IOR boats and the death roll

[Priscilla II 392]

From SA

 

From Fritz Kloepfel:

 

In the late 1980s, I was just getting serious about my love affair with racing sailboats. At an early Key West Race Week I met an interesting character named Larry Ruhland. He was unlike anyone I knew, but he was passionate about racing sailboats. Over the course of the week we became friends and over the next couple years, I invited him to come sail with me in Florida several times. And he did! Eventually, he invited me to come race in the Great Lakes aboard his boat, Dolphin. She was a fabulous old racing boat 54 feet long, with a mast reaching over 80 feet in the air. Big and solidly built, she required a talented crew to show her best. The crew was mostly Larry’s two sons and their friends and relatives. It was an interesting mix of backgrounds and talents, but they made a formidable team.

 

Larry’s two sons could not have been more different.

 

Mike was serious, studious and very focused. His hair was trimmed short and his dress was near formal. And he was analytical. Very, very analytical. He was enthralled with technology, information, and calculations. A bit of time spent with Mike could leave you believing that it was possible to THINK your way across the finish line first. And Mike was just the guy to do it. I felt an immediate kinship with him.

 

Pat was much the opposite. Casually dressed and very casually coiffed, he seemed to care little about the instruments, the technology or the details of strategy and tactics. On our first meeting, he was introduced to me as “Turbo,” a nickname that apparently reached back to his childhood where his mother used to wonder if he were turbocharged as he played around the house. But to me, he seemed the very embodiment of “laid back.” A yin to his brother’s yang.

 

The Dolphin was a demanding boat, and over the course of the first day and a half, we all took turns driving, spinning the “coffee grinders” to power the winches, and tailing the heavy lines that trimmed the sails. The crew all pitched in. Except for Turbo. Yes, he lent a hand in here and there, but he hadn’t taken the wheel that whole time and had not seemed to contribute much. I had started to wonder, to myself, why we had brought him along. But as it was starting to make me scratch my head the boat began to demand more of us. Well into the second day the wind was building and with it the waves. We were sailing downwind with a big running spinnaker up, and the boat was becoming a handful. The waves would get under the back of the boat and make it skew left or right, and the heavy winds in the sails had us rocking and rolling nearly out of control. The big wheel really needed to be manhandled to keep the boat standing up, and most of the crew were not quite skilled enough to keep it all managed. And, it was a workout. 20 minutes would wear you out, and 30 minutes was all anyone could do. We began to talk about reducing sail and slowing the boat, …not the solution you want when you’re racing. But the wind continued to build, and the waves looked like mountains.

 

Just when I thought we had no other choice Larry hollered out one word. “Turbo!!!”

 

And out of the bowels of the boat came Pat. He walked straight to the back of the boat, and without a word he took the wheel. And as though someone had waved a magic wand the boat stopped bucking and jumping. It stopped skidding left and right and pitching like a rodeo bull. Suddenly we were on a straight course, and using the waves to surf the boat along, instead of fighting us. I was flabbergasted. I sat there for some time just watching Turbo drive. I’d never seen anything like it. He seemed at one with the wind and the waves and a veritable part of the boat. Every motion was smooth, and he made it all look effortless. Without my ever voicing the question, Larry leaned over and said, “Now you know.”

 

Turbo stayed at the wheel for hours, occasionally steering with one hand while he lit a cigarette with the other. He didn’t swivel his head to see the waves. He simply seemed to know where they were coming from. He didn’t fight the boat. He seemed to caress it. The wind was not his opponent, it was his strength. I had never seen it done better, and in all my years of sailing, I never did. Eventually, the wind eased and the waves began to subside, and as the boat once again became controllable (by mere mortals) Pat quietly said, “Anybody want this?” and it was over.

[Island Time 1,235]

Great story!

[Kevin McCready 83]

From my sailing database:

Death Roll =  broaching to windward, putting the spinnaker pole into the water and causing a crash-gybe of the boom and mainsail, which sweep across the deck and plunge down into the water. The Death Roll often results in destruction of the spinnaker pole and sometimes even demasting of the boat. Serious injury to crew is possible due to the swift and uncontrolled action of the boom and associated gear sweeping across the boat and crashing to the (now) leeward side.  
Jeff Toghill in Sailing for beginners 3rd ed 1998 writes “Much has been made of the so-called death roll, which affects ocean racing yachts when under spinnaker. Basically what happens is that the yacht, running downwind with spinnaker up and full main out the other side, begins to yaw on the seas coming up from astern.
This sets up a roll, which is aggravated by the alternating pressure of wind in the spinnaker as the boat rolls to windward, and the main as it rolls to leeward. The roll increases as sea and wind effects synchronise to the point where, unless it is stopped, the yacht will roll to windward and dip its spinnaker pole into the sea. This drags the spinnaker down into the water, it fills, and the strain is enormous. If the spinnaker is attached to the top of the mast, chances are that the top of the mast will be pulled off. Even if no structural damage is sustained, the boat is pulled up to a standing halt, and a long process of cutting away must be started before the boat can get under way again.
The death roll is particularly prevalent in the Southern Hemisphere, where the long rolling swells coming up from the Roaring Forties can quickly induce a heavy roll. It accounts for a great number of dismastings in this part of the world. Although it is very difficult to prevent the roll developing, it can often be corrected by easing the spinnaker sheet before the roll develops.”
For dinghy sailors, a Death roll is a common type of oscillation while running downwind. It may, and often will, result in a capsize if the skipper does not take quick action to prevent one.
Methods to cure a death roll include sheeting in the sail, so that it exerts a definite force to leeward and no force to windward, slamming the centerboard down to stabilize the boat, shifting the skipper and crew’s weight to counter the roll and, if all else fails, luffing up slightly to sail on a broad reach instead of a dead run. It is always more efficient, and ultimately faster, to sail with the sail pulled in slightly than to risk a capsize.
 

[Myjane 40]

Old boats did roll on account of there beam aft and tumblehone , mine still does , but we used to strap the kite down ,or to the deck as best as poss and that controlled the beast well in 30 , 40 knots ok , alltho thoes old kites were high shouldered and full aloft so were hard to controll ,

[B00B00 310]

I heard and interesting theory the other day about IOR hull shapes and downwind sailing. Basically it was that when you try to get an IOR shaped displacement yacht to exceed hullspeed the resulting bow and stern waves combined with the dip between them and you basically end up sailing the boat supported by just on the bow and stern which are both pinched in and offer vertically no form stability at all. Therefore the boat becomes very unstable. Combined with the old school soft nylon spinnaker fabric and deep unstable sails the death roll was inevitable. Modern spinnaker fabric is much stiffer and moves around much less.

[raz88 96]

Good to know its not just us. We did our first Chinese gybe ever few months ago. Had the masthead kite up in what turned into gusting 25 by pilot bay. A particularly big gust coincided with a moments inattention on the helmsmans part and next thing we were on our side. Not the most pleasant experience but we have done 14 knots in flat water with a kite up which was pretty awesome.

I've been surprised after talking to Tom when we got ours that it doesn't seem prone to death roll. Have had the kite up in some fairly testing conditions including sitting on 14s with the fractional spin and a reefed main. Have original keel in original location too.

[Addem 95]

Don’t worry Razz, We didn’t do the death roll. We Chinesed because the helm (me) was distracted by a stuff up going amongst the foredeck and when the gust came through when we a little bit running by the lee. Pork Chop doesn’t really get the roll on and it is easy to prevent being so wide at the stern and we generally don’t run flat as angles are much faster.