August 15, 2010

On July 31, 2010 the Atlantic 57 Catamaran, Anna, with a crew of two, was capsized by a violent squall 125nm from Tonga in the South Pacific. This news came as a shock to me and most of the owners of Atlantic Catamarans, as well as sailors of other cruising catamarans. Fortunately neither the captain nor crew was injured beyond minor cuts and bruises.

Also fortunate was the fact that the EPIRB was located by the crew, switched on and a signal was immediately picked up by the satellite system. The owner had registered the EPIRB properly and the USCG was able to reach the owner's contact person to confirm details of the boat and crew before sending out an Orion search plane. The New Zealand Rescue Services plane located the catamaran quickly, and spoke to the captain by VHF radio. A ship that was less than 100 miles away was diverted and roughly 12 hours later picked up the two wet sailors.

As sailing calamities go, this could have been much worse. For decades I have dreaded the day when someone gets seriously hurt or killed sailing one of my designs. This accident certainly had the potential to do one or the other and I am very thankful that it did not.

In order to reduce the chances as much as possible of another capsize it is important to examine what happened and develop a methodology to avoid capsize. If capsize should occur it is also essential that some basic things are done beforehand to insure survival of the crew during as long a time as it might take to be picked up by another vessel.

Ten years ago I had the itch to learn to fly sailplanes and took the regular course of flight instruction. What was immediately apparent to me is how safety conscious the world of aviation is. In aircraft, accidents happen very fast and are often deadly. The major cause is pilot error, which is often due to either momentary confusion, lack of skill, or distraction. To combat this, many aspects of flying, such as takeoff, landing, and flying in turbulence are highly regimented. Each is performed with its own check list. You will not get a license to fly unless you can demonstrate that you know all of these check lists and have the skill to perform them properly.

Offshore sailing on the other hand is largely a free-form activity. Cruising sailors, me included, hate being told what to do at any level. Many of us are self taught and sail either alone or with small crews. We learn from each other- sometimes- but many sailors have not had the benefit of ever sailing long term with people of great experience. To complicate matters further, the boats are all so different that rules which may work for one size and type maybe useless for another. With that in mind I still think it will be wise to develop a protocol for multihull sailors to follow in squally or extremely gusty conditions.

Squalls come in all shapes and sizes. Most are benign, a little bit of rain, a few minutes of increased wind, then a stretch of near calm after it passes. They are often frustrating, but no big deal. Now and then a big one comes along, advertising itself long in advance with thunder and lightning, a black line of clouds and a froth of white on the sea surface as it approaches. These are the scary ones. You watch and wait, reef or drop sails ahead of time. The squall comes and does its thing, and in an Atlantic Cat, you stay nice and dry in the pilot house. Fine. No worry this time. The bark is often worse than the bite.

Then there is the dangerous squall. These are the ones that don't look that bad. There may be a large rain shield, it may not look too dark and or ominous, but within the squall, behind the first band of rain, lurk very strong winds. These are the squalls that can really bite. Only 2 weeks ago, as Kate and I sailed Javelin south along the Windward Islands in the Caribbean, a squall of this type hit us hard. There was a tropical wave passing through which was in the process of turning into a tropical storm, and atmospheric conditions were quite unstable with overcast skies and frequent squalls. It had been blowing 18-20 knots and we had a single reef in the main and the full self tacking staysail. We were sailing at a true wind angle of 50 degrees or so at about 9 knots. The squall looked like the others more or less, though I was concerned that its movement seemed different. In any case, a few minutes after the initial wind gust and rain, the wind really cranked up and headed us. Then it increased again and headed us more. There was way too much wind for the sail we carried, so I luffed up enough to depower Javelin, trying to walk the fine line between flogging the sails violently and keeping our boat speed down below 12 kts. It was exciting, too exciting, and when it did not let up after a few minutes we dropped the mainsail entirely. If truth be told, the whole event left me pretty rattled. We experienced an increase from 20 to 45 kts of wind in a fraction of a minute along with a 90 degree wind shift. I did not expect that at all. And that's the lesson. Sometimes a squall will dish out something that you don't expect and are not prepared for. It may only be one out of 50 or 100 squalls that are truly dangerous but you don't know and can never be sure which ones they are.

The report from Anna was the squall did not look any different than the others. But the last wind reading they noticed was 62 knots. That's a lot of wind. And they had the same sail up as Javelin did in the squall I just mentioned, a single reefed main and the full self tacking jib. Keep in mind that power in the wind increases as the square of the velocity. Doubling the velocity from 20 to 40 kts increases the pressure on the sails by FOUR times. Tripling the wind velocity from 20 to 60 kts increases the wind pressure by NINE times.

Reefing not only reduces the sail area but removes sail area from up high where the wind pressure exerts the most leverage trying to turn the boat over. The typical catamaran mainsail is large with a very rounded roach that increases the sail area near the top of the sail where it exerts the most heeling force. The combination of both reducing the sail area and reducing its height by reefing has a dramatic effect on stability, allowing the boat to stand up to much stronger gusts.

The autopilot is indispensable for short handed cruising. I love the autopilot on Javelin and use it almost all the time. It steers the boat very well, better than most helmsmen. But the autopilot is a dumb machine. It cannot see the black squall line coming nor the water being whipped white by the leading edge of a gust front. It does not deduce that since the wind velocity has increased from 20 to 30 knots in 6 seconds that it may shortly increase to 50 knots. The autopilot has no survival instinct. The autopilot cannot anticipate the future. It has severe limits and sometimes,

The Autopilot must be turned off!!

We sailors have to physically take control of the boat in a squall. Pilot off, hands on the wheel, ready to respond.

Putting it together:

On board distractions during moments of stress can overwhelm clear thinking. Discomfort from heat or cold, wet, fatigue, or motion sickness can and will diminish a sailor’s energy, mental acuity, responsiveness, and judgment when it is most needed. It is useful to remember the aircraft pilot’s invaluable, ever-ready, life saving tool in difficult situations. The pilot relies on familiar checklists and procedures to block out distractions, focus attention, and to make correct decisions quickly. The sailor can benefit from the same kind of help and preparation.

With the above in mind I offer the following procedure for sailing a cruising multihull in gusty or squally conditions:

STACS: it stacks the deck in your favor.
S – sail area
T - trim
A- autopilot
C- course
S- sheets

S- Sail area. Sail area should be adjusted to deal with the expected increased velocity of gusts. If there are numerous squalls in the area it makes sense to reef deeper than normal. The same goes for sailing behind high capes and mountains where strong gusts are often present. Most Atlantic Cat sailors report how little a double reef slows the boat when there is a decent breeze blowing. The boat is able to deal with far more wind with a double reef than a single reef. That does not mean that no harm can come with shortened sail, but it does mean the velocity of a gust will have to be much greater to endanger the boat- and therefore far less likely.

T- Trim. When it is clear that a squall will overtake the boat, the sail trim should be adjusted to better cope with gusts. Typically this means moving the main traveler to leeward somewhat and easing the sheets if not reducing sail further.

A- Autopilot. When the squall is at least a couple minutes away turn off the autopilot and take control of the steering. This will enable rapid response should an overpowering gust occur.

C- Course. Adjust the heading to an appropriate and safe course. Keep in mind that large wind shifts are common in squalls. If the boat is sailing against the wind (true wind forward of the beam) and a dangerous gust occurs it is normal practice to turn into the wind enough to de-power the sails. Ideally the course can be held on the edge between flogging the sails and overpowering the boat until either the squall subsides or sail can be further reduced. Fully battened mainsails are usually well behaved but the jib may flutter violently for a short period. If sailing to windward it can also be very helpful to have the engines idling and ready because there may be need to drop the mainsail and that will be easier if the boat can be held head to wind. If the cat is sailing down wind (true wind aft of the beam) normal practice is to alter course away from the wind. This reduces the apparent wind velocity by your boat speed and in most cases is the least painful way to weather the squall. The main boom preventer should be made up to guard against an accidental jibe.

S- Sheets. In the case of an overpowering gust the first sheet to ease is the main sheet. In most catamarans the mainsail is likely to be larger than the jib and its area is concentrated higher up which contributes more toward turning the boat over than the jib.

There are so many variables – wind direction and strength, maneuvering room, vessel size and type, number of crew and their level of experience – that being too specific is likely to be counter productive. What is important is to recognize the potential danger in violent squalls and to develop an easy-to-remember protocol for dealing with dangerous wind gusts should they occur.

In the book titled The Cruising Multihull, I wrote extensively on the subject of capsize. At the time I drew a distinction between wind induced capsize and wave induced capsize. At the time, I judged capsize by wind to be the less likely of the two, because the risk could be controlled by the sailor by reducing or striking sail and altering course. On the other hand there is far less that the sailor can do to avoid wave capsize if the conditions are sufficiently bad to roll the boat over by wave action alone.

In retrospect, I did not adequately consider the risk from short duration violent wind gusts. There have been two capsizes of Atlantic catamarans in the 20 years since that book was published. Both capsizes were from strong winds. One was an Atlantic 42 on Lake Michigan in 2004, the other was Anna, which happened a couple weeks ago in the South Pacific. Even though the circumstances were different, there is a remarkable similarity in how the boats were capsized.

To summarize:
1) Neither captain thought capsize was even a possibility until way too late
2) Both boats were under autopilot, which had the helm all the way through the capsize
3) The main sheet was never eased or released

Anna was a very well built and extremely sea worthy catamaran. Her loss is a “wake up call” to all of us who sail catamarans. Accidents do happen, typically when you don't expect them. The cruising catamaran is normally so easy and so forgiving that we can be lulled into complacency.

Be aware, be alert. Have a plan.