{"id":7993,"date":"2014-02-21T08:56:28","date_gmt":"2014-02-21T13:56:28","guid":{"rendered":"http:\/\/stephenlirakis.com\/?p=7993"},"modified":"2014-02-21T08:56:28","modified_gmt":"2014-02-21T13:56:28","slug":"comeback-ac-34","status":"publish","type":"post","link":"http:\/\/stephenlirakis.com\/?p=7993","title":{"rendered":"LOOKING AT THE COMEBACK AC 34"},"content":{"rendered":"
\n

Burns and Speer:
\nSecrets of the Comeback<\/h1>\n
Sailboat Racing<\/a>,\u00a0Sailboats<\/a>America’s Cup comeback<\/a>,\u00a0Ian Burns<\/a>,\u00a0Tom Speer<\/a>admin<\/a><\/div>\n<\/header>\n
\n

\"ACEA\/Guilan<\/a><\/p>\n

ACEA\/Guilan Grenier<\/p>\n

\u201cPlatform aerodynamics, I think, made the difference between the American boat and the Kiwi boat.\u201d Tom Speer, wing designer, Oracle Racing<\/em><\/p>\n

By Kimball Livingston<\/strong><\/p>\n

We could have titled this, Six Extra Feet of Wing, But Do You Know How to Use It?<\/p>\n

The way \u201cFresh\u201d Burns tells the story, and he should know, having been head of performance for Oracle Team USA, there were multiple turning points in Oracle\u2019s desperate, early losing days of the San Francisco America\u2019s Cup. The American boat was losing on every tack, every gybe. Then the Mere Grinders came to the Mighty Chiefs and said something like, \u201cLook, we can tell when the boards are loaded and when they\u2019re not loaded. Why don\u2019t we try moving them when they\u2019re not loaded?\u201d<\/p>\n

Boink.<\/p>\n

And if you\u2019ve been around even a little while, you\u2019ve heard someone on deck wisecrack, \u201cYou just keep grinding, and if I need any sheet, I\u2019ll take it.\u201d<\/p>\n

Well, sonny, that\u2019s pretty much how the Oracle crew was sailing USA-17\u2014with hydraulic pressure always on tap\u2014on those upwind legs where the comeback finally kicked in. Nonstop pumping. No-delay trimming. That was the context when Ben Ainslie yelled, \u201cThis is it! This is it! Work your arses off!\u201d<\/p>\n

Skiff stuff, translated. Advanced Sailing 101.<\/p>\n

And then the dazzled Kiwi press went to spinning stories about a \u201cHerbie,\u201d a Boeing-built gyroscopic stabilizing contraption that made quite a good story, if you needed a story. My headline ran, \u201cBigfoot Sighted on Grassy Knoll.\u201d<\/p>\n

These days, Burns commutes between his home in the California wine country and 201 Shipyward Way, Suite B, Newport Beach, CA. That\u2019s the street address of\u00a0Morrelli & Melvin<\/a>, where the next design rule is taking shape. If you\u2019re paying attention, you already know the basics: 60-65 feet long, certain components made one-design in the hope of achieving cost savings, fewer restrictions on control surfaces to make the boats, in turn, easier to design, safer to sail, and faster per foot of LOA. Oracle Racing CEO Russell Coutts has gone public with that much, and in my too-cool-for-school fashion I assumed that 60-65 feet was merely a gloss of an already established overall length, to hold something back for the press conference at the release of the next Protocol, presumably in March. Maybe. But when I threw that at Oracle wing designer Tom Speer\u2014returning for 2017\u2014 Spear allowed as how, \u201cActually, I think they\u2019re still working on it.\u201d<\/p>\n

Maybe.\u00a0Tom Speer<\/a>\u00a0is a straight shooter when he can be. I think we can take it for granted that it\u2019s a welterish job down at M&M, trying to sort through the gamut of the possibilities for a 2017 AC generation in the wake of all the unintended consequences of the 2013 generation.<\/p>\n

\"ACEA\/Guilain<\/a><\/p>\n

ACEA\/Guilain Grenier<\/p>\n

Speer spoke on Wednesday at a noontime gathering on the San Francisco cityfront, addressing wing development over the decades and, inevitably, in Q&A, the comeback. He went so far as to say, \u201cPlatform aerodynamics, I think, made the difference between the American boat and the Kiwi boat. We had that pod [below trampoline level] that effectively extended our wingspan two meters. That gave us the potential for the upwind speed that we eventually developed, and platform aerodynamics is the area in which we perhaps can make the biggest performance difference going forward.\u201d<\/p>\n

With that potential waiting to be exploited, and New Zealand close to clinching the win in spite of it, another key turning point in the 34th match came, gradually, as Oracle studied how to retrim to add more load to the back of the wing. \u201cThe boat had lee helm,\u201d Speer said. \u201cYou know that kills upwind speed. It was clear that we needed to retrim, so we raked the wing aft\u2014and no, that didn\u2019t work. It turned out that when we powered-off the upper elements\u2014when we added twist aloft\u2014the center of effort shifted down and forward. There was no relief in that. So instead we opened the slot. That gave us less lift on the main element and more lift on the flap [which funnels air aft]. Over the course of the regatta we increased the traveler load by 50 percent. That eliminated lee helm, helped the boat point, and simply made us faster upwind.<\/p>\n

\u201cSo, it was a bunch of boat-tune things that turned it around for us. Look at any one-design fleet, and the difference between the front and the back is huge. Most of that is fine tuning.\u201d<\/p>\n

Before we leave the subject of \u201cslot,\u201d we should listen to Tom Spear describe the effect of the slot from an engineer\u2019s point of view. Here goes: \u201cThe slot allows you to go to a higher maximum lift because of the behavior of the boundary layer, which is where all your skin-friction losses occur. The boundary layer is thin, but it wants to get stuck to the wing and not move. Meanwhile, at the leading edge of the wing, the pressure is very low. Toward the trailing edge, pressure increases. There is a tendency to push the boundary layer toward lower pressure\u2014push it forward on the wing\u2014and that\u2019s where you get flow separating from the surface and a big dropoff in lift. With a slot-and-flap arrangement, you are basically dumping slow air from the lead element into high-velocity air around the flap. Or, let\u2019s say that you are taking one bottom layer and handing it off to a fresh bottom layer on the flap.\u201d<\/p>\n

Wings have been a fascination in this space for years, but in Spear\u2019s figuring, \u201cWing development has hit a plateau. [in only one AC cycle, after decades in C-cats and A-cats!]. Given the motivation to control costs, it\u2019s likely the next design rule will constrain the design of the wing so that teams don\u2019t have to spend so much in that area.\u201d Again, if you\u2019ve been paying attention, you\u2019ve heard the talk in high places about making all or, more likely, parts of the wing one design.<\/p>\n

NEXT:<\/strong>
\nControl. Control. Control. Another just-in-time for Oracle, and the hydro that bit New Zealand.<\/em><\/p>\n

\u00a0<\/em><\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

Burns and Speer: Secrets of the Comeback February 20, 2014Sailboat Racing,\u00a0SailboatsAmerica’s Cup comeback,\u00a0Ian Burns,\u00a0Tom Speeradmin ACEA\/Guilan Grenier \u201cPlatform aerodynamics, I think, made the difference between the American boat and the Kiwi boat.\u201d Tom Speer, wing designer, Oracle Racing By Kimball Livingston We could have titled this, Six Extra Feet of Wing, But Do You Know … Continue reading LOOKING AT THE COMEBACK AC 34<\/span><\/a><\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[632,1675],"tags":[525,1958],"class_list":["post-7993","post","type-post","status-publish","format-standard","hentry","category-americas-cup-34-2","category-foils-americas-cup","tag-americas-cup-34","tag-controlling-the-foils"],"_links":{"self":[{"href":"http:\/\/stephenlirakis.com\/index.php?rest_route=\/wp\/v2\/posts\/7993","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/stephenlirakis.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/stephenlirakis.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/stephenlirakis.com\/index.php?rest_route=\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"http:\/\/stephenlirakis.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=7993"}],"version-history":[{"count":1,"href":"http:\/\/stephenlirakis.com\/index.php?rest_route=\/wp\/v2\/posts\/7993\/revisions"}],"predecessor-version":[{"id":7994,"href":"http:\/\/stephenlirakis.com\/index.php?rest_route=\/wp\/v2\/posts\/7993\/revisions\/7994"}],"wp:attachment":[{"href":"http:\/\/stephenlirakis.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=7993"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/stephenlirakis.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=7993"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/stephenlirakis.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=7993"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}