|Boy's Manual of Seamanship and Gunnery|
There are two sorts of blocks - morticed blocks, and made or built blocks.
The largest morticed block made is 28 ins., and the smallest for ship use 3 ins. ; smaller blocks are made for boats. The 28-in. single blocks are double scored, and used for double-brace blocks in first-class ships.
A made or built block can be constructed to any size; 50 ins. however is about the size of the largest used in any Government establishment. The number of pieces it is composed of depends upon the number of sheaves; as the partition between each sheave is a separate piece, they are bolted together by four bolts, two at the top, and two at the bottom, and are always fitted with metal sheaves, and a shoulder to one side of the shell.
Large purchase or careening blocks are always built or made blocks
Morticed blocks are used for all general purposes, as hereafter described.
The size of a block is denoted by the length, and its classification by the flatness or thickness of the shell, the number of sheaves, the number of scores, and the quality of the stropping.
For instance - if a shell of a block is 6 ins. in length, it is called a 6-in. block ; if it is 10 ins., 15 ins., or 20 ins., it is called a 10-in., 15-in., or 20-in. block, according to whatever length the shell might be.
A block, if one sheave, is called a single block ; two sheaves, a double block ; three sheaves, a treble ; four sheaves, a fourfold block, and so on, according to the number of sheaves.
If one score, it is termed a single score block ; if two scores, a doable scored block.
There are rope strops and iron strop-blocks, both double and single. The rope stropping is fitted in various ways: for instance, single strops, double strops, and two single strops, according to the stand the block is required to have to establish a fair lead with any given point. For Tables of Blocks, see pp. 30, 3 l.
A block is supposed to carry a rope one-third its length in circumference : that is to say, a 6-in. block a 2-in. rope, an 8-in. block a 2½-in. rope, a 9-in. block a 3-in. rope, and so on.
Blocks, either morticed, made, or built, are composed of several parts, and are named as follows:
Is the outside case of a block, and is made of ash, elm, or iron.
Is the wheel on which the rope travels, and is made of metal, lignum-vitae, or iron.
Is made of metal or leather, and is the centre piece of the sheave which travels on the pin.
Is made of iron or lignum-vitae, and has a head at one end : it passes through the centre of the shell, and the bouch of the sheave.
The Head and Ass
Of a block are the ends of the shell ; the latter is easily known, as it has a much deeper score than the former to receive the splice of the strop, and in most cases the standing part, of the purchase : it is also called the crown or tail of a block.
Is the open part between the sheave and shell.
Is the groove in the outside part of the shell to take the strops either single or double scores, according to what the blocks are required for. Double-scored are always double-stropped.
Are distinguished by the following names, viz. :
Blocks Common, Double and Single.
Brace Blocks, Single, Thin, and Double Score.
Stropped Bored Blocks,
Iron Stropped Blocks.
Are used for nearly all common purposes, reeving purchases, boats' tackles, gun tackles, &c., quarter blocks, span blocks for topmast studsail halyards, and peak brails, jewel blocks at the topsail and topgallant yard-arms for the studsail halyards, in fact, for most of the running gear.
Are made shorter and thicker, and have metal sheaves, which arc smaller in diameter than those of other blocks, but reeve the same size rope. Tacks and sheets are fitted with clump blocks.
Are single, thin, double-scored blocks. They are fitted with a double strop with a thimble, and a thimble rove through it, to take the yard-arm strop, which are called unity thimbles.
Fore and Main Topsail Brace-Blocks
Are single, thin, double-scored blocks, and are fitted with two strops and union thimbles. The yard-arm strop is fitted round the thimble that is rove through the thimble of the brace-block before the block is stropped.
Are made with a projection left on one side of the top of the shell, which bearing against the place of connection prevents the fall from being jammed, such as purchase and foretack blocks.
Are used for yard-tackle purchases, and reef-tackles of boom mainsails ; they are long single blocks, made on end in one piece with two metal sheaves, sometimes one metal, and one lignum-vitae one sheave being smaller than the other, but the same size score. The upper sheave is the smallest in diameter, which causes a loss in power, for all the parts of rope are kept more clear of each other in this kind of block, and as they do not cross, there is less friction.
Are tapered, the upper part of the block being smaller than the lower part, having a deep score, as they are seized between the foremost pair of shrouds in the topmast rigging ; they are thus constructed not to interfere with the spread of the rigging ; they are also two in one on end, the reef-tackle being rove through the upper, and the topsail lift through the lower sheave, they are sometimes fitted in separate pendants, and answer very well.
Are made with a projection on each side of the lower part of the shell through which the strop passes, and which is intended to keep small gear out of the swallow. They are used for reef-tackles, clew garnets, &c., &c.
Consist of two sheaves on end in one piece, but, unlike a fiddle block, the upper sheave stands in a contrary direction to the lower one, that is, the sheaves in the block are fitted swallow to swallow, and as the buntlines are rove up towards the tops, the whip is rove down on deck ; the sheaves being fitted in this way, admit of each rope being rove as it should be in the swallow of each sheave.
The sheaves of a fiddle block are fitted to reeve a rope leading in the same direction, therefore when used as a buntline block, the lower part or tail of the upper block or sheave is cut or burnt away to the size of the swallow, to admit of the rope being rove ; it would be a great convenience, when fiddle blocks are intended to be used as buntline blocks, if they were made in the sheaves like a shoe block, swallow to swallow ; two single blocks are frequently seized together in the same strop on end, crown to crown, a good seizing being passed between them for buntline block, forming a fair lead for each rope, and are also called shoe blocks.
Are fitted with a lug for shackling to the long links of the topmast necklace.
The shell abreast the swallow of the block is cut away, leaving a space according to the size of the block, the iron stropping over this space is fitted with a clamp on a hinge, the other end being secured when in use by a pin, so the clamp can be easily thrown back, and the bight of a robe or hawser, readily snatched and unsnatched, doing away with the necessity of reeving the end, these blocks are used as leading blocks, but should never be used for any heavy purchases.
Are iron bound, and are fitted with a hook to take the eyebolt in the cap for reeving the top-tackle pendant through.
Fall Blocks, for Top-Tackle Pendants,
Are iron-bound swivel-booked blocks, either double or treble, according to the size of the ship.
Blocks for Boats' Tackles
Are iron-bound, those in the davit-heads working on a swivel, the lower ones being fitted either with a hook or a thimble.
Is applied to a rack of nine sheaves, arranged horizontally, or to any given number of sheaves, fitted horizontally between the bitts, abreast of each mast on deck, to form a lead for the running rigging, or any rope to be led along the deck.
Is a large iron-bound block secured to a wooden chock bolted to the deck.
Iron Stropped Blocks.
Hanging blocks, tye blocks, top blocks, cat blocks, fall blocks for top-tackle pendants, double and treble blocks for boats' tackles, snatch blocks, &c., &c., are all iron-bound, and are either fitted with hooks, eyes, or lugs, standing or swivel, according to-what they are required for.
Are fitted with two iron lugs, and are secured to the eye-bolt on the topsail yard by an iron pin, and are swivel blocks.
Are either double or treble blocks, according to the size of the ship, fitted with a large open hook so as to take the ring of the anchor readily, and as a swivel block.
On the foremost side of the shell of this block are two small eye-bolts for fitting a rope to, called the cat-back or back-rope bridle, which is used in hooking the cat, as a support to the block ; the rope bent to the bridle is called the cat-back, and in large ships is led through a leading block secured to a convenient place on the bow, or in the head.
JEER BLOCKS, UPPER AND LOWER.
Upper Masthead Jeer Block
Is a double block, double-scored, stropped with two single strops, the four parts - or that is, the two parts of each strop - are seized together at the crown of the block, leaving two long bights or eyes, which are passed up through the after hole in the fore part of the top, and lashed on the after part of the mast head.
Lower Jeer Blocks.
These are single thick, double-scored blocks, fitted with two strops, one long and one short, so as the sheave shall stand fore and aft and correspond with the upper or mast head jeer block. The bight of the long strop is passed down abaft the yard, up before all, and lashed to the bight of the short strop with a rose lashing.
Are round, and made of elm; they have three holes at equal distances to take the lanyards of the rigging, with a deep score, according to their size, round them to take the shroud. The size of a dead eye is denoted by the diameter. Dead eyes, intended for wire rigging, have a smaller score. The largest size dead eyes are 17-ins., the smallest, 3-ins.
Are another description of dead eyes, used for setting stays up, are turned in the end of stays, and seized in the fore stay collars on the bowsprit. Lower ones, for main or mizen stays, are iron-bound. Like dead eyes, they are made of elm, something resembling a heart in shape, with one large hole through the centre ; in the largest heart there are four scores, and in the smallest three scores, for the lanyard to lay in. Round the outside is a rounded groove to take the stay. The largest size heart made for the Navy is 20-ins., 18-ins., however, being the largest in use; the smallest size, 4-ins., whether iron bound or for turning into the stay.
Is a wooden thimble, with a hole in the middle, rounded off at the edges, with a groove round the outside for a strop or seizing to lay in. They are generally seized to the lower shrouds in Merchant ships, to act as fair leader for the running rigging.
Or, as it is sometimes called, a Euphroe, is a long piece of wood rounded, the largest part near the middle, the upper end sloping gradually off to a point. The lower end resembling in shape a dumb bell, it has a groove for a stropping to lay in, cut in an up and down direction. A number of horizontal holes are pierced through it. Its length depends on the number of holes required. It is used as a crowfoot, fitted, with a number of legs, for ridge ropes of awnings.
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