Basic Survival Skills -Rigging- Part 1 (Terms and Rope)

Fig 1-1

Fig 2-1

Fig 3-1

Table 1-1

Fig 4-1

Rope splicing photo

Complex Ship's Rigging

Technical Rigging

I am not surprised that the kid across the street did not know how to tie a friggin knot, our societal culture has moved beyond the basic survival level along time ago. While going over a few basic knots with the teenager from across the street, I started to put together the idea for a series of articles dealing with some basic survival skills.

In the first couple of sessions of this series of articles I will discuss Rigging or "Rope Work" and the need for us humans to have the ability to lash, tie, sling, and lift things with rope. Now we all know how to tie our shoes, but how many people know how to create a shelter using only native materials and some rope, or lift a 5000lbs load 10 ft. into the air with a Gin Pole and a Block and Tackle? My purpose here is to give everyone a "quick and dirty" primer on Rigging, hopefully that will spur some to do further study in this most basic and useful skill.

A) TERMINOLOGY and DEFINITIONS

1) Rope (oftentimes called a line) - A large, stout cord made from strands of fiber or wire wrapped or braided together (See Fig 1)

2) Line (sometimes called a rope) - A thin string, cord, or rope, especially a comparatively slender and stout cord

2a) Cordage - The term is applied collectively to ropes and twines made by twisting together vegetable or synthetic fibers.

3) Running End - The working end of the rope

4) Standing Part - The rest of the rope (excluding the Running End)

5) Brite - A bend or U-shape curve in a rope

6) Loop - Formed by placing the Running End of the rope over the Standing Part, creating a circle in the rope

7) Turn - A Loop placed around an object (such as a post, ring, or rail) with the Running End continuing on in the opposite direction from the Standing Part

8) Round Turn - A Turn that has the Running end following the general direction of the Standing Part

9) Overhand Turn or Loop - Made when the Running End passes the over the Standing Part

10) Underhand Turn or Loop - The Running end Passes under the Standing Part

11) Bend or Knot - Used to join or fasten two ropes together or to fasten a Rope to a ring, post or Loop

12) Whipping (for a Rope end) - A method to keep the Rope ends from unraveling (see fig 2-1)

13) Splicing - A method of joining fiber or wire Rope by unlaying strands of both ends and interweaving these strands together (see fig 3-1)

B) SECTION I. FIBER ROPE

In the fabrication of fiber rope, a number of fibers of various plants are twisted together to form yarns. These yarns are then twisted together in the opposite direction of the fibers to form strands (see Figure 1-1). The strands are twisted in the opposite direction of the yarns to form the completed rope.

The direction of twist of each element of the rope is known as the "lay" of that element. Twisting each element in the opposite direction puts the rope in balance and prevents its elements from unlaying when a load is suspended on it.

The principal type of fiber rope is the three-strand, right lay, in which three strands are twisted in a right-hand direction. Four-strand ropes, which are also available, are slightly heavier but are weaker than three-strand ropes of the same diameter.

C) TYPES OF FIBERS

Vegetable Fibers - The principal vegetable fibers are abaca (known as Manila), sisalana and henequen (both known as sisal), hemp, and sometimes coir, cotton, and jute.

The last three are relatively unimportant in the heavy cordage field. Abaca, sisalana, and henequen are classified as hard fibers.

The comparative strengths of the vegetable fibers, considering abaca as 100, are as follows:

•Sisalana - 80

•Henequen - 65

•Hemp - 100

1) Manila -
This is a strong fiber that comes from the leaf stems of the stalk of the abaca plant, which belongs to the banana family. The fibers vary in length from 1.2 to 4.5 meters (4 to 15 feet) in the natural states. The quality of the fiber and its length give Manila rope relatively high elasticity, strength, and resistance to wear and deterioration. The manufacturer treats the rope with chemicals to make it more mildew resistant, which increases the rope's quality. Manila rope is generally the standard item of issue because of its quality and relative strength.

2) Sisal -
Sisal rope is made from two tropical plants, sisalana and henequen, that produce fibers 0.6 to 1.2 meters (2 to 4 feet) long. Sisalana produces the stronger fibers of the two plants, so the rope is known as sisal. Sisal rope is about 80 percent as strong as high quality Manila rope and can be easily obtained. It withstands exposure to sea water very well and is often used for this reason.

3) Hemp -
This tall plant is cultivated in many parts of the world and provides useful fibers for making rope and cloth. Hemp was used extensively before the introduction of Manila, but its principal use today is in fittings, such as ratline, marline, and spun yarn. Since hemp absorbs much better than the hard fibers, these fittings are invariably tarred to make them more water-resistant. Tarred hemp has about 80 percent of the strength of untarred hemp. Of these tarred fittings, marline is the standard item of issue.

4) Coir and Cotton -
Coir rope is made from the fiber of coconut husks. It is a very elastic, rough rope about one-fourth the strength of hemp but light enough to float on water. Cotton makes a very smooth white rope that withstands much bending and running. These two types of rope are not widely used in the military; however, cotton is used in some cases for very small lines.

5) Jute - Jute is the glossy fiber of either of two East Indian plants of the linden family used chiefly for sacking, burlap, and cheaper varieties of twine and rope.

6) Synthetic Fibers - The principal synthetic fiber used for rope is nylon. It has a tensile strength nearly three times that of Manila. The advantage of using nylon rope is that it is waterproof and has the ability to stretch, absorb shocks, and resume normal length. It also resists abrasion, rot, decay, and fungus growth.

D) CHARACTERISTICS OF FIBER ROPE

Fiber rope is characterized by its size, weight, and strength.

1) Size -
Fiber rope is designated by diameter up to 5/8 inch, then it is designated by circumference up to 12 inches or more. For this reason, most tables give both the diameter and circumference of fiber rope.

2) Weight - The weight of rope varies with use, weather conditions, added preservatives, and other factors.

3) Strength -
Table 1-1 lists some of the properties of Manila and sisal rope, including the breaking strength (BS), which is the greatest stress that a material is capable of withstanding without rupture. The table shows that the minimum BS is considerably greater than the safe load or the safe working capacity (SWC). This is the maximum load that can safely be applied to a particular type of rope. The difference is caused by the application of a safety factor. To obtain the SWC of rope, divide the BS by a factor of safety (FS):

SWC = BS/FS

A new 1-inch diameter, Number 1 Manila rope has a BS of 9,000 pounds (see Table 1-1). To determine the rope's SWC, divide its BS (9,000 pounds) by a minimum standard FS of 4. The result is a SWC of 2,250 pounds. This means that you can safely apply 2,250 pounds of tension to the new l-inch diameter, Number 1 Manila rope in normal use. Always use a FS because the BS of rope becomes reduced after use and exposure to weather conditions. In addition, a FS is required because of shock loading, knots, sharp bends, and other stresses that rope may have to withstand during its use. Some of these stresses reduce the strength of rope as much as 50 percent. If tables are not available, you can closely approximate the SWC by a rule of thumb. The rule of thumb for the SWC, in tons, for fiber rope is equal to the square of the rope diameter (D) in inches:

SWC = D2

The SWC, in tons, of a 1/2-inch diameter fiber rope would be 1/2 inch squared or 1/4 ton. The rule of thumb allows a FS of about 4.

E) CARE OF FIBER ROPE

The strength and useful life of fiber rope is shortened considerably by improper care. To prolong its life and strength, observe the following guidelines:

•Ensure that it is dry and then stored in a cool, dry place. This reduces the possibility of mildew and rotting.

•Coil it on a spool or hang it from pegs in a way that allows air circulation.

•Avoid dragging it through sand or dirt or pulling it over sharp edges. Sand or grit between the fibers cuts them and reduces the rope's strength.

•Slacken taut lines before they are exposed to rain or dampness because a wet rope shrinks and may break.

•Thaw a frozen rope completely before using it; otherwise the frozen fibers will break as they resist bending.

•Avoid exposure to excessive heat and fumes of chemicals; heat or boiling water decreases rope strength about 20 percent.

F) HANDLING OF FIBER ROPE

New rope is coiled, bound, and wrapped in burlap. The protective covering should not be removed until the rope is to be used. This protects it during storage and prevents tangling. To open the new rope, strip off the burlap wrapping and look inside the coil for the end of the rope. This should be at the bottom of the coil (see Figure 4-1). If it is not, turn the coil over so the end is at the bottom. Pull the end up through the center of the coil. As the rope comes up, it unwinds in a counterclockwise direction.

G) INSPECTION OF FIBER ROPE

1) The outside appearance of fiber rope is not always a good indication of its internal condition. Rope softens with use. Dampness, heavy strain, fraying and breaking of strands, and chafing on rough edges all weaken it considerably.

2) Overloading rope may cause it to break, with possible heavy damage to material and serious injury to personnel. For this reason, inspect it carefully at regular intervals to determine its condition. Untwist the strands slightly to open a rope so that you can examine the inside.

3) Mildewed rope has a musty odor and the inner fibers of the strands have a dark, stained appearance. Broken strands or broken yarns ordinarily are easy to identify.

4) Dirt and sawdust-like material inside a rope, caused by chafing, indicate damage. In rope having a central core, the core should not break away in small pieces when examined. If it does, this is an indication that a rope has been overstrained.

5) If a rope appears to be satisfactory in all other respects, pull out two fibers and try to break them. Sound fibers should offer considerable resistance to breakage.

6) When you find unsatisfactory conditions, destroy a rope or cut it up in short pieces to prevent its being used in hoisting. You can use the short pieces for other purposes.

End of Part 1, Next session will be Knots, Hitches, Slings, Ladders and Scaffolding

**Note** Material text and figures excerpted from the U.S. Army publication FM-5-125, then reformatted by me for Newsvine

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