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Thread: anchoring basics.........

  1. #1
    NBS Extreme Angler Jim's Avatar
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    anchoring basics.........

    Location, location, location - the battle cry of the real estate agent should also be your battle cry when preparing to anchor. On a boat, however, it is three-dimensional, and the water depth and nature of the bottom must be considered. The location must first provide some shelter from both wind and seas, the seas usually being the more critical of the two. Then it must have a bottom (sea bed) into which your anchor can set itself. Since the characteristics of sea beds vary greatly, it is wise to carry two anchors of different patterns but equal capability to give you the best chance to match the anchor with the sea bed at your common anchoring venues.

    From charts, cruising guides and by word of mouth, a skipper can get an insight into the character of the sea beds in which he will do most of his anchoring and for which he will choose a primary anchor. It is important to make this examination before buying an anchor to assure the most versatile anchor pattern for his needs. During the days of iron men and wooden ships, soundings of the anchoring site were taken with the "blue pigeon", a lead weight which had a pocket in the bottom into which tallow could be pressed. When the pigeon touched the bottom, the tallow picked up a sampling of the sea bed from which the skipper could determine the nature of the bottom.

    We have since learned that the surface of the sea bed does not necessarily represent its underlying composition. Descriptors on charts portray only the sea bed surface characteristics and not the underlying material. Instances have been reported in Florida (Sanibel) and Hawaii (Lahaina) where thin layers of sand cover an underlying hard surface. If you have anchored in only a thin layer of sand over rock or some other hard strata, you are destined to drag.

    The Great Anchor Debate
    It's a challenge these days to cut through the hype on anchors because of the large number of competing claims, yet that is what you must do in order to narrow the selection before the purchase is made. Too many factors are involved to enable complete objectivity and that is where you have to separate the few important facts from the hype.

    The function of the anchor is simple: It has to secure the vessel to the sea bed and prevent it from drifting at the mercy of wind and current. It does this by literally digging into the seabed at the location where you choose to position your boat. The anchor's ability to firmly grasp the sea bed depends on its design (pattern), its weight and its compatibility with the characteristics of the sea bed. There is no one anchor that excels in handling all sea beds and that seems to be the root cause of the debate. Sea beds vary the world over and a skipper has to choose anchor patterns to master the locales in which he intends to operate.

    Anchor patterns have been developed by inventive people over the years to handle different sea beds, usually one sea bed in particular with secondary capabilities in others. They tend to group themselves as 'burying' or 'hooking' patterns. Burying anchors deserve their popularity because most of the sea beds in shallow waters are composed of sedimentary matter deposited by large rivers in recent times (alluvium), and that is where most anchoring takes place. The burying anchor achieves its holding power in two ways ? by a suction created by the particular sea bed in which it is set and by the weight of the material that sets above the anchor. Hooking anchors, on the other hand, get their resistance by literally hooking onto the hard bottom.

    Lightweight, pivoting fluke anchors: (Danforth, SuperHooker, Horizon) These are great sand anchors and also work well in mud when the fluke area can be increased and/or the fluke angle can be changed from a general purpose 32? to a mud specialty 45? . Steel anchors in this pattern are light in weight to begin with, but aluminum models are even lighter. All have fantastic holding power per pound of weight, especially the aluminum models, giving the misconception that even a very small anchor will hold in bad weather. The sad fact is that the sea bed is never consistent enough to take full advantage of such efficiency and a bit of conservatism is important. Weeds can be their Achilles' heel.

    Plow and scoop anchors (CQR, Bruce): Heavy, solid construction characterizes these anchors and their weight enhances quick setting. Their smaller fluke areas prevent them from penetrating as deeply as the lightweights and their holding power is usually less in soft sea beds. In their favor is an ability to provide holding power, however moderate, in most sea beds and being able to reset reasonably quickly after the wind veers, but no anchor does this with 100% assurance. Single bill patterns are effective in penetrating weed and other sea bed vegetation. The open fluke design of plow and scoop anchors is advantageous in gravel-type bottoms.

    Boats that wander (coastal cruisers) should carry a second anchor because now the range of sea bed variables has been expanded and chances of needing a second anchor for a variety of reasons have increased. The anchor pattern chosen should complement the primary ?a plow/scoop pattern is a nice complement to a lightweight. Both anchors need to be of working anchor size (good for 30 knots of wind) and one should be carried "at ready" on or near the stem in a secure mounting. The second anchor (along with its rode) can be stowed below. Anchor designs that can be disassembled are particularly attractive for stowing below.

    The Matter of Scope
    The anchor rode is the archetypal example of the adage, "A chain is only as strong as its weakest link". This applies to an all-chain rode (used mostly on offshore cruising boats), an all-rope rode (rarely used), or the commonly used combination rope and chain rode. Each element needs to be at least as strong as the parent rope in the combination rode and that includes chain, shackles, splices, cleats, and other deck fastenings.

    The most popular rode for weekend and coastal operations is the combination rode consisting of a short chain lead and a long nylon rope. The chain lead helps to hold the anchor shank parallel to the bottom and absorbs wear from the sea bed while the rope provides the lightweight, elastic connection between anchor and boat. Some good rules of thumb to keep in mind when making up a combination rode are: (1) the weight of the chain lead (proof coil chain is adequate for this element) should approximate the weight of the steel anchor in use; (2) the size of the chain lead should be half the diameter of the nylon rode, i.e. a 1/4-inch proof coil (PC) chain connects to a 1/2-inch nylon rode; and (3) the overall length of a combination rode should be eight times the length of the boat to enable the boat to safely anchor at a 7:1 scope in waters as deep as the boat is long.

    The recommended rope for a combination rode is three-strand nylon whose material and construction provide the best blend of elasticity, strength, spliceability, and modest cost. (Braided nylon construction lacks the elasticity obtainable from three-strand construction.) When buying nylon rope for an anchor rode, ask for that rope that has been treated to minimize strength loss due to water absorption and to enhance its abrasion-resistance.

    With material and construction factors chosen, diameter is the next criterion in selecting a rope for an anchor rode. The required diameter (strength) is related to boat type (power or sail), boat size and expected weather conditions. The large majority of recreational boaters should opt for a working anchor system that can handle up to 30 knots of wind in a moderately protected anchorage. Cruisers, obviously, should be prepared to handle much higher winds. Loads can be calculated for a specific boat design or taken from tables for nominal boat designs.

    The chain lead (and the all-chain rode) works in the worst of all physical worlds ?it is ground away on the sea bed, corroded by salt water, and abraded by deck gear. As the Rodney Dangerfield of boat equipment, it gets no respect. That is unfortunate because at some time the safety of your boat will depend on it at a most critical moment?when the wind comes up unexpectedly. Most proof coil chain is hot-dipped galvanized steel to resist corrosion, but even that can be gouged and worn away and will eventually rust. Stainless steel chain is an alternative and not too expensive in short chain lead lengths. High test chain is overkill for the task. Plastic-coated chain (usually proof coil) is becoming a common market item, but should be viewed with some suspicion during use as pinhole leaks or breaks in the coating can allow treacherous rusting underneath, which is not visible during use. Polymer-coated chain seems less susceptible to this problem than vinyl-coated chain, but both are of concern. It is not recommended for saltwater use.

    Powered windlasses have become increasingly popular for larger size boats, say 35' and up, to minimize the physical challenge of weighing anchor as well as weigh anchor remotely. Past windlass designs used separate warping drums and wildcats to handle the rope and chain as the anchor is raised. This required an awkward and unsafe hand transfer of the combination rode from the rope on the warping drum to the chain on the wildcat. To overcome this problem, many windlass wildcats are now designed with a rope-grasping groove at the bottom of the wildcat to enable the rope to be hauled in by the chain wildcat prior to the engagement of the chain by the wildcat link pockets.

    To take advantage of this dual-purpose wildcat, the rope is spliced directly to the chain enabling a smoother run of the combination rode through the grooved wildcat with no hand manipulation required. Laboratory tests have shown that a rope-to-chain splice can be nearly as strong as the rope itself, but the durability and longevity of the splice remains open to question. The effects of the critically sharp bends made in the rope strands, their constant working around the link, and rust and dirt accumulation deep in the rope's interior yarns are still unknown. The convenience of use of this rope-to-chain splice should be balanced with a regular and careful inspections and resplicing if any damage to the rope is evident.

    Seamanship in Anchoring
    When initiating the anchoring ritual, make a slow pass through the anchorage, observing other boats' ground tackle setups while looking for the optimum spot for your use. While this is being done, another crew member can assemble and arrange the ground tackle gear for easy, unimpeded and safe run-out of the rode. Those who try anchoring on-the-fly to get to the shoreside barbecue first, often goof up and become the laughing stock of the anchorage. It is far better to deploy ground tackle in a slow, methodical manner, assuring crew safety in the operation as well as attaining a clean set of the anchor. Patience is a virtue when anchoring.

    Do not consider the anchor set just because it has touched bottom. Slowly back down from it deploying the rode evenly until a scope of about 3:1 is reached, at which time snub up gently and allow wind and current to give an initial set to the anchor. When satisfied that the anchor is holding, veer additional rode to about a 5:1 scope and then power-set the anchor. Finally, deploy the desired scope needed for your particular anchor and rode makeup. Some burying anchors like the Bruce and Max can hang on a 3:1 scope in a good sea bed, but most anchors prefer a 7:1 scope with a combination rode.

    If your anchor was chosen to match the sea bed and still hasn't set after a couple of careful tries, it may be fouled and should be retrieved and cleaned. Fouling of anchors can come from a variety of sources, both natural and manmade. While a clay bottom can provide excellent anchor holding, it can also ball up on the anchor bill(s) and prevent penetration. Rocks can wedge themselves between flukes and prevent penetration. Deadheads and other sunken debris can entangle the flukes and prevent penetration; this is a particular problem in popular anchorages where boats have deliberately or accidentally left anchors, rodes, and trash.

    Having established a secure anchor set, you are still not through with securing your boat. Belay the rode onto a capable Samson post or cleat and apply effective chafing gear in strategic places to protect it during the multitude of boat motions that will take place before you are ready to weigh anchor. Leather, canvas or patented anti-chafe tubing are useful.

    You are still not free to ride your dinghy to shore for the planned barbecue for there is the matter of swinging at anchor, called sailing or horsing, which occurs with both sail and powerboats. Winds are never steady in strength or direction and they can cause it to sail back and forth, possibly sweeping 30? or more each side of a nominal position. This not only tests your anchor set, but the nerves of your neighbor. Short of changing to bow and stern anchoring, try some other techniques that are simpler. Adding a bridle to your anchor rode will help minimize the swing, particularly if your boat has a broad beam to give a significant bridle angle?catamarans take a bow. Hoisting a riding sail on a trawler or a flat cut mizzen sail on a ketch will help to dampen out the horsing of the boat at anchor. If these passive means don't do it, try a hammerlock moor, which is the deployment of a small anchor at the stem on a rode having slightly more than a scope of one. The snubbing anchor will drag as the boat yaws and retard the sideways motion at the bow. A corollary of that technique is the deployment of a small parachute drogue over the transom to retard sideways movement at the stern. When adding extra gear of any kind to a single rode anchor system, keep in mind that fouling can occur and you will have to separate it before weighing anchor.

    If horsing of the boat is unacceptable and uncontrollable because of crowded conditions or the proximity of hazards, then consider using bow and stern anchors. This should only be done in mild weather and when you can keep an eye on the boat in case winds and current change. Other boats should be doing the same or that will cause a problem. The biggest social hazard of hanging on one hook in a crowded anchorage is the tangling of rodes. When rodes tangle, not only do tempers flare, but anchors become unset, leaving boats to drift.

    About the time you are ready to leave your anchorage, you may find the anchor is too well set and curse the good job you did earlier. Fret not, for there are ways to free the recalcitrant anchor without breaking your back or stripping the windlass gears. First drive up on the rode until it is "up and down" (we all know that no anchor will stay set at a scope of one!). Then move living ballast forward, taking up additional slack on the rode as the bow dips. Secure the rode to a cleat or Samson post (avoid letting the windlass carry the loads while you joust with a stuck anchor) and then move the crew aft and let bow buoyancy snatch the anchor free. Doesn't work? Then with anchor rode up and down and well secured, drive the boat forward until either the bow resists going down any further or the anchor has broken free. Still won't free? Back off to a scope of about 1 1/2 and circle the anchor, working it out of the fine set you put it into earlier. Again patience and smarts are the virtues that will get you on your way.

    You're Not Through Until the Fat Lady Sings
    Ground tackle housekeeping is often deliberately overlooked because it is a dirty job and ground tackle is thought to be robust enough to take care of itself. Wrong. During the weighing of anchor, wash and brush it off to minimize the amount of dirt remaining embedded in the rope and to eliminate stowage odors. Neatly flake, coil or otherwise arrange the retrieved rode for good ventilation and an easy run-out during your next deployment. Firmly secure the anchor in its chocks or stem roller so that it can't get loose should the seas become obstreperous. Cover your windlass, then clean up the remaining mess on the foredeck for safety and cosmetic reasons. All of this should be done while the boat is still in the shelter of the anchorage. Delaying cleanup until after exiting the anchorage can expose a crew needlessly to a dangerous foredeck.

    Cleanup and stowage completed, you can now sit back at the helm and resume your cruise in the knowledge that you have good ground tackle and the seamanship smarts to use it.

    Earl Hinz is the former Technical Editor of Sea and Contributing Editor at Cruising World. He has written several books, including The Offshore Log, Understanding Sea Anchors and Drogues, Landfalls of Paradise, Pacific Wanderer and The Complete Book of Anchors and Anchoring.

    Handling Anchor Chain
    Anchor chain quickly paying through a chock or windlass must be respected, even feared. A member in Alabama got a painful lesson in handling chain when his anchor began dragging late one windy night. The shore was looming ever larger when he went forward to let out more scope, and the boat was pitching violently?the sort of situation that encourages careless accidents. In the process of paying out the all-chain rode, he reached down, yanked the chain, and in an instant sheared off a finger. Claim #87039321A.

    Don't stick your fingers in the links or under the bow roller when the anchor is overboard. Should the chain become jammed, make sure it is well secured further forward before attempting to free it with your hands. Wearing heavy gloves?the heavier the better?is also a good idea. And with both rope and chain rodes, keep your feet clear of running coils! The latter can break your ankle, drag you over the side, or both.

  2. #2
    Where do you get such in depth material....Great Detailed report1

  3. #3
    Senior NBS Member Zac_S's Avatar
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    Sep 2006
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    That is a good read.
    So what kind of anchors is everyone carrying?
    I was carrying only a danforth, but I had to cut it on monday, so I am going out shopping soon....

    Sportfishing Forums | Saltwater Fishing, Deep Sea Fishing, Big Game and Sport Fishing Reports; for the serious Sportfisherman.

  4. #4
    74Formula233's Avatar
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    Jun 2006
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    Exeter, Rhode Island
    Quote Originally Posted by Zac_S
    That is a good read.
    So what kind of anchors is everyone carrying?
    I was carrying only a danforth, but I had to cut it on monday, so I am going out shopping soon....

    CQR Plow
    Sportfishing Forums | Saltwater Fishing, Deep Sea Fishing, Big Game and Sport Fishing Reports; for the serious Sportfisherman.

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