Hydrofoil Proas
This is Patrick Cudmore’s Seaflier, a solid wing, canted rig, hydrofoil proa built in 1984.
Neither hydrofoil sailboats nor canted rigs are particularly new, but Cudmore’s lightweight proa-configured craft with its cantilevered, articulating wingsall and inverted, elliptical arch, surface-piercing foils offers a glimpse of a future made possible by sophisticated design and strong but light composite plastics. -Keith Taylor, SAIL magazine
That was in 1984. Before that, Bernard Smith developed the Aerohydrofoil, a sailing hydrofoil based on the proa configuration. Proas and hydrofoils, they just go together. Combine the most efficient plan with the most efficient foils and you get record-breaking speed, from Crossbow to Yellow Pages Endeavor to Sailrocket.
And yet, all the modern big money hydrofoils are bilaterally symmetrical. What the hell happened?
Computers. I blame them. Hydrofoil sailboats require Fluid Dynamics software, which are based upon data gathered for airplane foils by NACA (now NASA) and there are no proa airplanes (Burt Rutan’s Boomerang not withstanding). No research done on optimizing foils that must operate within a reversing flow, no data, no software, no proas.
If an item does not occur in our records, it does not exist. -Star Wars
However, there is still, one hope in the sea of bilateral conformity. Boeing aeronautical engineer Tom Speer has created a foil section optimized for reversing flow. It may not be the Holy Grail of proa foil sections, but it puts us in the ball park. Imagine bi-directional sails, together with bi-directional hydrofoils - it becomes a simple package with a common simple theme running right the way through it. It has an elegance to it. Nothing would be an optimally efficient foil (hulls, sails and foils) but the combined effect of it could be startling in action…
With this section, go forth, and conquer.
Hello Michael
There have been some aircraft built that make use of bi-directional airfoils. I’m thinking of experimental VTOL designs which have a “fixed-rotor” or “stopped-rotor” configuration. Two such craft are the Boeing X-50 Dragonfly CRW and the Sikorsky S-72 X-Wing, but there are other examples that can be found.
The general idea for this type of design is the use of a rigid rotating wing to acheive vertical take off, but once the craft had transitioned over to a conventional flight mode, then the rotating wings would stop spinning and be locked into place, so they would then function as a conventional ‘fixed’ wing.
When that happens, what was the trailing edge on one half of the rotating wing would instead become the leading edge of the fixed wing. Even though the VTOL aircraft would be flying straight ahead, effectively half of the wing would have airflow moving over it in the ‘wrong’ direction.
Cheers,
Paul
It is hard to achieve an optimum L/D with a two way foil - so what makes this way to go so attractive.
Paul: thanks for the correction. Now that you mention it, I remember reading about those concepts. Perhaps if we could pry their data from their hands…
Don: Because then we get hydrofoil proas! But seriously, if a bonafide rocket scientist (and poetic visionary genius) like Bernard Smith thought hydrofoils and proas were the ultimate, then who am I to argue. He did the theoretical work, Tom Speer gave us the foil section, now… somebody build one, please.
I would like to see a sailplan that borrowed from the gyrocopter but the lightness to strength issues may be unresolvable or expensive, mind you Malcolm Tenants windmill plans are said to be cheap as chips, hmmm