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Post by jules on Jun 3, 2023 16:14:43 GMT
Hello Jan,
You did it! Looks great. Love the small diorama.
Which Dutch fluit did you choose?
Would you care to share on which Dutch forum we can find the build of your fluit? There are more than one...
Good luck with your new build,
Jules
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Post by jules on Mar 25, 2021 9:04:13 GMT
Hello Philemon,
My book is an ungoing project. It is getting bigger and bigger. Publishing date: just before I die. I just hope I get the timing right. Both Witsens, 1671 and 1690, are in my 'library' now. I was talking about the days when I was still a poor, young man. You're absolutely right: let's stop talking Hoving, let's start talking shipbuilding. Thanks for confirming that they could build every hull shape they wanted. It is a controversial statement you know. I understand now that you are writing a book as well. So, let me ask, what do you want from me on this forum? Do you want to ask me questions? Do you want to discuss certain subjects? I already offered to work on the reconstruction of the 155-footer here. Just let me know, so I can prepare something. Yes, I walked through the pinas. Impressions? You go first.
Hello Amateur,
I know Rene is not Ab's employee. He should be though. If Rene is doing all this for free, he must be completely mad. Ab's work strongly depends on Rene's work, as it depended on the work of Cor Emke. Ab owes Rene big, big time.
Jules
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Post by jules on Mar 23, 2021 11:59:22 GMT
Hello Philemon,
So you had a look at Hoving's reasoning on the American forum. Yeah, it is an impossible situation he created for himself, no way he could talk himself out of his own created mess. Blaming the computer is of course always stupid. Blaming the computer is blaming the man behind the computer. And in this case that is Hoving's long trusted employee Rene Hendrickx. Rene does not speak English, but if he knew what Hoving is saying about him on that forum, he would not be pleased. Hoving is actually putting his cad-capabilities in doubt. And, the strange thing is that Rene has shown that he is very capable of drawing chined hulls. The linesplan of the 'pleasure vessel' with a chine, which he drew, is in the same thread!
I have the idea that you do not know what I am working on. I am working on a book which includes the reconstruction of the threedecked ship Gouden Leeuw of 1666. My book will deal with 17th century shipbuilding in general, and the building methods of Witsen, and Van Yk will be described in detail. Yes, both. For me it is no question of Witsen or Van Yk, you have to use them both. I started my research with Van Yk in the late 1980s, because the facsimile edition was available at that time. I added Witsen in the early 1990s, when that facsimile became available. Before that, in the 1980s, I studied Witsen by visiting the Nijmegen university library during the evening, and copying large pieces... by hand. I was not allowed to take photocopies, or make photos. Ah, those good old days.
So, when you say that nobody ever read both Witsen and Van Yk thoroughly, I must protest: both these books are very dear to me, and I know them both by heart. How are you supposed to say anything about Dutch shipbuilding in the 17th century if you did not study both works thoroughly? I appreciate that you offer your help in interpreting Van Yk, but I fear I am beyond help, I have formed my own opinions already, and these will be presented in my book.
The website of the RCE is called Witsenscheepsbouw.nl, and it is only in Dutch. No problem for you of course, but for the others... I sent my letter of protest to the RCE yesterday, and I suggested that they rename their website into Hovingscheepsbouw.nl, because that is what the site shows: Hoving's shipbuilding, not Witsen's shipbuilding. If you send me a personal mail with your email-address I will send you a copy of my letter.
Kind regards,
Jules
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Post by jules on Mar 22, 2021 0:09:46 GMT
Hello Philemon, Good to see you're back. I am in no way saying that you can not build hull shapes with chines when you use Witsen's building method. They could build anything they liked with Witsen's method. As Witsen's technical drawings show: there are hulls with chines, and there are round hulls.
But, what Ab Hoving, not me, always states is that when you build with Witsen's method, you will always get a hull with a chine. To debunk Hoving's myth, I showed three hulls that were built with Witsen's method that are round. So, to stay in your terminology, I showed three black swans while only one would have suffised. So I can be very conclusive in stating that round hulls can be made with Witsen's building method. By the way, I brought this subject to Ab Hoving on the Model Ship World forum last week. He still says there that only chined hulls can be the result of Witsen's building method. I used my three round hull shapes as arguments, with Vasa as the trump, and now he does not reply anymore. That might also have to do something with that I said that I do not have to look at his models, or his replicas anymore to know how ships were built with Witsen's method, I can look at the real thing, at wrecks. So, please, have a look on that forum. The only thing I want is that Hoving's myth of 'the building method decides the design of the ship' finally stops.
You're no fan of Hoving's book of 1994 I guess. But hey, neither am I. I was just answering your question if an analysis was made of Witsen's building method. And that is what Hoving's book is. If it is a good analysis, is another question.
But, if you really want to enjoy Hoving's expertise on 17th century shipbuilding, have a look at the new website of the Rijksdienst voor Cultureel Erfgoed. They gave him a free ride there, so Hoving's vision is now the vision of our beloved state the Netherlands. Another great day for our cultural heritage. The 'chined hull'-myth is on the site, together with the 'no drawings were used in Dutch shipbuilding'-myth, the 'gunports were hacked in the hull'-myth, and some other Hoving-goodies. I will send my letter of protest to the RCE tomorrow. Please join in.
And now I go to bed,
Jules
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Post by jules on Mar 14, 2021 10:50:52 GMT
Hello Philemon, I hope you do not mind I used my reponses to your contributions as a way of ventilating my dislike with the whole situation that has evolved around this chine-myth. It really starts to piss me off that we have to have this discussion over and over again without there ever being produced any evidence for stating that Witsen's building method leads to hulls with chines. I hope my 'clues' explain where I am coming from, what built my frustration. But the thing that really pissed me of, were not your posts, but the things that happened on another forum while we were discussing your posts. Let me explain. In february 2021, last month, Ab Hoving posted that he had "made new plans, based on a statenjacht and with an interior that seemed useful for the ship". Subsequently he posted a hand sketch of how he thought this 'statenjacht' had to look. Here is his handsketch: It is clear, the bottom is straight and the transition between the bottom and the bilge is not round, it has a distinct angle, it has Hoving's trademark: the chine. But, have a close look at the bottom-bilge transition in this sketch: mister Hoving started of with a round shape, erased that, and replaced it with the chine. Then mister Hoving explains how he gave his sketch to his friend mister Hendrickx, and let him make the computer drawing of the linesplan. Here is a part of that drawing: Notice that the chine is no longer there, the transition from bottom to bilge has a curve to it now. This change has not gone unnoticed, and a forum member decides to ask mister Hoving a question about it: "I have a question about the drawings you are showing. In your first sketch of the lines plan, it shows a fairly sharp edge going from the bottom towards the bilge. I understand from your book on Witsen that this is the result of the building method/tools of that time. However, in Rene's drawing this sharp edge has become a short radius turn. As I am currently designing a statenjacht based on a contract, I am very interested to understand what shape I should aim for." And here is mister Hoving's reply to that, very intelligent, question: "In case the bottom is not entirely flat, like in fluits, the transfer from bottom to bilge is not so very pronounced. On top of that, computerprograms hate corners in a hull. As you can see in my original design the straight bottom is there. In Delftship it is gone. In this case of a yacht-like ship I did not mind too much. Good luck with your project." It is clear, the chine should have been there, but the computer programm could not handle it. That is certainly a strange argument because this thread, which was started back in 2019, contains the presentation of the lines plan of the 'pleasure vessel', which, as we've seen, has a chine! So it is certainly possible to draw chines with Delftship, but mister Hoving "did not mind so much" this time. But, the asker of the question is satisfied with mister Hoving's answer, and says: "Thanks Ab. For the time being I will aim for the pronounced, as the bottom is rather flat (1,5 inch rise over 16 feet). I may end up losing it either in the software or when building POB style. Interesting challenges with scratch building even before cutting wood!" And another forum member joins in and says: "Ab, Your work, both model making and your scholarship, is wonderful! The extent to which hull shape and hull structure is affected by construction technique is a sadly neglected subject. The idea that all wooden ships were built from a draught, with lofted regularly spaced frames seems to be a myth that won't die. ...". Mister Hoving did not reply to this anymore. Now why does this bother me so much? What we see here is that mister Hoving is knowingly and willfully pushing people into the wrong direction, the direction of the chine, while he knows, or should know, that there is a very good technical drawing of a 'statenjacht' in Witsen's book of 1671. Here it is: It is the technical drawing of the yacht that was built for the Swedish king in 1669 by Hooghsaet. And the drawing shows that the bottom-bilge transition is round, there is no chine. It is very unlikely that mister Hoving does not know about this drawing, because he included it is in his book of 1994. Here is the page from the book that shows Witsen's drawing of the 'statenjacht', and another drawing of a 'statenjacht': Why didn't mister Hoving inform his fellow forum member about the existence of this very good, genuine, well provenanced, seventeenth century construction drawing of a 'statenjacht'? Even when the forum member asks explicitly for information about the shape of the bottom-bilge transition, mister Hoving does not mention this drawing. I have a strong inclination to thinking that mister Hoving did not mention the 'statenjacht'-drawing from Witsen's work deliberately. He did not want to mention this drawing, because this drawing not only clearly shows that there was no chine, it also shows very clearly that the shipwrights from Amsterdam, working according to Witsen's bottom based method, were capable of building hulls with round bottom-bilge transitions. So, by publishing this drawing, mister Hoving would not only destroy his carefully constructed 'chine'-myth, but also his carefully constructed 'building method decides design'-myth. And maybe even a third myth that has been created by mister Hoving can be added to that list: 'the shipwrights did not use drawings for their designs'-myth. So, dear Philemon, I am sorry that I packed all this frustration into the answers to your posts. I hope you understand why now. Kind regards, Jules
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Post by jules on Mar 14, 2021 8:22:04 GMT
Morning Jan,
Hey, this was a quiz you know, and you have won! What do you want as a prize? Please don't say you want the collected works of Ab Hoving, it'll cost me a fortune!
Have a good sunday,
Jules
ps just saw you brought the subject to the MSW-forum. I wanted to do that myself, you beat me to it.
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Post by jules on Mar 13, 2021 16:49:21 GMT
Clue 6. We are fast forwarding now, and go from 2012 to 2019 in a hurry. Our author keeps on publishing, and for example publishes two devastating pieces for Dutch heritage in 2013 and 2017. But since these have nothing to do with our main subject, I will skip those. In 2019 our author decides to publish his findings with the building of the model of the pleasure vessel on a forum. The author explains that "this little pleasure vessel had changed my life forever", and that he finally got round to making a linesplan for it. He then shows this linesplan, but it is not finalised yet. But, it is clear that the vessel has a chine. In 2020 the author publishes the finalised linesplan of the pleasure vessel on that same forum. Since the author explains that it is free to use for everybody, here it is: It is clear from these computer drawings that, according to the author, the pleasure vessel had a chine. We've come a long way from the first conclusion of 1988, "they differ only slightly on the outside", to a very discernable chine. Since the linesplan was for free use, a modeling company contacted the author for asking if they could use the linesplan for developing a new model kit. The author was ok with this, and now we can by a model kit of a pleasure vessel, with a chine. We can only imagine what Witsen would have thought. Kind regards, Jules
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Post by jules on Mar 13, 2021 14:22:19 GMT
Clue 5.
After publishing his magnum opus in 1994, our man published some more books about the ship reconstructions he had made since. In one of those books, the one from 2004, we can for example find: "In the Northern Dutch style, which is described by Witsen, the bottom and the first plank of the bilge form a distinct angle. The width of the bottom is therefore often indicated in the certers. ..., it is probable that the ship was a Northern Dutch product and therefore must have had an angle between the bottom and the bilge plank."
So here it is clearly claimed by our author: Witsen's building style generates ships with a chine. And the author even expands on his unfounded theory of the chine: when we find a certer with an indication of the width of the bottom, the ship has a chine. It's getting weirder and weirder. To be clear one more time: Witsen does not claim, nor describe, that the ships built by his method had a chine, or should have a chine; on the contrary.
In 2012 part of the man's magnum opus of 1994 was translated in English and published. This publication of course showed the body plan of the pinas, with the two lines indicating the chine, and the reconstruction of the pleasure vessel. Both were accompanied by the texts we've seen in the 1994 version. For the author, nothing had changed since 1994.
Kind regards,
Jules
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Post by jules on Mar 13, 2021 11:38:18 GMT
Still no answer, so I continue giving clues: clue number 4.
In 1994 our man published a book. In this book he included his reconstructed 'body plan' of the pinas, and his findings about building the pleasure vessel.
The body plan of the pinas, again, contained the two lines for indicating the transition of the bottom to the bilge; the chine. And that a chine was intended, can be read in the accompanying text: "Because the first bilge strake was at an angle with the bottom planking, the transition from bottom to turn was visible. This was most obvious on very flat-bottomed ships; on sharply rising floors it was hardly noticable. When a ship had a very wide and flat bottom, the outer most bottom strake was often canted a little so the ship would not be like a trough (67 I 29). Angular constructions underneath the waterline were not favored because they were vulnerable and could result in leakage."
So, although our author notices that Witsen says that chines should be avoided, he insists they were present.
Now let's turn to what our author says about his findings while building the pleasure vessel models. And please remember the first conclusion that was presented by the same author earlier, in 1988: when comparing the hull shapes that resulted from the two different building methods, no significant difference could be seen: "they differ only slightly on the outside". And here is the new conclusion of 1994: "All other features of the shell-first method were present - the nearly flat bottom, the angle in the bilges, and the relatively arbitrary length of the frame timbers, which remained unconnected to one another and were fastened only to the ceiling and planking; there were also traces of where the floor planks and bilge planks had been temporarily joined with chocks spiked in place."
Let's just say that the conclusion had 'evolved' into something else in the 4 years between 1988 and 1992. For some reason the chine was now clearly present. And, think of captain Horjus again, who arrived at a round hull while using the bottom first method of building.
Oh, and I forgot to mention that the author was offered a job at a reputable museum after his presentation at the symposium of 1988. Which he accepted.
Kind regards,
Jules
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Post by jules on Mar 12, 2021 19:09:14 GMT
Hello Philemon, One more clue then. The last for today. In 1988 our man held a lecture at a symposium. There he presented what he had learned while building two models of the same vessel, a 'pleasure vessel'. The two building methods were: building according to the method of Witsen, the bottom base method, and building according to the method of Van Yk, the frame first method. One of the conclusions from this interesting experiment: "Once both hulls have been planked, they differ only slightly on the outside. Partly this is caused by the graceful lines of the model of the pleasure vessel. A ship with a flatter bottom would have shown a greater difference. The use of boeitangen caused a flat part of the bottom on both sides of the keel over a relatively long distance, without any curving. The transition to the vertical side of the ship happened in the bilge, so that a real brake could be seen. The flatter the bottom, the more visible the angles. With a bottom not so flat, as here, the transition between bottom and bilge was not so obvious." So, while the test revealed that the difference between the two methods was actually negligible, the author claims that the difference would be greater if only it would have been another vessel. Instead of repeating the experiment with a more suitable hull shape, the author left it at this: a chine would be present while using Witsen's bottom based method. That's of course unsubstantiated evidence, and, as we've seen, Horjus has shown that when building a model of a ship with a flat bottom, while using the bottom based method, it is possible to arrive at a round shape. Exactly the opposite of what our man claims. The author's lecture was presented in a guide published by the symposium in 1992. Ironically his piece was placed next to a piece that claimed exactly the opposite. A piece by Rob Oosting that presented the hull shape of the wreck of the E81 wreck. Here is the part of the lines plan of that wreck as published in the guide: Look at the round shape of the hull: no chine.And here is a part of the very interesting conclusions Oosting presented: "second, the bottom strakes of the 17th-century merchantman were built up to the tenth strake before frames were inserted. Spiles give us the location of the cleats inside and outside the lower hull planking. Further research should give us more information about the building-method and sequence above the 10th strake." So here we have archeaological evidence for round shapes in ships built with the bottom-first method: no chine. But we already found that in Vasa of course. Kind regards, Jules
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Post by jules on Mar 12, 2021 16:57:18 GMT
Hello Philemon, Still no answer, so another clue. The author I mentioned in my last post, wrote another article in the same periodical half a year later; in 1987. This time he presents the model he made of Witsen's pinas. He had taken Witsen's co-ordinates and had succeeded in transforming them into a 'body plan'. Here it is: Notice the two lines that mark the chine.The author then explains that it took him three years to build the model and: "Though I would very much like to have done so, it was not possible to build the model in the same way as the original, so I had to build the frames first and plank them later." This of course makes clear that the chine was 'designed in', and was not a result of the building method used to build the model. That it is possible to build a model with the bottom first method, is shown in the small book that was written by Ton Pronker. He describes how Captain J. Horjus built his model of Geelvinck. Here are two pages from that booklet: Captain Horjus, while working with the bottom first method, arrived at a round transition between bottom and bilge: no chine. Kind regards, Jules
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Post by jules on Mar 12, 2021 14:20:53 GMT
Hello Philemon,
Since you did not answer the questions I posed to you yesterday, I will give you another clue.
Who wrote this back in 1986?
"As a result of the use of the boeitangen the flat part of the bottom was actually flat. The bilge was formed as shown in figure 4, from three or four planks next to each other. It should be noted that there was a pronounced angle at the point where the flat bottom changed into the bilge."
And, in that same publication, of the same man, we also find:
"Is there any value in knowing that there were two methods of building ships in Holland? I think that there is. Take for example, the Wasa. If this ship, constructed by a Dutch shipwright, had been built in the Northern way, there would be a very obvious angle between the flat of the bottom and the bilge. There was no such angle, pointing to the fact that the shipwright must have come from the Southern parts of Holland. This is confirmed by the man's name - Hendryk Hybertsson. Hybert comes from Hubert, which is French, and this name does not occur in the Northern part of Holland. There were, of course, other small differences between the products of the two areas, but the foregoing was the main one. Such knowledge might be of help, therefore, in identifying ship models."
Vasa indeed has no 'very obvious angle between the flat of the bottom and the bilge', as the author rightly states, but we now know that Vasa was 'built in the Northern way', what the writer thought impossible.
More to come...
Kind regards,
Jules
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Post by jules on Mar 11, 2021 17:06:52 GMT
Hello Philemon, Jaap, It looks like you've given up on Witsen. I will try to convince you that you should not. First I'll try to give answers to all your points of criticism. I numbered them to stay on track. 1. Witsen is inconsistent. I think this is not the case. Just use his illustrations for what they are intended for. He uses them as illustrations for his text. Do not take the illustrations out of their context and use them for something else. So, do not use illustrations intended to show a building process, as design drawings. You keep on doing this. 2. Witsen's pinas is not a pinas at all. Strange criticism. If Witsen calls his ship a pinas who am I to disagree? But, what's in a name? You can call it what you want, it does not change the information Witsen provides for this ship. 3. Deviation measurements from theory. That's what I meant when I said that Witsen found out the hard way that the theory he had found did not match the reality he found on the shipyard. 4. The missing gunports. For me this is a detail in the complete construction of the ship. He does not describe how to make them, but I'm sure you can without his help. As you correctly say, there is no doubt that they were there though. Here is a list of all the plates that show them: plate XXXII, XXXIX, LVII, XLI, XLIV, XLV and LIX. You can hardly say he forgot about them, can you? 5. Trim is not mentioned. As said before, trim is indicated in the technical drawings. The amount of trim was created by the ratio between the height of the stem and the height of the stern. And, again, this is a design decision. And, again, Witsen does not do much design. 6. Missing descriptions of rabbet angles in the keel. You state again that these angles are important, when I showed you that they are of less importance than you think: the bottom and the garboard do not have the same angle. 7. The chine is not mentioned by Witsen but he shows the chine in his drawings. Again, do not use the drawings that are only intended as illustrations of the building method as design drawings. There are design drawings in Witsen's book though, you can use those: 'Noorts-vaarder', plate LX; 'Jagt', plate LXXII; and plate XCIII when Witsen talks about volume measurements. These real technical drawings all show round transitions from the bottom to the bilge. 8. Construction main profile does not work. True, it is tragic that Witsen could not find the way to draw the shape after he had determined the appropriate coordinates. That's probably why he decided to stay away from design in the rest of his book. I can only say one thing: do not use Witsen's book as a design manual, and you will be ok. To show you that others, long before him, could make these designs maybe gives you heart to continue. Here is an example of 1633: 9. Support of keel during building and launching is 'unbelievable'. Could you please explain what you mean? Are you saying these ships were not supported by wooden blocks? I do not get your point. 10. Does not mention how the profile of the stern post is made, and the building sequence is wrong. I guess you are refering to the description on page 149, II and 150, I. The description of the method is quite clear to me, so I guess you mean that he does not say which arcs should be used etc. But, hey, that's design. Like Witsen says in this paragraph: use a flexible ruler to determine the shape you want.
11. There are plates which show a flat bottom and there are plates which show an angles garboard-bottom transition. We've covered this, I think: use the drawings for what they are intended for. About the reliability of the information Witsen provides. I am sure Witsen's reliability is beyond doubt. He used the papers and designs his father left him, he took, as he says himself, measurements of sails and ropes, and I'm sure he took all these measurements of his 'pinas' himself on the shipyard. He had access to technical drawings, and made the effort to put them all in copper to use in his book. He published Grebber's table which explains that proportion rules were used. He published the famous figure W, which, with all its shortcomings, at least shows that arcs were used in determining the shape of the main frame. And I could go on. A better question would be: what would we have known if Witsen had not written his book in 1671? And I do hope you are not going to answer that by saying that Van Yk's information would be enough to design a ship, or even translate a 'certer' into a ship. After all, he uses the same design rules as Witsen: Width is 1/4 of the Length, Depth is 1/10 of the Length. And now look at your certer of 1664... Not even near these proportions. And, ask yourself: why did Van Yk republish Grebber's table? Where are the design parameters in Van Yk's book? Remember, Van Yk was not a shipwright, he was a ship's carpenter. He never designed a ship, he built them, he did what he was told to do. And he left the shipyard at a young age. He published the notes he took when he was young and threw in the information he inherited from his uncle, another ship's carpenter. That's Van Yk's book. And that's why I suggested to do your reconstruction together, so that all the problems with Van Yk's book would become clear. You say there is no analysis of Witsen's building process. How would you qualify Hoving's book from 1994 then? He built his book on the 122 building steps Witsen describes on page 144 till 146. You can agree or disagree with the comments Hoving gives, and with the exactness of the new illustrations, but the building sequence stays intact in his book. I have made that analysis of the building process for myself too. How can you claim to have read Witsen's book when you did not study his building sequence? The book was written to explain the building process! There is a clue in the title of the book; it has the word 'scheeps-bouw', shipbuilding, in it. I must advice you to study that building process thoroughly, before judging the book. If you do not understand the book, do not blame the book. Blame yourself, and work harder. And then there is that chine again. Whatever I say, it does not make you change your mind, does it? Even when you have to admit that Witsen does not mention the chine, you still insist it was there. Even when Witsen says that chines should be avoided, you still insist they were there. I asked you from the beginning, and several times afterwards, to come up with proof for the existence of these chines. You came up with exactly... nothing. This makes this discussion absolutely sterile for me. We are discussing a simple question: does Witsen's building method necessarily lead to ships with chines? I gave you several arguments for why his building method does not lead to ships with chines, but you keep on insisting it does, without any arguments. May I advise you to ask yourself the question where the idea that Witsen's building method leads to ships with chines comes from? And also, when did this idea came into existence? Where and when was the 'Dogma of the Chine' decreed? And by who? If you can answer these questions, there is still some hope. If you can not answer these questions, I will give you an answer tomorrow. Kind regards, Jules
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Post by jules on Mar 10, 2021 17:26:48 GMT
Hello Philemon, Jaap, Thank you for confirming the values I presented. And thank you very much for confirming that Witsen does not mention that ships had chines, or should have chines. I know we are both talking about the design in a theoretical way, but I feel I must warn you. Though Witsen draws the garboard at an angle that is equal to the bottom of the ship, this is not how it was built. The garboard and the bottom are not in a straight line. Have a look at figure R from Witsen's book:
Here we see that the angle of the garboard is different from that of the bottom. The bottom first stays horizontal from the top of the keel, and the garboard is tilted from its position in the rabbet, so its upper-inner side is horizontal to the top of the keel as well. This results in an angle between the garboard and the bottom. So the angle of the rabbet gives no indication for the angle of the bottom. The angle of the rabbet depended on the width of the garboard: the wider the garboard, the smaller the angle of the rabbet. As you have noticed, when you do not do this, you would need very wide garboards, or two garboards next to eachother; which was never done. I am looking forward to the shape of the main frame you will arrive at in the end. Please allow me to continue my explanation as well. In the end we will arrive at the same point, I hope. Let's have a look at Witsen's, now famous, figure W again. I showed before, on the extra page to Witsen's book, at what main frame shape we arrive when we use Grebber's method of drawing. Let's now have a look at what main frame shape we arrive at when we use Witsen's method, which he describes in his comments relating to figure W. Witsen describes that he divides the width in four equal pieces and that he uses one of the found points as the centre to draw the arc of the futtocks. Let's see what happens when we apply this method to the six 'normal' values we found for the width and depth for bottom and bilge in Grebber's table. And remember these values are confirmed by Witsen's formulas. Here it is on another additional page to Witsen's book, page 2: In A I drew the same rectangle I used to draw the Grebber-page: a rectangle with a 'normal' width-depth ratio of 2,5 : 1. In B I drew the same points f and g again for the ends of bottom and bilge. And, as Witsen prescribes, I divided the width in four equal parts; thus creating points e: the centre points for drawing the arc of the futtocks. In C we see what happens when we draw the arc for the futtocks with point e as the centre: the arc does not go through point g. This is of course a problem: we can not meet the design specification with Witsen's method. If we decide to ignore the problem and just call the new point at the end of the bottom g', we can continue like this: In D we continue by drawing an arc from g' to f. The arc is extended through f, or otherwise it is not possible to draw a tangent line to this arc in the following figure E. In figure E we draw the bottom line from the top of the keel tangent to the arc of the bilge. In figure F we see the final result. Not bad, but not up to spec. On the left side of the figure, I inserted the result we had with using Grebber's method. So it is possible to arrive at a solution adapting Witsen's method. But only if you are willing to accept that you can not meet the design specifications he himself prescribes. Simply using an arc with a radius equal to three quarters of the width for drawing the arc of the futtocks, is not a good method for fulfilling the design requirements. Can you agree with this presentation of the problem of Witsen's method, or do you think my reasoning is flawed? If you think it's flawed, please let me know. Otherwise I'll continue tomorrow. The best, Jules
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Post by jules on Mar 9, 2021 12:49:11 GMT
Hello Philemon, Jaap,
What I meant to say is that Witsen used the same principle as Grebber uses. And that is: take the measurements of a good ship, find out what the relations are between these measurements, find formulas so you can calculate these measurements, and then apply these formulas for every new ship you want to build. The thought is that when you take the measurements of a good ship, you can just scale these measurements to build a new ship, and that new ship will be just as good as the good ship you took the measurements of. Witsen probably found the Grebber table in the papers his father left him when he died in 1669. Grebber, the teacher of his father, was dead already, he died in 1666 if I remember correctly. Witsen could not just ask these two how he should interpret the table. He tried to find the formulas behind the values Grebber had calculated, and succeeded for a large part. Let's have a look, but, if you allow me, I will only limit myself to the six values concerning the lower part of the main frame. I will start with the values Grebber gives for the ship of 100 foot, because it is easier to calculate with those.
Grebber Length: 100', Width: 25', Depth: 10'. Ok, that's easy, the width is a quarter of the length and the depth is a tenth of the length. Let's move on with the values Grebber gives for the bottom. Width bottom: 16' 7,75", Depth bottom: 10". We see that the width of the bottom is equal to 0,668 times the Width. We can round that to 2/3. The depth is a bit more difficult to grasp. I'll get back to that later. Let's move on with the values for the bilge. Width bilge: 23' 3", Depth bilge: 3' 3". To find this width we need another value Grebber gives: 'De oplangen hangen over het boeisel', the futtocks hang over the bilge: 10". We have to take this value twice, and extract it from the Width. We get to 25' minus (2x10") equals 23' 2". It's not exactly the 23' 3" Grebber gives, but hey, it'll do. Now how did Grebber determine this value of 10"? I have to park this one for a while also. The Depth of the bilge is easier to understand: this depth is equal to one third of the Depth. 1/3 x 10' equals 3' 3,66". Again, not exactly the 3' 3" Grebber gives, but good enough. So now we have determined some formulas. And, as we've seen, these same formulas can be applied to all ship's lengths. As Witsen chose a ship of 134 foot as his main example, let's now look at the values Grebber gives for a ship of 135 foot. One foot difference in Length is close enough for demonstration purposes. Here are the six values for a ship of 135 foot: Width: 33' 8,25", Depth: 13' 5,5", Width bottom: 22' 5,5", Depth bottom: 1' 1", Width bilge: 31' 3,25" (overhanging: 1' 2,5"), Depth bilge: 4' 5,5".
Witsen, formulas Now let's have a look at what formulas Witsen gives for determining these six values. We can find those on pages 65 and 67 of his 1671 book. Here we go. Width equals a quarter of the Length. Same as Grebber. Depth equals one tenth of the Length. Same as Grebber. Width bottom equals two thirds of the Width. Same as Grebber. Deptht bottom: rises 1/2" per foot. I'll get to that later. Width bilge equals the Width minus two times the overhanging of the futtocks. Same as Grebber. The overhang equals the Length of the ship in feet devided by 10, in inches. Depth bilge equals one third of the Depth. Same as Grebber.
When we use the formulas Witsen determined for a ship with a Length of 134 foot, the length of his example pinas, we get to these values: Width: 0,25 x 134' = 33,5'. Depth: 0,1 x 134' = 13' 4,5". Width bottom: 2/3 x 33,5' = 22 1/3'. Depth bottom: 22 1/3' times 0,5" (in inches)= 11 1/6". Width bilge: Width minus two times the overhanging of the futtocks. Overhanging: 0,1 x 134' = 13,4". Width bilge: 33,5' - 2x13,4" = 31' 7". Depth bilge: 1/3 x 13' 4,5" = 4' 5". When we compare these values for a ship of 134 foot according to Witsen's formulas, with the values Grebber gives for a ship of 135 foot, we see that everything is in the same ballpark. No surprises yet.
Now let's have a look at the six values Witsen gives for his pinas of 134 foot.
Witsen, pinas Length: 134', Width: 29' or (2x 14' 7" =) 29' 3". Depth: 13'. Width bottom: 21'. Depth bottom: 5" or 6". Width bilge: 27' and (2x 13' 6" =) 27' 1". Depth bilge: 4' 5" and 4' 5,5".
When we compare these values with the values we found by using Witsen's method, we see some great differences. While the Depth is still close, the Width is more than 4' smaller, and the widths of bottom and bilge have decreased accordingly. The 'normal' width-depth ratio of 2,5 : 1 we find in Grebber's table and in Witsen's formulas, has been altered considerably to 29 to 13, or 2,23 : 1.
This is what I meant when I said that Witsen must have found out the hard way that all his formulas were not applied to build the pinas.
And then, finally, we get back to his figure W, the figure used to explain the design of the main frame. In this figure Witsen uses the 'normal' width-depth ratio of 20' to 8', or 2,5 : 1, not the width-depth ratio of his pinas of 2,23:1.
Before I continue, can we agree on this?
You say this whole discussion is only to determine if there was a chine or not. I thought we moved on from that, but I was obviously wrong. So one simple question before we start on this topic again: can you show me where Witsen says that the ships had a chine, or needed to have a chine?
Kind regards,
Jules
PS I am Dutch, like you. So here we are, two Dutchmen talking about Dutch shipbuilding in English. What is the world coming to...
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