2019 Dave Santos
Ferrocement Paravanes- fast, cheap, and durable.
Heavy wing construction in water is easily made neutrally buoyant. To make a high-quality energy paravane comparable in raw performance to Minesto's wings, all that is required is steel mesh and concrete of an aggregate-mix of specified buoyancy, like sand and polystyrene in engineered proportions. Mesh should be stainless or suitably anti-corrosion coated. Forms are ideal for high production, but a fine wing can always be shaped by a good eye, setting the mesh skin carefully. Internal wire-rope or rebar load-paths run from external towing and mounting points, to complete the structural system.
Such a concrete water kite could be "dirt cheap" and last many years. Small prototype wings can be clay slip-cast or otherwise formed and fired, and ballasted for water testing.