Afterbody

The afterbody is the part of the hull aft of amidships, from the midship section to the aftermost end of the waterline. Its shape sets the run, the wake field the propeller works in, and a large share of viscous-pressure (form) resistance. Naval architects fair the afterbody buttocks at a shallow run angle, ideally below about 18 to 20 degrees at the propeller plane, to keep flow attached and avoid separation that thickens the wake and feeds propeller-excited vibration. A full afterbody on a tanker or bulker raises the prismatic coefficient aft and the thrust deduction; a fine afterbody on a fast hull lowers both. The afterbody also carries the transom, skeg, and bossing geometry.