|
Post by jules on Sept 4, 2016 6:53:50 GMT
Morning Rein,
About your question of the framing on top of the stempost in the E81 wreck. These frames are not perpendicular to the curve of the stern. E81 confirms what the Sturckenburgh drawing shows. But, there are some interesting framing details in this part of the wreck,
Kind regards,
Jules
|
|
|
Post by tromp on Sept 4, 2016 20:01:23 GMT
Hello Peter (Tromp), Thanks for sharing the result of your very interesting experiment. But why did you use tape? Probably because it 'flows' easily against the hull, but wood doesn't. I would like to suggest that you do the experiment again with a strip of wood. The strip should have parallel sides, like the tape, and a width of approximately one foot (to scale of course). Also the strip has to be tapered from bottom to top: 1 foot, 11 inches, for the bottom, and half of that for the top: 5,5 inches. All this to get a closer representation of the real frames. And it would be nice if you could make two, three or more of these strips, so you can place them against eachother. Let's see what happens. Thank you for the sketches; very clear. But, as mentioned before, the 'inhouten' (frame parts) have to be placed against eachother in the bilge and at the lower wales: the contracts for these ships are clear: no spacing allowed. I think that when you place the frames with their perfect square sections against eachother, that will result in a wedgeshaped opening between the frames. To avoid this, the sides of the frames would have to be worked to make them sit flush against their neighbouring frames. Then, if you let me, to your 'the tilted frames really only make sense with the shell first method'. Like said before, E81 was built shell first, and shows parallel framing, not tilted framing. So we can maybe say that tilted framing only makes sense with the shell first method, but we can not say that the shell first method dictates tilted framing, or excludes parallel framing; E81 shows this. (Your remark 'There is no need for any tricky fitting process bevelling the frames to follow the lines of the planks', makes me think that you think that in the bottom first building method all frames were placed against the planking. This is not so: only the lower part of the hull, up to the highest plank of the bilge, was built that way. The rest of the hull was built frame first: the planking was placed against the frames, not the other way round. For the upper part of the hull, there was no way to simply place the upper frames with their perfectly square sections against the planking, the planking wasn't there yet. But, please forgive me if I got the interpretation of your sentence wrong.) Looking forward to the results of your experiment. Maybe we can establish in this way if your conclusion 'the HZM by chance being one of the last ships (models) to be built that way', is justified. Regards, Jules Jules,
I indeed used tape because it, when applied carefully, would follow the shape of the hull without me being able to manipulate it too much (provided I wanted to). I could use wood as you suggested but this would only work when very thin plywood is used. There is no way that thin oak or similar wood could be applied to the hull to follow the shape easily. I don't have thin plywood here so I used thin sheet styrene as an alternative. Several Sheets of 0.3mm sheet styrene were cemented to each other using that largest ruler I have as a guide to get the length required.
foto upload
Then three makeshift frames were cut out, 1 Amsterdam foot wide at the base and half an Amsterdam foot at the top in 1/21st scale. By then I could tell that the thin strips were very flimsy and I was beginning to wonder if the test would work.
foto upload
I then tacked small snippets of double sided tape to the frames.
foto upload
Then the frames were tacked to the hull, and this is what came out:
foto upload
I wasn't really happy with the outcome as the thin styrene Frames were way too flimsy. So I tried it again with a wider piece of styrene and this is the result:
foto upload
For this I used a strip that was 2cm wide at the top and 2.5cm wide át the bottom. There is no way that this can be distorted or manipulated into a direction that it doesn't want to take, you can take what you see for granted.
You wrote that in the shell-first system the upper hull was built frame first. I don't necessarily agree: I think we are all in agreement that the individual pieces of a dutch frame weren't attached to each other. So the upper pieces of the frames, the Stützen, had to be attached to something: the hull planks. So, as far as I can tell, the shell-first applies to the whole hull and not only the bottom.
Regards Peter
|
|
|
Post by Peter Jenssen on Sept 5, 2016 1:41:13 GMT
Hello Peter (Jenssen), Then to your sketch. Your remark 'not so large gaps of course' says it all. Like stated before: no gaps allowed at the overlapping of the frame parts. And when you place a tilted parallel framepart against another tilted parallel framepart with a different tilt, this results in a tapering gap. So you would have to work the frameparts to make them fit properly against each other. And over a long distance: as mentioned before, the overlap can reach a length of 2 meters. In my view, a lot of work. Kind regards, Jules Hi Jules, Just for fun, in an attempt to quantify how much work, I did a quick calculation. Suppose a hull is built with the same frame tilt as Vasa, but using the frame parts as per the Sturckenburgh drawing, assumed overlap 2m maximum vertical component. Frames then would need to progressively tilt from 90 degrees somewhat forward of midships, to 81 degrees by the aftmost gunports. Total nine degrees difference. Using the frame density from the Sturckenburgh drawing, I roughly estimate 40 frames for this interval. Since each 'frame' consists of overlapped timbers, there would be two gaps per frame. (One within the frame, and one towards the next frame) So tilt per frame is 9 degrees/40 frames = 0.225 degrees. Two wedge gaps per frame, each wedge gap 0.1125 degrees. Triangular wedge gives max gap = 2000*sin(0.1125) = 3.9 mm for two meters overlap (of course does not count at turn of bilge, as the vertical component would be smaller) Indeed, could be a lot of work, but depends on what tolerances you demand, what tools you use and if you are doing any finishing work on the timbers anyway that you could leverage for your shaping. Now, I don't know enough about the actual carpentry practices at the shipyards. Did they use planes for examples? Did they use them on the frame surfaces? If the answer is yes to these questions, perhaps taking 4 extra mm off towards the top of timbers is not such a huge job? (if indeed you are concerned about a 4 mm gap) (For a model builder working in 1:48 scale, the wedge shaped gap would amount to 0.08 mm at the thickest end. Only a couple of passes on a sand paper.) Cheers, Peter (J)
|
|
|
Post by Peter Jenssen on Sept 5, 2016 1:47:45 GMT
Hello Peter (Tromp), Thanks for sharing the result of your very interesting experiment. But why did you use tape? Probably because it 'flows' easily against the hull, but wood doesn't. I would like to suggest that you do the experiment again with a strip of wood. The strip should have parallel sides, like the tape, and a width of approximately one foot (to scale of course). Also the strip has to be tapered from bottom to top: 1 foot, 11 inches, for the bottom, and half of that for the top: 5,5 inches. All this to get a closer representation of the real frames. And it would be nice if you could make two, three or more of these strips, so you can place them against eachother. Let's see what happens. Thank you for the sketches; very clear. But, as mentioned before, the 'inhouten' (frame parts) have to be placed against eachother in the bilge and at the lower wales: the contracts for these ships are clear: no spacing allowed. I think that when you place the frames with their perfect square sections against eachother, that will result in a wedgeshaped opening between the frames. To avoid this, the sides of the frames would have to be worked to make them sit flush against their neighbouring frames. Then, if you let me, to your 'the tilted frames really only make sense with the shell first method'. Like said before, E81 was built shell first, and shows parallel framing, not tilted framing. So we can maybe say that tilted framing only makes sense with the shell first method, but we can not say that the shell first method dictates tilted framing, or excludes parallel framing; E81 shows this. (Your remark 'There is no need for any tricky fitting process bevelling the frames to follow the lines of the planks', makes me think that you think that in the bottom first building method all frames were placed against the planking. This is not so: only the lower part of the hull, up to the highest plank of the bilge, was built that way. The rest of the hull was built frame first: the planking was placed against the frames, not the other way round. For the upper part of the hull, there was no way to simply place the upper frames with their perfectly square sections against the planking, the planking wasn't there yet. But, please forgive me if I got the interpretation of your sentence wrong.) Looking forward to the results of your experiment. Maybe we can establish in this way if your conclusion 'the HZM by chance being one of the last ships (models) to be built that way', is justified. Regards, Jules Jules,
I indeed used tape because it, when applied carefully, would follow the shape of the hull without me being able to manipulate it too much (provided I wanted to). I could use wood as you suggested but this would only work when very thin plywood is used. There is no way that thin oak or similar wood could be applied to the hull to follow the shape easily. I don't have thin plywood here so I used thin sheet styrene as an alternative. Several Sheets of 0.3mm sheet styrene were cemented to each other using that largest ruler I have as a guide to get the length required.
foto upload
Then three makeshift frames were cut out, 1 Amsterdam foot wide at the base and half an Amsterdam foot at the top in 1/21st scale. By then I could tell that the thin strips were very flimsy and I was beginning to wonder if the test would work.
foto upload
I then tacked small snippets of double sided tape to the frames.
foto upload
Then the frames were tacked to the hull, and this is what came out:
foto upload
I wasn't really happy with the outcome as the thin styrene Frames were way too flimsy. So I tried it again with a wider piece of styrene and this is the result:
foto upload
For this I used a strip that was 2cm wide at the top and 2.5cm wide át the bottom. There is no way that this can be distorted or manipulated into a direction that it doesn't want to take, you can take what you see for granted.
You wrote that in the shell-first system the upper hull was built frame first. I don't necessarily agree: I think we are all in agreement that the individual pieces of a dutch frame weren't attached to each other. So the upper pieces of the frames, the Stützen, had to be attached to something: the hull planks. So, as far as I can tell, the shell-first applies to the whole hull and not only the bottom.
Regards Peter
Hi Peter and Jules, This only shows what the frames would do if made from bent timber. When you bend the timber at an angle (the turn of the bilge is not parallel to the keel for example), it has to change direction. Probably best to use another method, such as for example a laser? Cheers, Peter (J)
|
|
|
Post by jules on Sept 5, 2016 6:10:07 GMT
To Peter (Tromp),
This has to be short, got to go, be back later. Thanks for sharing the results. But I think I wasn't clear enough. The tapering should not be in the width of the strips but in the thickness. Will make a sketch later.
About the building sequence of bottom based: wil get back to you.
Regards,
Jules
|
|
|
Post by jules on Sept 5, 2016 6:15:26 GMT
To Peter Jenssen,
Again, this has to be short. Will be back to you later. Thanks for the calculations. But again, why would they want to do the extra work? What's the purpose of making the frames tilt? Peter (Tromp) suggests that it is because they put the frames against the planking to save work, and as a result the frames tilt. In my view this would result in a torsion of the frames. But at least it's a theory. The tilting is not a goal on its own, there has to be a reason for it.
Regards,
Jules
|
|
|
Post by amateur on Sept 5, 2016 6:51:09 GMT
Hallo Peter,
The 'oplangen' were not placed against the inside of the planking: after the bottom was build, a few oplangen were erected, to which the sheerstrook was placed. The remainder of the oplangen were placed to the inside of this scheerstrook: on the lower end tighlty fitted between the buikstukken in the 'kim', and on the upper side aginst the scheerstrook. Only after the oplangen were placed, the wales were fitted. Folowed by the planking. (As far as I understand witsen and van ijk)
There is a very nice set of etchings done by Sieuwert van der Meulen, in which he illustrates the building, use (and demise) of a ship. There is a drawing showing the first stage (bottom, consisting of planks, clamped together, without any inhouten), See here: www.rijksmuseum.nl/nl/zoeken/objecten?q=sieuwert+van+de+rmeulen&p=2&ps=12&st=OBJECTS&ii=5#/RP-P-OB-6658,17 and the second stage, where the inhouten are completely build up, on a fully planked bottom/bilge. See here: www.rijksmuseum.nl/nl/collectie/RP-P-OB-6659 Also visible in this series: the ship went into the water, before the upper parts are closed: www.rijksmuseum.nl/nl/zoeken/objecten?q=sieuwert+van+de+rmeulen&p=2&ps=12&st=OBJECTS&ii=6#/RP-P-OB-6660,18 Jan
|
|
|
Post by fredhocker on Sept 5, 2016 10:24:59 GMT
A lot of things to cover here, so this might be a little long...
Some quick answers first (and Jules can breathe easier, we already recorded the relevant information): much of the planking for Vasa was bought as rough-sawn planks in international timber markets (Riga, Königsberg and Amsterdam), while the compass timber was purchased in Sweden, from individual farms. Patterns and sawyers were sent out to the forests under the direction of a master shipwright, and many timbers were roughly shaped in the forest, to reduce transport costs. We see traces of sawing on the sides of the frames, and what traces we can see indicate trestle sawing. We see the same thing on the riders, knees and other big compass timbers, as well as the beams. Most of the saw marks on these timbers have been obliterated by later shaping, in which the surfaces were finished with adzes. The only evidence we have of machine sawing is on boards used in the internal bulkheads, which are spruce or pine and less than 6 cm thick. These traces clearly indicate an up-down saw, such as the one Jules showed in an earlier post. The marks on opposite faces of the boards, as well as parallelism, suggest that this was a single-bladed rather than gang saw. The planking has been surfaced, with adzes, so we cannot see enough saw marks on these heavier planks, to determine what sort of saw technology was used, but based one the origins, there might be some mill sawn planks among them.
Generally speaking, the frame timbers in Vasa are parallel-sided, within the limits of hand-finishing, but as Peter has clearly demonstrated, the amount of taper we are talking about is very small in an individual timber, and less than the amount that might be removed in finishing. It is worth looking at that again as a specific case. Some other relevant factors first:
1. Using timber straight from the saw presents problems as well as advantages. Jules has clearly laid out the advantages, so I won't repeat those here. But there are some challenges as well, Primary among these is rot resistance. Sawing leaves a surface finish with many cut and broken fibres, exposing the ends of the fibres all along the surface and providing small pockets where water can collect and remain under its own surface tension. For this reason, a sawn finish is not ideal for marine usage, and it has been a common practice to clean up sawn surfaces in critical areas to get rid of this rot enhancing effect. It is one of the reasons that saw marks are not as common in the archaeological record as one might think. The other challenge comes in fitting timbers against each other, as in the tightly packed framing at the turn of the bilge. No large-scale saw technology produces surfaces suitable for faying to each other. Slight wandering from the cut line as a massive timber is horsed through the saw, the natural variation in the saw stroke, knots which deflect the blade, and other variations mean that the sawn surface is not actually flat. I am speaking from experience as a large-scale shipwright, using modern ship saws and sawmills to side and mould framing timbers approximately the size of those in Vasa. If one puts these unfayed surfaces together, such as at the frame overlaps, it creates more pockets for standing water and does not make for a very solid structure. To relieve this problem, one either has to clean up the faces to make a better joint, or separate the surfaces enough that they do not trap water.
The process of cleaning up the face to get a smoother surface was traditionally carried out with adzes (the plane is not a traditional shipwright's tool, but a joiner's or boatbuilder's tool), and goes much faster than one might think. For example, when I was working as a shipwright, three of us could convert a pine log into a finished deck beam 8 m long and about 30 cm square in a working day, starting by siding on the sawmill, then moulding with hewing axes and cleaning up with adzes. The cleanup on the sawn face typically removed 2-5 mm of material, if we had been good and careful with the saw (a modern mill in which the log rides through in a carriage on rails). For framing timbers, it was not possible to get that clean a surface, and so one was removing up to 10 mm of wood on a face. This was for a large ship with a similar framing system to Vasa, independent futtocks rather than made frames.
To achieve the tight fit Jules shows in the E81 framing, there has to be some dubbing of the sides of the frames. As much as I admire the craftsmanship and speed of Dutch carpenters in the 17th century, I cannot believe that they could cut the timbers so cleanly on the saw that they could fit together so tightly without some faying.
With that said, let's look at taper (repeating a little of what Peter said). If we take Vasa as an example, there are 45 floor timbers between amidships, which we could take as a tilt of 0 degrees, and the last floor timber standing on the keel, which leans forward about 9 degrees relative to amidships. This means that each frame leans 0.2 degrees more than the one next to it.In most of the area of the overlap between the floor timbers and the first futtocks, the faying surface on a floor timber 350 mm deep has to be tapered 1.2 mm across its width, which is considerably less than what is normally removed in the cleanup process. If the faces are not tapered, the resulting gap at the bottom of the frame is is a couple of mm. THe amount of taper becomes a bigger issue in the sides, where the first and second futtocks overlap over lengths of a couple of meters, but even in a 3-meter overlap, the total amount of taper over the length is on the order of about 10 mm on each side, relative to a parallel-sided timber. This is readily accompished in the sawmill, if one uses a single-blade saw rather than a gangsaw - it is just two passes instead of one. If accomplished in the fitting/cleaning process after sawing, it is still within the range of normal cleanup and vastly less than the amount removed in bevelling the plank and ceiling faces to fair them.
Most of the argument so far on this point has been a subjunctive one, "it would have been easier to do it this way," rather than an argument based on evidence of what was actually done. I am a professional shipwright as well as an archaeologist, so I have some feeling for how I would solve this problem in the shipyard where I worked, but I am not a 17th-century Dutch shipwright, so I have to put my own preferences aside. How would we figure out what they did on the basis of evidence, rather than supposition? Here are some suggestions:
1. How are the frame sides finished in surviving ship remains from the period? Do the frames show sawn faces over their whole length or have the sides been cleaned up? If all surfaces have been dubbed, then tapering the frames a slight amount does not represent an insurmountable obstacle, nor does it represent a significant amount of increased work. In practice, there is really no practical difference between removing 2mm and 6mm from the surface. If the sides are left sawn (as we do see in some ships in other places), how do they deal with the poor fit that results, and did this mean that they accepted the higher chance of decay?
2. In surviving timbers with preserved sawn faces, how flat and parallel are those faces? Do we have hard evidence that Dutch sawyers were good enough that they could cut a frame timber several meters long, from a log weighing half a ton or more, with no wander or deflection, so that tight joints could be achieved? I'd like to meet those guys! In a gangsaw, how parallel and consistently spaced were the cuts made by multiple blades?
3. Do we have evidence, archaeological or historical, that both sides of a frame were sawn simultaneously? or was this technique more commonly used to convert straight logs to planks?
4. What do we know about how big curved timbers were passed through sawmills? Most of the information I have seen is about cutting straight logs into planks.
5. How tight is tight? Where frame timbers are fitted against each other, how carefully is this done? So tight you cannot jam a piece of paper in between the timbers? Or is there some slop? Are the joints tight all the way from the ceiling face to the plank face? Most drawings, such as Sturckenburgh, show the overlap as a single line, suggesting a well-fayed surface, but how do things look on real ships, before the timbers have dried out and shrunk?
With all of this said, I do not see a great savings in work between tilted and parallel frames, compared to the other process in building big ships. I think sawmills were a big improvement, because they drastically reduced the work in rough conversion of logs into planks, beams and other timbers. In shaping big timbers that would not fit on our sawmill, most of the work and time was in roughing out, removing the main mass of waste, not in finishing the last 5 mm. Once you are comfortable with an adze, it is about as fast as a hand power plane for surfacing large timbers (and a lot less obnoxious). But boy, the sawmill saves a tremendous amount of unpleasant grunt work.
I think we need to look elsewhere for the reason for change (if change it was). Sawmills and parallel frames do go well together, but that does not necessarily mean that one led to the other. As Jules writes, there had to be a reason for tilted frames in the first place. To me, the relative orientation between the frames and bottom planking suggest that tilted frames were a traditional part of the bottom-based method, and we see them in older versions of the bottom-based tradition, such as cogs and Roman river barges. It may go back to the raft origins of the method, or it may be related to some saving of effort in bevelling the floor timbers (which is more work than siding them).
COncerning whether the sides were frame-first or plank-first, the answer appears to be a little of both. In archaeological finds of bottom-based hulls (Vasa, OB71, B&W wrecks, etc.) the little nail plugs left from the cleats that held the planks together tend to be most plentiful below the turn of the bilge, suggsting that the upper works were constructed differently. Once the bottom was planked, and floor timbers in place, the first futtocks could be attached at their lower ends to the bottom planking. This left their upper ends free, and these could then be planked (frame-first). Once the top of the first futtocks were reached, then there was enough side planking to attach the second futtocks, etc. I have seen no evidence that the entire hull was planked up before putting frames in. Even in shipbuilding traditions which had edge-joined planks and were clearly plank-based, the construction itself tended to go in stages, either planks or frames leading. The absence of large numbers of spijkerpennen in the upper works of Dutch ships suggests that the frames led above the turn of the bilge.
Thank you, Jules, for reminding people that Vasa is one ship, built under specific circumstances, in one place. By itself, it is not a general indicator of anything - it has to form part of a larger, more broadly sources body of data in order to be relevant. In this case, it is useful to remember that while the master shipwrights and about half of the carpenters came from the low countries, the rest were from Sweden and Finland, and many were trained in a different tradition of shipwrightry. We see this in the details of construction, where the same problem is solved in different ways by different gangs of carpenters. What we see in Vasa is mostly consistent with what we see in other Dutch-built wrecks of the later 16th century and first half of the 17th, but there are variations and anomalies, so one should be careful about extrapolating general practice from it too much.
Fred
|
|
|
Post by jules on Sept 5, 2016 14:08:02 GMT
Hello Peter (Tromp), I'm back. Sorry if I made you do the wrong test. My intention was to make a wooden strip of even width and a tapering thickness. Like this sketch. Put your tape back on the hull where it was before, and try to make the wooden strip follow the tape. You can wet the wood, heat it, whatever, to make it flow against the tape on the hull. Fixate the strip with tape or so. Leave it to dry, take it off, see what shape it has, and see if a shipwright can reproduce this curvature in real life. If possible, place more of these wetted, heated strips of wood against eachother to see if it is feasible to do this without warping or creating gaps. What Peter Jenssen is trying to say, I think, is this: When you look at, say, station line '10', and at the intersections of this line with the waterlines, you see that the tangents to the waterlines do not line up, they all have a different angle to the center line. When you place a frame in the position of station line 10, and you want the frame to follow these tangents, the frame will show torsion. This, in my view, is hard to make in real life. But let's see what your experiment will show. For the second bit, the bit about the building sequence for the bottom first building method, I hope Jan (Amateur) helped you out: only the bottom was built completely plank first, the rest was mainly built frame first. Jan gave you the Van der Meulen drawings, I would like to add a drawing Witsen made: To check if the building method with the frames with the 'perfectly square sections' placed against the planking you suggest, was used in the second part of the 17th century, I checked if the frames had to be moulded (Fred), bevelled (you), or 'geslecht' (faired). Because the point of your method is to avoid the bevelling, I thought that if bevelling occured, it is not likely that they used your method. So I checked Witsen and Van Yk again. Witsen, in his building step overview, mentions that the frames needed to be bevelled inside and out before the planks could be placed (Witsen, Architectura, 1690, p.164, II, steps nr. 29, 30, 32 and 41, explanations p.170, II and 171,I). Look also at the guy on the scaffolding in Witsen's drawing: happily bevelling away with his adze. Van Yk, describing a different building method than Witsen's, mentions that all the frame parts need to be bevelled inside and out before the planking was placed (Van Yk, Open Gestelt, 1697, p.81). He also gives an example of what had to be done when some apprentices got the bevelling for the keelson wrong: all the floor timbers that got to thin, needed to be filled out with new wood. (He doesn't mention if the apprentices were fired.) Since both authors mention that bevelling had to be done before planking, we can say that it was pretty common for shipwrights of the second half of the 17th century to bevel frames before laying the planks. (Even in todays frame first building method fairing needs to be done. Take a look at: 'Traditional Maritime Skills'-series, part: 'Fairing Frames (large boats)'. Very informative.) Kind regards, Jules
|
|
|
Post by amateur on Sept 5, 2016 18:21:26 GMT
Scanning through Van IJk, I came across a few lines on the 'Oplangen'. (p78). I wonder: Is van Ijk describing tapered frames here?
I quote (in Dutch): Yder Legger heeft twee Oplangen nodig: Houten die van vooren tot achteren Schips Zyden formeeren, en met Haar ondereinden, voor een groot deel op de Leggers rusten. Haare dikte in de Kimmen is een tiende, en op de Scheerstrook een vierde minder als de leggers op de Kiel. Na Reden van haarde Dikte, verminderd desselvs Breedte: ook geevdmen agt op de zwaarheid der Krommers, uit welke zy werden gezaagd; want door somtijds een Duim van gestelde breedte af te wyken, kan 't gebeuren, dat ook sonder eenig Schips nadeel, uit een Krommer, een geheele plaat meerder, tot 's bouwmeesters merkelijk profijt, werd gesneden, als anders, de breedte juist in acht genomen sijnde, niet doenlijk soude wesen.
IN my translation (names of frameparts not translated) that reads as: ON each legger, we need two oplangen. These parts define the shape of the ships sides. The lower end of these oplangen sits on the leggers. Their thickness in the bilges is one-tenth, and at the scheerstrook one quarter less that the thickness of the legger on the keel. Their width should diminish at the same rate as their thickness. The shipwright should pay attention to the thickness of the wood he is using. Sometimes it is possible to deviate up to an inch in thickness, without harming the ships integrity, which allows the shipwright - to his profit - make an additional plaat [plank ?] compared to the number possible if he would strictly adhere to the exact width.
In my interpretation this means that the frameparts taper, in thickness and width between bilge and scheerstrook (lower wale). They also taper considerable amount: one quarter of the thickness of the legger is certainly more than a few milimeters. Therefore, the taper in width coudl also be considerable (even if it is less than the taper in thickness) Van IJk also states that the shipwright should be sensible, as slight deviations from the 'standard' measurements leads to less spillage of material, and therefore increase in his profits (without any consequences for the ship). That does suggest that the frameparts were sawn at the wharf, and at not completely standardized measurements. Or am I now way off in my layman interpretation of Van Ijk?
Jan
|
|
|
Post by jules on Sept 5, 2016 21:43:48 GMT
Hello Jan (Amateur), Yeah, interesting lines. I prepared a sketch to show what it means if the 'oplangen' taper, if we interpret Van Yk this way. I took a timber of 11 inch and a room of 9 inch. I tapered the oplangen from 11 inch to 8,25 inch (3/4 * 11 inch), and gave them a height of 16 feet (Depth in hold of a large ship. Taking a lesser depth would increase the 'banana effect'). I did not taper the 'zitters'; they are parallel. The oplang with the two small vertical lines is the 'hals-oplang', at 1/3 of the length of the ship. I took 13 oplangen forward of the 'hals', and 26 aft of the 'hals', resulting in a total of 40 oplangen. I think the sketch shows that this probably is not what Van Yk means; in 1697, when his book appeared, ships didn't have that much sheer. I think what he wants to say is that, in accordance with Witsen, the oplangen can have a lesser width and thickness forward and aft. But, I admit, if this is really what he wants to say, it is very cryptically formulated. About the second point: I do not necessarily read out of the Dutch text, that the wood was sawed at the wharf. Was the shipwright present to give directions when his wood was cut in the sawmill? In Amsterdam, for example, the mill was never far away from the wharf. (I wil check the job description of the Admiralty of Amsterdams shipwright to see if something is mentioned about him being responsable for the economical use of wood.) Kind regards, Jules
|
|
|
Post by Peter Jenssen on Sept 6, 2016 1:35:39 GMT
Thank you, Jules, for reminding people that Vasa is one ship, built under specific circumstances, in one place. By itself, it is not a general indicator of anything - it has to form part of a larger, more broadly sources body of data in order to be relevant. In this case, it is useful to remember that while the master shipwrights and about half of the carpenters came from the low countries, the rest were from Sweden and Finland, and many were trained in a different tradition of shipwrightry. We see this in the details of construction, where the same problem is solved in different ways by different gangs of carpenters. What we see in Vasa is mostly consistent with what we see in other Dutch-built wrecks of the later 16th century and first half of the 17th, but there are variations and anomalies, so one should be careful about extrapolating general practice from it too much. Thank you Fred, for this very interesting insight into the carpentry considerations. I see how adzes would have been a good tool of choice. Working all the surfaces are still preferred after sawing due to rot risk, -interesting. Good point, the Vasa is one ship, built under specific circumstances. It was not built in the Netherlands, so why is it relevant in discussing Dutch practices? Well, it was built in a shipyard leased by a Dutch master, so therefore to some extent built with Dutch methods that were introduced to Sweden by Dutch masters. But what are the specifically Dutch methods used? The bottom first method is usually the first mentioned. But does that mean some other method was used before? There were many ships built in the century before the Vasa during the establishment of an independent Sweden, some even larger than the Vasa. Masters from Sweden, Finland and Germany were employed as well as Dutch masters in various shipyards around Sweden as I understand. (Also in both Sweden and Denmark, Scottish?) How were the others built? How many shipwrecks of this time have been examined? Is there a pre-Dutch 'not bottom first' method used in the 1500s and earlier Sweden? Viking ships were bottom first as well I think? What I'm trying to understand is, -in the context of Swedish 16-17th century shipbuilding, what signifies 'Dutch building methods'? Seems Dutch influences would be strong, but there are others as well. Also, what is being influenced? (What's local practice?) Cheers, Peter
|
|
|
Post by Peter Jenssen on Sept 6, 2016 2:00:50 GMT
To Peter Jenssen, Again, this has to be short. Will be back to you later. Thanks for the calculations. But again, why would they want to do the extra work? What's the purpose of making the frames tilt? Peter (Tromp) suggests that it is because they put the frames against the planking to save work, and as a result the frames tilt. In my view this would result in a torsion of the frames. But at least it's a theory. The tilting is not a goal on its own, there has to be a reason for it. Regards, Jules Hi Jules, The purpose of the calculation was only to check how much extra work. It would appear that it is not a lot. I think a cause of tilt would be the placing of square sawn floor timber on the prepared bottom as the bottom rises up towards the stern. Cheers, Peter (J)
|
|
|
Post by amateur on Sept 6, 2016 6:24:34 GMT
Hi jules,
I admit, the sawing has to be in close cooperation with the wharf, not neccesarily at the wharf.
With respect to the tapering: there is no way to prevent this extreme banana-shape, when you want all packed very close together. (Unless you opt for a system with filling-pieces higher up the ships side. But then, what is the use of this extreme tapering...... Because this explicit mentioning of bilge and scheerstrook, i don,t see why he should mean front and aft. On almost the same page he is very specific over the placement of the forwarrd and aft frames. Can't understand why he should be so sloppy here.......
Jan
|
|
|
Post by jules on Sept 6, 2016 8:34:38 GMT
Goedemorgen Jan,
I don't understand why Van Yk is so sloppy, as you call it, either. I've read these lines several times in the past, but had to give up. At first I interpreted them like you did, made the sketch, and came to the conclusion that this could not be what he meant. And, Van Yk is describing the frame first method which preconnects the frame parts to make a frame, and then erects this complete frame. Why the need to taper the oplangen in this case? No bottomplanking to follow with this method, the frames were simply placed on the keel, and the bottom planking placed against the frames. So, I decided I had to move on... (to boldly go where no one's ever gone before ... E81, Sturckenburgh, Gent and beyond).
Good luck with the quest,
Jules
|
|