This guide breaks down every mainstream anchor shape, explains why each excels — or fails — in different seabeds, and shows how to size, store, and deploy it across North America’s diverse waterways.
Anchor-Selection Fundamentals
Boat Length & Displacement
Holding power is a product of anchor weight × design efficiency. A 22-foot runabout that weighs 2,500 lb often holds safely on a 10-lb high-efficiency anchor, whereas a 35-foot cruiser displacing 12,000 lb may need 35 lb or more. Always start with the manufacturer’s sizing chart, then add 10–20 % if you routinely overnight or anchor in gusty, open roadsteads.
Bottom Conditions Across North America
| Bottom | Typical Scenario | Anchor Traits That Matter |
|---|---|---|
| Rock & Cobble | Boulder-strewn shorelines, submerged ledges | Sharp tip, concave scoop, high tip weight (Rocna, Spade) |
| Sand & Shelly Sand | Wide sandy flats, gently sloping beaches | Wide flukes dig deepest (Danforth, Delta) |
| Soft Mud / Silt | River deltas, silty estuaries, lagoon bottoms | Large surface area and suction (Box, Danforth, Spade) |
| Light Weed / Kelp | Shallow bays with sparse weed or kelp | Concave scoop anchors cut through fronds (Spade, Rocna) |
Storage & Deployment Considerations
- Bow roller: Ideal for plows, Spades, Deltas, and Rocnas; claws work fine too.
- Locker only: Flat-folding anchors (Danforth, Box, Grapnel) nest best.
- Weight forward: Extra metal on the bow can affect trim; lightweight aluminum models help.
- Windlass compatibility: New-generation plows and scoops feed smoothly; hinged CQRs can jam on small gypsies.
Anchor Types in Detail
Danforth / Fluke Anchor
A pair of 30-degree plate flukes hinge off a stock, delivering huge surface area for minimal weight. In sand or firm mud the Danforth digs fiercely; in weed it can skate, and on bare rock it struggles. Its flat profile folds like a laptop and stows neatly in a shallow locker — one reason almost every runabout or tender carries one. Weakness: a 180-degree wind-shift can roll it out and leave you adrift.
CQR / Traditional Plow Anchor
Patented in 1933, the CQR (short for “Coastal Quick Release”) hinges at the shank to self-right, then plows forward under load. It resets reasonably well in soft or weedy bottoms and tolerates tidal shifts, yet its holding-power-to-weight ratio is modest by modern standards. Many long-range cruisers still trust a heavy CQR, but those upgrading often find a lighter Spade or Rocna out-holds it at half the mass.
Delta Plow Anchor
The Delta fixes the CQR’s shank, widens the blade, and sharpens the point. The result is a set-and-forget workhorse supplied as OEM gear on many production boats. It excels in mixed sand/mud and handles moderate weed. On slick rock ledges, however, its convex blade can skate before it bites.
Bruce / Claw Anchor
Originally designed for oil-rig moorings, the claw’s open scoop grips reliably in sand, soft mud, or coral rubble and resets instantly when wind or tide veers. It’s forgiving to novice technique but offers less ultimate hold than concave scoop designs. In thick clay, penetration can be difficult.
Rocna / Spade (Next-Generation Scoop)
Both anchors feature a deep concave fluke that scoops seabed like a shovel, generating class-leading holding power. Rocna adds a roll-bar; Spade relies on a weighted nose to flip upright. Independent tests show they set in one-third the distance of a plow and hold up to twice their rated load. Commercial lobster fishers working rugged coasts favor these designs for exactly that reliability.
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Box Anchor
Two intersecting plates form a cross-shaped box. Whichever face lands first, the flukes dig, giving impressive 360-degree holding. It folds flat for stowage but can feel bulky on small bow rollers.
Mushroom Anchor
A hemispherical “mushroom” settles into soft silt and, over time, builds suction stronger than its own weight—ideal for permanent moorings or swim rafts. For cruising use, however, it offers little holding until deeply buried.
Grapnel / Folding Anchor
Multiple tines fold against the shank, creating a rock-grabbing hook perfect for kayaks and dinghies among submerged boulders. It snags structure rather than digging, so retrieval often requires a trip line. Not recommended for overnighting larger boats.
How to Size & Match an Anchor
| LOA (ft) | Displacement (lb) | Danforth (lb) | Spade/Rocna (lb) | Delta (lb) |
|---|---|---|---|---|
| 16 – 20 | ≤ 2,000 | 4 – 6 | 6 | 9 |
| 21 – 25 | 2,000 – 4,000 | 8 – 10 | 10 | 14 |
| 26 – 30 | 4,000 – 7,000 | 13 – 16 | 15 | 22 |
| 31 – 35 | 7,000 – 12,000 | 22 – 25 | 21 | 35 |
| 36 – 40 | 12,000 – 20,000 | 28 – 35 | 27 | 44 |
Figures blend manufacturer charts with field feedback. Account for windage, chain size, and windlass limits before finalizing.
Best Practices for Setting & Retrieving
- Survey the seabed with sonar or lead-line.
- Approach into the wind, stop, and lower—not throw—the anchor to the bottom.
- Back down slowly while paying out a 5:1 scope (7:1 for overnight).
- Load test by increasing reverse throttle; verify the anchor holds without creep.
- Check reference bearings; a steady lineup signals a solid set.
- Retrieve by motoring up-wind until chain is vertical, then use the windlass. If stuck, drive gently over the anchor to break suction.
Tip for scoop anchors: a gentle forward burst often flips them out cleanly, avoiding the “plow ploughing” effect.
FAQ on Boat Anchor Types
Q1. How much chain versus rope should I carry?
Many coastal cruisers use 30 ft (9 m) of chain plus 150 ft (45 m) of nylon rode on 20-foot boats. All-chain rode adds abrasion resistance and catenary for heavier vessels.
Q2. Do I need a kellet (anchor sentinel)?
With modern high-efficiency anchors a kellet is seldom required, but a 5 kg weight 15 ft down the rode can reduce shock loads in steep chop.
Q3. How often should I inspect my anchor?
Rinse galvanized models after each trip and check zinc coating annually. Stainless models need inspection for hairline corrosion at welds. Aluminum Spades require only a freshwater rinse; check the lead-filled nose for seepage.
Q4. What’s the best anchor for a rocky cove?
Concave scoop anchors such as Rocna or Spade set fastest and hold strongest. Claw anchors are second-best; fluke and traditional plow designs often skate on bare rock.
Final Thoughts
An anchor is the cheapest insurance your boat will ever carry. Traditional plows and Danforths still work, but new-generation scoop anchors deliver twice the bite at half the set distance, a difference you’ll appreciate the first time a midnight squall sweeps through an exposed anchorage.
If you’re ready to make anchoring almost boring, explore our full range of galvanized, stainless-steel, and aluminum models. Whether you’re outfitting a small cruiser or a blue-water passagemaker, we have the right size in stock—and we’re happy to walk you through chain, rope, and windlass compatibility.
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