Sunday, January 26, 2014

Anchor System Planning

--Blog post written by Bob 

It's still the middle of winter and the only thing I can do to improve my anchor system is make a plan.  I will supplement this blog post with photographs of the new system as it is developed.  So, here is my plan…

The Old Anchor System

The old CQR Plow and the Bruce anchors nest well on the bow.
From my first winter cruising the Bahamas more than 20 years ago, S/V Rainy Days was equipped with two bow-mounted anchors--a 35-lb CQR plow and a 44-lb Bruce, both with their rope/chain anchor rodes.  During my first trip to the Bahamas, it was common to use both anchors at the same time in an arrangement known as a Bahamian moor.  (The CQR anchor was developed in the early 1930's by British mathematician Geoffrey Ingram Taylor, as an articulating plow anchor.)  There were a few occasions where the CQR plow didn't hold well in the Bahamas (and at least one occasion where it didn't hold well on the Chesapeake Bay--in a crowded St Michaels harbor one holiday weekend).  Anchors have improved significantly over the last 20 years I'm told and I understand that the Bahamian moor is used less frequently now, mostly as the result of improved anchor designs. 

The New Anchor System

We looked at the Ultra anchor at the 2013 Annapolis Sailboat Show and were impressed with its weighted flukes and the way the anchor dug into the sand.  It was made in Turkey and constructed from stainless steel--it costs about $2000.

Since the sailboat show I have also done some research on the Mantus and Rocna anchors--both are galvanized carbon steel anchors.  While both of these anchors seem suitable, I decided on the 20-Kg Rocna (weighing 44 pounds) based on a lot of positive feedback on the Cruiser's Forum and I just can't afford the Ultra anchor right now due to the unforeseen need to replace the boat's fuel tank.

The Rocna anchor design

The 44-lb Rocna anchor will be our primary anchor and used by itself for most anchoring situations in the Bahamas.  For use in the Chesapeake Bay and the ICW a (new to me) 33-lb Bruce would be perfectly suitable.  So, both the 35-lb CQR and the old 44-lb Bruce will be sold.  I am hoping that the 33-lb Bruce will fit alongside the Rocna anchor (with its built in roll bar) on the bow.  Although an all-chain rode seems to be preferred by many (or even most) cruisers, I decided to stick with a rope/chain rode because it is less weight on the bow.  Also, for the first winter in the Bahamas, I will not have a windlass installed--I will be pulling up the anchor manually.  Because a windlass may be installed in the future, I decided to hold off on replacing the 5/8-inch diameter anchor rodes, even though they are more than 20 years old.  I will be replacing some of the chain though.

The size of chain that best matches the strength of the 5/8-inch diameter rope is 5/16-inch.  On the primary anchor (44-lb Rocna), I will use 5/16-inch galvanized chain and a length equal to a little less than the boat's length, maybe 30 feet.  (Previously, I used a slightly shorter length of 3/8-inch galvanized chain.).  On the secondary anchor (33-lb Bruce) I will use some existing chain that I have (14 feet of 3/8-inch chain) since the this anchor is intended for use in  the Chesapeake Bay and ICW where the bottoms are mostly mud and clay.

Anchor Swivels

For the last 15 to 20 years, I have used swivels on both anchors.  I have always liked how an anchor swivel allows the anchor stem to easily come up over the bow rollers when weighing (a common term for "lifting") anchor.  The swivel is intended to keep the rode from getting twisted as the wind clocks around while anchored for several days or weeks.
A broken anchor swivel can cause catastrophic consequences.
(Photo courtesy of Attainable Adventure Cruising)

Even though I have never experienced any issues with anchor swivels, there is some concern among experienced cruisers on the use of anchor swivels.  The concern comes from the possibility of a pin coming loose and the swivel fails as shown in the photograph at right.

The continued use of anchor swivels in my anchor system is still an open issue for me.  I have always used LOCTITE Blue thread sealant on the pins and I have had a greater problem in removing them when I want to do than in them loosening.  In order to get a failure like the one shown, two threaded members would have to come loose since a screw on the opposite end locks the threaded pin in place.  A very casual inspection of the anchor system prior to every use would have caught this, in my opinion. 

However, if I can accomplish the function (rolling up over the bow rollers nicely) in another way, I may eliminate the anchor swivels from my anchor system.

An Improved System for Marking the Anchor Roods

Over the past decade or so I have used the common colored vinyl markers on the anchor rode to quickly determine how much anchor line was used.  For some reason they tear and pieces of the markers get removed which quickly degrades the effectiveness of the marking.  So, after some thought, I came up with new markers--multiple bands of whipping using a brightly colored twine on the anchor rode.

Since my minimum anchoring depth is probably about 8 feet of water--at a 7-to-1 scope, 56 feet (rounded up to 60 feet) of anchor rode would be used at my minimum anchoring depth--so, my first marking would be made at 60 feet (two bands).  Then, an additional colored band will be made for each additional 30 feet of anchor line length.

Sally B, a steel hull cutter, sits in her slip
in the iced over creek at the end of January.
S/V Rainy Days sits in the travel lift while work
is being done on installing the new fuel tank.
More on this subject in March when it gets warmer and I can work on the anchor system…

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