Testing Modern Anchors: Improved Design for Stronger Holding Power

There are important attributes that must be considered when selecting an anchor. Will it set quickly and hold in a variety of different bottom types? Can it withstand significant loads? Is it easy to deploy, retrieve and store? Is it right for your boat where you plan to cruise?

Anchor Types

There are essentially three categories of anchor. First are those with deep penetrating, lightweight, pivoting flukes such as the Danforth or Kewene. These are great for soft, muddy bottoms. Second are the plow-style anchors such as the Bruce, Delta, Manson Plow and Sarca. These have excellent structural strength, are good general-purpose anchors and they tend to set more easily due to increased weight. Finally, there are the new-generation anchors. Variations on all of these traditional designs exist and new ones seem to pop up all the time. Sand is relatively easy for anchors to penetrate. Most anchors hold will in hard sand. Danforth and Kewene anchors work well in sand. Mud, on the other hand, has low shear strength and requires an anchor with a wider shank-fluke angle and greater fluke area so that the anchor will penetrate deep to where the mud has greater shear strength. Mud is frequently thin and layered over some other material.

Fortress anchors (an aluminum Danforth style) work well in mud because they can be converted to a broad fluke angle. Rock and coral bottoms present different challenges. Here, holding power is more dependent on where you happen to drop the anchor than on the anchor type. As a general rule most anchors will stick (get stuck in) to rocks well but this is the best ground for a grapnel. Grassy or weedy bottoms present tough challenges for all anchor designs. Here, it is the tip weight and cutting edge of the anchor that are the most important factor. Let's take a look at a selection of well-known anchors

Kewene

Designed and made in New Zealand, it’s a general-purpose anchor that’s good for soft bottoms. For rockier conditions, it has a sliding shank to make retrieval easier. It’s a good-sized anchor for boats shorter than 30’ (9.14 m) otherwise the Kewene can start getting a bit too big for good bow fitting. It’s a popular small-boat anchor.

Danforth

The Danforth is good in soft, soupy bottoms. Its point design helps sets the wings. They are common anchor and it seems that every boat dealer includes one with a new-boat purchase. It’s important that you get one from a reputable manufacturer.

Mini Haul/Dreadnought

The mini haul is small for its weight, holds well and has a shank that slides back and forth to aid in retrieval. Because it has no sharp edges, it’s ideal for small inflatables.

Folding Grapnel

For easy storage, folding grapnels are good because they do what they say and fold down. They are popular on small dinghies, kayaks and small inflatables, but not suitable for bigger boats.

Fixed Grapnel

The fixed grapnel has been around for years and for anchoring around rocks. If it gets stuck, just pull on it until it gives way then just repair the prongs in the vice (oarlocks in your dingy) when you get home.

Spade

Spade anchors have been around about 10 years. They started the new generation of anchors and are suited for bigger trailer boats. They’re available in steel, stainless and aluminum, the aluminum models being suitable if weight is a consideration. With the highest amount of tip weight, they set quickly.

Rocna

The new generation Rocna is a designed and made in New Zealand. It’s a good strong anchor and has proven very popular with the trailerboat market. A Rocna attains the correct attitude for penetration and with its combination of chisel tip, roll bar and skids, it buries well in most seabeds – typically within 3’ 1 m). A Rocna’s roll bar ensures that the anchor turns itself to the correct attitude for setting. The skid-rails then direct the blade into the seabed. This also eliminates the need for dedicated tip-weight.

Manson Supreme

Also a new generation anchor from New Zealand, the Manson Supreme has a concave design that relies on surface area for holding power rather than physical weight. The twin slots on the anchor shank enable use in all seabed types. When anchoring in rocky or coral situations, switching the anchor rode onto the rock slot means that if the anchor becomes lodged or jammed, the shackle can slide to the front of the anchor and simply lift forward. The anchor has been reviewed by Lloyds Register of Shipping and Manson received SHHP (Super High Holding Power) status. It is the only production boat anchor in the world to do so.

Sarca

Originating in Australia, the Sarca sets well due to its shape and is well suited to firm bottoms, where it will dig into the hard surface and hold well. It has a sliding shank to help with retrieval. A downside is that it does disturb the sea bottom, so it’s not making environmentally friendly. On the positive side, it will churn up food out of the bottom for feeding fish, so your catch rate will improve.

Claw

The claw is basically a knock-off of the Bruce anchor. The Bruce has an excellent reputation, sets well and has good holding power. Most claws, as long as they are a good copy, are good quality. The claw does have a habit of letting go under extreme load. More popular on bigger boats.

Manson Plow

An old design, but exceptionally popular and highly regarded around the world. It sets reasonably well and works best if set slowly. They are good general-purpose anchors that work well in most conditions. The plow’s versatility and good holding power has made popular worldwide.

Delta

The Delta is a plow-style anchor and generally sets a bit better than other plows that have the swivel shank. A good general-purpose anchor, its low center of gravity and self-righting geometry ensure that the Delta anchor will set quickly. It is also available in premium grade duplex/high-tensile stainless steel.

In Summary

Generally, most anchors don’t like being set at speed. In fact, many people just drop the anchor and don’t set it at all and don’t realize that that’s not the best way to do it. You should lay your anchor as you’re moving slowly backwards, until you feel it begin to bite, then apply a little more power in reverse to set it into the bottom.

If you try to set an anchor too fast, it can skip along the bottom or suddenly set and cause damage to your windlass or cleats. This is quite likely with the new generation anchors because their design will cause them to set and stop quickly, so passengers need to hold on.

An anchor will work better with chain behind it and an anchor straight on the end of a piece of rope won’t work as well. You need a matched set. It’s important to realize that the main purpose of the chain is to provide sufficient weight to keep the angle of attack of the anchor within its design limits, and that the harder it’s blowing, or the faster the current flow, the more chain is required.

The weight of the chain also provides a dampening effect so you don’t shock load your anchor out of the ground or winch/cleat out of the deck. It also pays to buy quality rather than buying to a price. For instance, there are many knock-off plows, Bruces, Danforth anchors and chains that experts say aren’t up to the standard of CQR, Manson, Spade and other new-generation. When you consider the value of the boat an anchor is protecting and the fact it stops you from waking up on the rocks, an anchor is no place to economize.