In this study, one existing oil tanker side shell with longitudinal bulb flat profiles have been analyzed through Mars2000 software provided by the Bureau Veritas. This particular existing oil tanker construction is modeled. Main goal is to investigate the weight and shipyard manufacture cost which includes man-hour changes in parallel with the various longitudinal frame spacing applied to the calculation. The floors, deck and corrugated bulkheads of parallel midbody was assumed to be same as original construction plan of the existing oil tanker, then, side shell and the longitudinal profiles are being modified according to yielding criteria, minimum thickness and buckling criteria checked by the Bureau Veritas Mars2000 software. The longitudinal frame spacing of the existing vessel is 0.665 meters. Investigation is focused on starting from 0.55 meters ending at 0.85 meters with the step of 0.05 meters