The bow planes were moved to the massive sail to cut down on flow-induced noise near the bow sonar arrays. They were known as sail planes or fairwater planes. The "Skipjack"s were the first class built with sail planes; they were later backfitted on the "Barbel"s. This design feature would be repeated on all U.S. nuclear submarines until the improved , the first of which was launched in 1988. The small "turtleback" behind the sail was the exhaust piping of the auxiliary diesel generator.