Boat Mooring Upgrade Primer

Posted by Darrell Nicholson at 03:36PM - Comments: (6)

December 2, 2013

Helix screw-type anchors were installed off St. John in the U.S. Virgin Islands.

Now is the time of year that many mooring owners start investing in new equipment. As we prepare for our final report on mooring chains, I dove into some of our archival material on moorings to help guide people through the upgrade process.

There are plenty of variations in the details of permanent ground tackle, and PS has covered most, including mooring systems designed for sensitive seabeds. The standard rig is as follows: a mushroom anchor set well in the bottom (or a concrete block, but it had better be huge, or a screw-type anchor, which works well in hard bottoms), to which a length of heavy chain is shackled, then a swivel, then a length of somewhat lighter chain, a shackle, and a rope pendant that goes to the bow cleat. A mooring buoy is shackled to the top shackle. Some mooring ball designs let the upper chain run through their centers, with the pendant shackle resting on a steel lip at their top. Some newer designs, described below, even have a spot for storing a mooring pendant and pickup stick.

Some people put the swivel at the top of the operation, between the top chain and the mooring pendant, where it is easy to inspect. Others do away with the top chain altogether and replace it with rope. Some use two pendants. And so forth.

As for the proper length of the chains, opinions vary. Mike Muessel, owner of Oldport Marine in Rhode Island, has over 30 years’ experience installing and maintaining moorings. In the relatively deep, crowded, and protected confines of Newport Harbor, he uses a bottom chain a few feet longer than the depth of the water at high tide (the connection between top and bottom chains must be able to be inspected and replaced from a boat), and a top chain about 2.5 times the depth of the water. Others suggest a bottom chain twice the water depth. No one argues that more chain is better, both for the scope angle and because the heavy catenary of the suspended chain absorbs and dampens the pull of the boat. However, practicalities of swinging room, expense, and overkill intervene.

Some newer, elastic mooring-line products keep swinging radii small in light airs while still withstanding storm loads, but as marine surveyor Jonathan Klopman pointed out in response to our recent discussion of anchor rode elasticity, how much stretch is a good thing is a “hot” topic. Heat-induced friction in nylon rode, it seems, is on everybody’s mind.

New mooring expenses can add up quickly. Prices can vary by harbor.

How to handle stretch and chafe in a mooring system raises several questions. Although three-stand nylon is the most economical option, more esoteric (and expensive) double-braid and plaited products are being marketed. At the high end of pendant products is New England Ropes cyclone mooring pendant. The pendant, set between the mooring ball and the boat, is made of two components—a length of low-stretch Endura 12 to handle abrasion on the boat and a high-grade nylon mooring pendant that goes from it to the mooring ball. Prices start in the triple digits; a frugal sailor should be able to achieve similar results for much less money with good chafe protection. In our original and follow-up chafe gear tests, products from Fjord consistently performed well.

Also missing from the picture is the all-important pick-up stick to attach to the mooring pendant, which boaters almost always supply themselves. If you are tired of getting fiberglass in your fingers from that old pick up stick, you might want to look at Dan Homan’s nearly indestructible Deluxe Pick-Up Stick. Homan’s company, Island Mooring Supplies, is also introducing a series of soft, hull-friendly mooring buoys designed to hold the pendant and the pick-up stick ready for the owner's return—or for a new transient sailor to arrive.

Comments (3)

The mooring off the back of my house is on the edge of a channel in an otherwise muddy area. Being in the deeper water in a high current zone, the bottom is very hard mud, into which no mushroom mooring will dig. Not to mention the changing currents wrapping chain around the muchroom stem effectively shortened my scope alarmingly no matter how mahny swivels you'd add to the chain. A few times I was watching my boats take off during high wind and squalls. Fortunately as it drifted across the deep water, the chain unravelled, with the mooring catching on the up-splope on the other side of the channel. The resolution to this, after a few disagreements with my mooring service, was to use a 400 lb. Dor Mor, pyramid shaped mooring. So, then I move up to a much larger boat. The solution now... add another Dor Mor on a 10'chain extension from the original Dor Mor. This would work as well with granite blocks or concrete mooring I would guess. Still I had trouble convincing my mooring service to set it up like that, but I do pay my bills on time. During a nasty event, like the 70 mph squall we experienceon board the boat at the mooring, the boat did not move. The idea being that even if the 1st mooring were lifted off the bottom, the 2nd one is down there holding the fort. We never moved an inch, despite the boat (35' CAL, about 15,000lbs laoded)) being tossed around like the tail of a happy dog.

Posted by: ED W | December 4, 2013 8:42 PM    Report this comment

The above article missed two important points. First, a single leg system is only as reliable as the weakest part in the system, there is no redundancy. Be it a chain link, a shackle, or rope, when that breaks the boat is gone. Secondly, how is the average sailor going to handle that 400 pound weight to say nothing of handling 1100 pounds. The system I have been using since 1995 and was publish by Practical Sailor in the September 2003 Mailport, "Three-Legged Rope Mooring", eliminates those two limitations. The system worked for my 6,200 pound San Juan 28 for 11 years and was upgraded in 2007 to handle my 30,000 pound Tayana Vancouver 42. However, like all things related to boating, periodic maintenance is required.

Mike Hirko s/v Destiny Gig Harbor, WA

Posted by: MIKE H | December 4, 2013 12:26 PM    Report this comment

I devised a time tested system to moor our 12,000# Ranger 33. An 1100# concrete block with 6 feet of ship anchor chain was shackled to a 350# bounce block with six more feet of large ship anchor chain. One half inch 3 strand nylon lead from the end of this chain to the boat. Two feet from the bottom chain, I threaded a larger size fender-like net float to lift about three to six feet of the rope and chain off the bottom. About ten feet under water from the boat end, I placed about ten lead ring sinkers and flattened then enough so that they would not slide down the rope. This prevented the slack line from fouling the keel, rudder or prop at low tides in calm conditions. We had significant current to deal with. I allowed the nylon to collect a large growth of kelp and other leafy algae. The marine growth attracted numerous fish and acted as a perfect, very squishy sea anchor. I threaded three small net floats on the mooring line and bridles for a buoy and placed a ss swivel here which then lead to two bridles to the bow. In blows the boat would pull against the two bridles alternately and reduced chafe. Firehose over the line at the bow worked the best for chafe protection. The net floats acted as excellent rollers against the bow and kept the swivel and lines away from gelcoat. When we left on trips, I snapped a regular mooring ball on the line for better visibility.

If I were to redo the system today, I would use a screw anchor and no chain at all. A float (same as above) about two or three feet off the bottom keeps the line free of the screw anchor. The eventual marine growth would work as a soft drag on the line. Half inch line is plenty strong and lasts a long time. I use a scope of only 1.5x high tide depth because of minimal swing room.

Kenelm Russell, Rushwind, South Puget Sound

Posted by: KENELM R | December 4, 2013 11:18 AM    Report this comment


Add your comments ...

New to Practical Sailor? Register for Free!

Already Registered? Log in

Forgot your password? Click Here.