ABSTRACT

Modern synthetic fiber ropes have an advanced not only to the higher modulus materials like Aramids with high temperature properties, but to the use of hybrids or composites. Significant advancements have been made with special constructions and with newer designs and manufacturing processes. The life and properties of ropes have improved, and the synthetics have extended into cables, for electro-mechanical and umbilical applications. The more sophisticated testing, instrumentation, and methods of analysis have taught us the limits, and the modes of failure. In addition to extensive marine and military applications, the advanced materials, designs and knowledge have affected many industrial areas.

INTRODUCTION

The manufacturer of rope and cable monitors his product from yarn to reel, testing one end or the other, and publishes his list of properties. Large scaled continuous production of filaments, yarns and ropes have led to better quality and lower prices. But in the field, the linear tensile member is subject to the customer I s equipment and needs, so in self defense the limited warranties and caveats warn the buyer that the tables are a catalogue, and not an engineering handbook. The information is sound and the quality is the manufacturer's reputation and future, but always subject to the proverbial weakest link.

Most ropes and cables are bought on faith and sold from stock. Yachtsmen and oceanographers, designers and managers, fishers and farmers, all shop in tables of properties and prices, and base their buys on prior experience or best guesses. If the buyer's quantitative knowledge and records of the conditions of use or abuse are sufficient, then the safety factors and probable life of these linear bendable structural members can be estimated. Under conditions that call for special designs and production, such as for military and space, there must be analysis, prototypes, proof testing, and instrumentation. These special products are supported in the main by the sale of bulk commercial products. But now more than ever before, the foreign imports into the United States are at drastically lower prices, forcing the U.S. manufacturers big and small to the wall. While cutting costs to survive, too many will fail because there is little loyalty to old line names and history of quality. The chains, the buyers, and the public accept delivery from the lowest price supplier. An increasing amount of cordage is going to sea, and to the farm, based on faith and bargain prices.

NEW PRODUCTS

The manufacturer is new hope is in the development of specialty ropes and cables, new designs, fibers and methods. But there is rarely a sufficient mechanical analysis of rope or cable systems, old or new, because test dollars, time and instrumentation are usually not made available early enough or at all. Successful ropes are too often retired without testing or record, while post mortems of failures become sources of law suits rather than information.

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