Fatal Kiwi 35's probably as stable upside down as right side up
by Eric Sharp, Detroit Free Press on 22 Jul 2011
It happened during a race, and would not normally be covered by Sail-World Cruising. Two sailors died last week in the Chicago-to-Mackinac race, after the Kiwi 35 Wingnuts turned turtle without losing its keel. However, the safety issues involved in boat construction, are always a subject critical to the cruising sailor, and we therefore print an analytical article here by commentator Eric Sharp:
WingNuts - just as stable when ’turned turtle’ as when upright SW
Online sailing forums have been full of comments about the deaths of two people last week aboard WingNuts in the Chicago-to-Mackinac race. The Kiwi 35 capsized during a midnight storm on Lake Michigan, killing skipper Mark Morley, 51, and Suzanne Bickel, 41, from Saginaw. Six others were rescued.
Several yachts of similar design are entered in the Port Huron-to-Mackinac race, which starts Saturday, and some say those boats aren't safe offshore.
Yet a sailor who knows as much about Kiwi 35s as anyone, someone who helped Morley set up his boat two years ago, said Morley seems to have done everything possible to avoid the disaster.
Mike Kehew of Middletown, R.I., said Morley probably was the victim of bad luck and of the unconventional design that makes the Kiwi 35 so fast. From what I've been able to piece together, I tend to agree.
Keel yachts rarely roll over, but it isn't unheard of if the seas are big enough. What is weird is for a keel yacht to 'turtle' in modest waves and then stay upside down if it hasn't lost its keel. That's what happened to WingNuts.
But Kehew, who raced a Kiwi 35 along the East Coast for five years, said a yacht designer once told him: 'The Kiwi 35 was the only monohull he knew that was probably as stable upside down as it was upright.'
'The reason is the wings,' Kehew said. 'They are essentially buoyancy tanks. And below (in the cabin) you have lockers on either side that are basically airtight. Once it went over, it would stay that way until it was pulled back upright.'
Photos of the overturned boat also made me think the culprit was the hiking wings that extend beyond WingNuts' deck.
In one photo, the mainsail is stowed on the mast that sticks down into the clear water, something a prudent skipper would do with a storm approaching. So there's no big spread of fabric underwater to hold down the boat. You can see the fin keel is intact, including the 1,000-pound bulb at the bottom.
Most yachts over 25 feet depend on a heavy keel and internal ballast for stability. On a Kiwi 35, crew weight substitutes for much of the lead ballast.
Because it is so light, and with so little wetted surface area, the boat can hit 18-20 knots (20-23 m.p.h.) in 15-22 knots of wind. As the wind tips the boat to one side, the crew climbs out on the windward wing to keep the boat flat. It's simple leverage. More wind requires more weight on the wing.
It's difficult to understand why WingNuts turtled in what were reported to be modest seas of 4-6 feet, a bit rough but nothing extreme for Great Lakes sailors. A 35-foot boat should handle waves twice that big.
But if WingNuts was hit by a big wave or gust of wind and tipped to one side, the wing on the leeward side (away from the wind) would dig deep into the water. It would happen so quickly there would be little chance for the crew to get on the windward wing to hold the boat down.
If the high wing on the windward side was then hit from below by another heavy gust, it might be enough to lift the hull and pivot it upside down.
'I agree,' Kehew said. 'I think that's exactly what happened.
'If you got hit with a big gust, you'd be right over on your side; and if another big gust got under the wing on the high side, you wouldn't have a chance. On my boat, we replaced the fiberglass wings that weighed 150-200 pounds with aluminum racks that weighed 40. That really helped the stability.'
A sudden, violent flip also might explain why Morley and Bickel died of head injuries -- the Charlevoix County sheriff told the Chicago Tribune -- when the boat dropped on them.
But Kehew doesn't think the basic design of such boats is unsafe.
'We're building a new boat similar to the Kiwi 35 that will be a little bit shorter and lighter with the same sail area,' he said. 'It's going to be a rocket.'
Contact Eric Sharp on firstname.lastname@example.org. Order his book 'Fishing Michigan' for $15.95 at www.freep.com/bookstore
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