Gentry was instrumental for winning and keeping the America’s Cup

In the mid-1970s, Arvel Gentry was the one who debunked most of the myths and mysticisms found in ‘sailing books’ (slot effect, etc. etc. etc.), was the first to properly give correct aerodynamic explanation of “How Sails really work,” etc. Even the famous sailing aerodynamicist/hyrdodynamicist C. J. Marchaj cites Gentry as one of the current leaders in modern sail theory. Most of what is taught in US high schools, etc. about how wings work is simply BUNK and nonsense. . . even the Wright Brothers knew differently.

Gentry was quite instrumental for the USA keeping the America’s Cup for so long, especially when the cup was an ‘amateur’ venue. Most of the top-end world’s sail racers continue use these methods (or the electronic facsimile) for perfect trim and shape.

His ‘aerodynanmic’ explanations of sails may be somewhat difficult for the layman to understand .... but if you read and re-read several times, it will all begin to become clear. One should actually replicate his ‘pepper flakes on the water’ experiment to see the aerodynamic (hydrodynamic, actually) effect of flow stream action on a thin foil/wing — simple and profoundly amazing. . . air VISCOSITY is what makes a sail work!!!!!!!!!. Gentry has become, over the years, the key root source for much of today’s understanding of sails.

— SailboatOwners.com