To choose the correctly sized Rocna, match your vessel’s length with the most appropriate displacement range, also bearing in mind conditions of intended use (if in doubt, give preference to the larger anchor model).
(Insert Size Chart Here)
1 t = 1,000 kg | * Weights and areas may vary slightly
For multi-hulls: use the chart as instructed, then select the model one size larger
Unlike other manufacturers, our sizing recommendations are intended to provide an anchor adequate for use in most/all conditions. For more on our philosophy and rationale, see below.
The Rocna 150 (331 lb) and larger: we do not provide standard recommendations for boats larger than those for which the Rocna 110 would be the recommended size. Classification society rules and/or legal requirements are likely to dictate the anchor sizes mandated for these vessels.
The Rationale Behind our Sizing
Peter, the Rocna designer, comes from a background of world cruising, and we tend to consider gear inadequate if it is not suitable for extreme environments. By this we mean the anchoring scenarios found in high latitudes northern Europe, Greenland, southern New Zealand, Patagonia, Antarctica, et cetera.
Our sizing is conservative, intended to provide an anchor adequate for use in all conditions most boaters would ever endure. We base our calculations on 50 knots wind, associated surge, and soft moderate holding bottoms into which it is assumed the anchor has set. Adequate scope is assumed. This is far in excess of most manufacturers.
Windage and resulting forces is judged based on typical vessel profiles according to LOA and displacement.
Note that tidal flow generally does not generate a hugely significant amount of force and in most areas can be all but disregarded. On a typical 10m (33') yacht, it takes a 6 knot current to generate about as much force as a 20 knot breeze on the same boat.
Naturally there are many variables involved, and in many situations an adequately sized Rocna will easily handle far worse winds than 50 knots. There are others where even a Rocna will not hold well. However, our aim is to consider a realistic poor case scenario as the basis for our recommendations.
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