top of page

When Ran Tan lost her canting keel, mid-ocean

New Zealand's most high profile racing yacht lost her keel and nearly her three crew mid-Pacific in 2019. There was minimal follow up as to why it happened - yet other canting keel yachts could be affected by the same factors. That seemed a good reason to dig deeper.

It was a calm, mid-Pacific morning, around 1000 on May 31, 2019, when the keel finally let go.

The three crew of the New Zealand-registered Ran Tan II had known for 18 hours that the 50ft Elliott racing yacht had suffered a major keel failure and that it would soon fall off. They were prepared to abandon ship and knew rescue was on its way. They hoped it would arrive before the boat capsized.

The 13-year-old Ran Tan was one of New Zealand’s most ardent offshore campaigners. She’d been built in carbon fiber with a foam core and a lifting, canting keel in Auckland, New Zealand, in 2006. The lifting keel was later modified to a solely canting keel. In 2015, she was bought by Brian Petersen, 66, also a seasoned campaigner. His sailing CV includes the 5,500-mile, doublehanded Melbourne Osaka Race, which he sailed in 1991 and 1995 and won in 2003 as owner and skipper of the Elliott 45, Maverick 2.

Ran Tan II owner Brian Petersen is a veteran campaigner Photo by Andrew Delves

In 2016, Petersen raced Ran Tan from Auckland to Fiji, then sailed across to New Caledonia for the Groupama Race. In 2017, Ran Tan did the Sydney-Hobart Race, hitting more than 30 knots down the coast to finish 15 on the line in 1 day, 23 hours and 34 minutes. In 2018, Ran Tan won the Auckland-Noumea Race and scored second in the Groupama. She also raced nearly every Friday and weekend. No one had counted the miles, but she had done well over the equivalent of a circumnavigation.

For 2019 Petersen planned a monster goal: the 2019 Transpac Race, from Los Angeles to Hawaii. The shipping costs were prohibitive, so he decided the boat would cross the 6,000 miles across the Pacific to Los Angeles on her own keel. Petersen skippered her to the Marquesas, where he handed her over to delivery skipper Keith Hogan for the final leg. Also on board were Kosta Popov and Nic Finlayson. All three were Ran Tan regulars.

Now you see it (the damaged keel at top) now you don’t (below) Photos courtesy of Nic Finlayson

Keel Failure

On May 24, the three sailors departed the Marquesas, and on May 28 Hogan called for a thorough maintenance check, “making sure it was all tickety-boo for the upwind passage up to Los Angeles,” he says. The next day, they noticed an oily substance in the wet box, the chest that contains the seawater where the canting keel passes through the hull and the hydraulic rams cant the keel.

“We jokingly said, ‘Well it’s either the hydraulic ring seal let go, or it’s a cracked keel,’” Hogan says. “So, we checked the seals, and they were good as gold.”

On May 30, Ran Tan was 500 miles north of the Equator in a sunny 12 knots of breeze. Hogan finished his watch at 1600 and handed the helm over to Popov. “I clearly remember standing in the companionway, and the boat leaned over a little bit,” Hogan says. “I said, ‘Come on, guys, put the keel out.’” According to the keel indicator, though, the keel was already canted 40 degrees, in which case it should have been visible from the side deck. It wasn’t. That was so unlikely, the crew wondered if there was some kind of an optical illusion at work. They tacked over, relieved to see the white bulb from the new windward side. They tacked back. The keel failed to reappear.

Finlayson volunteered to go overboard with a GoPro camera. When he did, he found chaos. The keel was bent near the top and hanging straight down, despite the root being canted to port. The composite foam core covering the interior steel mandrel was mangled. A crack ran fore and aft near the top on its port side. It was evident that its 2.5 tonnes of ballast would soon spiral to the ocean floor.

“We were thinking, oh my God, what do we do now?” Hogan says.

What they did was prepare for a capsize. To maximise stability, they dropped the sails and made sure the forward daggerboard was down. They also tied the boom to the side rails, so it wouldn’t take them out in the event the boat turned turtle.

Over the next several hours, Hogan sent out a number of verbal mayday calls, rotating through the emergency channels on the boat’s SSB radio. After receiving no response, he pressed the red distress button on the boat’s HF radio activating its DSC (Digital Selective Calling) function as well to call any boats that might be in the area. (Although unknown to the crew, it did little good, because the radio hadn’t been properly connected to the boat’s GPS, which meant the alarm didn’t include position information.) He also texted Petersen: “Mayday, mayday, mayday. Keel failure. Boat still upright. In a [sic] cockpit ready to abandon. Call us.”

Finally, with no response to his SSB maydays, Hogan activated the boat’s EPIRB, which was picked up by New Zealand Maritime. New Zealand Maritime in turn rang Petersen at his home to confirm the signal was genuine and then contacted Joint Rescue Co-ordination Center Honolulu (JRCC).

It was a long cold night on Ran Tan. The crew stacked grab bags, food and water near the transom, where the liferaft lay, ready to be deployed. They huddled aft of the cockpit’s twin wheels to avoid being trapped if the boat rolled. The engine ran in neutral to charge the batteries for navigation lights and the AIS. The boat’s dinghy was inflated and tied astern. The three of them got out some beer and made dinner.

“There was a pretty strong range of emotions,” Hogan says, “just realizing that we were 1,200 nautical miles from somewhere. We may or may not get rescued. We talked about that a lot that night—the people that sailed on Ran Tan and all the fun we’ve had on it. That brought tears out in most of us.”

It was nerve-wracking. “Every time the boat rolled through a little swell, we‘d think, ‘Oh, is this it?’ Then it would settle down again,” Hogan says.

JRCC Honolulu was unable to communicate directly with Ran Tan, so Petersen ran relay: sending e-mails to Honolulu and New Zealand’s Northland Radio, which was in touch with various vessels on the Pacific, and texts to Ran Tan.

“I knew they were in a nice part of the world for that sort of thing to happen,” Petersen says, “in the Tropics, just out of the Doldrums and they had just run into the Northeast Trades. Having been in a liferaft, [following the sinking of Triomphe on a return trip from Noumea to Tauranga], I thought, they are not going to die. They’ve got a liferaft, and they’ve got an inflatable dinghy.”

Petersen searched Marine Tracker for a rescue vessel. A car carrier bound from Chile for South Korea looked good, until it was diverted to another mayday call 100 miles farther south. Finally, Honolulu advised him that a 1,000-ton Mexican fishing boat, Azteca V, was on its way.

Clunk, clunk… As day broke on the morning of the 31st, Popov felt the keel moving fore and aft. It was close to breaking off. Around 1000, Finlayson made another inspection and surfaced to ask Hogan to cant the keel slightly. Hogan “gave it a quick little punch of the button for one millisecond,” as he puts it. Finlayson ducked under for a second look, and the keel was gone. “We popped the liferaft,” Hogan says.

Now it was a race between capsize and rescue. From this point on the crew only went belowdecks to gather food, use the toilet and continue trying to send the occasional mayday out on the SSB. “We weren’t dawdling around down there,” Hogan says.

They also loaded up the liferaft so that it would ride a little more steadily should they have to abandon ship. “Basically, it was an eight-man raft, and there were only three of us, so it would have been pretty lively. We put as much weight in it as we could,” Hogan says.

At about 1500, a helicopter appeared. An hour later the blue-and-white bulk of the Azteca 5 arrived as well and immediately lowered a number of small red boats to take both them and their gear on board. That done, Hogan turned Ran Tan downwind and switched on the autopilot, at the same time leaving the engine on light throttle to charge the batteries for both it and the boat’s AIS and nav lights. He locked the companionway, so the items inside wouldn’t float out in the event of capsize, but left the vents open so she would sink.

“It was pretty hard to step off the boat,” he says. “It looked just fine. It just didn’t have a keel.” Eighteen hours later, Ran Tan’s AIS stopped transmitting. She was presumed to have gone down.

Azteca 5 was scheduled to spend another 45 days at sea, so her captain arranged a rendezvous the next morning with a sistership, the Azteca 10, which was heading back to port. Four days later, Ran Tan’s crew arrived safely in Mazatlán, Mexico, to a media maelstrom.

“It still hurts, losing my boat,” says Petersen. He had bought insurance to four degrees south of the Equator and had negotiated coverage for the remainder of the voyage until Ran Tan returned to below four degrees south. Unfortunately, although he’d filled out the paperwork the day before the keel failed, he’d forgotten to submit it. He estimates Ran Tan II’svalue at around $225,000.


Post Mortem

Of course, in the wake of such a catastrophic failure at sea, the question becomes, “What happened?”

To get some idea, I contacted Andy Kensington, managing director of Pure Design & Engineering in Auckland. Kensington’s specialty is structuring under load, in which capacity he serves as a consultant with America’s Cup Defender, Emirates Team New Zealand.

Broadly, Kensington says, there are three ways to manufacture a keel. The strongest, most expensive way is to mill it from a single, solid piece of steel. The second is to weld it together using vertically oriented welds, the technique used with Ran Tan’s keel. The third is to weld it together employing horizontal welds as well, a method unsuitable for high-performance keels.

Ran Tan’s designer, Greg Elliott, describes the construction of Ran Tan’skeel as, “Primarily a structural box-section lever that runs full length from the bottom, where the bulb is attached, right the way through to where the pin goes through to the hydraulic cylinder/ram.”

Elliott goes on to say, “There are no horizontal welds. All welds are vertical, with no interruptions. The pivot points are butt-welded on the front and the back of the box section and well supported by flanges.”

He adds that the internal box section was also oil-filled to prevent rust—the same oil that leaked into the wet box—and covered with an outer skin of carbon over fiberglass, which was faired to give the keel its hydrodynamic foil shape.

Of course, even under “normal” operating conditions, canting keels are subjected to much higher stress levels than fixed keels, because of the way they are angled outboard.

“Say, a fixed-keel yacht is hit by a strong gust of wind that heels the boat over to 30 degrees, which is quite high for a fixed keel,” Kensington says. “The load on the keel is, say, half of what it would be at knockdown…. [However], when you’ve engineered the keel, you’ve allowed for the knockdown a

nd the safety margin on that, so when it’s sailing, the stress level in the keel is quite low, relative to what it has to withstand in a knockdown.”

By contrast, Kensington says, “A canting keel is different because the boat heels over to say 30 degrees with the keel in its centered position, but then the keel is canted to generate more righting moment, taking the keel much closer to that 90-degree maximum it’s nearly always operating at a high percentage of a knockdown load.”

Something else to be aware of, Elliott says, is the fact that every time a keel experiences a stress change, it’s called a cycle. A tack or gybe, going over a wave, even a change in the degree of cant are all classed as cycles. “It’s all about how many times it bends through its life. Everything has a certain life span,” Elliott says. In other words, Ran Tan’s keel failure was not so much an issue of strength, but fatigue.

Further complicating the situation with respect to Ran Tan was the fact that it was one of the first privately owned, canting

keel yachts launched in New Zealand: built at the time before there were international rules in place for these kinds of then cutting-edge structures.

“It [was] a difficult period,” Kensington says. “ABS [American Bureau of Shipping] used to do approvals for offshore racing yachts. They had a little booklet on rules, so basically designers and sailing teams would be pushing that rule really hard, and it was getting out of date with where boats had got to. It was designed for a conventional boat, not for a full-on racing boat, let alone canting keels.”

Only in March 2008 did the International Organization for Standardization (ISO) release an international standard for hull scantlings (ISO 12215-5) with a keel scantling rule (ISO 12215-9) following in

June 2012. Today, a newly built offshore racing yacht must have its plans approved by World Sailing, which then issues a certificate stating compliance. However, such things were still in the future when Ran Tan was fitted with her then cutting-edge keel.

Which, of course, naturally leads to the question, how many cycles are too many?

Some round-the-world syndicates accept that a canting keel is good for around one million cycles, or a circumnavigation of the globe, say around 30,000 miles. After that, they replace it. In her active 13 years, Ran Tan IIwould have covered that distance and then some.

“In hindsight,” Petersen says, “probably the keel needed to be removed from the boat, stripped back to the metal and [then] undergone some method of testing for the fatigue. Even though we had the keel out several times, there were no visible signs that it was under stress, so you don’t even think about it.”

Canting keels, like the one aboard the IMOCA 60 Advens, need to be carefully inspected out of the water

Inspecting a Canting Keel

Neil Howe, engineering manager at Auckland’s Kawerau Engineering, says all keels need to be visually inspected on a regular basis, and that owners of canting keels built before the 2012 ISO standards, in particular, should also consider a professional checkup to ensure all is as it should be.

Especially with canting keels, he says, “The best way to check the keel is to remove it, remove any composites or fiberglass or fillers and then sandblast the entire keel and get it crack tested.” He recommends mag particle inspection (MPI), and if the keel has mixed, non-ferrous materials in it a dye-penetrant test (PT).

Even when these kinds of tests give the all-clear, engineers and the owner may still want to estimate how many cycles the keel has undergone and relate that that number to its construction materials. “Depending on the material, the number of cycles varies greatly,” Howe explains.

Howe emphasizes it’s important to regularly inspect all types of keels when they out of the water for any form of rust and, especially, electrolysis. “That can destroy a keel in months,” he says adding that with electrolysis a chip in the leading edge can quickly develop into a thumb-size hole.

He adds that keel fastenings should also always be inspected after any kind of incident, such as running aground or hitting a rock. “It may be that they’ve broken at the bottom of the keel, the studs are stretched or the front bolts are loose,” he says. “The issue with keels is that lives are at stake.”

See article here

85 views0 comments

Recent Posts

See All


bottom of page