GMT delivers carbon fiber antenna and instrument arch

GMT Composites designed the 600-kg structure to just fit inside a shipping container, for delivery to yacht-builder Holland Jachtbouw.

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GMT Composites (Bristol, R.I., USA) on May 5 reported that it has recently shipped a 12-legged carbon fiber antenna and instrument arch to Holland Jachtbouw (Zaandam, The Netherlands). The structure has been installed on a 140-ft/43m aluminum superyacht, Cassiopeia, due for launching later this year.

Langan Design Associates (Newport, R.I., USA) turned to GMT for building this 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/1323 lb, significantly improving the yacht's stability and performance.

Much of the challenge of the project involved the effort to ship the antenna to Europe. 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 3 mm clearance on either side and only a few millimeters more for overhead clearance once through the doorway. By CAD simulation, it could fit, but the final loading caused all observers to hold their breath.

The strength and stiffness of GMT's carbon fiber solution offers many advantages. The 12 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 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. The arch, for example, has two sets of three multi-angled, thin support legs on each side, becoming a unique signature element.

The entire arch structure weighs only 599 kg/1,318 lb. 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.

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.