Lürssen has long been a global leader in megayacht construction, but in the last year, the German builder has delivered some of its largest and most stunning vessels to date. Following the delivery last year of the 278-foot Ace and 483-foot Topaz, Lürssen has continued full steam ahead in 2013. In January the shipyard delivered the 289-foot Quattroelle, and in April it launched Azzam, which, at 590 feet, is the world’s largest megayacht (surpassing the 2010 Blohm & Voss–built Eclipse by 55 feet). Owners of…