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Old 09-07-2013
JonEisberg JonEisberg is offline
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Re: series drogue or para anchor?

Quote:
Originally Posted by capta View Post
Towing a drogue also has it's own problems. Though I have not had this happen to me, I have met people who have had their drogues end up in their rigging, which must be a real pain in the a**.
Alternately, I have had a drogue slow me to the point that I was constantly being pooped, filling the cockpit frequently. In the end, the only solution was to cut the thing free and allow the boat to sail unrestricted under bare poles. It is a tremendous amount of work to steer in those conditions, at times surfing across the face of the waves at ridiculous speeds, then pointing the bow directly down wind to allow the white water to pass underneath as it overtakes you.
But if I can keep the boat under control, I feel I am much safer than hampering her with a drogue, so I no longer keep either aboard. Should I ever (Neptune forbid) get into a situation where I feel I should drag something to slow me down, I can see no reason why one or two of my 6 anchors with 30 or so feet of chain, on a long anchor rode, would not do the trick.
Of the drogues you've used, have any been a series drogue? They're an entirely different animal, and I think really have to be experienced to be appreciated. There's good reason why they are the equipment of choice of most who cruise in the Southern Ocean, for example...

Experiences and discussions of heavy weather are so variable, so dependent upon both boat and crew, it's always a losing game to attempt to apply a broader consensus or "one size fits all" approach to storm tactics... No two heavy weather experiences of mine have ever been the same, and very often one's approach to dealing with a system needs to be modified as a storm progresses...

But, sailing shorthanded, no way would I want to be at sea without a drogue, I simply don't possess the physical ability to deal with actively steering a yacht in big conditions for what might turn out to be days on end...

The CG paper on drogue use is well worth a read:

http://www.jordanseriesdrogue.com/pd...uardreport.pdf

And, as always, Evans Starzinger brings a great perspective, and his very thoughtful analysis, to this subject:

Quote:

9. Do you use drogues or sea anchors in heavy weather?

We separate heavy weather into three distinct categories. First, is an approaching rotating storm. It's important to get as far away as possible from the center and the 'dangerous semicircle' of the storm. Moving even 100 miles in the right direction can lower your winds from 65kts to 30kts. There are quite clear rules as to which direction to go, depending on which semicircle of the storm you are in. In three of the storm quadrants ('navigable') its best to run and in one ('dangerous') its best to forereach. In none does it make sense to sit hove-to or on a para-anchor.

Second, is strong winds against an ocean current (most often the gulf stream, Agulhas or East Australian). The waves will be more than twice as high in the current as out of it. These currents are usually only 20 miles wide and no more than 100. So, in this case you want to get out of the current as quickly as possible. Again, it does not make sense to sit in the current if you can get out of it.

The third is a crush zone, where a low pressure system is pressing up against a large high. This can create quite a large zone of strong winds. If you are anywhere near the forecast track of the low, you want to move away, as there is often a very narrow extremely intense band of winds around the low. Moving even 50 miles will make a huge difference in wind strength and wave height. However, if you are not near the low track and the crush zone is too large to sail out of, and your destination is upwind you can sit and wait it out if that seems the best course of action - but these crush zones can sometimes persist for a week or more if the weather patterns are stationary.

So, from a strategic perspective, it is usually best to actively sail away from the worst weather. That means either forereaching or running (with a drogue if necessary to prevent surfing). You of course have to be getting good weather information while on passage to be strategic like this, and those recommending heaving-to and para-anchors as the magic solution usually are not using modern weather tools on passage.

We do carry a sea anchor and three different drogues. As suggested above, we prefer the 'forereaching' and 'running with a drogue' techniques and believe the sea anchor is a generally bad heavy weather solution for a vessel Hawk's size - uncomfortable in use, prone to chafed & broken rodes and difficult to retrieve. I can only imagine using it in a case where we were dismasted off a lee shore with the engine also broken, although even then I would try the series drogue first and see if that stabilized the boat and reduced our drift sufficiently.

One important fact to realize is that in severe storms the area with the worst weather and the really major breaking waves is usually quite compact, sometimes only 25 miles wide and rarely more than 100 miles - often along the fastest flow of an ocean current, at the edge of a continental shelf or right near the center of a low. It makes much more sense to use an active tactic (running with a drogue preferably or forereaching otherwise) to get as far away from this dangerous zone as possible (and secondarily make as much progress toward your destination as possible) than to sit on a para-anchor waiting for it to come smash you.

A second important fact is that storms conditions evolve, and while one tactic may be perfect early in a storm when the waves are short and steep, another tactic may be preferred later in the storm as the waves have matured. Thus it is useful to use tactics that are easy to execute and easy to change. Para-anchors, even small ones, are quite difficult to retrieve in storm conditions and are the most difficult tactic to change away from (unless you just cut the para-anchor away).

On Hawk, if we are going upwind and the conditions get so bad that we can not continue we will forereach on the double-reefed main or trysail. This technique was well proven with boats like Hawk (and many significantly smaller and less powerful boats) in extreme conditions in the ’98 Sydney to Hobart, and we used it successfully as a 956mb low passed directly overhead while we were off the Falklands. On Silk we hove-to with just the mizzen up and she sat in the perfect hove-to position - 45 degrees to the wind, no forward motion and just a slow drift downwind. But many fin keel boats will not heave-to in this sort of stable attitude. They want to keep sailing and if you try to stop them they will fall off until beam-to, then accelerate and drive up until then stop again. This is neither safe nor comfortable. In ultimate storm conditions, it is also possible that heaving-to and forereaching become unsafe when the bow starts getting knocked off by the waves, leaving the boat's beam exposed to the seas, although this did not happen to the boats forereaching in the extreme '98 Sydney to Hobart conditions. But if we did encounter that situation we would first try to sail the boat more aggressively to build momentum to punch through the waves. If our best helming and trimming did not help we would deploy our Series drogue (off the stern) to minimize the distance lost to leeward. Note: Our downwind drift rate under bare poles conditions (e.g. over 50kts) with the series drogue is about 1.5-2kts, which is not much more than the 1-1.5kts for our big para-anchor in similar conditions.

Running downwind (the other active tactic) in strong conditions short-handed (e.g. with self steering rather than a human at the helm) does require care in three areas. If you make a mistake and broach your forward momentum can be converted into a violent roll. The first area for care is in moving the sail plan forward. Many people initially make the mistake of trying to run with a deeply reefed main or trysail and no headsail. This is an unbalanced sail plan which will cause the boat to want to round up and will make the steering quite difficult. We typically drop the main entirely and sail with a staysail or storm jib. That causes extra work when we want the main again but provides much better steering control.

The second is in speed control. If you go too slow you lose rudder responsiveness and wallow around and could end up beam to the waves and you also take much more water into the cockpit, while if you go to fast you build up a tremendous amount of energy and if you do broach it will be fast and violent and could roll the boat. In storm conditions, Hawk likes about 6-7kts and Silk liked about 5kts. We vary the size of our headsail, and put a drogue out when necessary to maintain this speed.

The third is the best angle to take the waves. On boats which surf reasonably easily, like Hawk, we typically run square down the waves, taking care to control our speed and use a drogue when necessary to prevent surfing. On boats which don't surf, there is a theory that it is better to take the waves at a slight angle (about 15 degrees, just enough to prevent sudden acceleration down the wave front) and not use a drogue. Silk liked this. However it is more subtle and requires more seamanship than running square.

It should be noted some boat designs are fundamentally difficult to control while running, especially those with short/fat hulls, many late IOR designs and those with inefficient 'barn-door' rudders. Downwind these boats need to go to drogues much earlier than designs which run with better control.

If we are going downwind in really bad conditions, such as over 40kts blowing against a current, producing big steep waves, we use a drogue and Hawk really likes it. The drogue we have used most is a Galerider, set on a 600' rode (two 300' anchor lines tied together) with a bridle (a spare jib sheet tied to the rode with an icicle hitch, the rode led to a snatch block on one quarter, and the sheet to a snatch block on the other). We then set the autopilot or windvane to steer dead downwind. We retrieve this drogue by simply putting the rode on a winch or our anchor windlass and cranking it in.

This is very safe and comfortable, however, the Galerider will occasionally pull out of a wave face, allowing Hawk to surf forward until the drogue catches the water again. To solve this problem, we got a second drogue (a Paratech Delta drogue), and modified it by putting a Spectra strop through its center (pic1 & pic2), so I can shackle it in at the 300' point on the rode. This 'two-element series drogue' eliminates the problem because one of the two drogues is in the water at all times. We also carry a complete Jordan series drogue with 150 cones, which is the proven, most common, solution among Southern Ocean cruising boats. However, this drogue is more difficult to recover than my 2-element system because it can not be as easily winched in. So far we have not been in conditions where we felt unsafe with the Galerider or two-element drogue solution, so we have not yet deployed the Series drogue.

We have extensively experimented with rode length on our drogues in severe storm conditions and usually found two 'sweet spots' at about 100' (where the drogue is in the same wave surface as the boat) and at 500-600' (where the drogue is more than a wave length behind the boat). In these two sweet spots the drag device sits stably with relatively constant loading. 300' rodes have in our experience been exactly the most unstable length with the biggest slack and shock loading. However, much of our severe storm experience has been in long fetch Southern Ocean storms, and we know from personal experience that short fetch North Atlantic storms have different wave length dynamics.

There is unfortunately no science or scientific testing on optimal para-anchor rode length. However, it is obvious that no single rode length will be optimal in all storm/wave conditions (perhaps ranging from 100' - 600'). Also, once you put out rode in a storm it is very difficult to bring it back in until the storm winds have abated. So, one approach is to start with the shorter end of the spectrum (e.g. 100’), where our experience suggests the tension on the rode will be the steadiest and the likelihood of excessive slack developing the least, and then if the boat motion feels wrong, lengthen as necessary to find the sweet spot. Lengthening during a storm will be tricky given the enormous loads. To do this the rode must be properly led to a very strong capstan. (US Coast Guard study on drogues vs. para anchors)

The primary reason such a high percentage of para-anchor rodes break in actual use (perhaps 80% of para-anchors deployed in extreme conditions have broken their rodes) is nylon’s extreme vulnerability to chafe and internal heat damage. The US Coast Guard and New England Ropes both have extensive experience with nylon failure due to internal heat generated by cyclic loading and recommend Dacron as a better alternative for a para-anchor application. Dacron, while not as stretchy as nylon, is an excellent shock absorber in these 100-600' lengths. However, from a practical standpoint, most people do not have a dedicated rode for their para-anchor and use a spare anchor rode, which is typically nylon. But we must all be aware that nylon has proven to be very vulnerable to failure in this application.

Regarding rode retrieval - in theory with our primary winches we can crank in 1.25" of rode/turn in slow gear and with a heavily loaded rode we can do 1 turn in 1.4 seconds. That means we can retrieve 300' of rode in 67 minutes. Our electric windlass can bring in the rode about 25% faster, or 45 minutes/300' BUT we run the risk of burning it out/damaging it with that sort of continuous load. Our actual retrieval times have come quite close to these theoretical times. It takes about 50% longer to retrieve (so 100 minutes/300' of rode) the series drogue or the para-anchor. With the series drogue, you need to be extra careful guiding the cones in and off the winch to prevent damaging them, and with the para-anchor because of higher cyclic loads over waves/swell and dealing with the para-anchor shrouds when it gets close to the boat. We have found you can winch the series drogues without damaging the cones but you cannot use a self tailer, so it's best to have someone grinding and someone else tailing (who also makes sure the cones go in and come off smoothly). Notes:

(1) This all assumes you want to bring your rode back in while it is still breezy (say 35kts). If you wait longer for the wind to drop more, it will of course be easier/faster.

(2) These retrieval speeds generally apply to the typical modern sized cruising boat (say 38'-53'). Above this size you really need either a strong hydraulic winch or to motor up to the rode, below this size the gear and loads are much smaller and you can often retrieve drogues by hand.

(3) The rode loads are quite cyclic. Your boat speed drops as you go up the back side of a wave and you get slack in the rode and can crank in faster, then you speed up as you go down a wave and the loads build and you crank slower.

(4) If you have your drogue on a bridle, you can quite easily take one leg of the bridle off the stern and bring it around to the bow, and then pull the warp in from the bow, perhaps using the motor. We don't do that for two reasons: (a) I much prefer to work in the cockpit than on the foredeck in those sort of conditions (big waves), and (b) I don't fancy trying to motor upwind into those sort of waves. It's quite a bit nicer to retrieve a rode while sitting comfortably and dry in the cockpit, than on a pitching and wet foredeck.

All the available storm tactics have pitfalls. None is a cure-all magic bullet. Its simply a matter of picking the best one for the specific conditions (which will evolve) and the specific boat. If the first one you try feels wrong, then try another. It is worth noting that all these storm tactics should be reserved for truly ugly conditions with large breaking waves. All of them are quite a bit of work. In a garden variety gale they are not necessary (for a typical cruising boat) and in fact are likely to cause additional trouble.

Here is an article summarizing our thoughts on survival sailing (as distinct from heavy weather sailing).

Seamanship FAQ.
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