Bilge radius

The bilge radius is the radius of the curve joining the flat or near-flat bottom to the side shell at the turn of bilge. It is a primary line on the body plan and the offsets table and sets the midship section coefficient Cm: a small bilge radius squares off the section and pushes Cm toward 1.0 (typical of full tankers and bulkers at Cm above 0.98), while a large radius rounds the section and lowers Cm. The radius is also a structural choice, since a tight bilge concentrates plate forming and interacts with bilge-keel and docking-block layout. On full-form ships the bilge is nearly a quarter-circle of modest radius; on round-bilge hulls the curve extends well up the side.