Danish man-of-war Hummeren 1624 – entry of the round tuck stern

[-Waldemar-]

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Thank you, Roger. Everything you have written seems perfectly correct. I would only add, just to be sure, that in this particular case the calculations were carried out (if they were) actually not for ancient hull form, but for a quite fanciful shape, created in a pretty arbitrary way, or maybe better: without taking into account ancient design rules or procedures. This is precisely the crux of the matter. Then again, as in probably most ‘archaeological’ cases.

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[fred.hocker]

Roger's comments first: I would be willing to bet that there have been vastly more losses to fire than capsizing, and most of the safety procedures in the operation of modern ships (have some experience here as crew) usually are related to fire, man overboard, or abandoning a sinking (upright) ship. Capsizing (other than in brand new ships) is usually not the direct result of design but of mass shifting inside the ship, causing a change in center of gravity and thus metacentric height/stability. As a working crewman, I never worried about capsizing as a likely occurrence at sea in a ship with a proven performance record, although knockdowns are a concern in certain weather systems (but that is something slightly different to capsizing). It is always necessary to think about it when doing things that might change the center of gravity. Offloading ballast at haulout is a good example - ships do fall over in the process of drydocking. Firefighting is another area where one has to think about it, as spraying a lot of water into a ship to douse a fire can affect stability.

Most modern marine insurance actuarial tables are based on the premise, from statistical evidence, that the vast majority of ship losses are caused by human error rather than technical malfunctions (which includes poor design). Statistically, the two most common types of ship loss in the past 250 years are fire or running into hard things at the edge of the water or in the water (one of the reasons that most ship losses occur within sight of shore). Unprovoked capsize due to poor design is rare in operational ships.

In purely technical terms, Vasa did not capsize, in that it did not roll over. It heeled to an angle of about 15 degrees and reached equilibrium with the open lower gunports in the water and stayed there. So it foundered, rather than capsizing. But the design flaw did result in poor initial stability, as Roger notes.

It is interesting to consider that even thought Bougier formulated the first accurate mathematical model of ship stability and the metacentre in the mid-1700s, it was not used as a tool in the design of ships in any serious way for almost another century. There is an excellent book on the development of the stability mathematics by Larrie Ferreiro.

Fred

 

[fred.hocker]

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Fred, I admit that at this point, which is after discovering the Hummeren–Project creation, I have a bit of a problem with the competitive presentation of my reading and subsequent interpretation of this important and otherwise fantastic plan. Do you think it's still a good idea if there's going to be some wooden bubble floating around as a replica of Hummeren 1624 anyway?

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Waldemar, as far as I know the Hummeren project has been going for a decade or more but has not yet accummulated the funding necessary for construction and outfitting. This happens with some replica projects that never get built, and for others that take a while to generate enough momemtum to get to the stage of physical reality. I do not know the project well enough to be able to guess how this one will land. As I said, I know some of the people and have been approached about helping to recreate the armament, but I do not really know much about the current status of the project or the likelihood that it will build an actual ship.

Fred

 

[Roger Pellett]

Fred,
Thanks for your comments. I agree that current hydrostatic analysis techniques that were not available in the past should ensure that modern vessels have sufficient initial stability, but they cannot ensure that poor loading will not raise the center of gravity to an unsafe condition. It’s probably no coincidence that many serious stability related accidents today seem to involve ferries where loading is variable.

Vasa’s sinking is a classic example of poor initial stability. Eastland’s sinking approximately 300 years later exhibited some of the same characteristics. Leaving harbor she suddenly heeled to one side but didn’t capsize. She then rolled back to an even keel and completed her voyage. Those involved with her management apparently ignored the incident. Several months later, a “fluid” cargo (passengers), free surface water in her ballast tank, and a open gangway in the side of her hull proved to be the fatal combination. I agree with your point that in these two situations poor initial stability itself did not cause the accidents. To be precise they were “stability related founderings” My wordsmithing!

Laurie Ferriero’s book is indeed an interesting analysis of the scientific beginnings of Naval Architecture. I agree that shipwrights of the time lacked the ability to calculate Metacentric height even if they had been aware of its existence. He is one of several authors (myself included) with degrees in Naval Architecture and Marine Engineering from the University of Michigan who are published authors. They must put something in the water in Ann Arbor.

Roger

 

[-Waldemar-]

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Thank you again, gentlemen, for your entries.

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First, at Maarten's request, a reproduction of a graphic I found despite the still makeshift conditions, which depicts an English ship from the first half of the 17th century (British archives). If the museum description is to be believed – made most likely in 1648, and most likely depicting Swallow 1634 (although it has suspiciously un-English style decoration).

Regardless of the identification, it is reasonable to think that this time the artist probably reproduced quite reliably the breaks in the strakes, just below the ends of the wing transom, as vividly reminiscent of those found on the Swedish ship Bodekull 1659. It is true that there are not many such confirming examples of the transitional tuck form, nevertheless this period may have been quite short-lived, plus the artists may simply not have bothered with such insignificant and rather inconspicuous subtleties. After all, all the other butts of the planks that make up the strakes were usually not rendered by them either.

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To buy some time (I'm still away from home, and have additionally decided to make apparently minor but labour-intensive adjustments to the first variant), for now, a slightly out-of-sequence proposal for interpreting the original master frame design of the Hummeren 1624.

While it is true that the original master frame drawing can be taken quite literally as well, nevertheless, in my opinion, it rather captures the overall intention of the designer just in a quite conventional way, specifically:

– the use of only one (basic) sweep to shape the underwater section of the hull; given the low height allocated to this section (i.e. from deadrise level to maximum breadth level), the use of more sweeps would indeed be quite impractical and essentially unnecessarily cumbersome,
– together with the longitudinal projections determines the width of the ‘flat’ and its deadrise,
– finally, and very importantly, the garboard strake having a steep slope is a clear indication to the actual ship’s builder that the bottom of the ship should join the keel in the sharpest possible way, and this along the entire length of the hull.

In particular, adherence to the last-mentioned characteristic, due to the proportions and general shape of the hull, is of paramount importance in order to achieve at least satisfactory sailing properties of the designed ship, specifically its ability to keep to the wind. Otherwise, a broad ship with a shallow draft would have quite the character of a sail-powered raft, capable of moving basically only with the direction of the wind.

Also for exactly this purpose, the original design provides for a very large deadrise for a ship of this size and period. In these circumstances, the reconstruction should maximise both of these possibilities, as envisaged and given by Balfour, instead of rather haphazardly deforming the hull into a form of a bubble convex everywhere, as was unfortunately done in the Hummeren–Project reconstruction project.

For the practical realisation of this purpose in the proposed interpretation, that is, to maintain at least an acceptable weatherliness of the ship, two suitable sweeps replace the bottom („flat”) line, marked here in green. It is worth recalling at this point that this ‘bottom line’, connecting the hull body proper to the keel assembly, was usually depicted on period plans (both in the Mediterranean and North Continental traditions) precisely in a simplified, conventional manner as a straight line to be replaced by other curves according to the proper, full-scale procedures used in shipyards.

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In the period, the issue of the shape of this particular section of the hull, and the resulting properties, is perhaps most extensively commented on by the Englishman Robert Dudley, a professional shipwright among others, in his work Arcano del Mare, published in 1646, and which even merited an accompanying illustrative diagram, specifically made for this purpose (shown below). As an aside, it may also be added that Robert Dudley, still in the mid-17th century, described ship design exclusively in purely Mediterranean fashion.

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In contrast, taking into account the general proportions of the hull, it is quite safe to assume, even before its mathematical evaluation, that the lateral stability will not only not be compromised in any way in this particular case, but may even turn out to be still too high in practice, which is also not quite beneficial for either the ship or the crew. In this light, the slight loss of volume of the submerged part of the hull (the value of which also affects the stability of the ship), resulting from the proposed interpretation, should at least not be the source of any problem.

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[Roger Pellett]

Warships of the gunnery era did not favor high Metacentric height as very high initial stability caused quick rolling that interfered with accurate gunnery.

Roger

 

[-Waldemar-]

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Thanks, Roger, for an apt and, hopefully for some, a practically useful extension or addendum. Right or wrong, nevertheless, personally, in addition to my innate tendency to be laconic, I additionally try to be as concise as possible so as not to force readers to read endlessly. .

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[Martes]

If the museum description is to be believed – made most likely in 1648, and most likely depicting Swallow 1632 (although it has suspiciously un-English style decoration).

By the look of the decorations I would very carefully suppose this is not an English-built ship, more likely one of the Royalist Dutch-built privateers.

The Swallow's contemporary rebuild of the Lion seems to have looked like this:

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File:An English ship (The Lion?) c.1648 RCIN 912934.jpg - Wikimedia Commons

commons.wikimedia.org

 

[-Waldemar-]

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Thank you very much, Martes. Your post has even given me some relief about the rather questionable museum identification of the ship depicted in the reproduced above graphic .


@fred.hocker

Fred, with a bit of time on your hands, may I ask you to post as much as you wish and can here, just in the thread devoted specifically to Hummeren 1624, about the general configuration and perhaps other details of the artillery you and the organisation have planned for the Hummeren replica? In particular, the number and calibre of the main battery guns and others, their specific layout on board, and their nature (home-bored/some type of drakes, short cannons/ long culverines, bronze/iron, number and nature of dedicated anti-personnel specimens, if any, types of carriages etc.). Anything you seem fit.

I am very curious about your choice, and would particularly like to compare it to Solen 1627, my reconstruction of Sankt Georg 1627, and of course Vasa 1628, among others.

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[TheDukeOf Wybourne]

Hello there Waldemar et al,

Not sure if you've seen this since you didn't list this in your references; Niklas Eriksson has written a lovely piece on Hummeren and other ships built to her lines, with some preliminary archaeological information on one of the ships, To Løver, including a scetch of the surviving gun deck. Nothing on the stern though, it has sunk deep into the seabed. But he is stating further research is coming, so maybe someday...


Link: https://www.academia.edu/115910854/...n_text_shipwreck_and_a_constructional_drawing

 

[-Waldemar-]

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Niklas Eriksson has written a lovely piece on Hummeren and other ships built to her lines

An excellent monographic publication about this particular series of ships indeed, thank you very much for pointing it out (well maybe, personally for me, only apart from some otherwise overly conventional comments relating to ancient naval architecture).

Anyway, a great read, and among other things, news that it may be possible, in the future, to compare an authentic plan by Balfour with an authentic wrecked ship(s) built from that plan. Just need to find another few zillion of some currency for further excavation and research work .

To be honest, the specific form of the stern shape, suggested as a round tuck on the original Hummeren 1624 plan by that distinctive step visible on the sternpost, is not that quite important to me personally. Already more so – the possible ways of interpreting the shape of the master frame, and methods of its subsequent modification to obtain the whole shape of the hull. And there are quite few possibilities, which I intend to present in my next post. Indeed, if only this could be verified with the wreck (after it has been excavated or at least examined for this).

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