heavy strain may develop glazed areas where it has worked against bitt and chock surfaces. This condition may be caused by paint or the fusing of the fibers. In either condition, the effect on the line's strength is negligible. New cable-laid nylon hawsers tend to be stiff and difficult to handle. To alleviate this condition, put the cables under tension for 20 minutes at 30 percent extension; for example, 100 feet when under tension would measure 130 feet. Nylon  line  can  hold  a  load  even  though  a considerable  number  of  the  yarns  become  abraded. Where such a condition is excessive but localized, the chafed section may be cut away and the ends spliced together for satisfactory reuse. When nylon lines become iced over in use, they should be thawed carefully at moderate temperatures and drained before stowing. If a nylon line becomes slippery from contact with oil or grease, it should be scrubbed down. Spots may be removed by cleaning with light oils such as kerosene or diesel oil. Do not stow nylon line in strong sunlight. Cover it with paulins. In stowage, keep it away from heat and strong  chemicals. Synthetic lines under stress are far more dangerous than natural fiber lines. Remember synthetic line, unlike natural fiber line, will not give you an audible warning that it is under great strain and is in danger of parting. You must rely on visual cues; the line begins to smoke because of the heat generated by stretching, the line diameter will get smaller and smaller as stretching continues, and finally the tattletale cord will lay taut against the line. A tattletale cord is a bight of six-thread manila hanging from two measured points on the working line. When tensioned to its safe working load (SWL), the line will stretch to a certain percentage of its length. When this point is reached, the six thread becomes taut, warning that there is danger of exceeding the line's SWL. Table 3-1 shows the dimensions for tattletale  lines. NATURAL  FIBER  LINES LEARNING  OBJECTIVES:  Describe  natural fiber  lines.  Describe  the  characteristics  of natural fiber lines. When you have a new coil of natural fiber line to open, remember that if you open it backwards, or from the wrong end, you will have a kink for every turn in the coil. Every kink must be unwound by walking it out the entire length of the line. When you start to walk out a kink from the middle, you turn into the next kink and the next, until the line is one large tangle. The end of a new coil to be drawn out first is marked with a tag. Occasionally, it is tagged on the wrong end. The only way you can be sure that you are opening a coil properly is to know how to do it. The inside of every new coil is in the form of a round tunnel. At one end of the tunnel is the inside end of the line. This inside end always comes out first, usually from the bottom of the tunnel up through the tunnel. Reach through the tunnel until you find the end, and determine on which end to set the coil so the line will uncoil in a counterclockwise direction. Reach in, draw the end up through the tunnel, and the entire coil will run off without a kink. The important point to bear in mind is that when you pull on the inside end, the line must uncoil  in  a  counterclockwise  direction. STRENGTHS Until the development of synthetics, manila was the strongest line. It also was the most expensive. It was natural to compare other ropes with manila, and it still is convenient to do so. The following table gives the comparative  strengths  of  the  various  lines  using  manila as a base strength of 1. (All synthetics are stronger than manila.) Rope Type Strength  Rating Aramid (four-strand) 5.6 Nylon  (three-strand) 2.9 Polyester (three strand) 2.4 Polypropylene 1.7 MEASURING When you are sent to the Bos'n locker for 5 fathoms of line, you need not measure off exactly 360 inches with a tape measure. Your two arms, spread as wide apart  as  possible,  will  equal  approximately  1  fathom  (6 feet). With the end of the line in one hand, spread your arms, grab the line where your other hand reaches, and change  hands  until  you  have  spread  your  arms  five times. In measuring a long line, such as a boat fall, it is much easier and faster to measure a long stretch on deck and fake your line back and forth until the desired length is laid out. 3-6