Sizes and Types of Boat Anchors

A vessel should never leave the dock without a suitable anchor. Anchors not only provide a means of mooring a boat but are part of the required safety equipment onboard. Anchors may be used to stop a boat from drifting into dangers such as rocks or reefs. A grounded boat can be pulled back into deeper waters using an anchor. Anchor designs vary greatly in size and shape and how effectively they function.

  1. Anchor Size

    • Several variables determine the appropriate size of an anchor required to provide adequate holding capabilities. An anchor's performance will change according to sea-bed substrates, size and type of vessel, wind conditions, depth of water and amount of anchor rope or chain laid out. Although manufacturers can supply sizing charts for vessels, choosing a larger-than-specified anchor is beneficial. Edinburgh University chemistry professor John Knox performed a test that showed a 15-kg anchor will give two to three times the holding power of a 5- to 7-kg anchor. Anchor sizing is often analyzed by weight rather than by dimensions. Some lighter designs require a large surface area of the flukes to be effective.

    Fluke-Type Anchors

    • The fluke style anchor is the lightest in weight but has a large flat area to contact and dig into the seabed. The fluke design Danforth anchor is common on smaller boats. Once buried, this type of anchor has a very high holding power but does not stay embedded with large direction changes. Fluke anchors do not penetrate into hard surfaces or seaweed-covered areas well. They are a good choice for mud or sandy bottoms and have a high holding capability for anchor weight.

    Plough-Type Anchors

    • Plough style anchors, named for their design and function, look and work much like a farmer's plough. Two major plough style anchors are the CQR and the Delta. These anchors are a good choice for cruising boats as they tend to be effective in several different sea beds. Plough style anchors are a heavier design and lend themselves to being stowed on a boat's bow roller. To increase weight, plough-type anchors have extra lead weight in the point, making them effective in penetrating gravel, hard sand and seaweed. They are also highly effective in mud and clay bottoms.

    Claw-Style Anchors

    • There are several styles of claw style anchors available, the Bruce design being the most common. Claw-style anchors have the ability to set quickly and stay set regardless of a vessel veering or changing direction as a result of wind or tide. This style of anchor is effective in mud bottoms. However, it has a lower holding-power-to-weight ratio than other anchors.

    Considerations

    • Because of the variables with anchoring conditions, boat types and sizes and geography one particular style of anchor will not work effectively everywhere. Check with local boaters to see what they use, or carry more than one type of anchor for changing conditions.