Now this is just getting silly.
Pinched?
Frayed?
Cut?
lol
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Winch line Basics
Synthetic winch lines offer many advantages over their steel counterparts, including weight reduction, easier handling, and increased safety due to less kinetic energy stored in the line when under tension. The material used for almost all synthetic winch lines is an ultra high molecular weight polyethylene, or UHMPE. This brand of fiber used is either DSM Dyneema SK-75 or Honeywell Spectra 3000. Lucky8 ropes use Dyneema SK-75 because of a slight increase in the strength to weight ratio when compared to Spectra.
The natural color for Dyneema is white, and the rope color is achieved by coating the fibers in a polyurethane mixture. With Dyneema not absorbing liquids, the coating sits on top of the individual fibers, but does not dye them. Along with the color, the coating provides increased UV protection, increased chafe protection, and reduced fiber on fiber abrasion. Most other manufacturers either only coat the outside of the main strands, or the outside of the finished rope. However our Dyneema ropes are coated all the way through to better protect each individual fiber. This is important for applications like winch lines because the line is often used in rough conditions, where mud and dirt can become imbedded in between the line fibers.
While our increased coating does provide a superior level of protection, dirty lines should still be gently washed with a mild soap and water to remove debris. Over time and use without cleaning, the dirt will act like sandpaper and start to degrade the coating, and eventually it can degrade the strength of the fibers.
The largest downside of all UHMWPE fibers, including Dyneema, is its melting temperature of 266F. DSM, the manufacturer of Dyneema, recommends and maximum operating temperature of 180-200F for its fibers. As we all know friction creates heat, and certain winching practices can create heat that is detrimental to the strength of the rope. One source of increased heat is winching out while under load when using a planetary gear winch with a brake that is internal to the winch drum. This can be avoided by using a planetary gear winch with a brake external to the drum, or a worm driven winch.
Other fibers are available with a higher melting point than Dyneema, such as the liquid crystal polymer (LCP) known as Vectran. While strong, Vectran does not have the strength for size ratio that Dyneema offers, and it is in not nearly as chafe resistant as Dyneema.
Another source of heat that may not be as apparent is line on line friction. This is generally created when the winch is put under heavy load and the line is fed in over top of other layers of line that were put on loose, often with gaps in between wraps. As the line under tension wraps over top of the looser line, it will start to work its way between the wraps. This action will create friction and heat. Depending on the situation, and previous use, the heat from the friction can exceed the melting point of the fiber, thus causing a line failure. The line should be put on the winch under load, with no gaps between each wrap. This will greatly help reduce the chances of the line slipping between gaps in the layers.
For what is worth this same concept is useful when dealing with steel winch lines. While heat is not an issue, if loose, the lower layers of line can be crushed and distorted by top layers coming onto the drum under tension. While more forgiving to this type of abuse than synthetic line, this improper winch usage can still cause a failure in steel line.
The biggest advantage of Dyneema line is that it does not stretch like steel cable does. When a line is put under load it stretches, and kinetic energy is stored within the line. As a general rule, Dyneema line stretches less than 2% at breaking strength, while steel line can stretch between 20-30% at breaking strength. Because of the low amount of stretch, little kinetic energy is stored in the Dyneema line. While all the same safety precautions should still be used with Dyneema line as with steel line, the low degree of stored kinetic energy reduces the chance of the line causing damage in the event of a failure.