Choosing an Anchor

Anchor Gear · Ground Tackle

For most of the twentieth century, the CQR plow and the Danforth flat anchor divided the cruising world between them. The CQR — a hinged plow designed by Geoffrey Taylor in the 1930s — became the default offshore anchor for a generation of bluewater sailors. The Danforth, with its twin pivoting flukes and high surface-area design, dominated coastal and powerboat use. Neither was particularly good. Both benefited from being the only credible options available.

That changed in the 2000s when a group of independent designers — working mostly in France, New Zealand, and Australia — published both new anchor designs and, crucially, comparative holding-power data. The tests were damning. The CQR's hinged shank, intended to allow the anchor to swivel with tide and wind shifts, turned out to be its primary weakness: the hinge allowed the anchor to rock out of the bottom under variable loads. The Danforth performed well in pure sand and soft mud but failed badly in weed, rock, and harder substrates. The new concave-blade designs, arriving as the Rocna in 2004 and the Spade somewhat earlier, demonstrated holding power three to five times higher than the CQR in standardized tests in similar bottom conditions.

How Modern Roll-Bar Anchors Work

The defining feature of the modern generation of high-holding-power anchors is the concave blade — a deeply cupped fluke that digs rather than planes when load is applied. Unlike the CQR's hinge, which allowed the anchor to pivot in unpredictable ways, the new designs use a fixed or controlled-geometry shank that keeps the load axis aligned with the burial angle of the blade.

The roll-bar — the distinctive curved tube welded across the crown of anchors like the Rocna — solves the oldest anchoring problem: what happens when the anchor lands upside down on the bottom. A flat-fluked anchor lying inverted simply waits to be dragged over the bottom until it either rights itself or doesn't. The roll-bar is shaped so that the anchor cannot rest stably in any orientation except fluke-down. As soon as load is applied, the roll-bar rolls the anchor right-side-up and the fluke drives into the substrate. The self-righting action is reliable enough that experienced offshore sailors routinely lower the anchor rather than dropping it — the roll-bar handles the rest.

The Mantus achieves the same function with a different geometry: a large radiused shank that acts as its own roll bar. The Spade uses an internal ballasting system — a lead weight in the tip of the fluke — to keep the blade oriented correctly as it sinks. Different mechanisms, same outcome: the anchor goes in right-side-up, sets quickly, and buries deeply once loaded.

The Comparative Test Data

The most cited independent holding-power testing comes from two sources: the series conducted by French naval architect Alain Poiraud (who also designed the Spade), published in the late 1990s and early 2000s, and the extended series published by Practical Sailor magazine, which ran comparative tests in various bottom conditions over multiple years. Poiraud's tests were the first to document the CQR's instability under variable load systematically, using strain gauges and repeated extraction tests in controlled conditions. The Practical Sailor tests added real-world variables — different substoms, worn anchors, bent shanks — that production-boat CQRs actually exhibit after years of use.

The consistent finding across multiple independent sources: the Rocna, Spade, and Ultra anchors hold approximately three to five times more than a same-weight CQR in sand, and the gap widens in harder clay or mixed substrates where the CQR's blade struggles to penetrate. The Danforth-pattern anchors hold extremely well in soft sand and mud but fail abruptly in weed or rock — their large flat flukes skate along rather than biting through vegetation or finding purchase in hard substrate.

Sizing by Boat Displacement

The traditional rule of thumb — 1 pound of anchor per foot of boat length — represents a comfortable coastal minimum, not an offshore standard. A 40-foot cruising boat under this rule would carry a 40-pound anchor. Most experienced offshore sailors carry 60–80 pounds as their primary, with some choosing even heavier for storm anchoring. The logic is not primarily about holding power tables; it is about margin. In a 45-knot squall at 0200 in an unfamiliar anchorage, the cost of dragging onto a lee shore is measured in the boat. The cost of extra anchor weight is measured in a slightly heavier bow.

Displacement matters more than length. A heavy, full-keeled 40-foot cruiser at 30,000 pounds has far more windage and momentum than a lightweight performance 40-footer at 14,000 pounds. For displacement-based sizing, the rough guideline used by many offshore sailors: 1.5 lbs of anchor per 1,000 lbs of displacement as a coastal minimum, 2.5 lbs per 1,000 lbs for a storm anchor. A 25,000-lb boat would carry a 37–62 lb primary under this formula — consistent with the Rocna 33 or 55 for that displacement range.

The Anchors Compared

Rocna

The Rocna, designed by New Zealander Peter Smith and introduced in 2004, was the anchor that broke the CQR's commercial dominance. Its combination of a deeply concave galvanized steel blade, roll-bar auto-righting system, and fixed shank geometry produced holding power results in independent tests that were difficult to argue with. A decade of real-world use by offshore cruisers confirmed the test results. The Rocna is available worldwide, galvanized versions are moderately priced, and parts and replacements are stocked at major chandleries on most cruising routes. It is the baseline against which other modern anchors are measured.

Mantus

The Mantus is a US-designed and US-manufactured roll-bar anchor that solves a real problem the Rocna does not: storage aboard small boats. The Mantus shank bolts to the fluke rather than being welded, allowing the anchor to be disassembled and stowed flat — useful for boats without a dedicated anchor roller, or as a second anchor that needs to go below. Holding power tests rate the Mantus close to the Rocna in most substrates. The stainless steel versions are expensive; the galvanized versions are competitive with the Rocna at similar weights.

Spade

The Spade, designed by Alain Poiraud and manufactured in France, was one of the first of the modern high-holding-power generation. It uses a different self-righting system — internal ballasting rather than a roll-bar — and a blade geometry that performs particularly well in hard clay and mixed bottoms. The aluminium version is a meaningful option for weight-conscious sailors: a Spade A80 in aluminium weighs about 17 lbs but tests to the holding power of a much heavier galvanized steel anchor. The weight penalty of a bow-heavy ground tackle setup is real, and the aluminium Spade is one of the few ways to get offshore-grade holding power without it.

Ultra Anchor

The Ultra, an Australian design, has posted the highest absolute holding power numbers in several published test series, particularly in sand and soft mud. It uses an extremely aggressive concave blade geometry with a high fluke area. The tradeoff is that the Ultra can be difficult to break out in very deep burial — a problem that is much easier to manage with an electric windlass than by hand. For boats with capable windlass installations, the Ultra is worth considering as a storm anchor. Availability outside of Australia and New Zealand is more limited than the Rocna or Mantus.

Delta

The Delta is the OEM anchor fitted to most production boats in the 30–45 foot range and is adequate for its intended use. It is a fixed-shank plow with a weighted tip that helps it orient correctly, and it holds reasonably well in sand and light mud. It is not in the same holding power category as the Rocna or Spade — tests consistently show it performing closer to the CQR than to the modern roll-bar anchors. If your boat came with a Delta, it is not an emergency, but replacing it with a Rocna or equivalent is a meaningful safety upgrade for anyone planning more than coastal sailing.

Danforth / Fortress

The Danforth-pattern anchor — twin pivoting flukes with a large flat surface area — performs better in pure sand and soft mud than almost any other design of equivalent weight. The Fortress, the aluminium alloy version made in the US, takes this further: an FX-23 Fortress (6.5 lbs) tests to holding power comparable to a 22-lb galvanized steel Danforth. This makes the Fortress the logical choice for a kedge anchor — the second hook that gets set when you need to kedge off a grounding, anchor fore-and-aft in a tight berth, or set a windward anchor in deteriorating weather. Its failure mode — skating across weed or finding no purchase in rocky bottoms — is well understood and manageable with awareness of where you are anchoring.

Luke / Fisherman Pattern

The old-fashioned fisherman anchor — a long stock with two fixed flukes — looks like a prop from a nautical antique shop. It remains irreplaceable in specific conditions: very rocky bottoms, heavy kelp, coral rubble, and mixed substrates where modern concave anchors cannot find purchase. A fisherman anchor works by getting a fluke tip into a crevice or under a rock edge; it does not depend on burying into the substrate. Boats that cruise areas with consistent kelp beds or rocky anchorages — the Pacific Northwest, the Scottish islands, parts of Norway — often carry a Luke or similar fisherman-pattern anchor as their secondary for exactly these conditions. It takes a dedicated locker or deck stowage because it cannot be fitted to a standard bow roller.

Two-Anchor Strategy

The standard offshore setup is two anchors: a primary that is sized at or above the storm threshold for the boat, and a kedge that is lighter and purpose-built for different conditions or uses. The primary anchor — a Rocna, Mantus, or Spade at appropriate displacement weight — rides on the bow roller with its chain rode, ready to deploy in any conditions. The kedge lives below or on deck, connected to a lighter chain leader and rope rode, and comes out for kedging off groundings, fore-and-aft mooring in tight anchorages, or setting a second anchor into the wind when the primary's holding ground is uncertain. A Fortress in an appropriate size is the most popular kedge choice because it covers sand-and-mud conditions well and the weight savings in aluminium mean it is genuinely deployable by hand without assistance.

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Frequently Asked Questions

Why did modern roll-bar anchors replace the CQR as the offshore standard? Independent holding-power tests in the late 1990s and 2000s revealed the CQR's hinged shank allowed it to rock out of the bottom under variable loads — a fundamental design weakness. Concave-blade anchors like the Rocna and Spade demonstrated three to five times the holding power of a same-weight CQR in standardized tests in sand and mixed substrates. A decade of bluewater cruiser experience confirmed those results.

How does a roll-bar solve the problem of an anchor landing upside down? The roll-bar is a curved tube welded across the crown of the anchor, shaped so the anchor cannot rest stably in any orientation except fluke-down. As soon as tension is applied to the rode, the bar rolls the anchor right-side-up, driving the fluke into the substrate. This self-righting action is reliable enough that offshore sailors routinely lower the anchor slowly rather than dropping it.

What is the recommended anchor sizing formula for offshore sailors? The traditional rule of 1 pound per foot of boat length is a coastal minimum, not an offshore standard. Most experienced offshore sailors use a displacement-based formula: 1.5 lbs per 1,000 lbs of displacement as a coastal minimum, or 2.5 lbs per 1,000 lbs for a storm anchor. A 25,000-lb boat would therefore carry a 37–62 lb primary anchor, consistent with a Rocna 33 or 55.

In what conditions should you use a Danforth or Fortress anchor instead of a roll-bar anchor? Danforth-pattern anchors perform better in pure sand and soft mud than almost any other design of equivalent weight — the Fortress aluminium alloy version tests to the holding power of a galvanized steel anchor four times heavier. However, their large flat flukes skate across weed and find no purchase in rock, so they are best deployed as a kedge rather than a primary where bottom types vary.

When is a fisherman-pattern anchor still the right choice? The Luke fisherman anchor remains irreplaceable in very rocky bottoms, heavy kelp, coral rubble, and mixed substrates where modern concave anchors cannot bury. Rather than relying on burial, the fisherman works by hooking a fluke tip into a crevice or under a rock edge. Boats cruising the Pacific Northwest, Scottish islands, or Norwegian coast commonly carry one as a secondary anchor for these specific conditions.

What is the standard two-anchor setup for offshore cruisers? The offshore standard is a primary anchor sized at or above the storm threshold for the boat — typically a Rocna, Mantus, or Spade on a chain rode on the bow roller — plus a lighter kedge for secondary use. The Fortress is the most popular kedge choice because its aluminium construction makes it genuinely deployable by hand, and it excels in the sand-and-mud conditions where a kedge is most often needed for kedging off groundings or fore-and-aft mooring.