Saturday, May 30, 2009

Thoughts on Anchoring

We currently carry 5 anchors. Our primary bower is a 60lb (27kg) CQR. We have a kedge that is a 50lb (23kg) Danforth. There is a 60lb (27kg) fisherman with broad flukes for troublesome rock and weed. We have a secondary 25lb (11KG) Danforth that is suitable for rowing out in a dinghy as a kedge. Then there is a 10lb (4kg) dinghy mushroom.

Our primary rode is about 200 feet of 3/8 (10mm) chain. We have about 380 ft of chain in two more lengths. There is about 300 feet of coiled polyester three strand rode for shore ties and/or Med mooring. We recently added 300 feet of 5/8ths 3 strand rode for a parachute anchor that can be used as ground tackle.

We normally anchor with the primary anchor and chain hooked to a bridle. The bridle moves the load off of the bowsprit roller and greatly improves the angle of the rode lowering the point of pull down 5 or 6 feet.

I recently started looking into the concepts of an anchor kellet, chum or buddy that might aid in dampening swinging and further enhancing security with a shorter scope. During an Internet search I came across some interesting papers by New Zealander Peter Smith. Peter is the designer of the Kiwi next generation anchor, Rocna. The new generation of anchors is represented by Rocna, Manson, B├╝gel and Spade among others. The new generation of anchors is focused on maximum holding power. Multiple tests by Yachting Monthly/SAIL and Practical Sailor seem to bear this out.

Peter had an article on kellets that was a bit negative. His claim, which seemed logical enough, was that a kellet will not actually increase holding power. You are better served by a heavier, presumably Rocna, anchor. The paper did acknowledge that the kellet could be useful in dampening swinging and absorbing shocks along the rode.

The interesting things about the papers is that they all seem to emphasise role of maximum holding power. Unless an anchor is much too small, the issue of maximum holding power does not come up for the average cruiser very often. Most people do their best to avoid the big blow. When faced with one, they tend to look for more shelter and start resorting to multiple mooring techniques. The more common problems are a poor or failed set, swinging to the wind or tide that breaks the set and conditions that cause unwanted interactions with other boats.

To that end, Evans Starzinger did some "real world" tests that appeared in Practical Sailor. These tests focused on speed of set and reset as well as anchoring in some nasty conditions in the Beagle Channel in Chile. These test showed that a Bruce style Claw anchor (Manson Ray) usually set and reset faster than the new generation anchors from Manson and Rocna. Evans also reconfirmed that the Ray did not have the maximum holding power of the newbies. In poor conditions of mud and kelp the Ray set in places the newbies would not.

One interesting point that Evans made was that pulling an anchor too fast or hard could keep it from setting in poor conditions. This phenomenon was seen in the Yachting Monthly/SAIL tests where several proven anchors such as Claws and CQRs failed to set at all.

I will proceed cautiously with my construction of a kellet, hoping that it may improve the ease and safety of everyday anchoring.

If I was going to replace one of my anchors, I would probably pick a 75lb Manson Ray or one of the new generation. The new generation have roll bars which can also conflict with a bowsprit.

There are a lot of opinions out there. Many of them express important and valid, if not conflicting observations.

A couple other books that I have found helpful areThe Complete Book of Anchoring and Mooring by Earl R. Hinz and Staying Put!: The Art of Anchoring by Brian Fagan.

1 comment:

Craig Smith said...

A brief comment.

Concerning kellets, the point concerning their effect on ultimate holding power appears to have been poorly communicated by Peter. Kellets have a history, like heavy chain, based in tradition and myth which, when studied rationally, does not apply to small yachts which the majority of us are concerned with. The facts are that any half decent anchor, of an adequate size (not necessarily a Rocna nor an over-sized one), can sustain enough force to lift a kellet, and therefore such a point weight makes no impact on the force threshold at which the anchor will drag. A little common sense can be employed: does it really seem reasonable that a 10 kg weight (less underwater) might affect the force at which an anchor holding maybe 500 kgf will drag?

Kellets have uses, but improving performance is not one of them. Put the weight into a bigger anchor instead.

Concerning testing, an unfortunately complex and mired topic, the West Marine / SAIL testing in 2006 is really the only comprehensive testing of recent years to compare the old and new gen anchors. The choice of hard(ish) sand was fortunate, as this more difficult bottom type shines a harsh light on poor performing anchors. The simulation pulls were very realistic, using appropriate rode, and a boat capable of simulating extreme conditions. Some anchors performed well and according to design. Others, like the CQR and Claw, did not. And, not for any lack of attention - in fact it can be argued the CQR enjoyed a considerable bias, as the testers did not initially like the results, and "babied" the anchor for some time before giving up. The fact is, both the CQR and Bruce-design can totally fail to set on hard surfaces.

Regarding Practical Sailor, Evans' opinion piece rewritten by PS is not a very useful data point. Beth and Evans were cruising in Patagonia, and have no access to any equipment that would allow any sort of controlled testing. They did some limited pulls on a frozen rocky beach in Puerto Williams - even the people helping them at the time commented that it was a strange way to test anchors. Icy rock and sand is well outside of the Rocna design criteria, which aims to be the best possible general purpose boat anchor, not an ice pick. To that effect, a number of boats in addition to Evans' in the same area, including some of the Antarctic and Cape Horn expedition charter yachts, have abandoned their plows and claws, and are in fact using Rocnas. I cite Vaihare and Santa Maria Australis as just two examples well known in the region, the experience of both of whom would exceed by far that of most 'passing-through' cruisers. These are folk who routinely sail some of the most challenging and dangerous environments on the planet, who have a vast amount of knowledge concerning the real world use of anchors, and who demand something that will perform reliably in a great variety of difficult seabeds.

Moreover, Evans has both the Manson Bruce copy and the Rocna on his boat now. It would of interest to consider which he has on the bow and is using the more often.

The Cruising Yacht SiteRing

Previous | List | Random | Join | Next

SiteRing by