In Depth Info on Anchors

 
Selecting an Anchor
The type of anchor you choose is often dependant on the nature of the seabed you are anchoring to. Anchors are designed to anchor a boat to the seabed allowing for a boat to be held in position against wind, tide and current. The use of anchors is an ancient art as old as boating itself. Learning to anchor your boat effectively is an important skill to ensure safe and enjoyable boating.

Sand Anchors (Danforth Type)
These are great anchors in sandy or muddy bottoms as they rely on penetrating the sand or mud to grip. These are a very popular anchor as they fold down flat, are easy to stow once on board and have good holding power. The sand anchor should not be used on reef or rock, as it will not be able to penetrate and hold. The 'double fluke' design makes sand anchors prone to losing their grip when the tide and the direction of the pull changes.

Slip Ring Sand Anchor
This is a variation of the sand anchor with a design that allows for the anchor to be easily retrieved backwards.

Reef Anchors
This is another popular anchor which is very effective on rock, wrecks and coral. Reef anchors rely on 'hooking' onto underwater structures rather than penetrating the bottom. The great feature of the reef anchor is that it has bendable prongs which can be straightened when lifting the anchor. Once on board the prongs can be bent back to the optimal shape. Reef anchors are available with four and five prongs. When you purchase a reef anchor at BCF the prongs are in the straightened position which is easier and safer to transport. Due to the prongs' ability to be straightened it is not recommended to use a reef anchor overnight, especially in a high risk situation.

Plough Anchors
Plough anchors are based on a single fluke design which has better holding power in changing currents and tides. This is because it is easier to maintain grip with a single fluke as it follows a changing direction of pull. Plough anchors are very effective in sand and mud. They can be used on rocky bottoms, especially if the cable tie method (explained later) is used. The one big disadvantage of the plough anchor is that they are bulky and difficult to stow once on board. To counter this many boats using a plough anchor will stow the anchor on a bow roller. There are many variations of the plough type anchor but they are all based on the same single fluke design.

Grapnel Anchor
The Grapnel anchor is very effective for anchoring on hard rocky bottoms. These anchors have short, strong prongs which are able to hook onto underwater structure. They are equipped with a trip ring which (using the cable tie method) can be used to reverse pull an anchor that is held fast.

Folding Anchors
Folding anchors are commonly used in small dinghies, canoes and inflatable boats where space is limited. They are an acceptable anchor for small boats to use in safer estuary conditions.

Sea Anchors
A sea anchor is a valuable piece of safety equipment for any vessel venturing out to sea. When set it will slow the drift rate and keep the bow of your vessel into the wind. In an emergency breakdown situation this is a critical factor as it will discourage the vessel from rolling and pitching and will help the vessel stay in relatively the same location until help arrives. Sea anchors are also ideal for offshore fishermen and allowing bait to be kept on the bottom longer when drifting over a favorite fishing spot. The traditional sea anchor is conical in shape and effectively acts as an under water windsock channeling water through a small hole, creating drag. This design is being overtaken by the parachute type which has a larger surface area, creating more resistance in the water.

Rode Types - Chain vs Rope
The advantage of a chain rode is that its weight ensures a large proportion of the rode is positioned on the seabed, creating a horizontal pull on the anchor. However, the weight of the chain becomes a disadvantage once onboard a small boat as it is effectively the same as carrying another person onboard. The advantage of a rope rode is that rope has stretch and is more forgiving when anchored in lumpy seas. Further to that, rope is significantly quieter which is much appreciated when you are sleeping onboard! As a result, most small boats will use a rope and chain combination rode. As a rule, the length of chain should be equal to a minimum of two thirds the length of your boat. The longer the length of chain, the easier and more effective you will anchor. Legislation also requires a minimum chain length, therefore it is advised that you check local regulations.

Setting an Anchor
A common anchoring mistake is to throw out the anchor. This has the potential to foul the anchor with the anchor chain/rope. The correct way to deploy an anchor is to steadily lower it into the water.
Once an anchor has been deployed, let out the appropriate amount of rope or chain for the water depth and conditions (see section on scope below), tie off on the anchor bollard and gently reverse the boat in the direction of the prevailing force (i.e. wind, current, tide..) applying pressure until the anchor sets. If you are in a situation where it is critical that the anchor holds (i.e. anchoring in a crowded anchorage) make sure that you place a reasonable reverse strain on the rode to ensure that the anchor is set. In low-risk anchoring situations it is common to let the anchor go and drift back in neutral to set the anchor.
Please note: Propellers and anchor ropes are a dangerous combination so always take up slack rope and be very aware of where the anchor rope is positioned in relation to the propeller.

Scope
All modern anchors require a near-horizontal pull to work effectively. To achieve this you need to have a rode of seven times water depth. Therefore if you are in three metres of water you would need to let out thirty-five metres of rode to ensure a horizontal pull on the anchor. This is a general rule of thumb; this proportion will vary depending on the waters and conditions you are operating in. As the depth of water increases so does the curve of the catenary which increases horizontal pull on the anchor. As a result, in deeper water the scope can be reduced to 5:1.

Weighing Anchor
Please note: Before weighing anchor it is very important to ensure that your motor is running properly and you are ready to safely operate the craft once it is underway.  The reverse principle of setting an anchor applies in that a vertical pull is required to break the anchor's grip on the bottom. Gather the rode as you motor up towards the anchor until the anchor is directly under the boat (remember to make sure that slack rope is kept clear of the propeller). In most situations at this point the anchor will break free and will be able to be pulled to the surface. If the anchor is still holding tie off to the anchor bollard and gently power ahead until the anchor breaks free.

Floatation Method
Another popular anchor retrieval method is based on using the buoyancy of a float to pull the anchor to the surface. This is particularly useful when operating in offshore waters where manual retrieval of the anchor is very hard work! - Consult an experienced boatie on how to use the floatation method.

Cable Tie Method
Many modern anchors have the ability to be set up with a trip tie to allow the anchor to be pulled out backwards. Attach the anchor shackle to the trip ring and cable tie the chain to the shank as pictured. This will allow the cable tie to be broken when you gently power ahead and the anchor can be pulled out backwards.

Glossary
Rode: The total deployed anchor cable (rope or chain) between the anchor on the seabed and the boat.
Cable: The chain and/or rope used for anchoring.
Weighing Anchor: Retrieving a deployed anchor.
Catenary: The curve in the rode created by the weight of the cable.
Scope: The proportion of the length of the rode in relation to the depth of water.
Dragging Anchor: The anchor is not holding.
Bow Roller: The wheel at the front of your boat that the anchor is guided through when setting and retrieving.