 360 degrees without breaking out is an added bonus. However, it is not as formidable with soft sand and mud and can be awkward to stow without an anchor roller. It also struggles to penetrate thick vegetation.
  • Grapnel – Regularly used by small crafts such as kayaks and dinghies, Grapnels are not good all round anchors. They fail miserably in mud and sand, but instead specialise in grabbing a rocky seabed when a conventional anchor struggles. They are therefore most often used as a handy extra anchor or by fishermen over craggy outcrops. Retrieving the anchor after it hooks on a rock may be difficult also.

Where to Drop Anchor

When choosing where to moor there are several aspects to consider before dropping the anchor:

Bottom: The most common bottoms are sand, mud, clay and grass (or weed). Most of the popular anchor styles (Danforth, Plough, Bruce) are considered workable in all of these conditions. That said, in general rocky bottoms are the most problematic. Sand and mud are usually the safest bet for anchoring.

Position: Secondly, the spot should have as little tidal stream as possible. The stronger the tide, the stronger the anchor and cable will need to work to keep the vessel in the same position. Also, while it may be tempting to pick a readily small anchorage, larger ones are often safer, providing more time to react to drag without beaching.

Depth/Scope:The amount of rode that you have out (scope) when anchored depends generally on water depth and weather conditions. The deeper the water and the more severe the weather, the more rode you will put out. For recreational boaters, at a minimum you should have out five to eight times (5 - 1 scope for day anchoring and 6 to 8 - 1 for overnight) the depth of the water plus the distance from the water to where the anchor will attach to the bow. For example, if you measure water depth and it shows 4 ft and it is 3 ft from the top of the water to your bow cleat, you would multiply 7 ft by 6 to 8 in order to get the amount of rode to put out.In poor holding bottoms with high wind/ strong current however, a 10-1 scope may be required.

Anchoring Amongst Other Boats:  If you arrive at a spot first, your are considered to have priority over a boat that arrives later. This means that if a boat begins to swing into you, they are obliged to move.

However, if you arrive late, it is important to estimate the swinging distance of your craft in relation to the other vessels, bearing in mind that different boats swing to the tide at different times depending on the direction and strength of the wind, as well as the craft’s size. For instance, bigger boats tend to swing slower and in a larger circle than smaller ones, while vessels with a large windage (sailboats and vessels with big cabins) will swing faster in high wind.

Essential Tips for Safe Anchoring

  • Anchors should be chosen carefully to match the vessel and its purpose.
  • The gear that attaches to the anchor to the vessel is as important as the anchor itself. You should check your owner’s manual for how properly secure the anchor to your vessel.
  • To avoid losing an anchor it is essential to make sure it is correctly rigged before being dropped.
  • Scope is as critical as anchor design, with the minimum scope estimated at 4:1 to avoid the anchor pulling out when the chain is pulled taut.
  • Anchoring along a beach requires extra caution and precautionary measures, as there is the risk of low tide catching you unawares, or dragging onto land.
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