USCG Masters Captains License 25/50/100 Ton Upgrade

SEAMANSHIP - Lines, Purchase, Block & Tackle

Seamanship - Module 1

Lines, Purchase, Block and Tackle

Fiber Line can be made of either natural or synthetic (man-made) fibers.  Although the construction is similar, the qualities of the fibers are different.

Natural fiber line, such as manila or sisal, is relatively inexpensive compared with the better synthetics.  It is subject to rot and mildew so it must be rinsed and dried before it is stowed.  Open the strands to look for rot.  Also, never lubricate a manila line or any natural fiber rope.  Size for size, manila is only about one fifth as strong as nylon.  White line is made from cotton.  The larger sizes of manila line are normally indicated by their circumference.

The synthetic fiber lines (nylon, Dacron, and polypropylene) are stronger and will last much longer than manila if given proper care.  They can be stowed wet.  Mildew may form on the surface but it doesn’t reduce the strength of the line.  They should be protected from sunlight when not in use.   Any kind of rope should be protected from contact with chemicals or their fumes.  Nylon holds a load better than manila and stretches more.

Nylon line can be stretched as much as forty percent of its original length.  This property is a great advantage in an anchor line or tow line. Its ability to stretch helps absorb shocks which might part a manila line.  It can also be a danger to people handling lines.  If a nylon line parts under strain it snaps back in line with itself with great force.  People have been killed this way.  When tending a nylon line under strain, stand out of line with it so it won’t hit you if it parts.  Polypropylene rope floats, making it a great stern line or a man-overboard heaving line (certified vessel’s black heaving line).

The most common fiber line is a laid construction.  Fibers are twisted into yarns and yarns are twisted into strands, which in turn are twisted into rope.  The standard method of measuring fiber line is to measure the circumference of the lines.

Wire rope is made up of three parts:  the wires, strands and core.  Wire rope is galvanized to protect it from corrosion due to saltwater.  A wire rope that has been overstrained will show a decrease in the diameter where the strain occurred.   The strongest method of forming an eye in wire rope is with a wire rope socket attached with zinc (nothing can be substituted for zinc).  When attaching the socket, the wire should be etched with acid.  The manufacturer of the rope decides how many wires he is going to put in a strand and the number of strands that will make up the rope.  This is how the designation of a wire rope is made.  A 6 x 19 wire rope will have 6 strands with 19 wires in each strand.  The picture below shows the wires and strands.  Wire rope needs more care than synthetic and natural rope to prevent rust, kinks, corrosion, and fish hooks.  If kinking occurs while wire rope is being coiled clockwise, you should take a turn under.

The strands are laid around a core.  This core can be fiber or wire depending on the intended use of the rope.  A fiber core is used to help with lubrication and increase the strength of the wire rope.

To measure the diameter of a wire rope, always measure the largest diameter as shown in the picture. 

New fiber line or wire rope has been coiled by the manufacturer and must be properly uncoiled to avoid kinks.  For a coil of manila line, place the coil flat on the deck with the tagged end on the inside of the coil at the bottom.  The wrappings of the coil should then be removed and the tagged end pulled up and out of the center of the coil.   A rope made of a combination of wire and fiber is known as spring lay.

There are two methods to uncoil wire rope or any line on a reel.  The first is to mount the reel so it spins freely, and then pull the entire length of rope off the reel before using it.  The second way is to hold the free end of the rope and roll the reel until the wire has been removed.
When coiling a line, it must coil with the lay of the rope.  To determine the lay, hold the ropes vertically.  If the grooves in the rope run from lower left to upper right, it is a right-laid rope.  If they run from lower right to upper left, it is left-laid.  Coil a right-laid rope clockwise and a left-laid rope counter clockwise.  Braided line can be coiled in either direction.

The bitter end is the end of the line.  A bight is a loop in the line and the standing part is the section of line that leads to the rest of the line.

Faking and flemishing are two means of setting out line for different purposes.  When you fake out a line, it means that you set it out in long lengths, one alongside another.  This is done with lines that must be ready to run freely (anchor line).  Preformed wire rope conforms to the shape of the rope.  To flemish a line means to take the bitter end of the line and put it on the deck.  Then wind the rest of the line around so that it is flat.  When you are finished, a flemished line should look like a tightly wound clock spring.  The illustrations below show both faking and flemishing a line.

Heaving lines and messengers are two small lines used to carry across larger lines.  The heaving line, used to get a mooring line to the dock, normally has a small sandbag at one end while the other is tied to the larger line.  A messenger can be spliced to the larger line and is used when rigging blocks or when the large line must be carried farther than a heaving line can reach on its own.

Mooring lines are the large lines used to tie the ship to the pier.  Each of the lines has a name to describe its location.

The waist line or breast line runs perpendicular to the keel and is used to help hold the ship close to the pier when winds and currents are trying to push it off.  The after spring lines and stern line can be used to stop a vessel’s forward motion when mooring.  In the same manner, the bow line and the forward spring lines can be used to stop the vessel’s sternway (backward) motion.  The bow line can also be used to move a vessel along a dock without lighting off the main engines.  This process is called warping a vessel.

When mooring lines are put out, chafing gear should be used to protect the line from rubbing against chocks or other edges that will wear on the lines.  Chafing gear usually consists of canvas (cotton duct) or other material wrapped around the line at the point of wear.  The thickness of cotton duck is indicated by a number, with a smaller number indicating a heavier canvas. 


When handling lines, there are a number of standard commands used to indicate certain actions.  The table below lists the line commands and their meanings.

Commands & Meanings

  1. Hold the line – Do not allow the line to slip.            
  2. Check the line – Hold the line but ease it off when necessary so the line doesn’t part.      
  3. Ease the line – Pay out enough to remove most of the strain.          
  4. Slack the line – Pay out the line so all tension is removed.       
  5. Take a strain – Put the line under tension.           

When holding or checking a line, creaking indicates that the line is under dangerous strain.

Gypsies and capstans  are winches on which lines are wound for raising, lowering or pulling loads.  The major difference between the two is that the head on the gypsy is mounted horizontally while the head on the capstan is mounted vertically.  The power is supplied to the head through the drum gear.

Winches used for cargo handling have an automatic brake that engages when power is lost to the winch.  A devil’s claw is a second device used to prevent loads from falling.

When using the winches to haul on lines the turns around the gypsy head should be placed side by side.  If they overlap, the lines could jam, then break.  Care must be taken not to surge the line too much.  Surging means allowing the line to slip while the gypsy head turns.  If the line surges excessively, enough heat will be created by friction to melt the line and fuse it to the gypsy.

Knots and Splices

Knots and splices are two ways of joining two lines together or putting a loop in a line.  The differences between the two are that a knot or hitch is temporary while a splice is permanent.  The splice is stronger than a knot.  Both knots and splices weaken a line. Whipping can be used at the end of a line to prevent fraying.

Seizing is a method used to make an eye in a bight of line where it cannot be spliced and would include flat seizing, racking seizing, and throat seizing.  A lanyard is a piece of small line secured to an object to prevent it from going adrift.

An eye splice is used any time it is desirable to have a permanent eye (loop) in the end of a line, such as a mooring line.  It is stronger than any knot.  When properly made, it will be about 85% of the strength of the line.

A short splice, used to join two ends of a rope, is about the same strength as an eye splice, but does increase the diameter of the rope.  If the line has to pass through a block of the correct size for the rope, the short splice will jam in the block.  A tapered hardwood pin called a fid is used to open the strands of fiber line for splicing.

The long splice is used for running rigging which must pass through blocks and fairleads.  A well-made long splice is not as strong as a short splice but is nearly invisible.  Usually, four tucks is enough to lock a splice in.

Wire rope can be spliced using slightly different techniques and tools.  First, a marlinespike must be used to separate the strands.  A marlinespike is a taped steel implement 12 to 24 inches in length.  The tucks then go against the lay of the rope.  Next, the splices in wire tope should be parceled and served over because the most skillful rigger cannot avoid damaging the anti-corrosive coating (galvanizing) on the wires.  This provides some rust protection.  Also, some cut ends of wire will probably stick out from the rope, and the serving will protect the hands of a person handling the rope.  The serving mallet is used to apply the final protective covering. 

An eye can be formed with wire rope by clamping a thimble into the bight.  The clamps have a U-bolt and a saddle.  To put the clamp on properly, the U must be put on the short end of the wire rope.  (Old saying “never saddle a dead horse”).

How to Tie a Chain Splice

Remember that knots weaken a line. Several important knots are mentioned below.

Overhand knots are used temporarily to keep line from unlaying or turning through a block.  This knot jams tight and may have to be cut.

The Figure Eight Knot is better than an overhand knot because it will not jam.

The Bowline makes a temporary eye in a line.  It may substitute for an eye splice in a mooring line.  It is one of the strongest and most useful knots.

The Square Knot or Reef Knot quickly joins two ends.  It is secure only if the two lines are the same size and the knot is pressing against something.  It may come apart under strain if it is not supported.

Monkey Fist is good to use with heaving lines.

The Becket Bend or Sheet Bend is used to join two ends when a knot must stand alone in mid-air.  It works with lines of different sizes.

The Carrick Bend (Hawsers) joins large lines of the same size for heavy work such as towing.  It will not jam if the ends are seized to standing parts.  A Double Carrick Bend does the same job and is good to use to bend two hawsers together for towing.

round turn and two half hitches is a quick way to fasten anything of any shape.  It remains secure with or without strain from any direction.  It can jam and be difficult to untie.

Clove Hitch or Timber Hitch is quick to make and will not jam.  It is secure when made around cylindrical objects and the strain remains steady but can loosen if the standing part goes slack or strain comes from varying directions.

Rolling Hitch or Taut Line Hitch is quick, secure, and adjustable.  This knot can be slid along a spar or line without loosening.

Bowline On A Bight is handy if an eye is needed but the ends aren’t available.

Sheepshank is used to take up excess slack or strengthen a weak spot in a line.  It will hold if strain is steady and it is very carefully made.

When a line is cut it tends to unravel.  Whipping is twine that is wrapped around the end of a line to keep it from unraveling. 

Line Handling Devices

bollard is found on a dock and is used to moor a vessel.  The mooring line is dropped over the top. 

If two lines from two different vessels must be placed on the same bollard, a procedure called dipping the eye should be used.  The eye from one line is passed through the eye of the second line is passed up and through the eye of the second line before being placed over the bollard.

The term belay the line means to secure it to a cleat.  A chock is a fairlead for a line to pass through and changes its direction.  A set of bitts look like two bollards on the same base.  A cruciform bitt has arms extending at 90 degree angles.

Cleat, Chocks (three types,) and Bitts

Cargo Handling

The basic unit of any cargo handling system is the block and tackle.  The block or shell is a wooden or metal frame containing one or more rotating pulleys called sheaves (pronounced shivs).  When a line or wire is strung through the block or blocks the whole system becomes tackle.  The receiving line always passes through the block. 

The size block needed is determined by the circumference of the line used.  For fiber rope the size of the block must be three times the circumference of the line and the size of the sheave (pulley) must be two times the circumference of the line.  For wire rope the sheave should be twenty times the diameter of the rope.

snatch block (below diagram E) can be opened to receive a bight of line rather than having the line pass through the block.  This is used to change the fairlead or direction of a line quickly.

The standing part of a tackle is attached to a fixed point while the other is attached to the object to be moved.  A tackle is rove to advantage when the hauled line comes from the moving part of the tackle.  As the line is pulled, the two blocks draw closer together.  When they meet they are said to be two blocked.  A stopper line can be used to temporarily secure a line under tension.  Manila line should be used to stopper manila line, while nylon should be used to stopper nylon line.  Chain should be used to stopper wire rope.

The load is suspended from the boom, which is constructed so that the center is thickest where the strain is greatest.  Cargo booms are supported by the masts.  The lower end of the boom fits into a socket near the foot of the mast, with its upper end connected to the top of the mast by means of a tackle called a topping lift, which provides a means for raising and lowering the boom end to adjust the height.  This provides vertical control.  The topping lift would be on a guy post.  The wire used to lift the cargo is called a whip, or runner, and is usually powered by a winch.  The head block is at the upper end of the boom through which the whip runs, while the heal block is at the foot of the boom.  A Flounder Plate (fish plate) is a steel rectangular plate with a hole at each corner that holds the wires in place.

A guy provides for transverse (sideways) control and positioning of a boom in a conventional yard and stay system.  The preventer guy serves as a backup to the guys.  They run at an angle to the regular guy.  It equalizes the strain and is secured to a different point on the boom.  This will keep the load from swinging wildly if the guy lets go.  Topping the boom means bringing the boom to its upright position, or raising the boom.  Transverse or sideways motion and steadying of the boom are accomplished by tackles and cabled guys, outboard and inboard.  Spotting the boom means moving it sideways to its position over the cargo.  A shroud is a heavy wire extending from the mast, atwartships to the deck, to support the mast.  A spider band is a band or collar on the top end of a boom to which the topping lift, midships guy and outboard guys secure. Safe working load is often abbreviated as SWL and is usually found at the foot of the boom.

The mast is supported by stays which run fore and aft.  The fore stay runs from the mast towards the bow and the back stay runs from the mast back towards the stern.  The Pelican Hook is designed to open while under heavy tension.  This device is used in cargo handling and for anchor chains.

The size of shackles and anchor chains are also determined by the size line used.  To measure the size of the block, the shell is measured long ways as shown in the diagram.

A shackle is measured on the side above the pinhole.

Proper cargo stowage protects the ship and cargo from damage, protects the crew from injury, and makes maximum use of the space available.  Dunnage, which is placed in the holds to prevent cargo from shifting and allows for ventilation, is often made from rough boards or other pieces of wood.  The amount of cargo taken on board is measured in tons, with a long ton being 2240 pounds. 

Purchase refers to any advantage gained by using a mechanical appliance to raise or move a heavy object or to apply stress on anything, as by using a lever, screw, tackle or windless.  A block consists of one or more pulleys or sheaves fitted in a wood or metal frame, and tackle consists of blocks through which a rope is run to lift a weight or perform a specific task.  To draw blocks of tackle apart is called fleeting.  A reeving line can be used to facilitate passing the end of a large rope through a block.

In all simple machines, mechanical advantage results from using the device.  The mechanical advantage of a machine such as a block and tackle allows you to move a large weight by exerting a small amount of force.  This advantage does not result in increased work performed by the machine, but makes the work easier.  With every machine friction decreases the advantage received by the machine.  That is why it is important to reduce rust and corrosion.  Even when it is working effectively, a certain amount of power applied to a machine is lost through friction.  Friction usually produces heat, and can be evidenced by wearing in vulnerable areas.  Roughly 10% of the load must be added to the load for every sheave in the tackle due to friction.

Mechanical advantage of a machine is the relationship between the load you are lifting and the power it takes to lift the object.  For example, if a load of 20 pounds requires 20 pounds to lift, the mechanical advantage is 1.  If a load of 50 pounds only requires 10 pounds to lift, the mechanical advantage is 5:1.

You can estimate the mechanical advantage of a block and tackle by counting the number of ropes at the moveable block.  With a single whip there is no moveable block so therefore no mechanical advantage.  In looking at the above block and tackle graphic, Gun Tackle has two ropes off the moveable pulley, which is the lower pulley.  Therefore, the mechanical advantage will be 2:1.  In the Three Fold Purchase, six ropes come off the moveable pulley making the mechanical advantage 6:1.

Practical Exercise:  Answer the following questions using the Block and Tackle graphic.

Answer: There are 4 lines coming from the moveable block on #4. Divide 1,000 by 4 = 250lbs of force.

Answer: There are 4 sheaves for number 10, 10% of 1,000 is 100.  100 X4 (sheaves) = 400 equivalent lbs. of friction.  400 plus 1,000 = 1,400 lbs. total divided by 5 (number of lines on moveable block #10) equals 280 lbs. of force required.