Hakvoort Delivers 61-meter Superyacht "Just J's" Dutch yard Hakvoort recently delivered its largest superayacht to date, the 61-meter "Just J's". Diana Yacht Design (DYD) was responsible for the Naval Architecture. Sinot Yacht Design was responsible for the exterior and interior design. She was built under the project name 'Golden Age' and as hull YN248. Construction was in both steel and aluminum and she sits on four internal decks above the waterline with an open sundeck.