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Seeking information on determining load waterline


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#21
roach101761

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I have identified some design plans above.  What other well know design plans are there?  Also, do the original as built plans of ships acquired by the admiralty indicate a load water line.  Somewhere I have seen the survey of Bethia(The Bounty before she was  Bounty)   Also the cutter Lady Hammond before she was Lady Hammond.  Do these surveys have Load water lines on them?

 

I say, lets identify known plans or surveys and where they are published and take a look at what was recorded originally upon acquisition by the admiralty.

 

Phil


Edited by roach101761, 07 March 2015 - 03:06 PM.

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#22
trippwj

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Looking through volume I of the Humphreys Papers, there are numerous references to the draught of water, but I only find the following that hints at the process (note that the upper drawing was added by the transcriptionist to aid in understanding the process):

 

humphreys1.jpg

 

There are also indications that either Joshua or Samuel did utilize mathematical techniques during the 19th century:

 

The Franklin left Philadelphia June 24th 1817 at 8 o’clock AM. July 17 the Franklin took in 29 long 32 pdrs which weighted 1781 cwt. This weight settled the ship 3½ inches. Her draught of water after these guns were taken in was Aft 23 – 1, forwd20 – 3. At this depth it required 19½ tons to settle the ship 1 inch.

 

The originals can be viewed at the link below.  Note that this volume is a long term set of notes for use by the builder - starts with the 1719 Establishment and includes a bit of everything from brief descriptions of vessels to a design for a new ships steering wheel.  Some interesting stuff!

 

Humphreys, Joshua. “Volume 1: ‘Principal Dimensions.’  Joshua Humphreys Papers (Collection 0306).” Text. Philadelphia, 1770-1838. Historical Society of Pennsylvania. http://digitallibrar...object_id/10371and the description is at http://www2.hsp.org/...phreys306.html.


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Wayne

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#23
rybakov

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I went throug Nautical Sschool at a time when calculators were not programmable and computers were room sized affairs.

Sometimes in Naval Architecture we were asked to determine the displacement of a ship, at a given immersion, from the lines plan.

We would start by determining the areas of the sections, then plot the obtained results along the x axis of a graph, and then

calculate the area of the graph and that would be the immersed volume, wich multiplied by water density would give us the buoyancy.

To undertake all those calculation we used Simpson's Rule, so named ater an English mathematician Thomas Simpson (1710-1761)-

So I think that from approximately 1750 on the shipwrights would be quite able to figure out immersions and displacements.

 

Anyway, that's just my feeling.

 

All the best

Zeh


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#24
jbshan

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"Simpson's Rule"

That's certainly the first half of the equation, but they then have to get the weight of the ship, guns and stores, etc. correct, enlarging the hull if necessary.  The first US ships of the line sat fairly low in the water, if I recall, so the ports were too close to the water, and those were 1820 and later.

I have seen methods where you mark out squares of a curved enclosed shape, then little squares, then littler squares, until you have covered all of the shape, to measure the area.  Is this similar?


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#25
trippwj

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Mr. Berry (see my above post on the 1924 conference) offers the following:

 

The method used by Mr. (afterwards Sir Anthony) Deane of calculating the displacement of ships is unknown; but it appears that about 1700 this was effected by dividing the body by equidistant sections, calculating the area of each and thence obtaining the displacement by some rough process of quadrature. There is, however, no record of any such calculations, and it is probable they were but rarely performed.

 

Nowacki and Ferreiro, in their 2003 paper “Historical Roots of the Theory of Hydrostatic Stability of Ships”, offer the following:

 

Deane demonstrates two methods to calculate the area underneath waterlines at each “bend” or frame of the hull; using either (1) an approximation for the area of a quarter-circle or (2) by dividing the area into rectangles and triangles. Deane then sums the areas for each frame, multiplies by the frame spacing and multiplies the volume by the specific weight of water to obtain the displacement. He does this for several different waterlines, including the desired waterline below the gunports. When a ship is launched, he can immediately determine the light displacement, and then calculate how much weight should be added to arrive at the design waterline.


Edited by trippwj, 07 March 2015 - 08:25 PM.

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Wayne

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#26
trippwj

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Continuing to ponder and contemplate, let me ask whether anyone has found any contracts from, say, prior to 1750 that include the draught of water? 


Wayne

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#27
jbshan

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They put into the specs where they *wanted* the ship to float, but if wishes were horses ...


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#28
roach101761

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I reviewed my materials, and although I have no contracts from prior to 1750 I did review the Sloop of War Peacock contract found in the History of American Sailing ships.  No mention of the Load Water Line.  It gives the general specifics of the ship in the contract and advises it will be  built according to the plan provided by the Navy Department.  A William Doughty Plan.  This contract is with Noah and Adam Brown of New York.   The Dallas revenue cutter was built to the Doughty Mid sized revenue cutter plan and was also built by the Browns. See Post #      above. 

 

Maybe its time we think in a different direction.  My observations.

 

The Math was there to be able to determine the Load water line. However, there may have been relatively few mathematicians up to the task, and fewer who were shipwrights.  As time marches forward and more scientific principals are applied to ship design, more designers have the math skills and have a more formal education. 

 

In the design plans I have seen, no load water lines appear.

 

It is likely that the ship designer and shipwright has a very good Idea where the ship would float but did not put it on the plan.

 

If you look at the plans we have, even us ship modelers can look at the plan and see where the ship should float, or was meant to float probably within a foot.

 

Although ships have sunk at launching due to stability problems, I know of none that sank because the were too heavy and settled below their maximum sustainable load.

 

They always floated High and Dry as light ships.

 

The test for the new ship comes after it was fully outfitted with Masts, equipment and Ballast for stability.  I think in most cases the ship still floated High and was a light ship.

 

The test becomes whether it can carry the load that was intended.  Such as the stores for a 400 man frigate crew for a cruize of 3 to 6 months or longer together with all its guns.  I think the ship fails if it can not carry its intended load to be useful.

 

Achieving the Load Water line I think was easy because ballast and stores are a very flexible thing. If stone takes too much room, use Iron bar.  If Iron bar takes too much space use Kentledge.  In the end it comes down to how much beef, pork, peas, water and rum you can carry to support the crew or how much usable space you have for cargo storage.

 

Thinking about all that I have read, in warships , best sailing trim and the load water line was subject to constant management during a cruize. Every meal eaten by the crew changed the draft of the vessel.

 

Let us not forget that, depending on the Ocean, salt water densities vary.  In some waters you can carry more, in others you can carry less.  I pulled down my Nicholls's Seamanship and Nautical Knowledge, C.1942 together with a Blue Jacket Manual or two.  I reviewed Plimsoll lines and load marks.

 

In the merchant service the crews were smaller.  We know that many companies and their captains ignored loading conventions. After all if he can get it in the ship, the ship must be able to carry it.  Right?  On a trip the load line did not vary by much as the crew was too small to have an impact.  We all have seen the pictures and read the stories.

 

Saying all of this perhaps the load water line was not a primary design concern.  In fact, it might have been a minor thing.  The ship will float where it will.  You must add or subtract weight to make it sail correctly and efficiently.

 

Perhaps Load lines came much later as safety at sea regulations?

 

I reviewed all the posts above.  Many make the same points I am making here.  It looks like determining a load water line in an existing ship was learning exercise to determine if you could apply the knowledge to build the next ship.

 

Wayne, in any of your research do you have any references to load water lines as part of a design parameter, or is calculating it always an exercise on and existing ship?

 

Phil


Edited by roach101761, 10 March 2015 - 01:57 AM.

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#29
trippwj

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Phil -

 

I have come across secondary sources that indicate there were some calculations of displacement done as early as ~1634 in Britain (see, for example, the contract for HMS Sovereign of the Seas (later Royal Sovereign), pages xcii-xcv in The Autobiography of Phineas Pett, ed. by W. G. Perrin (1918) available at http://archive.org/d...hyofp00pettuoft) where both a "draught of water" (fully loaded WL) of 21' 3" and a "swimming line" (light WL) of 18' 9" are provided (these did change during development of the ship).  In the same year, two of Phineas Pett's relatives (his son and nephew, both named Peter) were building ships in Woolwich and Deptford, and providing accurate estimates of their draft and freeboard to gunports, well before launch.  See Trinity House of Deptford Transactions, 1609-35 London Record Society 19 pages 135 & 142 for details ( http://www.british-h...ecord-soc/vol19 ).

 

While these ships indicate that there was an ability, they are more the exception than the rule. By the 1600's, the importance of designing ships of war such that the lower gunports had adequate freeboard when the ship was fully loaded was a key consideration.

 

From several centuries earlier, in Venice, the Capitulare navium (Maritime statutes) of 1255, established load waterlines according to the age of the ship, using an iron cross fixed to the hull.  The Republic of Genoa (100 years later) adopted a statute that established freeboards for different routes based on sea conditions; higher for the open waters of the Bay of Biscay, lower for the protected Mediterranean (from Ferreiro, Down from the Mountain, 2004).

 

 


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Wayne

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#30
michaelpsutton2

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Tonight, I have spent a little time looking at a number of plans from the NMM website of ships from the latter half of the 1700's. The majority seem to indicate a load waterline.

 

On an awful lot of them the load waterline is parallel to a line drawn between the lower edges of the first and last ports of the lowest gun deck. It is set so that it is very near to the lower edge of the main wale at it's lowest point. On some ships it may be slightly above or below that spot . An example shown below is the 3rd rate HMS Alfred of 1778. It might be said to be a good representative of most but not all the draughts of this period.

 

The question though becomes .....were these ship designed in advance to float at this level or was the line arbitrarily placed on the plans in this position simply as a formality.

 

One reads time and time again that there was difficulty with getting the lower deck guns high enough out of the water.The plans show plenty of freeboard. 

 

Maybe the ships were designed to use these waterlines but their captains overloaded them.

 

Somebody with access to more of the archives than myself might compile a list of how much water the vessals were known to have drawn. This could be compared to the plans.

 

Obviously the ships rose and fell with the amount of supplies ballast etc.

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  • HMS Alfred 1778 (74 Alfred class) sheer & carving.jpg

Edited by michaelpsutton2, 11 March 2015 - 03:03 AM.

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#31
roach101761

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Michael

 

I have looked at the plan above and I can not see where the load water line is marked "load water line" or "LWL".  Also, on your copy of the plan, is there a date of the plan?  I am not referring to the title of the plan.

 

Phil


Edited by roach101761, 13 March 2015 - 01:57 AM.

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#32
trippwj

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Continuing on my quest, Ferreiro provides the following information (source: page 340-341 in Ferreiro, L., 2004: Down from the mountain : the birth of naval architecture in the scientific revolution, 1600-1800. University of London, 550 pp. http://ethos.bl.uk/O...bl.ethos.411610).:

 

In Venice, the Capitulare navium (Maritime statutes) of 1255 established load waterlines according to the age of the ship, using an iron cross fixed to the hull.  One hundred years later, the Republic of Genoa adopted a statute that established freeboards for different routes based on sea conditions; higher for the open waters of the Bay of Biscay, lower for the protected Mediterranean. There was a clear appreciation for the practical requirements of weight control, based on the expected weather and seas conditions and state of the ship, even if there were no means of predicting those requirements during its construction. The actual load waterlines were not marked on the hull, and were rarely marked on drawings in ship manuscripts prior to about 1650, however, most of Matthew Baker's hull elevations in his manuscript Fragments of Ancient English Shipwrightry mark the "swimming line", though there is no text or calculation to support it.

 

So, then, what we have to work from is that there was an awareness in the 13th century of the importance of an identified load waterline, if not a method to determine it during construction.  This would align well with the mass production method of Venetian construction (which is a fascinating topic to delve into - quite a bit of discussion around the concept of "Whole-Moulding" and similarity between the Mediterranean and European approaches, but I digress...)  and somewhat standardized proportions for the rising, narrowing and hauling down, for example.

 

We also see, then, that Mathew Baker (and others) had some ability to pre-determine the "swimming line" during the 16th century.  Richard Barker (1988 - “Many May Peruse Us”: Ribbands, Moulds and Dodels in the Dockyards. Revista da Universidade de Coimbra, XXXIV, 539–559. http://home.clara.ne...s87mmpu-txt.htm). notes that William Bourne ( Treasure for Travelers, 1578) describes the use of models, to scale to measure the displacement of the corresponding ship. He describes waterplanes and load-marks in the process. This may have been purely theoretical on Bourne's part when drafted in 1572 (it was published in 1578).

 

So - I am slowly narrowing the timeframe where initial calculations may have been used to pre-determine the "swimming line" and "draught of water" - but not there yet!  On to more French, Dutch and Italian research works! 

 

 


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Wayne

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#33
roach101761

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Wayne

 

Pulled down my copy of Dean's Doctrine of Naval Architecture, 1670 edited by Brian Lavery copyright 1981,Conway Maritime Press.  I do not know why I did not pull it down a couple of weeks ago.  I guess I presumed you had reviewed it as you mention Dean above, or perhaps I just forgot I had it.  Hard to keep track of my books.  I pulled it down for another purpose today. From reading above you may be reading from a copy of the actual manuscript.  I have only read parts of it today but Lavery's introduction explains exactly what the work consists of and why it was written in the first place.  There is a whole section on "The water-line or greatest depth of water the ship must draw, completely gunned, rigged, victualled,and stored".

 

Through this section and the sections that follow, it is apparent that he is aware, and has the ability to design a ship which will float on the  load water line he designed and fit for its intended purpose.   He explains how he does it but does not give the math.  It kind of reads like he backed his way into the result that proper math would have calculated.   As an example:   You have a pile of 49 objects and you desire to know how many separate equal piles of objects you can make.  Rather than solve with math, you keep physically dividing the pile until you get to 7 piles of 7 objects each.  

 

As to your earlier post in which you were looking for contracts for ships prior to 1750,  Lavery's book contains in its appendix  the specifications of a third rate of 1666 and states that the original before it was amended, was for the Speaker of 1649(renamed Mary in 1660) The designer of the ship was Christopher Pett who drew up the first version of the specification.     Alas it is only a contract specification for a builder.  It does not mention LOL.  This seems logical to me because the builder would not be responsible for its design, only its construction pursuant to the contract. 

 

Phil


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#34
mtaylor

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Wayne,

 

For French ships, Boudroit's The 74 Gun Ship gets into a discussion of this in passing.  He describes how the "Surveyor" training started with heavy maths and what was involved in the training.  Part of the drafting of new ships was determining the water line. I'm not sure (it didn't say or I overlooked it) when this practice started. 


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#35
trippwj

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So, to summarize key data thus far, I present this lovely chronological table.  Still a work in progress so no firm conclusions - please let me know if I have missed something germane (which is highly probable....)

 

chronology_1.png


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Wayne

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#36
lehmann

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I'm from the camp of roach101761:  LWL is a nice to have, easy to draw, but very difficult to predict.  Even assuming the mathematics for determining displacement were used and measuring the area of cross-sections were accurate (having tried it, counting squares to measure areas is not that accurate, and the planimeter wasn't invented until 1814 and not readily available until at least 1854 [Wikipedia: planimeter]) there is the other side of the equation: estimating weights and the distribution of weight (center of gravity).  I've designed a few small boats and the practical problem of estimating the weights of all the parts of even a 14 ft dingy is intimidating.  Specifying the location of the lead fin keel for a modern yacht is downright scary.  For a wooden ship, each piece has an irregular shape that is custom fitted to the preceding framework, so there are no drawings to base calculations.  I think modern ship builders can do this because they use 3D solid modelling and the steel plates, gussets, etc are laser cut.  Even then, major components are still weighed.  Furthermore, with wood, what is the moisture content?  The planking swells considerably after the hull is put in the water, so even if you weight each fitted plank just before attaching it to the frames, your numbers are suspect.

 

Another issue you need to consider is, as I understand it, that early design drawings were to the inside of the planking so that the builder can use them for directly laying out the frames.  My impression is that creating line drawings to the outside of the planking is a relatively new concept, which, I would assume, coincided with the development or acceptance of mathematical methods, which need the external shape.  This, of course, wouldn't apply to lines taken off existing hulls.  

 

Given the large uncertainty in the as-built weight and weight distribution of a large wooden vessel, I suggest that the only method of prediction is how a hull of similar form and construction floated.  Tradition isn't just from a lack of knowledge or an aversion to risk (or ridicule): staying close to successful designs allows builders to build.  The historian of engineering, Henry Petroski, has written extensively on the benefits and risks of the trial-and-error development. Since all ships carry a significant weight of cargo, the final water line for profitability, stability or best sailing trim is determined by the ship's officers.  Hull shapes or construction methods that couldn't do their job likely became evolutionary dead-ends.  In this sense, an interesting study would be to compare, with modern naval architectural tools for displacement, stability and seaworthiness, the design of hulls which were widely used to those that were only built once.  I suspect this happened quite often as construction technology with steel created more design options, which justified the cost of naval architects and marine engineers.

 

Lastly, I wonder if there were intermediate stages between the initial drawing and the final construction that could be used to empirically determine where a ship will float.  Half-hull models could be used to determine displacement; and builder's models could help with center of gravity.  As a research engineer, I like having a prototype to test new features for unintended consequences and to verify my estimates.

 

PS.  I just checked the drawings in Chapman's Architectura Navalis Mercatoria (ANM). (1768)  The lines are all to the inside of the planking.  I also see that Chapman, in Treatise on Shipbuilding, shows the calculation method for a ship's load curves (draft vs displacement).  The curves for many if not all the of the drawings are show in Plates XXIII and XXIX of ANM..  The calculation looks like it's based on Simpson's Rule using the areas of each water line, although I'd have to verify this as the multipliers aren't quite what I would expect.  

 

Also, quadrature methods of numerical integration were know before Simpson derived that general formula that is attributed to him.  Kepler used it long before that, so in German, its known as Keplersche Fassregel.  


Edited by lehmann, 12 April 2015 - 11:07 PM.

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#37
trippwj

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Bruce -

 

Thank you for this - you have summarized quite neatly many of the areas that I am trying to dig into in order to understand this transition to pre-determined draught (I am using draught here as meaning the level on the vessel that she is designed to float when fully burdened.  Measured from the base of the keel) and displacement!

 

I pulled some of your observations from your post and provide some partial responses - I still have a bunch more work to do!

 

           LWL is a nice to have, easy to draw, but very difficult to predict.

 

That is really the basis for my project – at some point, it became Need to know, not just nice to know, and thus a component to the design of a ship.  For example, as the gun port came into use, it became important to have adequate freeboard – to keep the wet stuff a safe distance below the openings into the hull.  While an existing vessel with adequate freeboard could serve as a model for the current generation, ships grew over time and the shape changed, so that what was good before no longer applied.

 

 early design drawings were to the inside of the planking so that the builder can use them for directly laying out the frames.

 

This is true – since the primary purpose was to determine the shape of the frames.  However, since the thickness of the planking was generally known (either “institutional knowledge” or specified in the requirements), adding that to the dimensions was an easy step for the designer. 

 

Given the large uncertainty in the as-built weight and weight distribution of a large wooden vessel, I suggest that the only method of prediction is how a hull of similar form and construction floated.

 

This is a good point, and an area that I am gathering more information on.  Some of the earliest treatise (British) discussing the determination of displacement (and draught) use “plug numbers” to come up with the weight of ships to then try to determine both the ballast required to reach a desired draught and the draught itself.

 

Since all ships carry a significant weight of cargo, the final water line for profitability, stability or best sailing trim is determined by the ship's officers.

 

This has always been an issue – many of the officers during the days of sail had a tendency to over-mast vessels, resulting in poor sailing qualities and reduced stability.  There was also a lot of fidgeting with ballast and stores distribution to alter the trim to that desired by the master – sometimes to the detriment of effective performance.  A good case study would relate to the early American frigates, where the Secretary of War basically threw up his hands and directed that each Captain and Constructor should mast the frigate as they saw fit.  Some performed much better than others….

 

Half-hull models could be used to determine displacement; and builder's models could help with center of gravity. 

 

There was actually an attempt to do this, although it failed miserably since building a model of true scale (not just dimensions, but also weights and trim) was not possible, and model testing was rudimentary and not an accurate indicator of 1:1 build performance.

 

Among the interesting research papers I have come across is one from 2008 entitled "Technical Writing in English Renaissance Shipwrightery: Breaching the Shoals of Orality" by Elizabeth Tebeaux - well worth the read if you get the opportunity!


Wayne

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#38
jbshan

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Just a couple of notes to show the difficulty the old boys had:

Records:

One of the reasons for having plans instead of just specs was that 10 years later you had a good, duplicateable record of a ships form.  You could then tweak it based on performance.  Slade was a master of tweaking.   A few times the British got caught when they had committed to a large number of ships so that subsequent vessels were being built before the first ones had a good trial.  I'm talking over a couple of hundred years' time.

Balance of rig to hull:

USF Constitution had real problems keeping masts whole until they reduced the ballast and increased the size of the masts.  The balancing out of the rolling motion (from too much ballast) the strength of the masts and the ability of the hull to carry sail took a while to work out.

Use or purpose of a vessel:

Nelson as a junior captain had the task of sailing a French prize to the West Indies.  He had to water from a tender partway there because he didn't have enough stowage.  If he had taken aboard enough water, the ship would have been too deep.  The French design was for quick raids, not long voyages.

You often see something like 'draft aft, draft forward with: 4 months' provision, home waters, foreign waters, 6 months' provision and 3 months' water; they were aware of most of these things but struggled to get the proper compromises in the design.  Even up into the second half of the 1800s they hadn't quite got everything figured out.  I think it was just a lack of maths or calculation capacity.  Titanic was still mostly worked out by arithmetic.  I use that example not because she sank, but because they looked very carefully into her construction so we have some records of the process.


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#39
druxey

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Perhaps another source for earlier design  (to add to your list, Wayne) is from the so-called "Newton Manuscript': a transcription by Sir Isaac Newton of a treatise c.1600. This gives instructions for designing ships, both naval and merchant. It is given in its entirety in an article in Mariners' Mirror, 1994, Volume 80, No.1. The 67 'Propositions' given describe how to design a ship.


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#40
lehmann

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Replies in blue...

 

           LWL is a nice to have, easy to draw, but very difficult to predict.

 

That is really the basis for my project – at some point, it became Need to know, not just nice to know, and thus a component to the design of a ship.  For example, as the gun port came into use, it became important to have adequate freeboard – to keep the wet stuff a safe distance below the openings into the hull.  While an existing vessel with adequate freeboard could serve as a model for the current generation, ships grew over time and the shape changed, so that what was good before no longer applied.

 

I alluded to this in my comment about the development of naval architecture. As the needs, more cargo, more guns, more sail, etc.,  increased, the rules of thumb could no longer keep up, so the engineering had to be developed to keep the risk tolerable.  Can you show a trend of how the use, not just the knowledge, of navel engineering increased as requirements increased?  Note, that it is difficult to tell whether needs drove new knowledge, or knowledge created opportunities.  

 

 

Given the large uncertainty in the as-built weight and weight distribution of a large wooden vessel, I suggest that the only method of prediction is how a hull of similar form and construction floated.

 

This is a good point, and an area that I am gathering more information on.  Some of the earliest treatise (British) discussing the determination of displacement (and draught) use “plug numbers” to come up with the weight of ships to then try to determine both the ballast required to reach a desired draught and the draught itself.

 

Chapman knew how to develop load curves in 1760's for estimating how cargo weight affected draught.   The basic question is could he predict the weight of a fully equipped vessel with empty holds?  

 

There is also the question of what tolerance would have been acceptable or detected?  Did ship owners require a performance test in terms of how much cargo could be stowed at an determined draught?   Are there records of ship owners taking shipwrights to court?  


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Bruce

  • USS Constitution: Scratch build solid hull 1:96 scale
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