Choosing The Right Anchor Weight For Your Small Boat

Choosing the right anchor weight for your small boat depends on several factors, including the length and weight of your boat, weather conditions, and the type of water bed you'll be anchoring in. As a general rule, you'll need a heavier anchor if you have a larger and heavier boat, or if you're dealing with strong winds and currents. The weight of the anchor also depends on the water bed conditions, as different anchors are designed for different surfaces like mud, sand, grass, or rocks. It's recommended to select an anchor with the highest weight-to-length ratio for your boat to ensure it holds in various conditions.

Holding power vs. weight

Holding power is the ability of an anchor to withstand the pull force required to hold a boat in place. It is formulated based on environmental factors, such as wind speed, and the weight of the boat. For example, a holding power of 90 pounds is sufficient for safely anchoring a 20-foot boat in winds up to 20 mph. For the same wind speed, a holding power of 125 pounds is adequate for a 25-foot boat.

The weight of the anchor is important, but it is not the only factor that determines its holding power. Anchors that rely solely on their weight, such as mushroom anchors, navy anchors, and river anchors, are limited in their holding power and are typically only capable of generating up to twice their weight in holding power. Therefore, a 20-foot boat using a 20-pound anchor that relies only on its weight will not have sufficient holding power.

When selecting an anchor, it is crucial to consider the conditions in which the boat will be used. If you plan to anchor in calm, protected coves, a smaller anchor may suffice. However, if you anticipate encountering strong winds or currents, you will need an anchor with greater holding power. Additionally, the type of water bed matters. For example, fluke-style anchors are ideal for hard sand and mud but are not suitable for rocky or grassy bottoms.

To ensure your boat remains securely anchored, it is generally recommended to carry the largest anchor that your boat can accommodate. If space permits, it is beneficial to carry two anchors of different types and weights: a smaller "lunch hook" for calm waters and a larger "working anchor" for overnight trips or gusty winds.

While holding power is essential, it is just one aspect of anchor selection. The size and weight of your boat, the weather conditions you expect to encounter, and the characteristics of the water bed all play a role in determining the best anchor for your small boat.

Anchor types

There are many types of anchors to choose from, and the right one for you will depend on your boat and the conditions you will be boating in.

The most popular type of anchor is the fluke anchor, also known as the Danforth anchor. It is often the only anchor on smaller boats as it is light and easy to weigh, and it stows flat. It has excellent holding power relative to its weight, but it doesn't hold well in grassy or rocky surfaces. Fluke anchors are best suited for lakes, rivers, mud and sand, but they are not suitable for rocks, debris, coral or strong currents.

Plow anchors, also known as scoop anchors, are another popular choice. They have the best all-around holding ability in varying bottom conditions and are simple and effective. They can provide reliable mooring in all water conditions and most beds, and they set quickly, making them a good choice in strong winds or currents. However, they are not suitable for rocky bottoms as they can get stuck.

Claw anchors, also known as Bruce anchors, are similar to plow anchors in that they set quickly and dig into soft bottoms. They are a good choice for gravel and rock, as they use smaller pins and are therefore less likely to get stuck. Claw anchors are ideal for large, open bodies of water and perform well in windy conditions.

Digger anchors are best suited for sand, mud, grass, gravel and strong winds. They have high holding power in gravel and rocky bottoms, even with strong currents and high winds. They are not suitable for bottoms with large debris.

Mushroom anchors are designed for small vessels in relatively calm waters with soft bottoms. They are typically found on light, electric motor-powered boats, kayaks and dinghy boats. They are not recommended for large boats, heavy currents or rocky bottoms.

River anchors are intended for small vessels in lakes and rivers, especially those with rocky bottoms and beds filled with debris. They work well in soft bottoms but have less holding power than a mushroom anchor.

Navy anchors are heavy and big, providing high holding power in all waters and conditions. Their size and shape make them suitable for rocky bottoms and debris fields, but they are not recommended for small, light boats as they are difficult to stow and add weight to the hull.

Grappling anchors are compact and can fold up for storage in small spaces. They are commonly used on jon boats, canoes, kayaks and aluminum skiffs.

Pontoon boat owners often opt for a hybrid fluke/navy anchor, which uses flukes/claws and a square shape to maximise surface area contact with the bottom.

Bottom conditions

Sand, especially fine-grained sand, is relatively easy for anchors to penetrate and offers consistently high holding power. Pivoting-fluke anchors and non-hinged scoop anchors are the best types for this bottom condition.

Mud presents a different challenge, requiring anchor designs with a broader fluke area and a sharper fluke angle to penetrate deeply and reach greater holding power. Anchors that can adjust their fluke angle, like the Fortress anchor, perform well in mud.

Rocky bottoms require anchors with high structural strength, such as plow-shaped or grapnel-type anchors. These anchors can sustain high point-loads and snag on protrusions to hold the boat in place.

Shale, clay, and grassy bottoms are more challenging for any type of anchor. In these conditions, the weight of the anchor becomes more critical than its design for penetration and holding power. Anchors like the CQR, Delta, Rocna, and Supreme are considered good choices due to their ability to penetrate vegetation. However, these conditions may also lead to false settings, as the anchor can catch on roots and protrusions instead of penetrating the bottom.

Additionally, when considering bottom conditions, it is essential to assess the depth of the water. In deeper waters, using an anchor one size up is recommended to allow for faster setting and less line usage.

In summary, when selecting an anchor for a small boat, understanding the bottom conditions is vital. The type of seabed and water depth will influence the anchor's performance, with different designs suited to sand, mud, rock, or grass. Choosing an anchor that can effectively penetrate the bottom and provide sufficient holding power based on the specific conditions will ensure a safe and secure anchoring experience.

Anchor weight vs. boat size

When choosing an anchor for your boat, it's important to consider the size and weight of your boat, the weather and anchoring conditions you'll encounter, and the characteristics of the water bed. As a general rule, the heavier the boat, the larger and heavier the anchor should be.

For small boats, such as those 22' or less, a 7 lb, 10 lb, or 14 lb anchor is typically sufficient for moderate conditions and day trips on small bodies of water. These anchors can also be used as a stern anchor to prevent rear swing. If you plan on anchoring overnight or in stronger winds, a larger anchor may be necessary.

The type of anchor you choose also depends on the water bed conditions. For example, fluke-style anchors are a popular choice for small recreational boats as they provide good holding power in hard sand or mud, but they are not suitable for rocky bottoms or grassy areas. Navy-style anchors, on the other hand, are better suited for heavy grass, weeds, and rocky bottoms.

It's also important to consider the holding power of the anchor, which is the ability of the anchor to hold a given weight. A heavier boat will require an anchor with greater holding power. Additionally, the windier the conditions, the more holding power you'll need.

When anchoring a small boat, it's crucial to never anchor by the stern, as this can result in swamping and flooding. Instead, always anchor from the bow and ensure you have sufficient anchor line or "rode" to secure your boat safely.

Anchor chain vs. rope

When it comes to anchoring, you might think that a chain is far superior to a rope. However, a chain only has two advantages over a rope. Firstly, it adds holding power, helping to keep your boat moored in rough water and strong currents. Secondly, it resists chafing and won't suffer damage from being dragged along debris and rocks.

Despite these advantages, a chain has a lot of disadvantages. It adds a lot of weight to your boat, which isn't a problem for large, sea-going vessels, but it can be cumbersome for smaller boats. Chains are also expensive and prone to rusting, even with regular maintenance.

On the other hand, modern synthetic anchor ropes are tough, abrasion-resistant, and withstand water and sunlight well. They are also lightweight and take up less space than a chain.

The most effective setup is a combination of both chain and rope. A short length of chain near the anchor, with the rest of the line made up of rope. This setup improves the scope of your line and provides the benefits of both chain and rope.

The scope is the ratio of the length of the deployed rope (or chain) to the height from the ocean, lake, or riverbed to the anchor point on the boat. A scope of 5:1 is the minimum required to properly moor your vessel, providing about 75% of the maximum holding power. A scope of 10:1 provides 100% holding power.

For small boats, an all-rope rode made of three-strand nylon anchoring line is a good option. It is lightweight, inexpensive, and easier to stow than a chain. However, it lacks the chafe resistance of a chain and is not suitable for anchoring near coral or rocks.

For larger boats, an all-chain rode is often used, providing extra security in open water and heavy-weather anchorages. However, the weight of the chain can be a significant disadvantage, adding hundreds of pounds to the bow of the boat and affecting its performance.

In summary, the best option for anchoring a small boat is a combination of a short length of chain with a nylon rope rode. This provides the benefits of both systems, with good holding power, shock absorption, and resistance to chafing, without adding excessive weight to the boat.

Frequently asked questions