Credit: Yachtpals

Some updates: here’s another image of BMW Oracle’s boat from a better angle for viewing the streamlined fairings. You can even see the hole in the fairing for the helmsman to stand.

Credit: BMW Oracle

Come to find out, Alinghi has similarly streamlined their structural crossmembers, as shown below.

Credit: America's Cup

In the meantime l’Hydroptère broke both the 500 Meter and Nautical Mile Records, and Banque Populaire V, the largest trimaran in existence, broke the 24 Hour Record. And as of September 15, 2009, there is a Speed Sailing Record article on Wikipedia. Thank you user Prokofiev2 from France!

In their latest News posting for April 1, 2009, the Wotrocket team point out that they’ve installed a “new Nexus instrument package…including a wind wand on the leading edge of the wing sail that gathers data which allows the co-pilot to trim to the apparent wind angle.” It’s worth mentioning here because trimming to apparent wind angle is vitally important to high speed sailing. It’s the one area in which,  I think, most high speed sailing designs come a little short because sailboats are not conventionally trimmed to the apparent wind angle in the most efficient way. Let me explain using an aircraft analogy, as I often do.

An aircraft wing remains at a constant angle of attack–oscillations aside–as long as the pitch control surface (elevator, stabilator, elevon,canard, etc.) is kept at a constant deflection angle. It’s a direct consequence of aerodynamic behavior that this is the case. Sails, on the other hand, are trimmed in a way analogous to the way aircraft control surfaces are deflected, i.e. through a physical connection to the pilot. In a sailboat’s case, that physical connection is the main sheet.

So why is this difference so important? It’s important because all wings–and all high speed sailboats use wings instead of soft sails–have an angle of attack at which the lift to drag ratio is a maximum. And in a well designed high speed sailboat, the wingsail should be oriented at this angle of attack relative to the apparent wind in order to achieve maximum speed. That’s not to say that wingsails on all high speed designs WILL be at an angle of attack for maximum lift to drag ratio, but rather that it should be a design consideration for maximum speed.

It’s also worth noting that Greenbird, the new land speed record holder, uses a wingsail that is trimmed in just such a way as I’m explaining. It uses an elevator-like “pitch” control surface aft of the wingsail to control the wingsail’s angle of attack. Right on Greenbird! And congratulations on hitting 126+ mph!

It has yet to be formally issued, but the patent for aeroballast has been allowed. Here’s a snapshot of page 1 of the Notice of Allowance from the USPTO:

In aeronautical engineering drag is a funny beast. The slightest bump, seam, or protuberance can cause seemingly disporoportionate amounts of associated drag. The goal, therefore, lies in designing and manufacturing aircraft that are mostly free of such characteristics. This is why the appropriately named sailplane is so effective at riding thermals. I say appropriately because gliding is analogouos to sailing. Two opposing forces, weight and lift, act together to “squeeze”–to use Bob’s analogy–the glider through the air. It’s best to think of a glider being kept in level flight by an updraft. Sailplanes minimize drag to the extreme, in addition to employing the use of high aspect ratio laminar flow wings, in order to achieve tremendously high (>50) lift to drag ratios.

I realized early on the connection between sailplanes and sailboats and decided, therefore, to focus my attention on reducing parasitic drag in my high speed sailboat design. I started by thinking of ways to modify existing designs, such as asymmetric multihulls and force-aligned boats, tinkering with novel ways of reducing supporting structures, streamlining existing structures, and using hydrofoils. Although I came up with what I thought at the time were novel configurations, the more I researched and hypothesized, the more problems and limitations I discovered.

For example, an inherent limitation of both Macquarie Innovation and Vestas Sailrocket is a need for “special” wind and sea state combinations. I say special because they are not natural and are not readily available at any one spot on this planet, except in the man made “French Trench” perhaps. And I guess I failed to mention my intent was to create a tackable and survivable craft to beat both outright and offshore records, negating the use of inherently restrictive designs. Another limitation of MI and VSR is the aerodynamic drag forces produced on their supporting structures, i.e. their “arms”, which substantially detracts from their top speeds.

So one day I had an epiphany. Why not put ballast on an actively balanced wingsail? In one fell swoop it removes ballast below the waterline, removes the requirement for supporting structure, and reduces the bending load on the mast step. It also allows for the use of high aspect ratio wings without a necessary increase in ballast weight or beam width, as would be required for a multihull. In other words, the opposing lift generated and ballast generated moments both scale linearly with wing span because both are produced on the same structure.

The downside, of course, is the need to actively balance an inherently unstable design, and this is where the fun begins. As I continue to analyze this concept I will update this site with my conclusions regarding its feasibility and practicality.