Keels and capsizes (from YNZ)

[Chewing Gum 17]

From INSPECTOR’S QUARTERLY - In the good old days one did not fear rough sea conditions so much, as yachts were built to take pretty much what nature could hand out (within reason). The racing machines that we see today are another breed however. Maybe some should not even see open water. These days keels and rudders can fail under quite reasonable sea conditions. The latest spectacular failure was during the Audi Sidney-Gold Coast Race in July this year.

 

Three miles offshore in a light breeze Wasabi lost her keel. By the lucky fact of good weather conditions, the water ballast carried, and rapid distribution of the 7 crew, the boat remained upright until she was able to retire from the race. There was no loss of life. Wasabi was a 12 metre Sayer design yacht built for the Osaka race 2007, by carbon infusion methods. The fabricated keel was socketed into the hull ( see photographs) in a similar fashion to Andar which had its keel work loose in the Round North Island Race. Andar however, had 3 vertical keel bolts to draw it up tight into its socket. Both yachts had a reasonable number of sea miles under the belt before their mishaps.

 

Now another yacht joins the infamous list. The Juan Kouyoumdjian designed maxi. This 100 foot Cookson built boat originally called Speedboat, and later renamed Rambler was launched in April 2008 and was said to be the latest design in advanced carbon thinking. Just as Rambler rounded the Fastnet lighthouse in moderate winds, the wind began to head them. As the 12 million dollar yacht began to beat into the seas, the fabricated canting keel snapped off outside the hull just where it attached to the canting keel mechanism leaving the hull still watertight. Thirty seconds later the boat assumed an 180° aspect, leaving some of the crew to scramble desperately out from the submerged cabin and forcing some of them to leave their life jackets behind. Sixteen of the crew managed to stay on the upturned hull. Five others floated away but clung together as they had been only recently taught, and being rescued some 2½ hours later.

 

Of course you don’t have to lose a keel to join the 180° Club, it’s enough to have sports boat genes in your ancestry and hulls built out to imitate racks, something like KZ1 for example.

 

Take WingNuts a Kiwi 35 of 1293 kgs displacement with a drop keel carrying 500kgs ballast. It capsized when a severe thunderstorm with winds in excess of 50 knots, occurred during the July 333 mile Mackinac Race on Lake Michigan around midnight. Tragically two of the eight crew members died, even though other boats were on the scene very quickly.

 

Then again, being a maxi multihull is no guarantee that you will not qualify also.

 

The 100 foot maxi trimaran IDEC flipped off the coast of New York in the same month, under triple reefed main. The solo sailor hoping to do a trans Atlantic record dash, used his escape hatch to good use.

 

 

Stability and safety – a designer’s comments

 

New Zealand yacht designer Brett Bakewell-White says that stability is not that well understood by many sailors.

 

“It’s not only about the keel, it’s about the shape and the total weight of the boat,” he told to a group that attended a seminar hosted by Royal Akarana Yacht Club in preparation for Sail Noumea in 2012.

 

At the seminar, Brett explained the GZ Curve – a graphical representation of the stability of a yacht, and the difference between small angle stability, which is what sailors experience, and large angle stability, which is what safety is about.

 

“Large angle stability is about what angle the boat wants to turn upside down. Most never experience that, and we hope most never do,” he explains. “Owners will get frustrated because they may believe their boat is stiff, whereas on the GZ Curve it is shown to not be stable. A boat can be stiff at low heel angles, but have poor characteristics at larger angles.”

 

The second area that Brett spoke on related to the structure of keels, how they are attached to a boat, and issues relating to maintenance.

“We sometimes talk about keels having a lifespan,” says Brett. “Some designers of extreme keels might give it a WOF of 60,000 miles, and that sort of thing.”

 

He says that owners can contribute greatly to the performance and safety of their keel by regular cleaning and inspection.

 

“The keel has to do the same job as the sails, and looking after the surface of a keel is very important for performance.”

 

From a safety perspective, he says that an owner should check regularly for cracks and corrosion around the keelbolts, and inspect the plates over keelbolts. If a boat hits the bottom, even if it’s minor, the boat should be removed from the water and the keel checked. Welds in a steel keel can be inspected via a portable x-ray device.

 

Finally, to obtain Cat 1 for an offshore passage or race, it is necessary to prove stability.

 

The first port of call, says Brett, is to the designer of the boat or the keel. The designer should be able to provide a certificate, but if not, then to a marine designer or engineer, such as Bakewell-White Yacht Design. “We do it for a minimal cost because we want to see boats out there."

 

If you own a production boat such as a Beneteau, then this is something your agent or manufacturer should be able to assist with.

And if you own a multihull? Keel issues and maximum heel requirements may not be an issue, but as Brett says, they make a pretty good liferaft, and that is where escape hatches and survival equipment comes in.

 

Bakewell-White Yacht Design >

Sail Noumea are running regular seminars prior to the race start in July