Before revision: Arvel Gentry demonstrated in 1981 that the genoa and the mainsail interact in a symbiotic manner, owing to the circulation of air between them slowing down in the gap between the two sails (contrary to traditional explanations), which prevents separation of flow along the mainsail.
After revision: his series of articles published in "Best of sail trim" published in 1977 (and later reported and republished in summary in)Arvel Gentry demonstrated in 1981 that the genoa and the mainsail interact in a symbiotic manner, owing to the circulation of air between them slowing down in the gap between the two sails (contrary to traditional explanations), which prevents separation of flow along the mainsail.