When stowed on the bow, the anchor must be securely retained. Tension from the windlass should not be relied upon.
The Rocna does not come with a hole designed to accept a retaining pin. There exists a hole at the top of the anchor's shank, above the tandem anchor attachment point, which may be used for lashing. On occasion of course it may happen that this lines up with the retaining pin of an existing roller assembly – or a boat owner or designer may think to construct a pin to fit though this hole. This is not recommended.
Where to position?
The position of the hole can be flexible; there is no accepted position for the location of such a pin, and nothing that can be maintained constant across all anchor types and sizes, boats, and roller designs. This is one of the reasons the Rocna does not feature one. In any case, as below, it is not recommended that an extra hole be drilled at all.
We do not recommend the use of restraining pins
We advise against the use of pins in order to restrain the anchor. We receive many enquiries asking about drilling holes through the shank in order to accept a bar (or there exists the possibility that a standard pin will happen to fit) and we usually caution against this. The Rocna has a large fluke, and a body of green water hitting this while at sea can easily bend the pin, so jamming it. We have seen this happen on many larger anchors with strong restraining pins, and hack-sawing a steel pin in the dark while motoring around in circles after a hard sail is no fun.
Pins also usually always allow a small amount of movement to remain, which can be noisy and introduce wear. Alternatives are strongly recommended.
Drilling issues and consequences
The steel of the Rocna's shank is high tensile and it is difficult to drill. After drilling, the exposed raw steel must then be re-coated in zinc, or accelerated deterioration of the anchor's galvanizing will be experienced.
A hole in the position normally desired will weaken the anchor's shank by the amount the hole's diameter subtracts from the shank's height in that area. For example, a 10mm diameter hole at a shank height of 100mm will equate to a 10% reduction – it's that simple. The Rocna is a very strong anchor and there may exist enough margin for most boaters, but another consideration is that an unapproved modification could possibly have ramifications with regard to insurance should the anchor shank fail, although we cannot speak for your insurance company and its policies.
Lastly, should the shank bend and fail in the general location of where an unapproved hole was drilled, this would likely invalidate the warranty and/or guarantee on your Rocna anchor.
Alternative retaining systems
Whatever system is used for anchor retainment, if the anchor is used frequently, it is very important that the system is simple and permits fast and effective deployment.
The anchor should hold itself vertically when pulled back tight, as the shank kicks back so it cannot move up and down on the roller. Rocking can be a remaining issue, particularly on smaller rollers. A chain stop should be used as a more reliable method than tension from the windlass, although some play in the order of half the length of a chain link will remain. It may be desirable to deal with this. A devil's claw would be one alternative.
Lashing with rope is recommended as the normal solution. Rope can be easily tied and tightened, and is easily undone or cut if necessary.
For those designing and constructing the ideal set-up, the construction of a dedicated over-the-top restraining latch is recommended en lieu of a through-pin. The photo on the right shows the aluminium roller assembly on Steve Dashew's FBP 83, with dual hinged latches (note the second toward the bottom of the photo) to easily secure the 115 kg Rocna.
Wire and hook
A wire and hook with a rigging screw type of tensioning system can work well.