trippwj

Nice work, Elijah. To respond to your interrogatories, the stern post and rudder would not be planked. The stern post serves to relieve the ends of the planking (see rabbett), but the copper plating would continue around the post and the rudder would also get coppered .

Looks sweet, Denis. I like the color on the deck.

Age, my friend, is all relative. In my case, it is relatives that remind me that I am older than dirt... I wonder if they would consider a cross cultural location - she would look awesome moored here in Eastport, or maybe as the border bridge at the narrows in Lubec....

You are doing a great job, Elijah. The photos are quite fine enough to see the care you are taking with each step. Until next time -

Thought it might be polite to provide the other 3 figures used in the above Scale of Burden for a Privateer.

Chapman's work is, indeed, of great interest, and will represent a seperate posting when the time comes - I am working with the Inman translation of his Tractat om skeppsbyggeriet, first published in 1775 to complement the author's Architectura navalis mercatoria. The plates and figures related to many of the calculations are included, and detailed methods discussed. Additionally, it is long out of copyright so the figures and text are freely available for quotation and so on. I am working though some of his details and it is quite interesting! As one tidbit: To construct from hence a scale of burden. (182.) Draw two lines perpendicular to each other, the one in a horizontal direction, the other in a vertical direction; make on the horizontal line a decimal scale at pleasure to represent lasts, and on the vertical another scale of feet also at pleasure, as is seen in Fig. 50. Below the horizontal line and at the distance from this superior line of 1.62, 3.24, 4.28, 6.48, 8.1, 9.72 and 11.2 feet, draw parallels thereto. On the scale of lasts, take the quantities, which have been found, in lasts 45.16, 85.89, 120.88, 149.75, 171.45, 184.6 and 189.58; set off these quantities on the corresponding horizontal lines, from the vertical line. Through all the points so determined pass a curve, and you will have a scale of solidity. The horizontal scale is in French tons, English tons, and Swedish lasts. The method of using the scale is this. The line a b (NOTE 53.) on the sheer plan is the load water-line, the privateer being laden. Suppose that the water-line before it is entirely laden, were cd; then the distances ac, bd are taken, which by the scale of the plan give 4 feet 1 ½ inches and 5 feet 1 ½ inches; these two quantities are added, and half the sum is taken, 4 feet 7 ½ inches. Take this quantity 4 feet 7 ½ inches on the scale of solidity" you will have e g, which must be transferred perpendicularly to the line e f, until it meet the curve in h. From h draw the line hi perpendicularly to f e, or what is the same thing, parallel to e g; this line marks on the scale of lading the weight, which must be put on board to bring down the ship to the line a b, namely, 175 Swedish lasts. (183.) If the ship be quite light, one may in this manner find the lading, which it can take; or if the water-line of a ship ha~. been once observed, supposing another to be found, one may be able" by means of the said scale, to obtain the weight which the ship has taken on board, or of which it has been discharged, to render it so much more brought down, or more raised.

This approach to ship design was fairly common in the 15th and 16th centuries. Bellabarba (1993) observed that Many ships have been built, right up to our times, using a few measurements and proportions between the main parts, and the 'master's eye' dealing with all the rest. Although this method provided respectable, indeed admirable, results, it did not permit a successful example to be reproduced exactly, nor any mistakes to be corrected intelligently. Any possibility of making progress depended on individual masters' memories and insight and their willingness to share their experience with others (colleagues or successors). With this intuitive yardstick, it was impossible to build a series of identical units which was particularly essential for the fleets of Mediterranean galleys and likewise to prefabricate parts of the hull. But, in contrast, the ancient method of design allowed a hull shape to be reproduced exactly the same as any other one or its characteristics to be subtly varied by means of a set of 'rules' which, in addition to simple measurements (length, height, width, proportions etc.) included indications for defining the hull curves geometrically. These instructions could be memorised and easily communicated, with no need for either drawings or mathematical calculations. This distinguishes the ancient method described here from all the other, more or less contemporary ones, based on mere intuition (the 'master's eye') or the ribbands, which we shall come back to later. The set of 'rules' were numerical instructions which could be used directly in the yard during shipbuilding. So the method could be described as a 'method of rules' as opposed to the more recent method of drawings. Bellabarba, Sergio. 1993. “The Ancient Methods of Designing Hulls.” The Mariner’s Mirror 79 (3): 274–92 . doi:10.1080/00253359.1993.10656457. Loewen (1998) offered a brief description of the process: Three major steps made up the ship carpenter's process of designing a hull. First, he worked out the four basic dimensions of the hull: its breadth, its keel, its length from stem to sternpost and its depth of hold. These dimensions mirrored those used by ship surveyors to gauge a ship's tonnage and, in practice, allowed a carpenter to convert to a merchant's desire to build a ship able to carry a certain tonnage of goods into real measures. Second, within the parameters of the breadth and the depth of hold at midship, the carpenter worked out the shape of the master frame, using as his fundamental elements a series of five tangent lines and arcs: the floor line, the bilge arc, the futtock arc, the arc at the greatest breadth and the tumblehome line. He then devised a master mould from this shape, and marked off the points on the mould at which his lines and arcs touched. Third, using the master mould, he worked out the shape of frames fore and aft of the master frame by means of three systematic adjustments to the master mould, namely: the rising of the floor, the narrowing of the floor and adjusting the aspect of the frame from the bilge upwards. Loewen, Brad. 1998. “Recent Advances in Ship History and Archaeology, 1450-1650: Hull Design, Regional Typologies and Wood Studies.” Material Culture Review / Revue de La Culture Matérielle 48 (1). http://journals.hil.unb.ca/index.php/MCR/article/view/17791. In A Treatise on Shipbuilding: And a Treatise on Rigging, Written about 1620-1625, the anonymous author offers a detailed description of the process of “whole moulding”: 'Suppose I would mould out the 20th bend of timber aft: 1st: I strike a ground line upon the foot of the timber and cross it at right angles with a middle line for the depth. 2nd: I set off the rising of that bend from the ground line, at the length it is marked upon the floor mould. 3rd: I seek the depth of that bend, which set off from the rising line I draw a parallel to the gound line for the breadth. 4th: I take the narrowing aloft out of the greatest breadth and at that breadth draw a parallel to the middle line. 5th: I set the narrowing alow upon the middle line of the timber and score out by the mould both within and without the frame of the mould. 6th: I bring down the sine mark of the lower part of the futtock to the haleing down thereof upon the wrong head and score out that part of the futtock. 7th: I bring down the lower end of the upper futtock to the haleing down marked upon the lower part, and score out the upper part of the futtock. 8th: I put up the top timber upon the end of the futtock according to the mark of putting up, that it may fit his breadth at the upper surmark, and score aut by it the top timber mould. And so is the whole bend truly moulded with all his parts'. Salisbury, W, and R. C Anderson, eds. 1958. A Treatise on Shipbuilding: And a Treatise on Rigging, Written about 1620-1625. Occasional Publication No. 6. London: Society for Nautical Research.

Having stuck my neck out by making this broad a statement, let me offer some of the reasons behind this assumption. While the processes and methods used to design vessels are as old as the use of ships, for the purposes of this discussion I am going to limit the time frame to about 1400 through 1800. This period includes a variety of design and construction methods, as well as increasing awareness of the science of flotation and resistance. The upper end point is very carefully chosen as representing the point where, particularly in Great Britain, there was a paradigm shift about to occur in how the ship builder thought about the form and design of the ship. Sepping’s bow, diagonal riders, stability calculations, the advent of steam and iron construction – all of this and more influenced a paradigm shift during the first half of the 19th century, worthy of study separate from the earlier periods. The modern approach to designing a ship is generally thought of in terms of measured drawings and plans drawn on paper and then transferred to the mould loft floor. These drawings were used to determine the exact shape of the ship - before the start of building. The drawings were also used to store good designs both for review and reuse. Neither measured plans nor even the technique for making them existed in the Middle Ages. Ship design, in terms of determining final dimensions, was carried out in the shipyard while the ship was being built. While the overall shape of the vessel was easily envisioned, determining the dimensions of hundreds if not thousands of individual parts that had to be cut from timber and assembled together was the challenge. What methods were used to store the “good” designs and retrieve them for later use? In 1434, Michael of Rhodes sat down to write out the manuscript for which he is remembered. He recorded his full name of Michalli da Ruodo twice in the 440-page text. In his treatise on shipbuilding, he provides two approaches to the challenge of ship design. For the types of ships built in private shipyards, he describes a system based on a proportional approach; for the galleys built in the state-run Arsenal, his approach reflects the recording of actual measurements on paper. Michael's manuscript contains some of the earliest known ship-design drawings, marking an early stage in the transfer of design from the shipyard to the drawing office. Most of a galley's frames were shaped by proportion, or "moulded." The geometry, however, did not extend all the way to the bow and stern which were shaped by hand, using thin wooden battens, or ribbands, as guides. The shapes of most of a galley's frames were determined by proportion, but the geometry did not cover the shape of the bow or stern. These were determined in the yard, using string to get the proper curve. This drawing was intended to illustrate part of the process. The top diagram provides dimensions relating to the shape of the stempost; the bottom diagram, dimensions relating to the stern. Source: Stahl, Alan M., ed. 2009. The Book of Michael of Rhodes: A Fifteenth-Century Maritime Manuscript, Vol. 2: Transcription and Translation. Trans. Franco Rossi. Vol. 2. 3 vols. Cambridge, Mass: The MIT Press. Also see The Michael of Rhodes project. Accessed April 28, 2016. http://brunelleschi.imss.fi.it/michaelofrhodes/index.html.

John – You bring up some interesting considerations – thank you! One of the aspects that comes out in trying to research this topic, esoteric as it may be, is that there was a distinction to be drawn between the theorist and the builder. Many of the mathematicians (Bernouli, Euler, Fourier, Newton etc.) were mathematical theorists. They developed methodologies and approaches to the task, yet were not ship builders themselves. Nor, for that matter, did they design ships. There was, of course, the mathematically oriented ship builder – people like Deane, Pett, Baker (and Tom Wells) and Chapman. They not only designed and built ships, but also applied the mathematical theories in their work. Now we come to the pure ship builder of old. They had enough mathematical background to determine the measurements of components (often based on simple rations, arcs and so on – see Rees and Steel, publishing someone else’s narrative, for examples), but did not apply the mathematical theories to the effort. The frustration in English naval architecture can be found in the publications by The Society for the Improvement of Naval Architecture (Society for the Improvement of Naval Architecture. 1791. An Address to the Public, from the Society for the Improvement of Naval Architecture. Instituted 14th April, 1791. https://archive.org/details/someaccountinst00unkngoog.) To promote this important object as effectually as possible, the society purpose to encourage every useful invention and discovery as far as shall be in their power, both by honorary and pecuniary rewards.—-They have in view particularly to improve the theories of floating bodies and the resistance of fluids—to procure draughts and models of different vessels, together with calculations of their capacity, centre of gravity, tonnage, &c. —to make observations and experiments themselves, and to point out such observations and experiments as appear best: calculated to further their deigns, and most deserving those premiums which the society can bestow. But though the Improvement of Naval Architecture in all its Branches be certainly the principal object of this institution, yet the society do not by any means intend to confine themselves merely to the form and structure of vessels. Every subordinate and collateral pursuit will claim a share of the attention of the society in proportion to its merits; and whatever may have any tendency to render navigation more safe, salutary, and even pleasant, will not be neglected. We also find, in 1860, the Reverend Wooley reflecting on the progress and state of mathematics in Naval Architecture (Wooley, J. 1860. On the Present State of the Mathematical Theory of Naval Architecture. In Transactions of the Royal Institution of Naval Architects, I:10–38. The Institution. https://books.google.com/books?id=xR-oHqNU7RIC) In former times, the constructors of ships in the Royal Navy were restricted to certain relative dimensions of length, breadth, and depth, which in fact gave a small amount of natural stability, and necessitated a recourse to ballast. Sir William Symonds was the first surveyor of the Navy who obtained the power of building ships without those unnatural restrictions, and he gave considerable beam to his vessels, and with it great natural stability, and so was enabled to reduce very materially the quantity of ballast--a very important gain. Whatever may be thought of the form of his vessels in other respects, it cannot be denied that, so far as increasing beam and diminishing ballast are concerned, he effected an immense improvement in the vessels of the Royal Navy. The scientific constructor would do well, however, not to confine his investigations to mere formulae derived from analytical processes, and to inferences drawn from them; but he would derive immense information, and add most materially to the breadth and practical value of his views, by examining from first principles, and in a more geometrical method, the several elements on which stability may be made to depend. In this way he may gain most valuable experience as to the twofold nature of stability which I have already indicated. Interspersed among a multitude of period writings are observations concerning the limited mathematical skills of most ship builders and shipwrights. Indeed, more recent scholarly research has drawn the similar conclusions (see, for example, Tebeaux, E. 2008. Technical Writing in English Renaissance Shipwrightery: Breaching the Shoals of Orality. Journal of Technical Writing and Communication 38, no. 1: 3–25. http://jtw.sagepub.com/content/38/1/3.) The information was there, but most of those who were in a position to use it and benefit from it were not trained in how to use it. Time for a working hypothesis. The central question: At what point did shipwrights shift from marking a load waterline based on where they felt it should be to determining where the load water line would be based upon the form and structure of a vessel. The Hypothesis: Early shipbuilders developed their methods and designs based largely on trial and error. As the size of vessels increased, methods became more formalized in an attempt to maintain the relationship between form (shape), function, and performance. Systems such as “whole moulding” and “shell first” construction were developed over many years of trial and error, to guide a builder in forming the body of a ship. No attempt was made to predetermine accurately the immersion of these vessels, but rather institutional knowledge (what had worked for similarly built vessels) guided the builder.

Very impressive! You are going to need a bigger house to keep this big girl in appropriate style! Enjoy your vacation, kind sir. Are you bringing the gnomes with you?

I am still trying to locate the 1914 Admiralty investigation - have found a snippet or two, but not yet able to locate the full report. Will try again in the morning - time for me to tuck it in. Only have the one day off each week (Sunday) from work, so try to get up early to make the most of it! Dafi - let me know if any of the documents listed are helpful. Will keep searching for the Admiralty one from 1914.

Daniel - I think this may be at least a couple of the documents to which Robin was referring. James, W. 1826. The Naval History of Great Britain, from ... 1793, to ... 1820, with an Account of the Origin and Increase of the British Navy. Vol. 4. https://books.google.com/books?id=NpF7KhRs8RcC. Desbrière, E. 1901. Projets et tentatives de débarquement aux Iles britanniques: 1793-1805. Vol. 1. Chapelot. https://books.google.com/books?id=NiMEn3UHHIgC. Desbriere, E. 1933. The Naval Campaign of 1805: Trafalgar, Vol. 1: Text. Trans. Constance (translator) Eastwick. Clarendon Press. https://books.google.com/books?id=tMOoYgEACAAJ. Additional volumes are listed on that same page.

Jud - Gun Port stops function much the same as the soffit (stops) on modern doors. If modern carpenters, with thousands of years of institutional knowledge behind them, not to mention untold bazillions of doors installed, have found the stop an effective way of ensuring that a simple household door doesn't move further into the opening than intended, why should we think a ships carpenter, working in a non-planar building surface, would be so presumptuous to think that the port lid (all 110 or so for the largest ships) would fit right, every time, at sea or anchor? That series of holes in the side was the Achilles heel, so to speak, of nearly every war ship afloat. In a rough sea, if a port broke open (the port lid pushed through the port), the volume of water admitted could, in a short time, create major stability issues as the vessel settles lower due to water accumulation in excess of the pump ability to remove. In terms of protecting the interior planking from the gun, that was not a major concern. The waterway was designed as the stop for the carriage wheels. The pressure of the gun carriage against the side was planned for - that was how a gun was intended to be used and stored. The bigger design challenge was to come up with a design for the eye bolts used to anchor the various gun tackle to withstand the recoil after firing. The gun, accelerated to a velocity due to recoil, wants to stay moving in that direction at that velocity. Inertia (the resistance of any physical object to any change in its state of motion) and momentum (product of mass and velocity) mean that it takes a large or prolonged force to bring it to a stop afterwards. That force is applied by the various tackle, all anchored to very small sections of the hull by the eye bolts.

Interesting thought, Dan. I can come up with several definitions (interestingly, none in english) that describe it as essentially a rudder angle (tiller angle) indicator. The other definitions all describe a method using lenses to determine alignment, also for use in fitting spectacles. Will keep looking.

Were the anchors rigged so both were raised/lowered at the same time? Nope - as the references provided describe, only one at a time. These were brutally heavy with massive cables some 22" or more in curcumference. Man handling these into the cable tiers was anything but simple, as these thick cables were not particularly flexible. Add to that the capstan could only bring one at a time due to the weight and technology. The above, of course, covers weighing (raising) the anchor. Setting the anchor is a whole 'nother adventure in semi controlled violence!

Welcome back, Elijah. Hope you had a good time! What part of Virginia did you visit (I think I missed that post....)

She is a beauty, Sjors. Your zoo is doing admirable work!

Very nice work, Tony. Love those little details for the interior!

Thanks, Dave! Interesting side bar: Lord Barham set up a Commission of Revision which reported in 1806, among other things, that there should be a deeper study of the principles of ship design. It was recommended that the best apprentices in the Royal Dockyards should be given special instruction in Naval Architecture and related subjects. The first School of Naval Architecture was set up in Portsmouth in 1811 but, following a change of Government, was abolished in 1832. Inman and Fincham were among the faculty. Indeed, at that same time Robert Seppings was replaced as Surveyor of the Navy by William Symonds. Seppings, you may recall, published two significant treatises on ship building - On the Great Strength Given to Ships of War by the Application of Diagonal Braces and On a New Principle of Constructing Ships in the Mercantile Navy. Quite the uproar over appointing a non-shipbuilder but rather a Naval officer (and purely political patronage appointment) to the position of surveyor of the navy!

Several times during our discussion the point has been made that design waterlines were just that – the desired draught for a fully loaded ship. Indeed, that was the intent, but it was also a critical design element. By the 18th century, a warship was designed with a desired number and weight of guns on a specified number of decks. This primary design criterion brought with it a host of other specifications – the intended crew size and composition (as well as the accommodations for officers &c.), the weight in powder and shot for the typical mission profile, the quantity of spares and materials for repairs, the victualling and water, and on and on. It also, based on the weight of gun, drove the scantlings to support the guns and facilitate their use. While the weight of all of these could be estimated (see earlier posts), they were far from firm – there was always variability. The ship designer needed to consider these factors, along with the form of the vessel for best sailing and handling, to ensure that when fully loaded the vessel maintained a safe freeboard (well defined by the 1700’s as 3 to 5 feet from LWL to lowest gun port). I suspect that it was the increased focus on the builder delivering a ship which achieved an appropriate compromise between these various factors (handling, speed, draught of water and ability to carry intended weapons and supplies) which ultimately forced the shipbuilder to actually determine the displacement and determine whether the ship design could achieve what was desired. While there was a certain amount that could be done to mitigate the draught by adding or removing ballast, this had implications for the handling and seaworthiness of a ship – the ballast was intentionally there to bring the center of gravity (even if not understood as such) lower and improve the roll and pitch – to keep her from becoming crank, as it were. Too little ballast resulted in a top heavy ship that rolled excessively. The same holds true for merchant ships – the ballast was much more variable (and there are many documented cases where ballast was added or removed for specific cargos), but the builder (and owner) wanted to maximize the cargo capacity for a given set of tunnage admeasurement rules, while ensuring adequate speed, handling and (of some great importance for some routes) keeping the overall draught of water within a given limit (particularly for bays or harbors with shallow entries or bars). At the same time, the merchant wanted to use a small a crew as possible, so the types and nature of the rigging was also a major consideration. How did they balance all of these, in the absence of slide rules, spreadsheets and calculators

Bruce - You bring up some excellent points! For constructors, the emphasis on cargo tunnage as the measure of the ship (even for warships) meant that they had little reason to think in terms of displacement tons when measuring their ships. This fact partly explains the long delay in many countries in adopting displacement tonnage as a unit of measure, as both constructors and owners (including admiralties) continued to apply the simpler admeasurement rules and avoided the more exact measures required for correctly calculating displacement. There is evidence that some British constructors were estimating load waterlines by the 1630s, although it was probably not common practice. For example, see the examples in this post http://modelshipworld.com/index.php/topic/9892-seeking-information-on-determining-load-waterline/?p=296187 And this one http://modelshipworld.com/index.php/topic/9892-seeking-information-on-determining-load-waterline/?p=300218 Ferreiro, among others, makes the point that displacement calculation as a matter of routine was unique, perhaps, in that usually the need to accomplish something drives the development of a methodology. In the case of displacement, and the subsequent stability calculations, the need to calculate the curves and so on was driven by the development of the capability – which, to a certain degree, was driven by the financial interest in accurate determination of cargo capacity. Much of the theory related to displacement was driven as well by interest in determining the best forms for a ship to “divide the water”. A great deal of effort was expended in model basin testing to try and derive the best shape – and some interesting detours into false premise and failed designs followed, as well as some successes. We know that there were successful efforts to identify the swimming and LWL as far back as the 1600’s. We have the plan for the Danish ship Elephanten (1705) built and designed by Olaus Judichær showing clearly marked waterlines (see facsimile in Ferreiro, Ships and Science). We have the contracts and information by the Pett’s, and also by Deane. We have the LWL beginning to routinely show on plans by the mid-1700’s in British ships. By the late 1700’s we have Humphreys and other American designers discussing the design draught for their ships. What we also have, though, is a clear indication that while it was possible, it was not routinely done. In 1791, we find the establishment of The Society for the Improvement of Naval Architecture in Great Britain. Among their early awards, was the following: The Societv offer a Premium of Twenty Guineas and the Silver Medal for the most ready and accurate method, by approximation or Otherwise, for determining the tonnage of vessels and ships of every description, from an admeasurement of all the principal dimensions. Among the contributions was one by Chapman discussing the Swedish methodology. It is an interesting and worthwhile read. Society for the improvement of naval architecture London. 1792. Some Account of the Institution, Plan, and Present State, of the Society for the Improvement of Naval Architecture: With the Premiums Offered by the Society, List of Members, and the Rules and Orders of the Society. To Which Are Annexed Some Papers on Subjects of Naval Architecture Received by the Committee. http://archive.org/details/someaccountinst00unkngoog. We also have, slightly later, Steel (1805) bemoaning the fact that displacement is not calculated: By this rule, all vessels, whether their bodies be extremely full or. extremely sharp, will appear to be precisely of the same burthen or capacity, if the length of keel and extreme breadth be similar. Thus, the sharpest cutter will seem to carry as much as the fullest merchant-ship of the same length and breadth extreme. This method is, of course, exceedingly detrimental to that principle which promises velocity; as the ship which is narrowest above, and widest and deepest below, will measure least in proportion to her real capacity; the very reverse of which is necessary for fast sailing. In order to ascertain the true burthen of a ship, we ought to find the place of the light-water line, and thence calculate the number of cubic feet below the line of floatation: as the product, deducted from the number of cubic feet contained at the load-draught, would shew the real capacity by which the tonnage may be computed: and, if the difference be multiplied by the weight of a cubic foot of sea water, 64 3/8 lbs., the product, divided by 2240 (the number of lbs. in a ton), will give the true burthen in tons. Or, in other words, by deducting the weight of the ship at her light-water mark from her weight when brought down to the load-water mark, the remainder will be the tonnage.

By all means, feel free to print it off and peruse at your leisure! I keep going back to that Humphreys calculation and pondering why the tunnage is so great. Here is a direct paste from his 1793 letter to Samuel Hodgdon: Dec 16, 1793 Dear Sir I think it necessary to inform you in what manner the tonnage is calculated that I have made the estimate from. In the first place to find the length of straight rabbet forward you take 3/5 of the beam as usual from that point to the after part of the stern post allowing its width for measurement not to exceed 1/12 of the beam. That length being determined you then multiply it by the length of beam & that product by the height of the gundeck beam amidship on the top of the beam added to half of her waste amids which last product divide by 95 which will give the number of ton required. I am respectfully yours &c Joshua Humphreys It is that additional factor (1/2 her waste amidship) that results in the dramatic increase in tunnage. I pulled up another description from him dated 1804 (in response to an inquiry from the auditor of the navy concerning builders measure in Philadelphia in 1799). In this letter, he does NOT include that addition to the depth of hold! 'Dear Sir I shall with pleasure endeavour to explain the Mode of ascertaining the Tonnage you require I hope it will be satisfactory. The rule for ascertaining of Tonage of Vessels Carpenters Measure in this Port in the Years 1799 & 18oo was as follows- Breadth of Beam was ascertained from the outside to outside of the timbers - or the Moulded Breadth at dead flat or widest part of the Ship or from inside to inside of the plank or Wales at the same place, which is the same thing. When the length of Beam is so found you take three fifths of its length which is allowed for the rake of the Stem, let the rake be what it may either more or less - but the rake is generally less- In order to assertain the point of straight rabbet on the Keel, you must set 12 inches before the rabbet of the Stem at the height of the Gundeck from that point let fall a line at right Angles with the rabbet of the Keel then Measure from that line 3/5 of the Beam & wherever that distance terminates on the Keel is the point called straight rabbet & from which to the rabbet of the stern post is the length of Keel for Tonage Carpenters measure of this Port - then Multiply the length of the Keel so found by the Breadth of the Beam as above & that product by half the length of the Beam- which last product divide by ninety five which will give the Number of Tons required. (transcription provided in M. V. Brewington. 1941. Notes: Tonnage Rules in 1799. The American Neptune: A Quarterly Journal of Maritime History and Arts I, no. 3: 295–296. http://phillipslibrarycollections.pem.org/cdm/compoundobject/collection/p15928coll3/id/939). When I change the depth of hold to 1/2 the beam, the calculated tunnage is much more agreeable - 1080 & 68/95 tuns carpenters measure. Mr. Humphreys was an interesting character, and regrettably his working notebook (compilation of all sorts of tidbits around shipbuilding &c.), while containing a great deal of information, is NOT chronological, in the sense that it traces events in order, but rather a sequential listing of information in the order it was entered. For example, the first entry is a transcription of the British 1719 Establishment, followed by a description of some method of ascertaining tunnage (NOT either of the two above given), then followed by more of the 1719 Establishment. This is then followed by an entry titled "Navy Office, August 1st 1737 Dimensions", and about 20 pages later "An abstract of numbers, natures, lengths & weight of cannon according to several rates of ships as proposed at a meeting of Flag Office and established by His Majestic Council on the 6th of July, 1716."

The next step in the process, then, is to look at how these various measures compare when looking at a single vessel. I opted, for convenience sake, to work with the design specifications for the 36 gun frigates from Joshua Humphreys, primarily because I had a good detailed set of specifications available. Note that the actual vessels “as built” differed from these specifications, but for my purposes here that was not important. The calculations here are preliminary – I still have some additional tweaking to do, but they serve to illustrate how broad the tunnage can be when the different admeasurement methods are used. K = length of Keel for tunnage B = Beam (maximum breadth) D = Depth of Hold for tunnage

There are several dozen potential ways that have been identified by Salisbury (among others) for measuring tunnage. For the sake of simplicity and illustration, I am only going to highlight a few of them. Mr. Bakers Old Rule (from about 1582): The old way, which was established in Queen Elizabeth's time, and never questioned all King James time, is this: The length of the keel, leaving out the false post, if there be any. Multiply by the greatest breatdh within the plank, and that product by the depth taken from the breadth to the upper edge of the keel produceth a solid number which divided by 100 gives the contents in tons, into which add one third part for tonnage, so have you the tons and tonnage. K = Length of keel excluding false post B = greatest breadth within plank D = depth from B to upper edge of keel Divisor = 100 Naval Papers of Peter Pett (about 1650) Take the Length from the inside on the Upper Deck between the Stem and the Sternpost, and the greatest Breadth from Outside to Outside: likewise, the Depth from the underpart of the Beam of the Upper Deck to the floor by the side of the Keelson. Multiply the Length by the Breadth, and that by the half Breadth, except the Depth exceed the half Breadth, then you are to multiply by that and divide the quotient by 110. K = Inside on upper deck between stem and stern post B = greatest breadth outside to outside D = depth from underpart of beam to floor by side of the keelson or ½ B, whichever is greater Divisor = 110 The Massachusetts Rates and Duties Act. (In The Acts and Resolves of the Massachusetts Bay (Boston, 1869-1922), I, pp. 207-8.) (from about 1695) ... the breadth at the main beam within board, the depth to be accounted half the said breadth, and the length three times so much as the breadth, after the usual manner of multiplying, and dividing the product by one hundred. K = 3 x B B = width at main beam within board D = ½ B Divisor = 100 An Act for Making a Convenient Dock or Basin at Liverpool (1709) Take the length of the keel of every ship or vessel so much as she treads on the ground and the breadth to be taken within board by the midship beam from plank to plank and half that breadth shall be accounted for the depth ... Then the tonnage will be (L x B x D)/94… any custom practice or usage notwithstanding. K = Length of keel treads on ground B = width at midship beam within board D = ½ B Divisor = 94 13 Geo. III, c. 74 (pg 1) (The Smuggling Act.) The' Old Rule', adopted for general use in all later Acts until the 'New Measurement' of 1836. (1772) The length shall be taken on a straight line along the rabbit of the keel of the ship, from the back of the main-post to a perpendicular line from the fore part of the main-stem under the bowsprit; from which subtracting three fifths of the breadth, the remainder must be esteemed the just length of the keel to find the tonnage; and the breadth shall be taken from the outside of the outside plank, in the broadest place in the ship, be it either above or below the main wales, exclusive of all manner of doubling-planks that may be wrought upon the sides of the ship; then, multiplying the length of the keel by the breadth so taken, and that product by half the breadth, and dividing the whole by ninety four, the quotient will be deemed the true contents of the tonnage. According to which rule the tonnage of all such ships and vessels shall be measured and ascertained, anything in the said recited act of the sixth of George I, or any other act or acts of parliament, to the contrary notwithstanding. K = Along rabbet of keel from back of main post to perpendicular from forepart of main stem below bowsprit, minus 3/5 B B = greatest breadth outside to outside exclusive of doublings D = ½ B Divisor = 94 U.S. Stat. L, vol. I, p. 55. United States Tonnage Law, passed 1st September 1789. Known as 'Custom House Measurement'. (1789) The length was measured from the fore part of the main stem, to the after part of the sternpost, above the upper deck. From this, 3/5 of the beam was deducted in order to obtain the Length for Tonnage. The breadth was measured at the broadest part above the main wales. The depth varied. In single decked vessels the depth was measured from the underside of the deck plank to the ceiling in the hold. In ships with two or more decks, the depth was taken to be half the breadth. K = the fore part of the main stem, to the after part of the sternpost, above the upper deck minus 3/5 B B = the broadest part above the main wales D = Single decked: underside of deck plank to ceiling in hold. Double decked = ½ B Divisor = 95 Joshua Humphreys, War Department Papers TNB06 (1793) http://wardepartmentpapers.org/document.php?id=9527 In the first place to find the length of straight rabbet forward you take 3/5 of the beam as usual from that point to the after part of the stern post allowing its width for measurement not to exceed 1/12 of the beam. That length being determined you then multiply it by the length of beam & that product by the height of the gundeck beam amidship on the top of the beam added to half of her waste amids which last product divide by 95 which will give the number of ton required. K = length of straight rabbet forward minus 3/5 B to after side stern post B = width at midship beam within board D = top of gun deck beam to floor plus ½ B Divisor = 95 The following are provided in Steel’s Vade Mecum (1805) THE GENERAL RULES OBSERVED FOR MEASURING THE TONNAGE OF SHIPS IN THE KING'S AND MERCHANTS’ SERVICE, ARE AS FOLLOW. Let fall a perpendicular from the foreside of the stem, at the height of the hawse-holes*, and another perpendicular from the back of the main post, at the height of the wing transom. From the length between these perpendiculars, deduct three-fifths of the extreme breadth+, and likewise as many 21/2 inches as the wing transom is high from the upper edge of the keel, and the remainder is accounted the length of the keel for tonnage. Then multiply the length of the keel for tonnage by the extreme breadth, and that product by half the extreme breadth; then, dividing by 94, the quotient will be the burthen in what is denominated Builder's Tonnage. Or, Multiply the length of the keel for tonnage by the square of the extreme breadth, and divide the product by 188, the quotient will be the burthen in tons. K = length from foreside stem at hawse holes to back of main post at wing transom minus 3/5 B minus 2 ½ “ per height of wing transom above upper edge of keel. B = extreme breadth outside to outside D = ½ B Divisor = 94 * In the merchant-service, this perpendicular is let fall from the foreside of the stem, at the height of the wing transom, by reason of the hawse-holes being generally so very high, and their stems also having a great rake forward. + By the extreme breadth, is meant the breadth taken from timber to timber outside, with the thickness of the bottom on each side added; or, which is the same thing, the thickness of the bottom on each side added to the moulded breadth. RULES BY MR. PARKYNS, LATE OF HIS MAJESTY's YARD, CHATHAM. RULE I. For Sharp Ships, particularly those of the Royal Navy, Take the length on the gun-deck, from the rabbet of the stem to the rabbet of the stern-post, or between the perpendiculars. Then take 23/24 of this length, and call if the keel for tonnage: To the extreme breadth add the length of the gun-deck, or length between the perpendiculars; then take 1/23 of this sum, and call it the depth for tonnage, Set up this depth from the limber strake; and, at that height, take a breadth also from out to outside of the plank at dead-flat, and another breadth between that and the limber strake; add together the extreme breadth and these two breadths; take one-third of the sum, and call it the breadth for tonnage. Multiply the length for tonnage by the depth for tonnage, and the product by the breadth for tonnage, and divide by 49. The quotient will be the burthen in tons nearly. K = Length on gun deck (between perpendiculars) x 23/24 B = at height D above limber strake take breadth outside to outside. Add to extreme breadth plus breadth at limber strake divide the sum by 3. D = extreme breadth plus LBP x 1/23 Divisor = 49 Rule II. For Ships of Burthen, or Commercial Ships, in general, Take the length of the lower deck, from the rabbet of the stem to the rabbet of the stem-post; then take 31/32 of this length, and call it the keel for tonnage. To the extreme breadth add the length of the lower deck; then take 3/55 of the sum, and call it the depth for tonnage. Set up this depth from the limber strake; and, at that height, take a breadth also from out to outside of the plank at dead-flat. Take another at two-thirds of this height, and another at one-third of the height. Add the extreme breadth and these three breadths together, and take one fourth of the sum for the breadth for tonnage. Multiply the length for tonnage by the depth for tonnage and the product by the breadth for tonnage, and divide by 36.6666 or 36 2/3 and the quotient will be the burthen in tons. K = Length on lower deck (between perpendiculars or LBP) x 31/32 B = at height D above limber strake take breadth outside to outside at dead flat. Take second at 2/3 this height and a third at ½ the height. Add to extreme breadth plus these three breadths and divide the sum by 4. D = extreme breadth plus LBP x 3/55 Divisor = 36 2/3 (36.6666)

Well, I’m back. I have taken a brief detour into the realm of tunnage admeasurement, not simply for my personal education, but because it is so closely intertwined with the development of accurate determination of displacement for a vessel. I won’t bore you with a history of tunnage admeasurement – that is very well covered in numerous other more detailed studies (See attached bibliography) Tunnage References.pdf Saulisbury (1966a) offers the following very concise description of admeasurement: Some sort of tonnage measurement, based on some arbitrary and artificial unit of capacity or weight, was necessarily closely connected with the development of merchant shipping. Warships could be described satisfactorily by the number of men or guns carried or by the number of oars or men required to propel them, and even today some small craft can be classed by such 'natural' units. Ships designed to carry cargo, however and particularly those driven by sails-needed altogether different treatment. In default of statutory enactments, an artificial unit which was to be generally acceptable had to evolve by usage alone, and this demanded a state of economic activity in which large quantities of a common commodity were frequently shipped over a wide area. Many of the references (see attachment) address the inaccuracy of the methodology used – essentially, the maximum breadth was a key factor, the length of keel for tunnage was a derived measurement (that is, it was not a measurable length but rather derived from other values, of which more below), and the depth of hold was, likewise, generally derived from the breadth. The result was that two vessels having the same breadth and length (whether on gun deck or between perpendiculars) would have the same tunnage, with no account of the shape of the ship. A sharp vessel with large deadrise would have the same tunnage as one with a flatter bottom and full body. While this was good for the collection of customs duties, it was not equitable across vessels nor a true reflection of cargo capacity. For a model builder, some important considerations arise – The Length of Keel provided in many references works (such as Winfield) are not always able to be identified as actual length of keel or length of keel for tunnage – two very different values! Period documents are not always clear as to which methodology is used to determine the tunnage, and in many cases (as we shall soon see) the value is not able to be recreated based on available data. Methods for determining the tunnage changed many times over the more than 300 years of interest, varying not only by nation but also by region. Some terminology may be of use before I look at a few of the methods used to admeasure tunnage. Admeasurement: The measurement of cargo capacity, usually in volume (tuns) Ton/tonnage: The term "ton" can describe both weight and volume, so to avoid confusion, ton and tonnage will be used for weights and displacements. Tun/tunnage: These terms will be used for volumetric measures (admeasurement).