Anchoring 201
There are times when simply figuring out scope and dropping the hook just isn't enough... 

 

By Frank Lanier
Illustrations by Jan Adkins
Chesapeake Bay Magazine (2004)
Offshore Magazine (2005)

 

            While Iíve often heard anchoring referred to as a ďblack art,Ē successful anchoring has more to do with knowing tried-and-true techniques and when to employ them than it does with spells and curses (although Iíve heard plenty of the latter directed towards dragging anchors and the like).  At some point all boaters encounter conditions where the basic anchoring techniques theyíve employed with no worries a hundred times before just arenít cutting it.  An anchor that wonít stop dragging no matter how many times you reset it (or wonít let go when youíre ready to leave), an otherwise perfect gunkhole with limited swing room, trying to anchor in shifting current and winds or heavy weatheróall are problems that can be addressed when you know the tricks and can pull them out of your top locker if the need arises. 

Current Change



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         Letís say youíre cruising the mouth of the Amazon (or visiting Chestertown, Md) and you want to anchor in the river and dinghy to the beach for some grub and maybe one of those drinks with pineapple and a little umbrella in it.  The problem is how to feel comfortable about leaving your boat anchored in an area that experiences rip-roaring 180 degree current shifts that your standard single anchor setup just canít deal with it? Try the Bahamian moor (figure 1), an anchoring technique that gets its name from the contrary winds and tidal currents found in that region.  One anchor is deployed upstream and one downstream as your boat rides between the two with both anchor rodes attached at the bow. As the boat swings 180 degrees during the current shifts, the first and second anchors alternate between being the riding anchor (the one upstream under tension) and the lee anchor (the one down current with no load), with your boat always pointing bow up.  The Bahamian moor not only provides a secure mooring in areas with reversing currents, but can also be used to limit a vesselís swing radios when anchoring elsewhere.

            Downsides to the Bahamian moor include the possibility of twisted rodes (a result of vessel swings or circles during current shifts) and the potential chafing of combination rodes (rope and chain) if the slack rode rubs against the vesselís hull or even snags on the keel or running gear, possibly preventing the vessel from swinging to its new position with each current change. The latter can be prevented by bridling or attaching the rodes together at deck level, then lowering them until they reach below the keel.  When one of the rodes is all chain, the chainís weight is normally enough to accomplish this, but you may need a kellet if you use two combination rodes (more on kellets later).

 

Wind Shifts


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             If the problem is shifting winds rather than contrary currents, give the dual anchor mooring a try (figure 2).  Set two anchors to windward 45 to 60 degrees apart, so the rodes form a V with the boat centered in its apex.  The simplest way to accomplish this in light winds is to let go the first anchor, motor at a right angle across the wind the intended length of the first anchor rode and then release the second anchor, adjusting the rodes as needed afterwards while falling back between the two.  In strong winds set the first anchor as you would normally (with the length of rode you need) then motor upwind at a 45-degree angle.  Drop the second anchor when abreast of the first, then fall back between the two, again adjusting the rodes as necessary.

            Be sure to monitor rode locations during both procedures to avoid sucking them into your prop Ė use of marking buoys will make it a lot easier to keep track of anchor positioning during all this.  While use of matching rodes (either combination or all chain) for both anchors make it easier to correctly position the boat, you can also mix rode types if necessary Ė just increase the scope of the combination rode to match the holding power of an all chain rode.

            An added benefit of the dual anchor mooring is the option of paying out additional rode as the wind pipes up. This reduces the angle between the two anchors and increases their holding power (35 degrees is considered optimal in gale conditions).  Placing your largest anchor in the direction of the strongest expected winds will also improve holding power.

Crowded Anchorage

 

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            Letís say you got a late start getting underway and by the time you get to your chosen anchorage for the afternoon itís standing room only.  Thereís one slice of water left thatís doable, if you can limit your boatís swing radius. Or how about that perfect gunkhole with deep water right in the middle, but no room for swinging without bumping into a shoal?  One possible solution for both cases is the fore and aft mooring (figure 3).

            Setting the fore and aft mooring is similar to Bahamian moor, except when finished the rodes are located one each at bow and stern, rather than the bow alone.  The trick to fore and aft mooring is visualizing where youíd like to end up once both anchors are out and then set them accordingly.  For example, if you want 100 foot of rode out, drop the bow anchor that amount forward of the spot youíve chosen, then back down 200 foot and drop the second anchor.  Next take in 100 foot of the bow anchor rode while letting out the same amount rode for the second or aft anchor, finally snubbing up both anchors at bow and stern, centering the boat between the two.  If both anchors are located at the bow, simply lead the rode for the second anchor aft to a suitably strong cleat or other such attachment point.  Having both anchors ready in advance and briefing the crew (so everyone knows what their role is) before anchoring will make deployment smoother.

            There are disadvantages to fore and aft anchoring, however.  While it makes more efficient use of available anchorage space, unless everyone does it you may end up having someone else bump into you if thereís a wind or current shift.  Itís also not recommended if there are significant crosswinds or currents, both of which can place high side-loads and unwanted strain on your ground tackle.

 

Heavy Weather Anchoring


 

 

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            The hammerlock moor (figure 4) is a technique thatís hard to beat if your boat is horsing about in gusty winds.  It consists of dropping a secondary anchor on short scope beneath the boatís bow Ė the primary anchor continues to take the brunt of the load, but the boatís horsing will be dampened by the secondary, which also reduces ground tackle strain considerably.  During substantial wind changes, this secondary anchor will likely drag to a new position relative to the wind shift. Relax. Itís all part of the master plan of drudging, the intentional dragging of an anchor. Once settled in the new position, itíll continue to operate as before.

             The tandem anchor rig is a quick, easy way to increase the holding power of a single anchor rode by deploying two anchors on the same rode.  Stock-stabilized, pivoting fluke anchors (like Danforths) work best in this application, particularly in mud Ė U.S. Navy tests show use of tandem anchors increases total holding power by as much as 30 percent over the same two anchors if deployed separately.  These tests also showed holding power in sand increased only slightly overall when setting tandem anchors, most likely because the anchors themselves were designed for use in sand Ė in other words, use of a tandem rig closed the holding gap a bit between sand and the poorer holding quality of mud.

            When preparing a tandem rig be sure to attach the second or aft anchor rode to the forward anchorís crown rather than its ring and if using a plow type anchor (such as a CQR) be sure NOT to attach the rode it to the trip eye, which may cause the anchor to roll and unset during wind shifts.  For even more holding power when using a single rode system try the dual tandem mooring (figure 5) which combines the increased holding power of two anchors in line plus a third storm anchor set in the opposite direction for even more security.  The dual tandem mooring works particularly well in cases where wind shifts are expected, such as during the passing of a tropical storm or hurricane. 

                 Another excellent option for heavy weather anchoring is the modified star mooring combined with an oversized kellet (figure 6).  The star mooring utilizes three separate anchors and rodes, each of which can be all chain, rope, or a combination of the two.  Deploy each anchor 120 degrees apart with the largest anchor set towards the direction of strongest expected winds (once again, buoying the bitter end of each rode after setting each anchor will make deploying and maneuvering much easier). 

              
Gather the bitter end of each rode and shackle them in the center to a large mooring swivel, which in turn will be shackled to a bridle of two suitably sized lines of 3 stranded nylon, each having a galvanized thimble spliced at one end Ė the other ends (which are attached to the vessel) should be properly whipped to prevent unraveling.  Use a large shackle to secure the thimbled ends of the bridle to the mooring swivel, ensuring all shackle pins are properly secured with stainless steel mousing wire.  Each side of the bridle should be 10 to 15 feet longer than initially required with the extra length secured on deck, which allows you to increase the scope of the bridle or shift lines as necessary to prevent chafe at chocks or hawseholes.  Another option when using all rope rodes would be eliminating the mooring swivel altogether and bringing each of the three rope rodes to one side of the vessel at a single point, then forming a bridle by attaching a second line (using a rolling hitch) to the three where the swivel would be.

           
           
As is the case when planning any heavy weather anchoring strategy, be sure to take storm surges and higher than normal tide levels into consideration when determining lengths of bridles and anchor rodes for your modified star mooring.  For example, if your favorite hurricane hole is 15 foot deep at normal high tide and the approaching storm is due to hit at high tide with a predicted storm surge of 10 foot, your bridle should be at least 45 feet in length (15 ft for your hurricanes holeís normal depth, 5 ft for trapped high tide, 10 ft for the storm surge, and finally that extra 15 ft of reserve line on deck mentioned above).

            Based on a scope of 7:1 for normal anchoring and a projected maximum depth of 30 feet in your hurricane hole during the storm, each of the three anchor rodes in the above scenario would need to be 210 feet, however this can be rounded down to 200 feet as the pull of the boat will almost always be divided between two anchors at any given time.  Itís also true that as this 7:1 scope is meant to cover use of combination rodes, you may be able to shorten the lengths of all chain rodes and be OK, but if youíve got the chain, put it out Ė you may appreciate the additional holding power before the storm is over.

            Adding an oversized kellet (50 Ė 60lbs) to the center of the star mooring produces even greater holding power, with the added benefit of reducing vessel swing radius and anchor sailing should you need to pay out more scope on the bridle.  Finally, be sure to provide plenty of chafe protection at all chocks and fairleads the bridle or any part of the anchor rode comes into contact with.  

             

Advanced Heavy Weather Preparation

          
 

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                 Of the many keys to successful heavy weather anchoring, none is more important than preparation.  From scoping out your hurricane hole months before you need it, to making sure that mooring swivel really is large enough to accommodate three anchor rode shackles, the time to plan is now, not when a hurricane is bearing down on you.  Practice deploying your anchoring system beforehand, which not only allows you to correct issues you may have missed (such as deck chocks that are too small to accept larger storm rodes and chafing gear) but also familiarizes you with deploying your system, making it easier during the real thing.  Afterwards, you can store your storm gear and start enjoying the peace of mind that comes with both having a plan and knowing itís ready to put into action.

                 Although storm gear varies, a few general considerations can be applied to most any system.  First off, storm anchors and rodes should be oversized Ė at least one size larger than your vesselís typical anchoring requirements.  When basing storm gear selection on your everyday ground tackle (i.e. at least one size larger) make sure what youíre currently carrying is correctly sized for your vessel to begin with (to avoid short changing your heavy weather tackle).  Probable the best advice for storm anchor selection is to grit your teeth and buy the largest one you can physically manage.  It may not be the most glamorous investment youíll make, but itís one that will continue paying dividends  in service and piece of mind for years to come.

            Rope to chain connections in combination rodes (figure 7) will normally be made utilizing an eye splice and thimble, which in turn will be attached to the chain portion via an anchor shackle.  Although bulkier than a direct rope to chain splice, this method is simple and reliable.  A proper eye splice should have a minimum of six full tucks and should be seized at each end while the eye is under tension (to prevent the thimble from falling out should the eye stretch when placed under load). 

            While the open ended ďteardropĒ shaped galvanized thimble commonly used may be adequate for most situations, they should not be used in your storm anchor rodes if possible.  Under extreme loading the thimble may work, allowing the sharp edges of the open end to chafe the rode.  A much better choice is an oval thimble or closed ear thimble (as shown in figure 7).

            Chain rode can be bent directly to your anchor using an anchor shackle, but if thereís a chance the vessel will shear or swing in circles (particularly when laying to a single anchor) then installation of an anchor swivel between anchor and chain rode to prevent twisting should be considered.  Some sailors donít like swivels, viewing them as potential weak links and itís true that any moving part can fail under load if not properly designed and constructed.  As such, if you decide to install one buy the best quality swivel you can find. 

            Anchor swivels should be drop forged (not screwed, riveted, or welded together) and should be the largest size that fits the chain link without binding Ė and contrary to popular belief they can also be installed backwards.  Ensure the jaw fitting of the swivel is attached to the chain, not the anchor shank, and that the swivel eye is attached to the anchor shank with an anchor shackle (which is more bell shaped than a standard shackle) to prevent binding.

            Finally, donít forget that all chain rodes require the use of an elastic bridle or riding stopper to act as a shock absorber between anchor rode and vessel.  Bridles are typically constructed of 3-strand nylon rope (vice braided) due to itís increased elasticity. 

   

BAG OF TRICKS


At ease at anchor

            There are additional tricks to improve your boatís performance on the hook that have nothing to do with the hook itself.  One is a kellet (also known as an angel or sentinel) which is simply a weight sent down the rode once the anchor is set to steepen its entry angle and decrease the anchorís lead angle on the bottom.  Kellets can be useful in many situations, such as dragging anchor in a location where the anchorage is too deep or crowded to make paying out more rode a viable solution.


            Kellets should weigh between 25 to 35 pounds for a typical 35-foot vessel, but this can be increased in severe weather to generate additional holding power.  Ideally the kellet should be positioned roughly halfway along the rode between bow and anchor (figure 8), but this can be varied to compensate for local conditions. For example, placing it further up increases the shock absorbing qualities of the rig, while lowering it closer to the anchor increases holding power.  The kellet retrieval line should be attached to a bow deck cleat and kept fairly taut to reduce chances of fouling.

            You can buy a kellet or make one from materials at hand, such as scuba diving weights, weighted canvas bags or even a small anchor (figure 9) Ė they can also be constructed from a one to two foot section of large diameter PVC pipe capped at both ends and filled with lead or chain.  A large shackle can be used as a rider for the kellet on all chain rode, but if you have a combination rode of rope and chain youíll need to use a saddle rider, snatch block, or other suitable means of attaching the kellet to prevent chafing of the rode. 

            Another common problem while on the hook is ďanchor sailingĒ or sheering, which is caused by windage from a boatís hull, superstructure and rigging.  With each wind shift the bow falls off, only to be brought up short by the anchor rode, which in turn forces it to point in the opposite direction.   Sheering is most pronounced in modern boats with wide beams and narrow keels, but any vessel riding to a single anchor is susceptible.  Sheering is not only annoying, but potentially dangerous due to the severe side loads it places on ground tackle, which could lead to dragging or failure.   

            Use of twin bridles or simply forming a bridle by attaching a second length of rope via a rolling hitch will reduce or eliminate sheering in lighter winds, however in windier conditions the addition of a riding sail is an excellent strategy.  Ketches and yawls have the option of using their mizzen as a steadying sail, but what weíre talking about here are riding sails designed to be flown from a sloopís backstay.  How large a riding sail youíll need depends on factors such as hull design and displacement (youíll probably want to consult with a sail maker to determine size), but overall they should be flat cut and heavily constructed (10-ounce cloth or greater) with heavy duty stainless rings and closely spaced bronze hanks. The cloth itself should resist ultraviolet light and chafe due to flogging.

            Riding sails are normally hoisted using the main halyard and are typically set with the head roughly a third of the way up the stay, which of course would be adjusted depending on conditions and your particular boatólower is better in strong winds. Riding sails are also useful in light air, keeping the vessel heading into the wind to help hatches and wind chutes provide maximum ventilation below decks.

Fouled Anchors  


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            As we try so hard to get our anchors to set quickly and hold fast, itís only a matter of time before weíre faced with the opposite problem Ė the anchor we canít get to break free.  Probably the easiest thing to try first is using the vesselís own buoyancy and whatever wave action there is to help out.  Position your boat so that the rode is vertical, then snub it up as tight as you can with each successive dip of the bow, letting the pumping action of the vessel work the anchor free.  If this doesnít work, let out a little scope (2:1) and motor forward in efforts to back the hook out Ė circling the anchor while keeping the rode tight may work as well.  Finally, if you remembered to install a trip line (figure 10) you have the option of retrieving the buoy and trying to trip or pull the anchor free from the opposite direction with it.  The above tricks will put your anchor on deck 95% of the time, but at some point youíll drop the hook and Davy Jones just wonít let go (and Iím not talking about that guy from the MONKEYS either).  What you do then will be based on circumstances and what you have in your bag of tricks.


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            If the waterís clear and the weather nice, grab you snorkel or diving gear and check things out.  If thatís not an option, take a look at the chart for your anchorage and try to figure out what you could be hung on (rocks, cable, etc) and take appropriate action.   If you think a cable or old anchor chain is the culprit, utilizing an anchor rider or chaser (figure 11) may do the trick.  Shackle a short length of chain together to form a loop around the anchor rode, then lower it down to the anchor using a messenger line of double braided nylon (3/8Ē minimum) Ė double braided line has less stretch than three-strand and wonít snapback if it breaks or when the anchor is comes free.  Once youíve worked the chaser over the anchorís shank (keeping the rode tight and vertical will make this easier) use the messenger to pull the anchor backwards and hopefully free from the obstruction.


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             In extreme cases you may have to buoy the rode, cast it off, then try backing out the anchor with the messenger by pulling 180 degrees from where you were originally anchored.  You can also try fishing for the troublesome chain or cable with a grapnel (figure 12) but be sure to attach a trip line to the grapnelís crown to aid in retrieval in case it gets stuck too!