Ground Tackle

Posted on Wednesday 2 July 2008

Recently, I was asked why I have such an oversized anchor hanging off the bow roller on the Pretty Gee. That’s a good question. The primary anchor I have on the Pretty Gee is a New Zealand-designed Rocna 15. It weighs 33 lbs., and is the same anchor that an acquaintance of mine uses on a Canadian Sailcraft 36T, which is a much larger, heavier boat.

The answer is fairly simple. For weight reasons, I didn’t want to carry a primary anchor, secondary anchor and a storm anchor on the boat. I wanted my primary anchor to be capable of functioning under all the conditions I might be anchored out during, including storms. I spent a few months researching anchors, and the next generation anchors seemed to be significantly better than the older, more traditional designs, so I decided to concentrate on deciding between the next generation anchors.

There are really seven next generation anchors that I considered. The Bulwagga was out, due to its very odd three-fluke design and the fact that the pivot point for the anchor shaft is a weak point in my opinion. The XYZ was out due to the excessively large fluke that makes using it on a bow roller almost impossible. I wanted one that could be used and stowed on the bow roller most of the time. That left the Buegel, Hydrobubble, Manson Supreme, Rocna and Spade anchors.

The Hydrobubble I dropped, mainly because I see it as a gimmick. If the design really requires the “bubble” to set properly, what happens if the bubble is damaged? That left the Buegel, Manson Supreme, Rocna and Spade anchors. The “bubble” also effectively reduces the weight of the anchor underwater, and in many cases, weight is what helps the anchor set properly and helps hold it in place initially.

The Spade I eliminated since it is a two-piece anchor. I wanted the simplicity and reliability of a single-piece anchor as my primary. Granted, a single-piece anchor is harder to stow, but it can’t be assembled incorrectly and it is much more unlikely to come apart in a storm. That left the Buegel, Manson Supreme and Rocna.

That Buegel has a flat fluke. It has less surface area than an equivalent weight Rocna or Manson Supreme. So the Buegel was out, leaving just the Manson Supreme and Rocna anchors.

These are both rollbar-equipped, concave-blade anchors. They are fairly close in surface area, given the slight weight advantage to the Manson Supreme, the Rocna actually has a bit more surface area. The main thing that decided it for me was talking and e-mailing the users of both anchors. The Rocna users replied very openly and at least one had previously used the Manson Supreme, and switched. The other thing was the construction techniques used in building the Rocna, compared to the Manson Supreme.

The Rocna is made up from three pieces—the blade, the stock and the roll bar. The blade is formed using high-pressure brake presses, similar to how the mast-mounting blocks on my mast step were made. The three pieces are then assembled and then welded. The finished welded anchor is then hot-dipped galvanized.

The Manson Supreme’s blade is made up of several pieces that are welded together. Manson actually mentions this fact in their advertising copy, touting a “Reinforced Double Skinned Laminated Toe”. However, the pieces are welded only along the edges, and as I understand it, the finished anchor is then hot-dipped galvanized. This means that if there is any damage to the anchor’s welded edge, the interior of the two pieces isn’t properly protected from corrosion, as it isn’t galvanized.

The Manson Supreme also has a slotted shank. The slot, in my opinion, merely weakens the stock by removing a good portion of metal from it. The “rock slot” is designed to allow you to easily retrieve the anchor by pulling the shackle up to the head of the anchor, where the anchor tripline would traditionally be attached.

My question about this is simple: How does the anchor know if the shackle has moved up to the head because your trying to trip the anchor and not because the current or winds have shifted 180˚?

Answer: Simple, the anchor doesn’t. So if you’re using the rock slot and the wind or currents shift 180˚, there’s a very good chance that you’re going to be dragging—not a good idea in my opinion.

Real World Performance:

How well does the Rocna 15 work in the real world? It is an excellent anchor. It sets very quickly on the first try. The main difficulty with the anchor is the fact that whenever you weigh anchor, it comes up to the boat with 20-30 lbs. of mud and sand on it. That isn’t a big problem in my book, since it is clearly doing its job.

To give you an idea of how quickly and strongly the Rocna anchor sets, most of the time when I set the anchor under power, I have to be very careful not to strip line through the windlass gypsy. After the first few times, I now cleat the line off, rather than relying on the gypsy to hold it when setting the anchor. The anchor also sets so suddenly, that I’ve nearly lost my bowperson over the pulpit when it set.

Additional Information

One interesting thing I found after all the research I did was the testing that Sail Magazine went and did. Their test results can be read here (warning PDF file). The graph from their tests is quite interesting.

Sail Magazine\'s Anchor Testing Results Graph

The Rocna is clearly the best anchor of those tested, with a release point strain 30% higher than the second best anchor. While the Fortress may have done a bit better in maximum holding strength, it did far worse in maximum before releasing.


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