Hedderwick: Marine Architecture (1830)



1st, Of the Keel. — The keel should be sided one half for every foot of the ship's extreme breadth. And the hanging under the rabbet is equal to the siding; it should therefore be in depth equal to its siding dimension, adding the breadth of the rabbet for the garboard-strake.

2. The Stem. — The stem should be sided at the lower end 11-12ths of the siding of the keel in midships, and the same as the keel in midships at the top. It should be moulded to 14 or 15-12ths of its siding dimension.

3. The Stern-post. — The stern-post should be sided at the lower end 11-12ths of the keel in midships, and at the upper end the same as the keel in midships. It should be moulded at the lower end about double of its siding, and at the upper end equal to its siding at the same.

4. The Dead-woods. — The dead-woods are commonly sided the same as the keel at their lower edges, but the upper part of the apron on the stem, and fore-edge of the inner post, about 1-5th or 1-6th larger. The dead-woods are moulded according to the size of the vessel.

5. Scarphs of the Keel. — The scarphs of the keel should be in length twice the breadth and twice the depth of the keel, and be fastened with eight bolts, varying in diameter according to the size of the ship.

6. Scarphs of the Stem. — The scarph of the stem, should be in length about three times its moulding dimensions, and fastened with six bolts.

7. Floor-Timbers. — The floor-timbers, at the keel, for coasting vessels, should be moulded one half inch for every foot of the ship's extreme breadth, and sided about 10 or 11-12ths of their moulding dimension. Large vessels rather a less proportion.

8. The Kelson. — The kelson should be sided as the keel, and should be in depth one inch for every foot of the ship's breadth, and the scarphs should not be shorter than five times the depth. They should be secured with eight bolts.

9. The Transoms. — The transoms should be sided, first, the wing-transom the same as the midship floors; all the others about 7-8ths of the wing-transom. They should be moulded the same as the floors.

10. The Breast-hooks should be sided and moulded as the midship floor, and their length be 5-8ths of the ship's extreme breadth.

11. The Deck-beams for a Smack. — The beams for a smack, or any other large vessel, which is chiefly bound by the beams of the upper deck, require more strength in proportion than for those vessels which have two properly bound decks. Smacks, therefore, should have three or four of their midship beams sided one half inch for every foot of their length, and moulded in the middle to the same. Their ends, when the vessel is to be bound with iron hanging knees, may be moulded 2-3ds of their depth in the middle; but when the vessel is to be bound with sunk water-ways and stringers only, the beam ends should not be thinner in the middle than 5-7ths of their mouldings.

12. The Beams for a Brig. — For the siding and moulding in the middle, take 3-7ths of the length of the beams in feet, and call that inches: and make the mouldings at their ends 5-8ths of the middle; and the same proportion will answer for a ship's main and 'twixt-deck beams.

13. For the round of the Beams. — For the round of the beams of the main-deck: to the length of the longest beam add the thickness of the timbers on each side; then take 3-8ths of an inch for every foot of that length for the round-up; and the round of the lower or 'twixt-deck beams is the same as that of the under side of the main-deck beams.

14. The Pawl-bitt. — This piece of timber stands in a vertical position at the fore side of the windlass, and to it are attached the pawls which prevent the windlass from turning round in the reverse direction. As there are very great strains occasionally on the pawl-bitt, it ought to be a good, sound, strong piece of timber, as the safety of the ship and lives of the crew frequently depend upon the security of the windlass. The windlass, therefore, with its connecting parts, should be of the best materials and workmanship. The pawl-bitt should not only have sufficient strength to withstand the heavy jerking strains to which it is exposed without breaking, but also to be strong as will prevent it from springing back at the top, by which the upper pawls are thrown off the centre, or from being drawn back from the ratchets in the pawl-ring, leave the whole strain upon the lower pawls, which are sometimes broke in this manner, and the windlass is then useless.

As the strain upon the cable of a vessel when at anchor is in proportion to her magnitude, the strength of the pawl-bitt, as well as the cable, should be estimated by the length, breadth, and depth of the ship, but particularly by the breadth. In order to find the size of the pawl-bitt, first deduct the thickness of the keel from the ship's extreme breadth as taken for register, and add one half of the same to itself. Call the feet inches, and inches parts, and one-third of that sum will be the siding dimension of the pawl-bitt; also 3-8ths of the same will be the dimension the fore-and-aft way; or by taking half the reduced breadth for the siding way, and adding 1-8th of that to itself, will give the depth the fore-and-aft way. Thus, suppose the ship's breadth 27 feet, and keel 1 foot; required, the size of the pawl-bitt? — 27 - 1 = 26, and 26 + 13 = 39, and 39 ÷ 3 = 13 inches for the siding dimension. Again, 39 × 3/8 = 14 5/8 inches for the fore-and-aft dimensions.* * It may appear at first that some easier rule than the above might be given; but we must observe, that it was found impossible to devise any other that would give the dimensions of the pawl-bitt in so fair, correct, and just a proportion, for all sizes of vessels from 40 to 50, up to 400 or 500 tons.

15. The Chocks for fixing the Windlass-bitts should be as strong as the beams at the place to which they are fixed.

16. The Length of the Windlass between the bitts is commonly one-half of the breadth of the ship's main deck amidships.

17. The Diameter of the Windlass. — Take the extreme breadth of the vessel, and call the feet inches, and the inches parts, and 2-3rds of it will be the diameter of the windlass in inches and parts; or, what is nearly the same, make the diameter of the windlass 2 nches for every 3 feet of the ship's extreme breadth.

18. Size of the Windlass Spindles. — These are commonly 1-8th part of an inch for every foot of the ship's extreme breadth. For such vessels as are deep in the hold, it will be necessary to proportion them thus:— To one and a half of the ship's breadth, add one-half of what the depth of the hold exceede the half of the ship's breadth; by dividing the sum by 12, the quotient will be the diameter of the windlass spindles in the round. Thus suppose a ship's extreme breadth is 27 feet, and depth of hold 20 feet; required, the diameter of the windlass spindles in the round? — By the first rule, 1-8th of 27 is 3 3/8 inches for the diameter; by the second rule, 27 + ½ = 40 ft. 6 in., and 20 - 13"6 = 6"6; and ½ 6"6 = 3"3; then 40"6 + 3"3 = 43"9, and 43"9 ÷ 12 = 3 5/8 inches, for the diameter. So that the diameter by the first rule is 3 3/8 inches, which is a little stronger for a deep vessel.

19. The Windlass Bitts. — These may be proportioned either by the breadth of the ship, or the diameter of the spindles of the windlass: if by the breadth of the ship, make the thickness of the bitts 5-8ths of an inch for every three feet of the ship's extreme breadth; if by the diameter of the spindles, double the diameter of the spindle, multiply it by five, and divide the sum by six, and the quotient is the thickness of the windlass, they will be in a good proportion.

20. The Cat-Heads. — These should be sided equal to 1-3d of the ship's extreme breadth taking inches for feet, and may be 1-7th or 1-6th more in depth.

21. A Smack's Fore-sheet Horse, if made of wood, should be one inch thick for every three feet of its length, and clear of knots on its upper edge.

22. The Capstan. — The following proportions will give the diameter of the capstan spindle, the size of the barrel, the breadth of the top, and the size of the whelps:— 1st, To find the diameter of the Spindle. — Add the depth of the ship's hold to her extreme breadth, and dividing the sum by 12, the product is the diameter of the spindle in inches. Thus suppose the ship's breadth 27 feet, and depth of hold 18 feet, — 27 + 18 = 45, and 45 ÷ 12 = 3¾ inches for the diameter of the spindle.

2d, To find the diameter of the Barrel. — Take 3-7ths of the ship's extreme breadth in feet and inches, and the product is the diameter of the barrel in inches and parts. Thus 3-7ths of 27 = 11 4/7 inches, the diameter of the barrel.

3d, The diameter of the Drum-head is 12-10ths of the ship's breadth, inches for feet. Thus 12-10ths of 27 = 32 5/8 inches, for the diameter of the drum-head.

4th, Fore the size of the Whelps. — These are commonly made one half or 5-9ths of the diameter of the barrel.

23. The Rudder. — I shall offer a few observations regarding the dimensions of the rudder. The good or bad performance of the rudder depends upon the various particulars, the chief of which are the construction of the bottom of the vessel, the situation of the masts and sails, and the dimensions of the rudder itself. The proper dimensions of the rudder is, perhaps, the most important of these; for a vessel may have a well-constructed bottom, her masts and sails properly placed, and yet, if the rudder be not duly proportioned to the vessel, she will not steer well. The following dimensions are considered to be the best for the rudder.

1st Dimension. — Make the rudder one and a half inches broad at the lower end, for every foot of the ship's extreme breadth, or between 1-7th and 1-8th of the ship's extreme breadth, exclusive of the breadth of the bearding of the fore-edge, and let the breadth at the load-water line or lower hance be about 2-3ds or 5-8ths of the breadth at the keel or lower end. This dimension is found to answer very well for regularly-built merchant ships, even allowing them to be rather sharp; this breadth, therefore, must not be much diminished, for although a vessel is thin and sharp abaft, whereby the water will reach the rudder more freely, yet it is certain that the thinner the heel and after-run of the ship are, the greater will be the effort of the rudder required to push the stern of the vessel round; and for this reason, sharp vessels require nearly as broad a rudder as those which are only sufficiently sharp to allow the water a free passage to the rudder.

The above dimensions for the rudder, although the most suitable for vessels regularly formed in the bottom, and whose dimensions of length and breadth are also in a fair proportion, would be found rather small for vessels of a long construction, such as steamboats or the like, because the additional length not only increases the weight, but also presents a greater surface of the bottom and runs to the horizontal pressure of the fluid, while the vessel is coming round. In such a case, the length as well as the breadth of the vessel should be taken into consideration in finding the just proportion of the rudder; and hence this second dimension for the breadth of the rudder:— To the length of the ship at the load-water line (or to the length per register, which is nearly the same in most vessels), add one and a half the extreme breadth of the ship in feet, and inches, and of the sum take 1-3d for the breadth of the rudder in inches and parts. Thus suppose a ship's length is 94 feet; ditto extreme breadth = 27 feet. Then 94 + 27 + 13 ft. 6 in. = 134 ft. 6 in., and 1-3d of 134 ft. 6 in. = 44 5/8 inches for the breadth of the rudder.

When a ship will not steer with this proportion of rudder, she is either too full abaft, or there is something faulty in the placing of the masts. When this is the case, a few inches of breadth may be added to the rudder, such as 1-10th of the above proportion; if this be still found insufficient, enlarge the breadth of the stern-post, by means of a false post, or piece put to the after-side of the stern-post, rather than increase the breadth of the rudder to any greater extent.

In order to proportion the breadth of the rudder more exactly to the ship, according to her particular construction, it will be proper to divide shipping into three classes generally, and then make the proportions suitable.

Let the first class consist of vessels that have pretty sharp bottoms, such as are for fast sailing; let the second class be those that are regularly built for trading merchant ships; and the third, of such vessels as are very full, being long narrow burdensome vessels. For the breadth of the rudder for a ship of the first class, take 1-8th part of her extereme breadth; for the rudder of a vessel of the second class, make its breadth at the lower end 2-15ths of the ship's extreme breadth; and for the breadth of the rudder of the third class, take 1-7th of the extreme breadth of the vessel.

24. The Rudder-head. — The rudder-head or rudder-stock, is that part of the rudder which passes up through the counter to the deck, and into which the tiller is fixed. The rudder-stock should be a piece of timber of the best quality, because the whole strain of the rudder in steering the vessel is constantly acting upon this piece, as the tiller is acting in direct opposition thereto; if this piece of timber be weak or shacky, it will soon become loose and twist, and yielding to the force of torsion, prevent the full action of the rudder.

The dimension of the rudder-stock, like that of the rudder itself, should be in proportion to the bulk of the vessel; therefore see the method of finding the breadth of the rudder by dimension 2d, but in place of taking 1-3d of the sum, take 1-10th for the square of the rudder-head in inches and parts, and, if the size of the timber will allow, the rudder-head may have its breadth the fore-and-aft way made 1-10th more than the cross way.

25. The Rudder-bands are the hinges on which the rudder turns in steering the vessel. They are sometimes made or iron, but oftener of a composition of copper and tin, as the latter is found to be more durable, from its not corroding by the action of the salt water; the bands below water being composition, those above may be made of good wrought iron. Each of them consists of a pair of legs or braces joined together, the width between the legs being equal to the thickness of the stern-post or rudder. Those which fit on the stern-post have a round hole in their after-end, and are called the braces; those which fit on the rudder have a strong pin or pivot on their fore-end, standing commonly at right angles to the edge of the legs or braces, which pin or pivot passes down through the hole in the braces on the stern-post, and connecting the rudder to the same, constitutes the hinge. The size of the legs or bands is made proportional to the diameter of the pivots or pintles, which is their most common name. In proportioning the rudder-bands, therefore, to the size of the vessel, we must first find the diameter of the pintles, and from them the size of the legs or bands.

These dimensions are seldom mentioned in contracts; it is only stated whether they are to be made of copper or iron, while their number and dimensions are left undetermined. This circumstance often causes disputes between parties, as to what their exact size should be.

Peter Hedderwick: A Treatise on Marine Architecture, containing the theory and practice of shipbuilding, with rules for the proportions of masts, rigging, weight of anchors, &c including Practical Geometry and the Principles of Mechanics; observations on the Strength of Materials, Hydrostatics, &c. with many valuable tables calculated for the use of shipwrights and seamen; also the proportions, scantlings, construction, and propelling power of steam-ships. Illustrated with twenty large plates, containing plans and draughts of merchant-vessels from fifty to five hundred tons, with mast and rigging plans; plans and sections of a steam-boat of eighty-horse power; and eight quarto plates of diagrams, &c., by Peter Hedderwick.
Printed for the Author, Edinburgh, 1830. pp 157-161.

Transcribed by Lars Bruzelius

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