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Ordinary
Requirement #7b - Rope Materials
Requirement 7b: Name the various materials used for rope, the advantages and disadvantages of each, and the characteristics of laid and braided rope.
Rope Materials
- A rope is a length of fibers, twisted or braided together to improve strength, for pulling and onnecting.
- It has tensile strength but is too flexible to provide compressive strength.
- It can be used for pulling, not pushing..
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Natural Fiber
- Made from plants
- Easily made by hand
- Affected by moisture and humidity, and rots easily.
- Best available is manila.
- Weakest is cotton.
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Synthetics
- Have mostly replaced natural fibers
- Much stronger than natural fibers
- Doesn't rot from moisture
- Synthetic Materials
- Nylon
- Polyester (Dacron)
- Polypropylene, Polyolefin
- Polyethylene
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Nylon
- First and strongest of common petroleum plastics used for fiber.
- Very strong but very stretchy.
- Deteriorates under UV.
- Slippery, needs special attention w/ knots.
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Polyester
- Nearly as strong as nylon, somewhat heavier.
- Very little stretch.
- Not quite as slippery as nylon and holds knots better.
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Polypropylene
- Lighter, cheaper, but weaker than nylon or Dacron.
- Tends to be stiffer and slipperier.
- Polypropylene ropes float.
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Polyethylene
- Light, cheap, weaker and stiffer than other synthetics
- Fairly immune to UV.
- Floats.
- Common as hollow braided water skiing rope.
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Rope Construction
Laid vs. Braided
- Laid
- Less expensive
- Easier to splice
- Less likely to be damaged by snagging on wood pilings
- More stretch and shock-absorption qualities
- Good choice for anchoring and docking.
- More forgiving on cleats
- Less likely to cause anchor break-out when quickly loaded.
- Braided
- Easier on the hands
- Slightly stronger
How is Rope Made?
- Rope making is essentially a series of twisting operations.
- The only process, which does not involve twisting, is the blending and preparation of the fibers into roping or sliver.
- Rope is put together in three twisting operations.
- The roping is twisted from left to right to spin the thread or yarn.
- The threads are twisted from right to left to form the strand.
- Three or more strands are then twisted from left to right to lay the form a hawser laid rope.
- This is the standard procedure and the result is known as "right-laid” rope.
- Three or more hawsers can be laid into a cable.
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