GMT Composites (Bristol, R.I., USA) reported on Sept. 5 that it is in the final stages of building a 35-ft/10.7m carbon fiber furling boom, the company's largest PowerFurl boom to date, for a custom 70-ft/21.4m catamaran being built in Brazil. Designed for the high loads of a catamaran, it is a resin-infused, foam core, carbon structure with up to 29 layers of laminate in load sections. It will be shipped to Brazil via ocean container ship, along with the large carbon mast also built by GMT, in custom-made wooden shipping crates.
GMT Composites released its first carbon furling boom in 2008. The company came out with a second, smaller version two years later for boats with booms of the less than 21.5 ft/6.6m. There has been a steady increase in the use of their booms with both custom and production boats installing them on new commissions and refits.
GMT recently shipped PowerFurl booms to be installed on a new Hylas 56 and Southerly 57. In a telling refit, GMT just replaced one of its own in-mast furling carbon spars with a standard GMT carbon spar and a PowerFurl boom on an Able 58. They were able to reduce weight aloft by 220 lb/100 kg while incorporating a full batten main sail with a modern roach profile, yet retain the push-button furling convenience.
By mounting the furling motor inside the mandrel, the GMT PowerFurl carbon boom lets users raise, reef or furl the main on any point of sail. This is an important improvement over in-boom furling systems that use a universal joint and thru-mast shaft because they require the boat to be headed straight into the wind before the sail can be furled. GMT's design uses a low-profile track with no set-back or cutaway notch required in the mainsail tack, and simplifies line management in the cockpit.
These design features, coupled with GMT's ability to fully customize its PowerFurl boom's load requirements and component lay-out, brought the Brazilian creators of the 70-ft custom catamaran to GMT. The PowerFurl I & II booms have been designed to suit yachts from 45 to 90 ft (13.7 to 27.4m), with structural engineering completed for even larger yachts.