Wednesday, March 7, 2018

Getting my Small Boat Anchoring Mojo Back

I've done a lot of testing related to anchoring, almost always related to anchoring with all-chain. After all, that is what cruisers do. It is cut proof, reduces swing in tight anchorages, and is easy to handle with a windlass.

But my cruising started on a Stiletto 27 catamaran, weighing only 1300 pounds and anchoring with rope and hooks of no more than 12 pounds. Soft mud, sand, rocks and packed shell. I did a lot of things differently, by instinct, and now I'm determining by load cell and scientific method just how many of my judgments were right.

The new break-down 13-pound Mantus anchor is a godsend for shallow lockers, fitting where only pivoting fluke anchors once would. Disassembly takes only 20 seconds and requires no tools. This is the only new generation anchor that will work in this locker. The only other non-Danforth style anchor that fit was a 12-pound Northill Utility, which although a nice anchor, has an exposed fluke that is a little scary if you swing overnight.

Note the red webbing chafe guard. I use only 5 feet of chain, so this protects the first 20 feet of rode. It is slid over the first few links of chain and sewn in place, through a seizing might wear better.

I still like Fortress/Guardian Anchors for soft mud. They have no equal.  

Bridles and Snubbers. Multihulls always used bridles to reduce yawing. However, where I have long pitched nylon for use with chain, to reduce snatching, with a nylon rode the rule is reversed. A non-stretch bridle is more stable (does not bend from side to side), and by reducing the amount of nylon, horsing (fore-aft surging) is reduced. I used polyester double braid on the Stiletto and I am using Dyneema on the F-24.

Scope. I don't care what they say about new generation anchors holding at short scope. Based on every bit of theory and testing of many anchor models, it just ain't so. Because smaller boats can anchor is shallow water, long scope is no big problem. I very, very rarely use less than 8:1 scope.

Scope Holding
Greater than 20:1 100%
10:1  95%
7:1 80%
5:1 60%
3:1 30%
Less than 2:1 variable to nil

[This relationship is based on testing of anchors of all styles, including new generation, and holds true for mud and sand, and for sizes from 2 pounds to 5 tons. The exceptions are pivoting fluke anchors by Danforth and Fortress, which are much better at short scope, but only if well set first, which is basically impossible for most small sailboats (the engine is too small).]
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Rode Size. Go bigger than recommended, not because you are paranoid, but because if you check the numbers, most rope recommendations seem to be based on fishing and lunch stop anchoring. I guess they figure you would use chain if you were a a "real" cruiser. Remember that the WLL is only 12% of the breaking strength (ABYC H-40, Table AP-1), and that is before UV and chafe are included. Finally, larger ropes are easier to pull by hand and wear MUCH slower (lower load/area and the rope fibers are under less stress).

Chafe Guards. We use tubular webbing on dock lines and mooring pendants to prevent chafe. Why not on the anchor rode? Because it floats loose, it is practically wear proof. 2-inch Blue Water ClimbSpec webbing slides over  a 1/2-inch chain splice and 1/4-inch chain. $0.45/foot.

Coating with Yale MaxiJacket or Flexdel RopeDip is also effective against chafe, but not cutting. It also stiffens the rope slightly.

Short Chain. I hate handling chain. If you have to use momentum to break out the hook and have no roller, chain will tear up the top sides.  I don't need chafe protection if I use a guard, and the rode + webbing cleats easily.  The weight of 10-20 feet of chain makes no difference once the wind is above 15 knots. It's off the bottom, I've checked. It doesn't change the way the boat swings. Skip the long chain.

Use Two Anchors. Not all the time. But learn how to lay two and you will see that it takes only a few minutes on a smaller boat. [One simple way is to set the first anchor at 20:1 scope, walk the second anchor to the stern and lower, and then bring the boat to about 10:1 scope and tighten them against each other. You can even use a cockpit winch. Then moor the second rode to the bow--I don't believe in fore-aft anchoring. Add 20-50 feet slack, since you  don't actually want the anchors in a straight line, you want a triangle.] .A particularly good idea if you have only pivoting fluke anchors, which don't like direction changes. The trick is to have a relatively short (100 feet?) rode on the second anchor so that if the boat spins, untangling is easy. Put eyes in the ends and it is easy to extend with needed, which will probably be... never.

Minimize Yawing. Taking the dingy off the bow helps (like a riding sail at the wrong end). Lift the rudder (moves the lateral plain forward). Take down the furling reacher. Use a hamerlock mooring.

Puny Engine? No Engine? Bump Set! After getting your initial set and deploying full scope, power set with reverse. Then gather up some slack and back up at speed; 2 knots for heavier boats, 3 knots for multihulls. So long as you have at least 50 feet of line out, the effect will be no more than a severe storm (I've measure the forces). No engine? Haul up slack and the let the wind push you back (you may need to wait until there is some wind).


I like to anchor with absolute certainty.

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