Delta anchor

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Delta fixed shank plow anchor

The Delta, or "Delta Quickset", is a decent performing anchor. In fact, Peter Smith, the Rocna designer, used one for many years including his trip all the way from the UK to New Zealand. However, its flaws, made obvious in certain locations on that trip, were partly the incentive behind the Rocna design. While the Delta was the best anchor in the early 90s at the time Peter's yacht was outfitted, there was much room for improvement. The Delta is probably the best of the 'old generation' – but has nothing on the 'next generation' Rocna.

History and current status

The Delta was developed in the 1980's for commercialization by British marine manufacturer Simpson-Lawrence. The Delta is a fixed shank plow, as opposed to the articulating variant of the plow concept (i.e. the CQR) of decades earlier. The need for articulation was avoided with more careful balancing of the anchor's weight and shaping of the rear end of the fluke in order to better guide the fluke through the setting process. The basic shape nonetheless remains a plow, with a brake-pressed plate heel and solid steel cast tip (welded together to form the only joint attaching the tip to the rest of the anchor) which comprises the fluke. Like other plows, this design relies on tip-weight for ballast and setting, an inefficiency which detracts from fluke surface area and ultimate holding power.

The genuine Delta brand is now owned by Lewmar. The anchor has been out of patent for a few years now, and poor copies abound, most of worse performance and questionable construction quality. The Delta, by no means perfectly engineered, nonetheless utilizes a high tensile steel shank, an element which is typically the first to be sacrificed in the pursuit of cost savings by knock-off producers.

The relative performance of fixed shank plows

Switching to the Rocna took some adjustment for me. It sets quickly, so I had to calibrate where I expected the anchor to set differently (we had a Delta 88 lb prior to the Rocna). I have also noticed more work is required to raise the anchor (snug up the chain, pull the boat forward slightly to break the anchor loose, then raise). I am very pleased with the Rocna.

Steve Hogan, SV "Robin Ann" USA

Maerin was equipped with a Delta Quickset 45 as primary... The Delta's name belies its capability, although it may set quick, it's very easy to drag it around in a blow. My experience is that it's difficult to set, doesn't stay set... We've used the Rocna extensively... It has performed superbly... I really love the Rocna, it's improved our rest on board, and had really improved our confidence in anchoring ...sets quickly, and securely. Best $1400 of insurance I ever bought!

Steve Sipe, MV "Maerin" USA

The Delta, per its design criteria, did deliver a significant improvement over its ancestral plow type, and jumped ahead of the Bruce to become the best anchor at the time of its release (with the possible exception of the then relatively unknown Bügel). In the history of anchor development, it occupies a nether region between the old and new generation types, certainly superior to all old generation patterns, but still far from the ultimate general purpose anchor.

  • The Delta fluke shape is a plow, with a convex fluke like the articulated CQR. It holds poorly in soft mud and does not like weed or grass (these are key areas where Rocna is drastically superior). The Rocna on the other hand has a massive fluke surface area, with a concave fluke designed to hold the ground.
  • The Rocna sets faster and more reliably in a greater variety of seabeds, including difficult bottoms like very hard compact sand, grass, weed, kelp, and others. This is confirmed by comparison testing and feedback from those boaters with comparative experience.
  • The holding power of Rocna is better on a weight for weight basis. This means that a smaller Rocna can be used to replace a larger Delta, and still provide a superior anchoring solution. The Rocna is both more efficient in terms of pure holding power, and a more reliable and consistent performer per se, irrespective of the anchor size.

From the averaged test data of the West Marine 2006 testing, which incorporated multiple pulls at multiple scopes in multiple locations, we get a holding power performance factor of 145 for the Rocna (i.e. it held an average force of 145 times its own dry weight), and a respectable but clearly inferior 92 for the Delta. This is calculated from the "max before release" figures for each anchor, being:

  • 4800 lb-force (2180 kg-force) for the Rocna 32 lb (15 kg) and
  • 3250 lb-force (1475 kg-force) for the Delta 35 lb (16 kg).

The comparative factor, if we consider 145 vs 92, is therefore 1.58. Even if one is conservative with this data, it is clear that any given Delta anchor can be replaced by a Rocna model one or two sizes smaller, or, conversely, the same size Rocna will offer significantly better performance.

Bow roller compatibility and stowage

Finally, the Rocna enjoys a small advantage over the Delta with regard to fit on bow rollers. The two anchors are fairly similar in profile presented to the roller, but the Rocna does offer marginally better tip clearance. More importantly the shank kick-back (crank) missing from the Delta is present to keep the anchor vertically secure when pulled home, with no vertical movement to annoy crew or damage the roller. Otherwise, the Rocna usually fits any roller designed for a Delta.

The graphic on the right illustrates a Rocna 15 and a Delta 16 kg positioned on a typical roller, the two anchors overlaid for comparison.

Further general comparisons to the Rocna

  • Rocna produce a larger range of anchor sizes. A notable example is the presence of a 33 kg (73 lb) model, while the Delta jumps from 25 kg (55 lb) to 40 kg (88 lb). Production Rocna sizes are easily available over 70 kg (154 lb).
  • Every Rocna sizes 10 (22lb) and larger features a dedicated tandem anchor attachment point for extreme weather, along with other thoughtful features appreciated by both those new to boating and more experienced cruisers.

Independent testing

There is a large amount of independent testing of both the Delta and Rocna. However, the following summary comments from West Marine in the USA relating to their 2006 comparison testing best sums up the true differences.

West Marine
2006 testing

Quotes complete
& verbatim

Delta 35 (36 lb):
Variable results ranging from around 1,500lb. to 4,500lb. Drags at limit.
Rocna 15 (32 lb):
Superb, consistent performance. Held a minimum of 4,500lb and engaged immediately.

The Delta is HHP (High Holding Power) classified by Lloyd's. The Rocna however has SHHP (Super HHP) classification. The SHHP standard requires the anchor to resist pulls at least 200% that of a HHP anchor, over three different seabeds.

Comments from Peter

Before deciding that the world needed a better anchor design, Peter Smith (the designer of the Rocna) used a Delta anchor for years at countless hundreds of anchorages during a semi-circumnavigation. Below are some comments from Peter based on his extensive experience with the qualities and performance of the Delta.

The Delta is a fixed shank plough anchor originally designed and produced by Simpson-Lawrence in Glasgow, Scotland. I have owned and put some 20,000 nautical miles (on a voyage from England to New Zealand) on a 40 kg / 88 lb original Scottish built model. It was this voyage and the problems experienced – such as dragging in the soft mud of the Chesapeake and New Zealand rivers, the grassy bottoms in New Zealand's lower South Island, difficulty getting a set in the thin coral layer in the Bahamas, problems with swinging room in the crowded anchorages of Rhode Island and Maine, and disconcerting events such as the boat not being where we left it because the wind changed direction! – this all led to the development of a new generation anchor.

The original Delta versions were very well built, with nice detailing such as the bottom edge of the shank which had a milled V section to reduce resistance to the anchor burying. Good quality high carbon steels were used for bend resistance in the shank. The design lends itself to most bow roller configurations. The original design uses a cast toe providing the essential tip weight for this type of anchor, providing a strong long wearing tip that does not need removing or melting (such as articulating ploughs with lead inserts) when re-galvanizing.

The Delta sets reasonably quickly and consistently in ideal conditions when compared to older generation anchors such as articulating ploughs.

However. Simpson-Lawrence now comes under the Lewmar umbrella, and the quality of current anchors which I have seen are nothing like the original production models. No shank bevel, all steel edges are sharp with no pre-galvanizing chamfers, and no cleaning of intermittently rough galvanizing.

Further: the shank design has a straight neck with no gusset were it joins the blade, and therefore the anchor just sits on the bow roller where it tends to wobble and even jump in a seaway, with no way to restrain it other than a lashing or pin, or a specially configured custom roller arrangement. This design element has proven to be a major design weakness. The shank, heel, and cast toe are all welded together with all three components meeting at a critical apex. The shank is only in effect welded to the heel which is in turn welded to the toe. I have personally seen three anchors which have broken at this junction. (With the Rocna, I designed a gusset into the equivalent neck point, spreading the shank loads down into the heavy plate toe where it acts as a reinforcing beam across the toe-to-heel joint. At the same time, the gusset forms the shape required to lock the anchor into the bow roller preventing vertical movement when in a seaway.)

The design uses the tip-weight to roll the anchor around the curved heel plate edges into the setting position. This turning moment is critical to the anchor's performance and yet is observed to be marginal at best, only just rolling the anchor on a flat concrete floor. The heel blade edges settling into soft mud or a build up of mud etc on the shank surfaces would explain a failure to set, especially in a re-set situation. The Delta has a disturbing tendency to come free on a severe veer (90 degrees or greater) and worse still, often will not re-set, especially if dragged at any pace by a boat in any degree of wind.

(The Rocna on the other hand has a very positive righting moment created by the heavy toe which rotates the anchor around the roll-bar, the supporting skids, and the shank end. With careful design and weight cut where it's not required, and putting it where it is needed, ~33% of a Rocna's weight is at the tip where it is most effective. Also, one feature of the Rocna is its ability to stay set after a 90 or 180 degree veer, and to re-set immediately if dislodged for any reason. The design is made to be roll-stable; i.e. it will remain embedded if dragged beyond yield and will not surface or hop out as the Delta is prone to once dragging.)

Due to the plough shape and relatively low projected area for anchor weight, the Delta's holding power in soft mud or any semi-fluid medium is little better than its predecessors.

The Delta's setting performance is reasonable in soft mediums but the cast tip is relatively blunt, without the 'chisel' cutting tip characteristic of for example a Rocna, meaning that setting performance drops off dramatically in more difficult material, and will not work at all in weed and grass mat. On the other hand, it is in these more difficult areas of soft semi-fluid mediums, coral rubble, weed mat and kelp, that the Rocna with its quick set high hold characteristics has developed its enviable reputation.

Since conception in 2000, my original prototype anchor, now known as a Rocna, has never failed to set nor ever dragged in some 20,000 nmls mostly in high latitudes including a circumnavigation of NZ and 8000 nmls in Patagonia and the Antarctic.

Peter Smith, designer of the Rocna anchor