Sean is correct concerning the snap roll issues resulting from a large sail at high speeds and tight turning radiuses. This wasn't really realized until the Navy’s experimental, hydrodynamically-shaped USS Albacore became operational and they were developing tactics for future subs of this shape. To counter the snap-roll effect, consideration was given to placing a counter “sail” below hull to negate the forces developed in a turn. Suggestions of doing away with the sail have been fought by traditionalists that were accustomed to the Attack Center (Con) being located in the sail. With the move of the Con to inside the main hull, there was still a need for the sail to house the many masts in particular the periscopes. This is being readdressed now with the advent of electronic scopes that no longer require optics to bring the image down into the hull. The Russians have reduced the height of their sails and faired them into the body of the hull to reduce the snap roll issue. R/Jay Resepectfully, Jay K. Jeffries Andros Is., Bahamas Save the whales, collect the whole set. -----Original Message----- With regard to "banked" turns, control surfaces which can impart a rolling moment on a large sub are not included so as to be able to effect such a turn, but rather to provide counter torque to the snap roll effect. Snap roll occurs when the sub initiates a turn, and the change in angle of attack of the sail with respect to the water flow (since the sub "slips" in the water during a turn) pushes on the sail, forcing the boat to roll to the inside of the turn. Often, the natural snap roll will be to an extent that exceeds the angle of roll necessary to accommodate the centripetal acceleration and keep the apparent gravity vector perpendicular to the deck. Consequently, control surfaces are positioned to effect a torque in opposition to the snap roll. -Sean |