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Thank you for sharing that!
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Vasa 1628 – engineering a ship
- Thread starter -Waldemar-
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And yet another great video to show. It will be particularly appreciated by users of the Unimat 3 lathe with its original, rather unsuccessful, power transmission system. As can be seen, I converted the whole thing to use toothed belts, instead of smooth belts that slipped and tore quite often. Enjoy!
View attachment Unimat 3 modified.mp4
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Hi Waldemar,
thanks for your reply and for the interesting advice.
In fact I was thinking of studying the behavior of ships of this type at high inclinations. I know that the Vasa is not a reference but, given the particularity of the case, I have been guided so far by curiosity. I was wondering if it was possible to definitively exclude for the Vasa the case of an alist ship (that is, for those who do not know, that case in which the ship, although initially unstable, returns to having a positive restoring moment for further inclinations. Simplifying, the ship tends to float permanently list), net of, I would believe, a fatal defect in the positioning of the gun ports.
At this point, however, I would say that given the high degree of uncertainty, perhaps it is better to fall back on other ships. It probably makes little sense to even try to correct the shape of the stations following the indications contained in Witsen's treatise.
Regarding the question you asked, I should actually take a closer look at the characteristics of the ships you showed me, but I wouldn't be surprised to see poor stability even for these. In order to ensure a certain resistance to heeling, in fact, it is necessary that the weight of the ship is distributed low down as much as possible, in addition to having a large waterline and a large reserve of thrust. Therefore, compared to a merchant ship, for a warship of the type mentioned above I would generally expect both worse stability and worse buoyancy. I hope I have been exhaustive!
Renato
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Yeah, my earlier assessment based on visual observation alone is pretty much the same. That is why I put forward the idea of computational confirmation, or actually more so — an attempt to quantify these properties.
Please let me know if you decide to do this, and actually when/if you get concrete results. I guess the hardest part will be assigning the correct weights and their computational position for the different components of the ship, but that too can be found in the literature of the period.
Good luck, Renato!
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GO FOREIT DON
heres a thought, in the olden days of the 1990s, it was said that the ships of the mediterranean, and of most of europe were designed on teh basis of rule of thumb... width is this much of length, and so on..
In china, the junks have always been designed by proportions.. so if they find an abandoned rudder post or rudder on the river bank, they can measure it and tell you how long the junk was.
or should we consider the theory that the builder was angry about being paid in copper coins and built a really bad ship as revenge?
In china, the junks have always been designed by proportions.. so if they find an abandoned rudder post or rudder on the river bank, they can measure it and tell you how long the junk was.
or should we consider the theory that the builder was angry about being paid in copper coins and built a really bad ship as revenge?
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Why not take a look at the sources on this matter (as indeed on others). Here is a fairly typical contemporary account that touches on this issue (Georges Fournier, Hydrographie, 1643, rep. 1667, p. 21):
To be honest, I personally know an even better magician, incidentally a historian by education and employee of the maritime museum. He claims that one can faithfully reconstruct an entire vessel solely on the basis of a short piece of ship's keel found.
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Ive seen the articles years ago, how chinese experts have dredged up a piece of ships rudder and been able to give a complete blueprint of the junk or sampan by using the 2,000 year old "rules of thumb" used to build junks and sampans in that time.
Since 1990 the US Brig Niagra has been used to conduct 2, possibly 3 separate "tests to determine the impact upon a ships hull by ordnance launched by a carronade". I know that possibly 2 research groups in Europe did similar work.
What I am curious is, other then studying SOLID shot fired into a simulated ships hull, has anyone ever studied
chain shot, bar shot, expanding bar shot, or even grape shot upon actual sized rigging, masts, or sails.
Id really like to know how much impact those projectiles going through a sail will have on how well it draws.
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As a kind of summary of both this thread and the issue itself, the following can be added:If the hull shapes of the Vasa 1628, as rendered in the museum plans from 1970/80 (nothing newer has been made public to date), can be relied upon, then it can be concluded that Hein Jakobsson, successor of the actual designer of the ship, must have been aware of the final design flaws and did indeed attempt to remedy the problem by increasing the volume of the hull, and this in turn by increasing the breadth of the ship (he testified to this effect during questioning in the investigation into the causes of the sinking). Strangely, for some reason, he was unable to increase the depth of hold, which, given the overall proportions proper for intended seagoing nature of the ship, would have yielded much better results, instead of creating a sort of shallow-draft, coastal artillery pram from the hull shapes point of view. Perhaps due to a lack of timbers of sufficient length at the start of construction and at the same time in the face of categorical king’s urgings to commence the building immediately.
However, the actual way to increase the breadth of the hull, with the intention of increasing its underwater volume, was similarly carried out in a rather chaotic and ill-considered manner, doing as much harm as good. The point is that Hein Jakobsson only marginally increased the actual maximum breadth of the hull (for lack of longer deck beams?), while at the same time excessively increasing the width of the bottom, especially in the aft part of the hull. The result was that this intentional remedy simultaneously geometrically lowered the maximum breadth of the hull to the level of the waterline, which ruined the so-called shape stability (for ships of this size and with a high centre of gravity, mainly due to the weight of artillery, the line of maximum breadth should be a few feet above the waterline).
And, as a graphic illustration, again the explanatory diagrams taken form the entries #16 and #39 of this thread:
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This sounds like a very reasonable explanation of the hull shape. Making the hull deeper under the water was what was really needed, or at least reducing the headroom in the gundecks. A couple of factors that may have affected the shape:
1. It appears that the transom remained the original width as first set up, for a much narrower ship, which limited how much the height of the hull could be raised, and required the widened maximum breadth to swing in dramatically at the stern, which contributes to the terrible run of the breadth curve. We can see from the wreck of Äpplet, which was built to the same specification, that it was begun with a wider and taller transom, so that the maximum breadth carries higher and does not have to swing in, it carries aft in a much flatter curve as one would want. I suspect Hein knew that Vasa was a dog and tried to fix what he could. The ships he designed from a clean sheet, Scepter and Kronan, were considered good, seaworthy ships capable of carrying their armament, and were in service for 30 years or more.
2. The method of preparing timber probably limited Hein's options to a certain degree. Because the frame timbers were roughly shaped at the site where the trees were felled, adjustments in the hull shape had to be made by shifting or tilting the timbers, with options for reshaping them very limited. Because the hull was built in the bottom-based tradition with relatively flat floors, it was possible to widen the floor and maximum breadth of the hull by shifting the first futtocks outward, but it was not so simple to raise them higher. The first futtocks run from close to the keel around the turn of the bilge and up to the maximum breadth, so effectively define the height of breadth. It is possible to make the topside above the max breadth higher by shifting the upper futtocks upwards, but not really possible to shift the maximum breadth upward without cutting new first futtocks. The maximum breadth towards the ends could be increased very slightly by tilting the lower futtocks outward, but their already cut shapes limited how much. Beam length is probably not a limiting factor, as beams were essentially made from straight trees, which we know from other timbers in the ship were available in even longer lengths than the longest beams (which are less than 11m long).
At the inquest, more than one of the experts consulted on the flaws in the ship noted that it did not have enough "buk," or belly, which meant specifically that there was not enough flare in the bottom between the turn of the bilge and the waterline, just as Waldemar has noted above. And as Waldemar has explained very clearly, the particular method of widening the hull in this case did not improve things.
Not all of the widening of the hull can be attributed to Hein Jakobsson. The specification for the ship gave the breadth to the outer face of the frames as 34 feet, but as the ship was built the breadth is closer to 38 feet. At the inquest, Hein claimed he widened the ship 1 foot 5 inches (or very near 1½ feet to a shipwright from Amsterdam), so it may have been Henrik Hybertsson who had already widened the ship by 2½ feet.
We know from the detailed measurements of the ship he built just before Vasa, Tre Kronor, that Henrik liked shallow hulls with the depth in hold/height of breadth only about 1/12 of the overall length, considerably less than the 1/10 considered a minimum even in Holland.
Note that the weight of the guns is probably not in and of itself a significant issue. The guns carried at the time of the sinking weighed 62 tonnes, which is nearly exactly 5% of displacement. Most successful multi-decked warships of the 17th century have armament in the range of 4-7% of diplacement, so Vasa lies comfortably in the lower half of that range. Where they are carried does matter, as does the excessive weight of the deck structure under them. The beams are overdimensioned for the weight of the guns and more closely spaced than necessary (only about 1.5m apart). By comparison, the structure of the middle deck on Kronan in 1668 was much lighter (smaller beams, more widely spaced, with less elaborate riders) for exactly the same type of guns.
Fred
1. It appears that the transom remained the original width as first set up, for a much narrower ship, which limited how much the height of the hull could be raised, and required the widened maximum breadth to swing in dramatically at the stern, which contributes to the terrible run of the breadth curve. We can see from the wreck of Äpplet, which was built to the same specification, that it was begun with a wider and taller transom, so that the maximum breadth carries higher and does not have to swing in, it carries aft in a much flatter curve as one would want. I suspect Hein knew that Vasa was a dog and tried to fix what he could. The ships he designed from a clean sheet, Scepter and Kronan, were considered good, seaworthy ships capable of carrying their armament, and were in service for 30 years or more.
2. The method of preparing timber probably limited Hein's options to a certain degree. Because the frame timbers were roughly shaped at the site where the trees were felled, adjustments in the hull shape had to be made by shifting or tilting the timbers, with options for reshaping them very limited. Because the hull was built in the bottom-based tradition with relatively flat floors, it was possible to widen the floor and maximum breadth of the hull by shifting the first futtocks outward, but it was not so simple to raise them higher. The first futtocks run from close to the keel around the turn of the bilge and up to the maximum breadth, so effectively define the height of breadth. It is possible to make the topside above the max breadth higher by shifting the upper futtocks upwards, but not really possible to shift the maximum breadth upward without cutting new first futtocks. The maximum breadth towards the ends could be increased very slightly by tilting the lower futtocks outward, but their already cut shapes limited how much. Beam length is probably not a limiting factor, as beams were essentially made from straight trees, which we know from other timbers in the ship were available in even longer lengths than the longest beams (which are less than 11m long).
At the inquest, more than one of the experts consulted on the flaws in the ship noted that it did not have enough "buk," or belly, which meant specifically that there was not enough flare in the bottom between the turn of the bilge and the waterline, just as Waldemar has noted above. And as Waldemar has explained very clearly, the particular method of widening the hull in this case did not improve things.
Not all of the widening of the hull can be attributed to Hein Jakobsson. The specification for the ship gave the breadth to the outer face of the frames as 34 feet, but as the ship was built the breadth is closer to 38 feet. At the inquest, Hein claimed he widened the ship 1 foot 5 inches (or very near 1½ feet to a shipwright from Amsterdam), so it may have been Henrik Hybertsson who had already widened the ship by 2½ feet.
We know from the detailed measurements of the ship he built just before Vasa, Tre Kronor, that Henrik liked shallow hulls with the depth in hold/height of breadth only about 1/12 of the overall length, considerably less than the 1/10 considered a minimum even in Holland.
Note that the weight of the guns is probably not in and of itself a significant issue. The guns carried at the time of the sinking weighed 62 tonnes, which is nearly exactly 5% of displacement. Most successful multi-decked warships of the 17th century have armament in the range of 4-7% of diplacement, so Vasa lies comfortably in the lower half of that range. Where they are carried does matter, as does the excessive weight of the deck structure under them. The beams are overdimensioned for the weight of the guns and more closely spaced than necessary (only about 1.5m apart). By comparison, the structure of the middle deck on Kronan in 1668 was much lighter (smaller beams, more widely spaced, with less elaborate riders) for exactly the same type of guns.
Fred
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Naval architects analyze transverse stability in two separate calculations: stability at small angles of heel; also called initial stability and stability at large angles.
Vasa’s sinking appears to be a case of poor initial stability. She heeled over with a slight wind puff and paused. Sinking occurred because of downflooding via gun ports.
Ships with poor initial stability can and do operate satisfactorily until a combination of factors causes their loss. The tragic sinking of the Great Lakes Passenger Steamer Eastland is eerily similar to that of Vasa although happening nearly 300 years later. Leaving port with a full load of passengers she unexpectedly heeled, paused, and returned to an even keel successfully completing the voyage. The incident was ignored. Several years later while moored at a pier in Chicago she boarded a large load of passengers. The engineer ordered to take on water ballast to reduce the center of gravity instead caused a free surface by only partially filling the tanks. She heeled, down flooded via an open gangway in the side of the hull, and sank drowning over 800 passengers.
Initial stability is determined by the Metacentric height; the vertical distance between the point where the vector of the ship’s upward buoyancy crosses her centerline in the heeled condition less the height of her center of gravity.
The height of the metacenter is proportional to the breadth of the hull raised to the third power and inversely proportional to its underwater volume. So, waterline breadth is the determining factor. If Vasa was not floating at maximum breadth it would have made a big difference in her initial stability.
Roger
Vasa’s sinking appears to be a case of poor initial stability. She heeled over with a slight wind puff and paused. Sinking occurred because of downflooding via gun ports.
Ships with poor initial stability can and do operate satisfactorily until a combination of factors causes their loss. The tragic sinking of the Great Lakes Passenger Steamer Eastland is eerily similar to that of Vasa although happening nearly 300 years later. Leaving port with a full load of passengers she unexpectedly heeled, paused, and returned to an even keel successfully completing the voyage. The incident was ignored. Several years later while moored at a pier in Chicago she boarded a large load of passengers. The engineer ordered to take on water ballast to reduce the center of gravity instead caused a free surface by only partially filling the tanks. She heeled, down flooded via an open gangway in the side of the hull, and sank drowning over 800 passengers.
Initial stability is determined by the Metacentric height; the vertical distance between the point where the vector of the ship’s upward buoyancy crosses her centerline in the heeled condition less the height of her center of gravity.
The height of the metacenter is proportional to the breadth of the hull raised to the third power and inversely proportional to its underwater volume. So, waterline breadth is the determining factor. If Vasa was not floating at maximum breadth it would have made a big difference in her initial stability.
Roger
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Many thanks, gentlemen, for your insightful explanations. Roger, if you could please supplement your apt comment with an illustrative diagram for those with less imagination in this area, showing the essence of the metacentre idea, that would be already absolutely perfect (even despite the fact that such diagrams are already widely reproduced in thousands of other places 
).Fred's additional explanations on how the wood for construction was obtained are further confirmation that ships could not be built ‘by eye’, as has been commonly accepted until now, and especially with the possibility of ‘arbitrary’ modifications to shapes during construction itself, but were actually designed in advance in terms of the their geometry. How else could timbers of the right dimensions and curvatures have been selected and gathered before construction began? Attempts at excessive manipulation of this kind, during the actual construction, ended or could have ended as in the case of the Vasa 1628.
I would also like to briefly refer to the popular keyword ‘bottom-based’ that you used in your explanations. I have recently completely changed my view on the meaning of this term, based on numerous analyses of a specific nature, which are indeed undertaken by very few people, perhaps due to their particular complexity and time-consuming nature (Brian Lavery, Niels Probst and Taras Pevny should be mentioned here in particular).
It can be said that, until now, maritime archaeology has understood the ‘bottom-based’ method as a kind of way of constructing ships ‘by eye’, by starting the physical formation of the hull with an intuitively created bottom made of planking without the use of guiding frames, i.e. omitting the preceding conceptual stage of proper design, and still characterised by a flat hull bottom. At least, no one has yet been able to explain whether and, if so, how ships built using this ‘bottom-based’ method, understood as a carpentry technique of joining elements, were designed. In other words, merely the carpentry technique of connecting hull elements and in a specific order was confused with or replaced proper design using geometric methods, which has been attempted to be explained in numerous scholarly works in a more or less semantic way
.However, it turns out that this is not the case, because now it can probably be said that all ships in the Northern tradition (as opposed to the Mediterranean and derivative English traditions) were designed ‘bottom-first’. This includes the English capital ship Mary Rose from 1511 as well. Starting construction by laying the bottom of the hull with planks (without guiding frames) is only a carpentry issue and is not actually a conceptual element. I have presented various details and further explanations with numerous examples in other threads.
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Fred, would you like me to explain, in addition to all the cases shown so far, how exactly the French frigate l'Aurore from 1697, sporting very sharp shapes, was designed? This frigate was also designed using the Northern method, i.e. ‘bottom-first’ or ‘bottom-based’, and yet she was actually assembled ‘skeleton-first’, similar to the Mary Rose 1511 and ships built in the southern Netherlands or Denmark in the early modern era.This cannot be found in either archaeological or commercial monographs. In fact, I do not know of a single archaeological monograph in which the concept of a discussed wreck has been correctly reconstructed, if such attempts have been made at all.
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Transverse stability diagram as requested:
M. Metacenter
G. Center of gravity.
GM sin (theta). Is the Righting arm.
RIghting Arm x Displacement = Righting moment
M. Metacenter
G. Center of gravity.
GM sin (theta). Is the Righting arm.
RIghting Arm x Displacement = Righting moment
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... and not only that. I find that the general lack of analytical skills of this kind in a community (that is, after all, expected to be at the forefront of research) results in the creation of other fanciful hypotheses, such as the never-existing Ibero-Atlantic shipbuilding tradition, which can be considered already a classic bending of facts (in this case archaeological evidence) to fit a false theory. How simple is that?
And this is not changed in the slightest by the circumstance that all those as much misleading as useless ‘accomplishments’, not to say crap, are repeated over and over again in so-called prestigious publications by largely humanities scholars and authors of even the highest ‘standing and seniority in the academic world of maritime archaeology and shipbuilding history’. ‘Standing and seniority’, just great, but should we really continue this way…?
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For the benefit of scholars and the academic world of maritime archaeology and shipbuilding history in general, the current state of knowledge regarding design concepts in the early modern period, based on the author's latest research, can be summarised as follows (for the underwater part of hulls):
Southern or Mediterranean tradition — geometric construction of the master frame consisting of three sweeps of constant radius (sometimes more, which is not particularly significant for the essence of this method); one fixed master frame template transformed (moved and rotated) over the ‘entire’ length of the hull, or at least between the quarter frames, and guided by the line of the floor and the so-called ‘bocca’ line, the latter coinciding with or parallel to the deck line; geometric elements of the hull bottom, connecting the hull body proper with the keel assembly, defined at the end of the design process.
It is also necessary to mention separately the variant featuring a breadth sweep of variable radius, which I intend to demonstrate in detail when discussing the work of Robert Dudley (both its published and unpublished part), created in the first half of the 17th century.
Northern tradition — geometric construction of master frame normally consisting of two main sweeps of variable radii (except in the simplest cases or sporting additional reconciling sweeps of an auxiliary nature); the hull bottom, guided by the line of the floor, is defined first; breadth sweeps guided by the line of greatest breadth (as opposed to the ‘bocca’ line in the Southern tradition); bilge sweeps, connecting the hull bottom with the breadth sweeps, defined at the end of the design process.
Ships in the Northern tradition could be built employing both the ‘skeleton-first’ and ‘shell-first’ techniques, however, these techniques are purely carpentry-related and do not replace proper design. In other words, both of these carpentry assembly methods are merely the practical implementation of properly understood designs.
English tradition (developed around the second quarter of the 17th century) — is, in a sense, a synthesis of the two previous methods or a derivative of the Mediterranean design method, depending on which evaluation criteria are considered more important. The geometric structure of the master frame typically consists of three main sweeps, which may be of fixed or variable radius (this applies to all these three sweeps), and now guided by the rising and narrowing lines taken from the Northern tradition (i.e. the line of the floor and the line of greatest breadth); the general design sequence is as in the Mediterranean tradition, i.e. the geometric elements of the hull bottom, connecting the hull body proper with the keel assembly, are defined at the end of the design process.
Thank you,
Waldemar Gurgul
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Do you have any basic pictures of these sweeps for the benefit of those new to ship design? It is difficult to envision the role of these curves and their position on a draught with when one has no understanding of the terminology, i.e. sweep, master frame, breadth sweep, etc.
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Of course, there is a whole host of explanatory images that I did not consider appropriate to quote in what is, by its very nature, a brief summary. As for the meaning of basic concepts and the specific ways in which various solutions are applied, one can look at my numerous threads on this forum and on the MSW forum (I suggest the most recent ones, as they are the most mature). However, if there are problems finding them, I will be happy to provide specific links.
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