The Rocna was designed to address the limitations shared by all older and most newer anchors available. These designs suffer from a combination of the following:
limited resistance and holding power due to small blade areas (inefficient distribution of weight)
blade shapes designed to furrow, i.e. to move through the ground
poor penetration in difficult seabeds such as kelp and grass
a tendency to roll-out under heavy or veering loads, especially common in claw and Danforth-style flat blade types
poor designs that do not consider stowage on your boat’s bow, resulting in slack fits that allow movement at sea which can be damaging as well as annoying
insufficient strength in the shank or other load-bearing sections
moving parts, i.e. a reduction in strength and a hazard to personnel
The Rocna successfully addresses each and every one of these points, amongst others.
the roll-bar
The roll-bar serves one main purpose: it ensures the Rocna will adopt the correct setting attitude, which is loosely described as being on its side with the complete anchor weight supported between the skids, the end of the shank, and the chisel-tip of the blade. As well as ensuring that the anchor will always achieve the correct orientation, the roll-bar means that the toe does not need to be weighted with extra lead or cast iron. This in turn allows a much larger total blade area and generally more optimal weight distribution.
This lack of dedicated tip-weight has numerous other advantages. In terms of setting performance, it reduces the profile of the fluke, facilitating setting in weed and grass. The absence of lead is better for the marine environment, and it also eliminates complications in years to come when the anchor requires re-galvanizing.
A secondary use of the roll-bar is as a handle: if lost or fouled, and a buoyed retrieval line has not been used, the Rocna may be recovered from the surface by snaring the roll-bar with a grapnel or other hook.
penetrating the seabed surface
Once in the correct setting orientation or attitude, the pull of your boat on the anchor rode creates a turning moment, forcing the chisel-tip toe (point of the blade) into the bottom. As resistance grows the dynamics alter, and the anchor will roll toward an upright position, placing yet more downward pressure on the tip.
From a simulated backward landing position, a prototype Rocna 20 turns, and digs straight in
about roll-stability
Once a Rocna is set, it will remain buried even under high loads. Many other anchors will roll, or "trip", out when overloaded, but a Rocna will remain embedded and maintain its attitude. Even if the anchor moves under extreme load, dragged beyond its yield, it will not trip-out once set.
Lack of roll-stability is a common problem with plough designs. They don’t offer much holding power to begin with, and once they start to drag, they tend to roll-out and let go completely.
Veering loads such as rapidly changing tides, or unpredictable wind conditions, will also cause most other anchor designs to abandon their set position and let go. A Rocna will remain buried under most changes of load-direction, working its way around to a new orientation under the surface. If it is jerked out violently, it will instantly re-set owing to the properties that give it such good initial setting characteristics.
No roll-out: this Rocna has been intentionally dragged beyond yield, and its load veered by 90 degrees
how a Rocna mates with your boat's bow roller
The shanks on many anchors are not designed with installation on a bow roller in mind. They are either too loose and do not lock home at all, or are too tight (as is the case with some new 'exotic' designs), and do not allow the anchor to be pulled completely home.
The shank of the Rocna is designed to "lock home" on most bow rollers, leaving little room to move. This is particularly important when the boat is pitching, as the vertical movement of an anchor can cause considerable damage.
self-launching and retrieval
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The weight distribution of a Rocna is such that it will self-launch on most bow rollers. This means you should be able to simply release the chain, and the anchor will fall straight off your bow. Similarly, it should return home without any manual guidance or assistance.
The footage in the little video on the right shows a Rocna 55 self launching, and coming home alone. This footage can be seen at higher quality by watching our proper short video (click here).
The shank of a Rocna has a slotted attachment point large enough for the head of a shackle to pass through. This eliminates the need for two shackles, and allows the use of the maximum size that is compatible with the chain.
For more about shackles, check out our knowledge base article on shackles (click here) .
