Distortion control

Distortion control is the set of yard methods that keep welding shrinkage and angular deformation within tolerance: balanced welding sequence, back-step and skip patterns, strongbacks and jigs, presetting plates against the expected pull, controlled heat input, and line heating or flame straightening to correct what remains. Fillet and butt welds shrink transversely and rotate the joint, so a panel can buckle or a block can lose its fair shape. The driver is heat input per unit length, kilojoules per millimeter, which sets the weld metal volume and the residual shrinkage. Class fairness standards in IACS Rec. 47 fix the acceptable out-of-plane deviation for plating and stiffeners.