Aerodynamic Wing Control and . . . Other Stuff
By Kimball Livingston Posted April 23, 2014
Suddenly we have anecdotal evidence in plenty that there’s nothing like a hot lime-colored wing on a sailboat to set people a’wondering, and we were able to address the collective WTF in our piece about Richard Jenkins’ prototype of a wing for a wind-assisted ferry of the maybe-future.
If you haven’t seen that story, and you want to, and if looking around the Home page is below your pay grade, you can find the story here.
Among reactions to the piece, there was a posting on the forum of BAMA, the Bay Area Multihull Association, by Oracle Racing wing designer Tom Speer. When Tom speaks, people listen, and he gave me permission to repeat his post here. He describes Harbor Wing, and we’ve written about Harbor Wing before. They were on a roll until funding dried up. I’ll let Tom take over, but before I make the handoff, there’s this. I note that Tom refers to the Scripps Flip, a truly unique contraption that I toured in San Diego as a perk of calling on Mark Ott of Harbor Wing. Lots of folks have been around boats a lifetime and never seen anything where the facilities can be rotated 90 degrees, as they have to be on the Scripps Flip.
Okay, Tom, take it away . . .
“In addition to Richard Jenkins’ prototype, there’s the Harborwing X2 prototype (photos: Harbor Wing}. Mark Ott has also worked with Morelli & Melvin on the conceptual design of a wingsail powered cruising cat.
“I had a chance to visit with Mark Ott onboard the Harbor Wing X2 when it was in San Diego, tied up to the Scripps Flip. It is a modified Condor 50 trimaran, and it’s capable of operating offshore. At the time, Mark was looking to do some voyages to show the offshore capability, and was trying to find the funding to continue the boat’s development. There was a lot of the interior taken up by the mounting structure of the cantilevered wing, but that’s to be expected with a prototype. I think a purpose-designed boat wouldn’t sacrifice as much to the rig. But it is really important that the wing have very good bearings and a support structure that won’t bind up when it flexes or be subject to fatigue failure.
“Both boats use an aerodynamically controlled wingsail. Jenkins’ tail is an innovative application of an aircraft configuration in which boom-mounted tails extend the span of the wing for reduced drag. The twin tails of the Harbor Wing configuration avoid the problem with “hunting” at low angles of attack, when the wake of the wing can affect the ability of the tail to precisely control the wing near zero lift, as when the wing is feathered when moored. Harbor Wing’s X1 prototype, a modified cruising cat, uncovered the fact that even though a wing can be feathered to produce zero net lift when moored, wind shear could still generate a dangerous heeling moment. That was the genesis of their split wing approach, in which the upper and lower halves can move independently, controlling heeling moment as well as lift.
“My experience with an aerodynamically controlled landyacht rig showed that the rig was quite good at gust load alleviation and was better than my manual wing-trimming skills when sailing in light, shifty winds.
“I think there’s a lot of potential for aerodynamically-controlled wing rigs on cruising boats. The big question is how well they will work under extreme conditions. In principle, a wing can be feathered to produce less drag than bare poles. But whether or not the wing will respond quickly enough in gusty conditions, or be affected by motion in a heavy seaway, will determine if wingsails are safe for use offshore.
Cheers, Tom Speer”
Footnote from the editor:
The Harbor Wing concept of a cruising cat includes a wing computerized sufficiently to appeal to a powerboat skipper who wants to dial in a course and speed and walk away. Probably, that capability a matter of when, not if.
As for Wind + Wing Technologies
A few years ago, when they were in-concept but not yet sailing a demo platform, we published the following about their collaboration with Morrelli & Melvin. The M&M in-house man who was front and center on the project was Bobby Kleinschmit:
“At Morrelli & Melvin, we started in early 2008,” said Kleinschmit. “First we did a comprehensive feasibility study. We modeled winds over San Francisco Bay ferry routes for a full year to develop a basis for estimating fuel savings. It was interesting because the route from the San Francisco Ferry Building to Sausalito and back is ideal for wind assist—or for being fully wind powered on some of the runs.”
Let’s note, further, that it would be a reach-out, reach-back between Fisherman’s Wharf and Alcatraz for the commercial operators who carry tourists out to “The Rock.” I figure that’s even more ideal for sail, considering the bias toward reach-reach and the bias toward a summertime (seabreeze) timeframe.I will share with you that, when Jay Gardner did a presentation on this forward-thinking subject at the St. Francis Yacht Club (programs that are open to members of all recognized yacht clubs), there were leaders of commercial ferry companies who came to meet and listen.
Gardner recalls that he first approached Golden Gate Transit in July, 2008, “and right off the bat the meeting started with an admission that if diesel weren’t $4.75 a gallon they would not even be talking to me.
“But, we went to them because they’re the most operationally experienced. We knew we’d have to convince the most hard-nosed ferry guys.”