Re: Can someone explain roach to me?
While increasing roach on an existing boat will increase sail are, that is not why modern designs are moving to high aspect, large roach designes. And really wind shear (wind further above the water is faster) has only a minimal effect.
The real answer is that the higher aspect a sail is the more efficient it is because it reduces tip vortexes, and maximized the lift generated by entire sail. This is why a number of classes that have maximum sail area restrictions on fixed height masts are also switching to a high aspect sail. This is the same reason that gliders have extremely long but narrow wings, you get a lot more lift out of the same surface area (read drag) with a long skinny foil than you do with a short stubby one.