Armare s.r.l.
via Meucci, 3 - Z. I. Aussa Corno
33058 San Giorgio di Nogaro (Udine) - ITALY

Composite Cables: the construction part #2

Sling construction in continuous winding. The internal fiber, which ensures the specific performance of the cable, is pre-tensioned starting from bobbins and is wrapped, with a technique called “sling”. This process is based on continuous winding of the fiber, between two fixed points, until the reaching of the desired number of filaments. Successively this loop is joined, consolidated and protected by two different layers of special tape, which warrants stability and protection against external agents. Finally, a strong braid in Dyneema® covers the entire cable, giving to it the definitive appearance, while the two terminals in resin are melted at the ends of the cable, with the permanent inclusion of the technical fiber loops.

Three technical fibers. Armare cables are built using all the most advanced technologies and with the use of the best high-tech fibres. For every rigging utilization is important to identify the correct technical fiber, which composes the core of the cable, depending on the expected performance, the final use, and the quality-price ratio. The most important fibers, that are used for rigging applications and other performances, are identified with PBO, Aramid and UHMW-PE initials, which represent the commercial names of PBO-Zylon®, Kevlar® and Dyneema®.

PBO-Zylon. In the last years PBO has achieved excellent levels in terms of performance and durability, when is employed to build the core of the cables for rigging use. Thanks to the incomparable dimensional stability of its oriented fibres, PBO is the top in terms of performance under statics loads. It represents the best choice for the manufacturing of high performance standing riggings, because it assures maximum lightness together with minimum possible diameter, steadiness, resistance and creep equal to zero. Armare suggests choosing PBO for standing rigging, for forestay and backstay, and for Torsional Cables, where high performance are always required.

Kevlar. Armare also produces cables made with Kevlar 49 core, using the same Sling technology, the equal assembly methods and the identical materials as for the production of PBO cables. The performance of Kevlar 49 cables is lower compared with cables made with PBO, but have the same high durability, high breaking loads and low stretching, maintaining reasonable diameters and reduced weight. The price makes these cables more accessible, in particular on cruising boats, when better performances are required, in particular for Backstay, and to lighten the Runners, Checkstays, Staysails and Torsional cables.

Dyneema. The excellent dynamic resistance, the low elongation and the lightness of Dyneema, make this fiber the perfect choice for the construction of Backstay, Runner and Strops. On the other hand, even if Dyneema is lighter than PBO, it is about 10% heavier and it has a diameter 25% thicker, in comparison with the dimensioning of a cable under the same stretch. Moreover, Dyneema has a higher creep than other technical fibres, so it is unsuited to be used as standing rigging. It is possible to select among different types of Dyneema: SK75, SK78, SK90 and SK99, or DM 20, which has a lower creep.