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Materials used for Ropes:
Polyester

Polyester is sometimes called Terylene, Dacron, or Trevira, these are trade names for the same material. Polyester is widely used for boat lines and for sail material because it combines good strength and durability, relatively low stretch and reasonable prices.

Polyester fibres are very fine and hair like, typically about 0.023 mm dia. These fibres are almost always white. It is virtually impossible to distinguish between nylon and polyester by appearance alone.

Polyester Physical Properties

  • Polyester has a specific gravity of 1.38 which means it does NOT float.
  • Polyester is very strong, it has a similar tensile strength to Nylon 6, and is slightly stronger than regular Nylon.
  • Unlike Nylon or Polypropylene, Polyester is not stretchy. Usually any stretch present in Polyester is minimized by pre-stretching during the manufacturing process. It also has low creep under load.
  • Unlike Nylon, Polyester retains its strength when wet.
  • Melting Point 240 degree Celcius. Varies with different composition
  • UV resistance is Excellent. Typically a polyester rope will only lose 10% of its breaking strength after 2 years of outdoor use. This is excluding cuts or severe abrasion. Polyester is often chosen as the outside coating for a cored rope made from a stronger but uv sensitive materials such as kevlar.
  • Excellent abrasion resistance.
  • Polyester is non conductive to electricity.
  • Strength and Weight of Polyester Rope

    Diameter Weight Average Strength
    Inches mm. lbs per ftkg per m PoundKilogram
    3/16 4.8 0.01 0.015 1 175 533
    1/4 6.4 0.02 0.03 1 088 2 400
    5/16 7.9 0.031 0.046 3 400 1 542
    3/8 9.5 0.045 0.067 4 800 2 177
    7/16 11.1 0.061 0.091 2 993 6 600
    1/2 12.7 0.08 0.12 9 000 4 082
    5/8 15.9 0.125 0.19 15 500 7 037
    3/4 19.1 0.179 0.267 18 000 8 172
    1 25.4 0.319 0.475 32 000 14 528

    Polyester Chemical Resistance

  • Good resistance to Alkalis and Acids at room temperature. As the temperature increases, the resistance decreases.
  • Polyester has excellent resistance to Petroleum based products, Bleaches and Solvents. That doesn't mean it is not affected. Don't soak your lines or sails in strong bleach for long periods, they will be weakened.
  • Advantages and Disadvantages of Polyester

    Advantages

    Disadvantages

    Polyester Uses

    Among the conventional synthetic ropes available Polyester has the lowest stretch and best abrasion resistance, combined with good UV resistance.

    It is commonly used for halyards and sheets. for example Novabraid supplies Marine lines: NOVABRAID XLE Double Braid Dacron Sheet Halyard Line 3/8" x 100' white/Blue and 1/2" X 100' Double Braid/Yacht Braid Premium Polyester Halyard Rigging Line

    Polyester is the most common readily available sail material. The fabric is treated to improve rigidity and resistance to UV. It is often referred to as Dacron or Terylene. Sailrite sells fabric by the yard.

    It also finds use for anchor rode. It is stiffer than nylon and not as stretchy.

    There have been cases where nylon anchor lines have failed because high temperatures have been generated during strong weather, particulaly when it's hot. This caused the nylon anchor/mooring lines to soften and fail.

    Polyester rope or polyester combinations are often found for winches, capstans and block and tackles. Its low stretch and low creep.

    It is extensively used for cargo lifting straps, tow straps: CESS 3 Inch x 20 Ft Polyester Tow Strap Rope 27,000lbs Real Heavy Duty , and slings, where a stretch and bounce effect could destabilize a load.

    There are a number of ropes offered that combine polyester outer braid with nylon inner core to get the low stretch and resistance to wear of polyester with the cushioning effect of nylon. It helps control the stretch of nylon in some climbing roopes: Samson Arbormaster Black/Red/White 16 Strand Climbing Rope (1/2") - 150' Hank

    It is also combined with aramids again to provide protection and wearability in the outside layer, while the core provides more strength. Many such ropes are marketed as survival rope: Sleeved Spectra Kevlar Cord Durable Orange 100ft 325lbs Strength

    The safe loading of a rope is a 1/10 to 1/12 of its breaking strength. Remember that knots weaken a rope as does age, wear, chemical attack etc.


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    I try to be accurate and check my figures, but mistakes happen. Check the suitability of any material against the technical information provided by the manufacturer.

    email me if you find mistakes, I'll fix them and we'll all benefit: Christine