Patent Published
The patent for aeroballast has been published here. I’m currently working on the scale prototype for testing. Hope to have pictures soon.
Apparent Wind Angle & Congratulations Greenbird
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!
Patent Allowed
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:
Design Approach
In the post entitled ”Beyond 50“, Bob Imhoff shares his insight about “barriers” to high speed sailing. I’d like to discuss one of these barriers myself, drag.
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.
Patent Application
Click here to view a PDF version of the patent application. I’d forgotten how hard it is to navigate the USPTO website and hope this helps for those of you interested in taking a look at the concept.
Status
The patent application, filed in April 2007 and published in October 2008 in its original form here, is pending a final response from the USPTO, which should be received in the coming weeks.
Welcome to our new WordPress website
The Radboat Team welcome you to our new WordPress website!
Hello, no updates
No updates for you unfortunately. Schedule is looking good, however, to put in the time to start building the first molds in the coming weeks. Should be fun!
New name and updated website
As you can see we’ve decided on a name, RAD-boat. Let us know what you think. We’ve also updated the website to include more multimedia and some info about other high speed sailboats on the Images page. More details about our design will follow soon. We’re even in the process of submitting proposals to the US Navy for some composite materials research opportunities. Perhaps I could include some sketches to show where we’re at, where we’ve been, and what we’re thinking throughout this design effort. It’s crazy how time flies when you’re busy with multiple projects (that pay) and how difficult it is to start building when you could seemingly tinker with design details forever. In any case it’s a lot of fun but it will be MUCH more fun once a prototype gets on the water and starts turning heads.
Being the nerd that I am, this is one of the coolest things I’ve read about in the recent past - The N-Prize.
Where does it go?
Busy working out a detailed prototype design…sounds like an oxymoron. Here’s a video of the workbench assembly…nothing special and just provided a means to experiment with the new video capture software we recently acquired. All the tools and supplies are here and we are ready to start building. The only thing holding us back is…well…time. Where does it go?
On another note congratulations to Antoine Albeau for setting a new world sailing speed record of 49.09 knots on 5 March 2008. In additionSailrocket and Macquarie Innovation are making good progress.
