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Sea anchor survey

Jan 1, 2003

In November 1998, nearly all participants in the West Marine Caribbean 1500 Cruising Rally experienced high seas and strong winds generated by the remains of tropical storm Mitch as it roared from the Florida coast eastward past Bermuda. Most of the boats coped with the conditions successfully by heaving to. Some chose to run off under minimum sail or bare poles, while a few elected to lie ahull. At least four deployed a sea anchor, a tactic that had only been used on two or three occasions in the previous eight years of the rally's history. Their experience was enlightening.

I have long suspected that using a sea anchor is a heavy-weather tactic that is underused and hence misunderstood by voyagers. The experiences of the four boats that used sea anchors in the 1998 rally lend credence to the view that, with proper preparation and deployment, a sea anchor can provide a highly effective method for riding out storm conditions not only in safety but in relative comfort. One rally boat opted to lie ahull after attempts to heave to proved unsuccessful. It was subsequently rolled and dismasted by a breaking sea. There is no doubt in my mind that, had they possessed a sea anchor and deployed it to keep the boat's bow pointed into the wind and seas, the crew would not have been injured and the boat would not have been dismasted, damaged, and lost.

Of the boats that deployed sea anchors, only one reported completely unsatisfactory results. The rest had success that was moderated by difficulties, most of which related to chafe damage to the rode that connected the boat to the sea anchor. The unsuccessful case was a product of improper deployment. The details are unclear, but the skipper and crew had no experience with sea anchors, and in their efforts to launch the anchor they got it fouled under the hull. The skipper commented that he thought they might have put too much chain in the rode, which caused it to sink rapidly, allowing the boat to drift over the rode. The rode snagged on the prop and they were unable to free it in the high sea state, so the line was cast off or cut and the sea anchor was abandoned. The problem clearly seems to be one that could have been prevented by crew training, better preparation, and careful compliance with deployment instructions provided by sea anchor manufacturers.

Sea anchor authorities such as Victor Shane (author of the premier reference book on the subject, Drag Device Data Base, now in its fourth edition) strongly recommend deploying a sea anchor from the foredeck with the boat head to wind and stopped. This permits the anchor to be dumped overboard from the bow, the rode veered out, and the strain taken up gradually as the boat drifts back away from it. This is all well and good if the decision to deploy the sea anchor is made early in the game, when working on the foredeck with a hundred square feet of parachute material, floats, trip lines, shrouds, and several hundred feet of anchor rode does not pose an unacceptable risk to the crewmembers selected to do the job.P>Don't delay

In actuality, sea anchor deployment is often delayed until conditions have seriously deteriorated. By then it has become too rough to continue sailing, and wind strength and sea state may have made it difficult or impossible to get the boat to heave to on an acceptable point of sail. This is also a situation in which extended foredeck work will be hazardous, indeed. According to Earl Hinz, author of the book Sea Anchors and Drogues, "Deploying a large lightweight cloth canopy held under your arm on the foredeck is akin to para-gliding in a wind tunnel. It can be done, but it is challenging." To cope with these circumstances, a technique for deploying the sea anchor from the cockpit is necessary. Unless preparations are made well in advance, some foredeck work will still be required, but the majority of the effort can be applied from a less exposed location.

Victor Shane refers to this technique as a "flying set," and it entails some definite risks of its own. To use this procedure, bring the anchor and its rode, which may incorporate a length of chain to improve the rode's catenary when under strain, to the cockpit. Lead the bitter end of the rode forward on the lee side, outboard of all structures and rigging, and bring it in through the bow chocks. Secure the rode to the cleat(s) or samson post from which the boat will ride when anchored. Be sure there is sufficient tail on the rode to allow a boat length or two to be paid out later to adjust the rode's length. With the wind broad on the opposite quarter and the boat moving at minimum speed (no main, preferably bare poles, possibly using the engine for brief periods to maintain steerage), heave the float and its line overboard (to leeward) from the cockpit. When it is dragging astern, dump the entire sea anchor from the lee quarter and allow the rode to pay out as the boat moves slowly away from the anchor. Excess speed at this stage can turn bights of rode into lethal dangers, so maximum caution is essential.

Timing of the next step is crucial to avoid sudden and excessive loading of the rode and the attachment points to which it is connected. With two or three boat lengths of rode remaining, turn the boat smartly to leeward, bringing the stern through the wind and away from the rode, which is about to fetch up tightly. Continue to turn the boat until it is head to wind and the rode takes up a strain to hold it there. Douse any sail and secure the rudder amidships.

Although not discussed in detail in other literature, it should also be possible to deploy a sea anchor while hove-to by using a modification of the flying set. Prepare the anchor and rode in a similar fashion, but rig everything on the weather rather than the lee side. The slight headway that usually accompanies being hove-to should allow the float and anchor to be deployed from the upwind side of the cockpit, streaming out to windward of the drifting hull. As the rode approaches its full length, douse any remaining headsail and use the rudder to help the boat swing head to wind as the rode takes up its strain. Quickly drop the main if set and secure the rudder.

Once riding from the sea anchor, the length of the rode should be adjusted to keep the boat and the anchor body in the same part of the wave pattern. When the boat is on a crest, the anchor should be in a crest, and both should be in a trough at the same time. If the two are out of phase, cyclic loading of the rode will result, placing excessive strains on the parachute, the rode, and the fittings to which it is secured. In anything approaching storm conditions, the load on the rode will be too great to permit you to heave in on it to adjust its length. Thus it is essential to have enough tail on the rode to allow it to be eased out to the proper length. With the boat lying more or less head to wind and substantially more stable than when underway, it is possible to fine-tune the arrangement to give optimum results. If the boat yaws too much, with the wind first on one bow and then the other, setting a riding sail all the way aft may help. Even a small (six- to 10-square feet) triangular sail set with the top hoisted by a halyard or topping lift and the two lower comers made off to quarter cleats has been known to increase windage aft sufficiently to keep the boat head to wind. Another technique is to employ a spring line from a stern cleat to a snatch block that rides on the rode. Popularized by Lin and Larry Pardey (see their Storm Tactics Handbook), this permits the boat to be hauled up so it lies at an angle to the rode. It is especially useful if the wind and seas are from divergent directions.>

Fighting rode chafe

This is also the time to take measures to defeat the chafe problems that caused one of the four Caribbean 1500 boats to lose its sea anchor before it could be recovered. In this case, the rode chafed through and parted after about six hours (just as they were about to get underway again, in fact). It broke right in the area where the rode had passed through the bow bulwark. This despite its having been padded with heavy chafing gear, including leather. Nevertheless, the sea anchor enabled the boat to ride through the worst of the weather in safety and relative comfort. "The market has yet to produce decent anti-chafe gear for rodes," said Hinz. "A major problem is the fact that the rode is continuously stretching and finding new places to chafe." TA second boat experienced chafe damage of a different variety. When deploying the anchor (for the first time, at night, in storm conditions with winds above 50 knots), a gust blew the sea anchor off the foredeck prematurely and to the wrong side. As a result, the rode was riding across a section of teak toe rail aft of the pulpit stanchion, rather than through a fairlead. The strain on the rode was so great the skipper described it as being like an iron bar. The crew found it impossible to work any chafing gear between the rail and the rigid rode, which immediately began wearing its way down into the wood. Every hour for the next eight hours, the skipper went forward and eased the rode out a few inches to prevent chafe from being concentrated in one spot on the rode. This tactic was a tremendous success. To her surprise, the line seemed to experience minimal chafe, but it sawed about halfway through the teak toe rail before conditions began to ease. The boat continued to ride to the sea anchor for another 24 hours while the crew recuperated from the accumulated stresses of the storm. The rode was eased on a regular basis, although only a few inches at a time since there was only about six feet of tail left at the bitter end.

> Manufacturers describe several techniques for recovering a sea anchor. he choice must be made prior to deployment, because it affects the way the anchor is rigged. One method uses a full trip line. This line attaches to the float that marks the end of a line secured to the crown of the anchor parachute. It runs all the way back to the boat. When it is time to resume sailing, pulling on this line causes the parachute to collapse, which allows the crew to haul it on board, crown first. A catamaran used this system in an earlier rally but found it ineffective. While the boat was riding to the sea anchor, the trip line got tangled in the rode and it could not be pulled loose. As a result it couldn't collapse the parachute.

A second method uses a partial trip line. This is usually a length of polypropylene line that attaches to the same float mentioned above. Instead of running all the way back to the boat, however, it stretches about 75 feet (presumably downwindi.e., toward the boat) to a second float. During recovery, it is necessary to haul the boat toward the sea anchor with the rode until the second float can be retrieved. Heaving on the polypropylene line will then cause the parachute canopy to collapse and permit retrieval. This method was attempted by a rally boat. They found that, although the weather had begun to improve, they were unable to haul the boat up-weather to the sea anchor for recovery. They finally chose to cast off the rode in order to resume their passage. This boat's crew also reported that their second float rode so close to the sea anchor itself that it offered little advantage over the third approach.

This method is to haul the boat toward the sea anchor until the swivel and the shackle joining the rode to the parachute canopy shrouds are on deck. Pulling on two or three adjacent shroud lines will then gradually dump the canopy and allow the parachute to be picked up. Note that the two latter techniques assume it will be possible to pull the boat toward the sea anchor by hauling in on the rode. Until the wind has moderated and the seas have subsided, this will be a very difficult task (or as one boat discovered, impossible). It may be necessary to use an anchor windlass, if available, or to carefully time efforts to recover a bit of line each time the sea motion causes the rode to slack. This is the way the crew of Dragon recovered their anchor after 30 hours of use. It took about an hour and a half to recover 300 feet of rode, and this was after the wind had dropped close to 15 knots and the seas were down to 18 to 20 feet. Once they had sufficient line recovered to lead it aft to the cockpit, they were able to use the primary winches to help haul the rode in between waves.

One crucial element in the sea anchor tactic is the rode. Obviously, it must be as strong as normal ground tackle rode, and there is agreement by all experienced sea anchor users that it must be long. Authorities cite figures such as 10 times boat length or 20 to 40 times wave height. The skipper of Dragon, a narrow-beam, 38-foot Hinckley, concluded that 300 feet was insufficient. "My recommendation for rode length is 600 feet," said Hinz. "A little chain between the rode and swivel is good to help keep the canopy immersed. I would split the 600 feet at 300, 400, and 500 feet with four- to six-foot lengths of Hi Test chain spliced into the rode by a professional rigger. That will give you a sort of variable-length deployment capability with built-in chain chafe protection at the bow roller. In my opinion, a fully variable length is unwarranted in most cases since wave lengths are neither determinable nor constant in chaotic seas."

Another issue, also raised by Dragon, concerns the choice of rode construction: laid vs. braided line. Laid line (usually nylon) has much greater stretch, which can soften the impact of shock loading, but it also tends to twist as it stretches. Unless there is a swivel in the system, this can cause the parachute to rotate and broach to the surface, or it can cause the shroud lines to twist and gradually choke the parachute canopy closed. One manufacturer doubts the reliability of swivels in an ocean environment and prefers to use braided line, which does not introduce the twist factor. He would compensate for the loss of shockabsorbing stretch qualities by adding chain to the center of the rode and using a longer rode. Dragon's skipper concluded that her double braid transmitted too much shock loading to the boat. She's replacing it with 400 feet of single braid and adding a pair of oversize 50-foot lines to serve as a bridle. This will spread the load better and provide bitter end slack for adjusting length.On the basis of voyaging rally experience, sea anchors offer voyagers an excellent tactic for coping with heavy weather. They can be equally useful for less threatening occasions when it would be helpful to "park" the boat for a whileperhaps to make critical repairs or simply to rest and have a good meal. To use them successfully, however, requires planning and practice before the weather turns foul, and careful watchstanding to prevent, detect and/or correct chafe damage before it leads to equipment failure. It also means being willing to wait until conditions have settled considerably before starting a recovery.


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