GMT Composites recently shipped a twelve-legged carbon fiber antenna and instrument arch to Holland Jachtbouw. This has just been installed on an in-build 140-foot aluminum superyacht, due for launching later this year. Langan Design Associates (Newport, RI - USA) turned to GMT for building this stylish, eye-catching structure in carbon composite to reduce the weight of the arch that carries Cassiopeia's wide array of antennae, navigation and communications gear.
The use of carbon fiber saved nearly 600 kg (over 1300 lbs), significantly improving the yacht's stability and performance while allowing the structure to be more stylistically sophisticated. But...
... there's quite a story about the dimensions and engineering - the challenge being to produce an arch of appropriate size for this yacht that could be securely shipped to the builder. The fore-and-aft length of the arch was designed to fill the inside width of a standard shipping container, and the height of the unit required sliding the structure into the container at an angle to get under the upper door sill. Entering the container, the entire structure had less than 3mm (1/8") clearance on either side and only a few millimeters more for overhead clearance once through the doorway. By CAD simulation, it could fit in, but the final loading caused all observers to hold their breath.
The strength and stiffness of GMT's carbon fiber solution offer many advantages. The twelve legs and crossover roof are slim yet provide ample interior space for hiding the wiring requisite to the many systems to be mounted above. Carbon fiber also resists and dampens vibration which improves the performance of the high-tech topside electronics this yacht will rely on. Saving weight this high above the yacht's waterline avoids the need to add thousands of pounds of ballast in the bilge to restore stability; thus, displacement weight is reduced, allowing the yacht to ride higher in the water which then improves her fuel efficiency and environmental greenness.
Carbon fiber's ability to deliver great strength, while used in complex thin silhouette shapes, permits designers much more latitude in design than would be reasonably feasible in aluminum. This arch, for example, has two sets of three multi-angled, thin and elegant support legs on each side, becoming a unique signature element. Langan Design is known for crisp detailing and distinctive yacht profiles and this arch provides consistency in that for a very conspicuous component in Cassiopeia's design.
While the GMT-built arch will support all of the satellite systems, electronic equipment and antennas required to safely navigate the vessel anywhere in the world, the entire arch structure weighs only 599 kg (1,318 pounds). It was shipped unpainted and will be polyurethane finished when the rest of the yacht is painted. The underside of the arch's roof is removable to provide access to mounting hardware for gear and the electrical connections. The dimensional precision and stability which GMT has achieved in carbon fiber permits tight tolerances for fit and finish, well suited to the demands of today's ultra-luxury yacht owners.
Cassiopeia is being built by Holland Jachtbouw to Lloyds and MCA regulations, has a design cruising speed of 15.5 knots from twin MTU 16V-2000 diesels, and is fitted with zero-speed stabilizers. She is the second Langan-designed yacht of the same name for an experienced superyacht owner.