Anchoring Part 22: Moorings
A mooring is a semi-permanent or permanent anchor of many types, from a five pound mushroom anchor to multi-ton Bruce anchors, securing oil rigs. Focusing on ocean small craft use, this is a description of what they are and how to use, set and maintain them and most importantly, when not to use them.
Tags: bollard, buoy, cleat, coral, directional mooring, fixed mooring, messenger, mooring, mud, omnidirectional mooring, reef, self-burying mooring, splicing, static mooring, tensioned mooring, whiping, windlass, Wreck
January 20th, 2010 at 12:04 pm
What Is A Mooring, Why Use One and When Are They Appropriate? A mooring is a permanent anchor. They can be of many types, from a five pound mushroom anchor that has been left for months in a mud-bottomed lake to anchor a canoe in the spring to multi-ton Bruce anchors, securing oil rigs. Cheap moorings are often simply cement blocks, though I saw one that was a dozen toilets chained together and just dumped on the sand! When you use a mooring, assume the rope will break and the mooring will drag when conditions kick up. Most moorings are set by people who do not understand the forces involved or who don’t have the budget, equipment or knowledge of how to set a mooring correctly. Many moorings set in corals to protect them from anchors are cores drilled in the coral with a very long eyebolt set in cement in the hole, much like rebar in a foundation. It’s a great solution.
Moorings can have one or several anchors of possibly different types and they can also be in a number of configurations. The options are limited only by imagination and there is often merit in combining techniques to take advantage of scarce equipment and local terrain. The basic types of mooring systems are:
* Directional or omnidirectional
* Fixed or self-burying
* Tensioned or static
An example of a single directional mooring is a regular anchor and rode left with a float, to be picked up later. It’s a great way to daysail and not have to worry about the hassle of anchoring: Just slip your rode and leave it on a float, then pick it up with a boat hook on your return. A simple omnidirectional mooring is two or more anchors set towards each other, connected together to a rode with a float.
If the mooring is fixed, as in the coral example, the only need for chain is to protect the rode from chafe. Specifically for the coral example, though, the purpose of the mooring is to protect the coral, so the best answer by far is to have a short all-rope rode that is buoyed, thus keeping the rode well clear of the endangered corals.
If two anchors are simply chained to a ring that the rode is attached to, they make a static system because the two anchors are independently buried. In a dynamic or tensioned mooring (In this case, with only two anchors), the first anchor’s chain runs through a large ring at the end of the second anchor’s chain before it is attached to the rode. The advantages in a tensioned mooring are that
* They can be set correctly and efficiently from the surface.
* A pull in any direction buries both and the disadvantage is that they will pull towards each other constantly, until they are buried deeper and more firmly than the boat can move or until they pull so closely together that the angle of their combined rodes pulls them up and out.
For this reason, tensioned moorings must have the following to be successful:
* They must be placed carefully with plenty of setting room, to allow for further anchor movement.
* The anchors, rodes, shackles and rings have to be appropriately sized to the forces involved.
* The anchors must be set well: One anchor dragging in a tensioned mooring can easily foul the rest and cause the whole arrangement to be a useless, unmanageable and very heavy tangle.
How To Pick Up A Mooring A mooring is commonly seen as a float or pole buoy. This is attached to a light (messenger) line that in turn is attached to the mooring rode, usually with a loop spliced in the end. If the mooring is fore and aft, the mooring line will have an additional line, leading to the aft mooring rode.
(1) Approach the mooring as slowly as possible from downwind, stopping as you pick up the buoy. Once you have cleated your bow, shift into neutral or turn your engine(s) off. The last thing you want is to foul the aft mooring line in your prop.
(2) Moor your boat by picking up the buoy – If it’s a pole, just grab it and if it’s a buoy, use a boat hook, sweeping under it with the hook forward until you feel the line, then haul the float up and lay the boat hook carefully where it won’t fall overboard or trip you.
(3) The line you have is the messenger line and is lightweight and usually floats, to allow the light float or pole to easily float. Do not moor to the messenger line – It’s weak as a kitten! Haul the messenger in and you’ll find the mooring line, which is commonly an eye splice.
(4) Use this eye splice to cleat at the bow. If the mooring line is too large for your cleats, use the bitter end of your anchor line to attach to it with a rolling hitch and cleat your anchor line as usual. Running your anchor line over your roller will leave the slimy mess of the mooring line overboard but prevents casual ondeck inspection of your knot.
If you’re unsure of your rolling hitches, a trace figure eight is the most secure knot. In either case, as in every critical situation, a secure follow-through knot is needed. I use a double fisherman for that. A fat rolling hitch spreads the force over a greater area of the mooring line and prevents kinking at the join, which significantly weakens the mooring eye. A poorly-tied rolling hitch, though, easily comes undone and is worse than useless because it gives the illusion of security where there is none. If you have any question of your knotting ability, stick with one you know that is secure and tie a follow-through knot, to prevent the end from pulling through, as extra insurance.
If the mooring is a single, rather than a fore and aft mooring – Congratulations! You’re safely moored and that’s all there is to it.
(5) If the mooring is fore and aft, pick up the aft messenger line (It’s the heavy line attached to the mooring eye, going aft.) and walk back along your deck, keeping it, hand over hand, with you, until you are at your stern. If you have chosen a mooring of the correct size for your boat, you will have the stern mooring eye in your hands at the stern of the boat. Cleat at your aft cleat in the same manner as you did at your bow and you’re done!
Once again, I must remind you that public moorings are almost all insecure for heavy weather. If you find yourself on a public mooring with a squall or storm approaching, get to sea or anchor in the lee of land in a nice, secure place.
How To Leave A Mooring
(1) Check your boat to make sure everything’s stowed and ready, your blower’s been on, no fumes are present, etc., then to see you’ve got a clear path and are not leaving at the same time as the clumsy idiot upwind of you.
(2) Start your engine(s) or raise your sails, if you’re sailing off your mooring. Because so many moorings are right next to each other, don’t try sailing off a mooring unless you are an expert sailor in a boat you know intimately and have supreme confidence in. In order not to encourage people to try this tricky maneuver before they can do so confidently, I will save those instructions for private lessons.
(3) Cast the aft mooring line loose first, then the first.
(4) Engage power or sails and leave, steering straight until you have passed the buoy and making sure to swing your stern well clear of it so you don’t foul it in your prop.
Mooring Equipment Considerations A mooring is especially stable for wind shifts and if properly designed and built, will not drag in the directions it is designed for. The strength of a mooring is only that of the anchors and stability of the rode and design allows, so setting a mooring with the same anchor and rode you normally use won’t hold your boat any better. There may be some gains if your chain is not heavy or long enough, because a well-designed mooring will keep your rode flat on the ground but the main strength of moorings are in the strength of multiple anchors, securely set.
The best way to increase the holding power of a mooring is to use oversized anchors and rodes. The rodes need to be strong enough to hold the force of the combined, oversized anchors, so the line will need to be especially thick. If you usually use 5/8″ line with a tensile strength of 12,200#, a mooring line holding two anchors will need to be 7/8″ with a tensile strength of 23,500# and if you use oversized anchors, will need 1″ line, with a tensile strength of 29,400#. The line will also need to have 10:1 scope and will probably need to be a full spool of 600′. This, the chain and storm anchors is quite a lot in bulk, weight and expense. 600′ of 1″ line will fill a large lazarette. 60′ of 3/8″ BBB chain weighs 102#, so carrying an extra two lengths for a mooring is substantial weight, as well. An extra three oversized storm anchors also takes a lot of space that’s just not usually available onboard. This and the current retail price of well over $5,000 for a good mooring set of four storm anchors, each with 60′ of 3/8″ BBB chain and a spool of 600′ of 1″ line is why few boats carry a proper mooring set. They are much cheaper than losing your boat and possibly death and injury, though. For heavy weather, I strongly suggest using a heavy kellet in conjunction with a mooring.
I don’t carry a mooring set because I don’t like sitting out storms aboard. I plan my trips around Mother Nature’s tantrums. This means, of course, I’ve spent more vacations than I’d like to remember doing something else, with my boat in port, safely waiting out a storm… Enjoying myself a lot more than battling that storm!
Few consider replacing or backing their cleats, bollards or windlasses but I strongly suggest that: Generally, only larger or high-end pleasure boats or commercial boats have capable cleats and sound structure. Common production boats have infuriatingly small, weak and poorly mounted cleats. Replacing them with properly-sized cleats is really not that much of a job and adding stainless plate backing plates is also straightforward and inexpensive. A good shipwright will be able to tell you what is involved for your boat.
Setting A Tensioned Mooring
If you are setting a mooring in a shallow location, you can do it well, entirely from the surface. You will need a six-inch or larger, welded, (Cold-galvanized is best.) steel ring greater than the thickness of the chain you use. Generally, set the anchors within the radius of your chain, to eliminate stretch and chafe in the system and allow for strong attachments throughout. Plan the location in the same way you ordinarily would for anchoring and set the anchors independently, buoying them until you’re ready to connect them. This will allow you to set them closely without worrying about fouling your prop(s). Set the anchors in pairs, shackled together at the end of their chains to their swivel and dropping them one at a time, so they will make a 30° V. If this is a temporary mooring, such as used in sitting out a storm, be sure to attach retrieving lines on buoys to each anchor because otherwise, the only sure way to retrieve the mooring is to dive and disconnect it (It is possible to grapple the chains and pull them out one by one but that is problematic.). Take extra time and very slowly build at least twice the force you would otherwise use to set them – You are setting two anchors at once and have the additional requirement of not having any room for the anchor to drag in setting. If an anchor does drag, you’ll have to reset it before going on to the next one. Be sure to set them in precisely the direction you expect the blow to come from and buoy them with a short rode, to mark the end of the chain accurately. This will help greatly in positioning the other anchors.
If there are two directions you have to protect against, two pairs of anchors will suffice. Drop the second set of anchors, connected to the ring by shackle, with the first set’s line threaded through the ring and retrieval lines buoyed, if needed. Use this line to set the second set of anchors and you’re done!
If there are three or more directions you have to protect against, three pairs of anchors will work well. If more holding power is needed, set another mooring or better yet, scale the size of your anchors and rodes. To set three pairs of anchors,
(1) Set the first as I have shown, above.
(2) Attach both the second and third sets of anchors to the ring and thread the ring with the rode from the first set.
(3) Carefully place the second two sets of anchors at the directions you expect the wind to blow from (Down canyon, through passes, etc. – Asking locals and experienced cruisers always helps, as does checking historical data on weather sites with plenty of buoys in the area.). If you can’t accurately predict this, place them at 120° apart – You can hardly go wrong with that. Pairs of anchors are stronger than individual anchors equally spaced, even though the angles are smaller with individual anchors.
(3) Set the second and third sets of anchors as described above.
Setting A Static Mooring Static moorings cover everything from the coral anchor previously described to huge cement blocks with rebar loops to semi-permanent or permanent anchors and groups of all of these, chained together. Rope is sometimes used for the bottom connection but that’s not advisable because it will abrade and break a lot sooner than chain. A static mooring of anchors is set with the individual anchors as you normally would, with a boat. Once set, a diver attaches the chains to the ring and from that, to the rode. The diver is needed to attach the chain as tautly as possible, to keep the ring in the center of the anchors, so dragging around does not dislodge them. If you are including a boulder or other feature in your mooring, just wrap it with chain and attach it to the ring. Beware of chafe with wrecks, boulders, etc. and generally keep clear of them: Though tempting because they don’t move, they can often abrade through your rode and that’s a lot worse. Use good sense in diving as well and don’t ever get in a place where you can become stuck and drown – This includes your arm. Also remember that crevices are usually the home of creatures that will defend their homes. Moray eels will bite and hold until you drown, so please don’t thread the chain behind boulders in a reef.
Removing an Anchor Mooring Pull the secondary anchors up with their retrieval lines, disconnecting them from the ring and then retrieve the primary anchor(s). That’s it!
Mooring Maintenance Tensioned moorings need to be kept tensioned, so any forces will not yank at the anchors but pull smoothly. It is this ability of a tensioned mooring that gives it such terrific stability. Each season and after every storm usage, the mooring needs to be inspected to ensure the anchors are where they ought to be, that the chains and ring are not tangled and the seizing wires are strong and in place. Swivels tend to rust at their bolts and if you see any rust on a swivel at all, replace it. The anchor line, especially at points of attachment, need to be inspected for abrasion. It is a good idea to cut the eyes off and resplice it when they start to look worn and replace the eye at that point. If you’re resplicing one end, do the other: It has had the same pull and while the bottom eye has more abrasion, the top eye will have a lot more UV damage and so is weaker. You can see this in the brittleness of the fibers: Brittle = “Cut that section of line away.” If you have to cut so much out of the line that you have lost your needed scope, you will have to replace the entire line or take a 15% penalty in strength and short-splice another to it. Contrary to what the name might indicate, a short splice needs at least five tucks and in a permanent mooring, I make seven tucks, melting the ends smoothly into the rope and whipping immediately before the ends, as well as at both ends of the eye and immediately before it, at the base of the eye, on the throat. Whips of this sort are structural and need seven passes through the rope to secure each end of the whip.