Then and Now
I wanted to talk a little bit about why the VOR 65 amazes me, and in particular how it differs from the boats I raced on growing up. And it kind of got long, so here’s a cut. :-)
The left image above is Desperado, a Swan 65, sistership to Sayula II, the boat that won the first Whitbread (which later became the Volvo) in 1973-74. On the right is SCA, one of the boats currently sailing south through the Atlantic on Leg 1 of this year’s race. All the boats this year are identically built VOR 65s.
Both boats pictured above are the same length, and are sailing downwind with a decent breeze, conditions that allow them to reach their top speed. Desperado is going about 11 knots. SCA is sailing closer to 30.
To be fair, Desperado doesn’t have as much wind as SCA does. But even if it were blowing harder in the Desperado photo it wouldn’t make much difference. The fastest that Desperado can ever sail is about 13-14 knots — and that requires big following seas, with the boat on the edge of control.
Why is a VOR 65 so much faster than a Swan 65? Mainly, weight. A Swan 65 weighs (displaces, in nautical terms) slightly more than 76,000 pounds. A VOR 65 weighs less than a third of that.
If you wanted to race a boat around the world in 1973, a Swan 65 was the boat you wanted: big, strong, and heavy. A Swan 65 is built like a tank. The hull and rig are made strong so they don’t break in rough conditions. The boat is heavily ballasted, with 30,000 pounds of lead in the keel, meaning the boat has a lot of “righting moment”. That is, when the wind pushes sideways on the boat it can resist heeling, generating a lot of power. Because the boat is already so heavy, it can carry a lot of gear and provisions without much of a performance penalty. A Swan 65 interior is luxurious, with lots of wood-paneled accommodations. Those were the days…
But let’s switch gears for a second and talk about waves. The speed of a wave is directly related to its length. The longer the wave, the faster it travels.
When you push a heavy boat through the water, that water has to get out of the way, and it does so by forming a standing wave that travels along with the boat. You can see it in that picture of Deperado above. There’s a crest up by the bow, another near the stern, and a deep dip in the middle.
A heavy boat sailing at maximum speed builds up a standing wave that is roughly as long as the boat itself: in this case, 65 feet. A wave that length always travels at the same speed: 11 knots. That’s pretty much the Swan 65’s speed limit, its so-called “hull speed”. The boat can’t go faster than that, because it gets stuck in the trough of the standing wave it’s creating. To go any faster it would have to climb up on top of its bow wave, to leave the water, no longer displacing it but instead planing on top of it like a surfboard.
Which is exactly what SCA is doing in the photo above.
If you push a Swan 65 hard enough it can surf. But it’s not good at it. The hull is built curvy, to fit into that standing wave. That’s great at sub-planing speeds; it means the hull has minimal drag and can reach its hull speed quickly. But it’s awful for surfing.
But the main problem in getting a Swan 65 to surf is weight. It takes a huge amount of energy to lift those 76,000 pounds out of the water.
People back in the 1970s knew how to make a sailboat that surfed. High-performance planing dinghies like the 470 surfed great. All you had to do was give the boat a lot of sail area, a flat-bottomed hull, and make it super light.
Ta-da! A boat that surfs:
Look familiar? Except for the size of the boat, that picture is pretty much identical to the one above of SCA.
Back in the 1970s a few people had tried building bigger racing boats designed to surf offshore. But those boats were considered specialized toys only good for races that were mostly downwind, like coastal races from southern California to Mexico, or the Transpac race from California to Hawaii. They weren’t good for sailing upwind because they didn’t have enough righting moment. And you wouldn’t think about taking one in the Around the World Race.
A planing dinghy like a 470 can sail fast upwind because despite being very light overall, what weight it does have is mostly in the form of the crew’s body weight, and that ballast is highly mobile. If you hike out (as the skipper and crew are doing in that image above), you can get enough righting moment for the boat to power its way upwind. And then you turn around the windward mark and zing! It’s off to the races.
A VOR 65 is built to do the same thing:
- The boat’s hull has the same fine entry and long, flat sections aft that a planing dinghy has.
- It uses lightweight daggerboards for lateral resistance.
- Its ballast is in the form of a lead torpedo that can be canted to windward using hydraulics. In effect, a VOR 65’s crew hikes their ballast to windward just like a 470 does.
- The boat also has ballast tanks that can be filled with sea water, or emptied when sailing off the wind.
- The crew constantly shifts the boat’s gear to the upwind side. That happens below, on every tack, and on deck as well, where the onboard video shows the crews constantly wrestling the big sausages of the sails they’re not currently using into the optimal position.
- Finally, the boat itself is light, light, light.
A Swan 65 was built from hand-laid fiberglass. It was strong, but heavy. On a VOR 65, everything is made from carbon fiber. The boat’s interior is super spartan. Every ounce that can be eliminated has been. Except for necessary structural elements, the interior is completely open and unfurnished. The bunks are carbon-fiber pipe berths — and the crews only sleep on the upwind side. The galley is a tiny station with a single-burner camp stove. The nav and media stations can be reconfigured to be operated from either port or starboard, so the crew using them always have their bodies on the high side.
The boats don’t carry drinking water — the fuel to run a desalinator weighs less. The interior of all the boats is black — because the carbon fiber they’re made from is black, and paint would be needless weight.
Basically, a VOR 65 is a 65-foot 470. The people who sail it are committed enough (and skilled enough) to take such a boat into the roughest, most dangerous waters on the planet and race it flat-out.
So much respect. And bogglement. It’s just… amazing.
Reposted from http://ift.tt/1DKC7Q0.
