Mr Smith's Amazing Sailboats

The Aerohydrofoils
(Section 2 of 6)

The Model Aerohydrofoils
In 1962, the next step Bernard took was to incline both the airfoil and the hydrofoils in the same direction - windward.  This was a breakthrough, as this model proved to be fast. Once the cranked hydrofoil (called an anti-drift hydrofoil) was added, the model became fast AND stable! This model Aerohydrofoil (as he termed his designs), was successful enough for him to give it a name - the "Little Merrimac" in 'response' to a hydrofoil sailboat of the 50s called the "Monitor". 

By inclining the airfoil, the force vectors of the hydrofoils and the airfoil were now added together to create very effective lifting and propulsive forces, but in such a way as to virtually cancel out any torque or heeling tendancies. This made for a yacht design that, in theory, would never need ballast, regardless of wind speeds!

The following year,1963, Bernard published "The 40-knot Sailboat", an account of his experiments and the theories that came from them. The "Little Merrimac" model came to represent the work of Bernard Smith in general, as it graced the cover of that book and was presented as the logical conclusion of his work, at least to that stage. A plan of a large, crewed, Aerohydrofoil (the "Merrimac" obviously) was also detailed in the book.   

Over the following years, more small free-running models were developed, which allowed the Aerohydrofoil design to be refined as knowledge was gleaned from these models.  The hydrofoil layout was reversed. The kink in the anti-drift hydrofoil was done away with, the foils now being fully inclined in the same direction, but with the two windward foils having a steeper inclination than the leeward one. Ultimately, the air-rudder idea fell away in favor of using steerable foils. 

By 1969, Bernard had made the jump from free-running models to a large RC model. This machine proved to be a very able demonstrator of his Aerohydrofoil concept, achieving good speeds over a wide range of sea states. This model was also important as it incorporated design features that Bernard would use in most - if not all - of his subsequent machines. The use of a tubular wire-braced tetrahedral framework, the single surface tensioned sail, the foils/floats being attached to the tips of the framework - these can all be seen in the craft Bernard made subsequent to his 1969 model. The analytical work done up to this point was presented in a 1969 paper simply called "The Aerohydrofoil", details of which are listed in the "Resources" section.

The Manned Aerohydrofoil
With the success of the RC model behind him, Bernard was now able to have a manned Aerohydrofoil designed and built. Based on the design of the RC model, the crewed version was meant to be a two-person machine, though events proved otherwise. The photo below is the only known published image of this craft. The small enlargement of the rearward foil shows the spray being generated by it.

The craft had a number of positive traits; it had good boat/wind speed ratios achieving 20 knots in 12 knots of wind. Control was good and lively. Most notably, though, it was very stable - the Aerohydrofoil didn't pitch or heel whenever it was sailed. As with any radical design however, it wasn't a perfect craft. Under no circumstances was it able to "fly" with a two-person crew, the additional weight of the second crew member simply being too much. The boat was also impossible to lift off in light winds, as at slow speeds the buoyant hydrofoils were working as simple stubby displacement hulls, creating too much drag to achieve takeoff. The long downward curves of the windward foils meant it also couldn't move about in shallow waters, making it difficult to operate.