Waldemar

From my observations, the simplest possible explanations and methods are usually correct. In post #9 you will find my brief interpretation of this phenomenon, and after every hull I draw I am more and more sure of it. On the surface it may seem that the method of drawing used by designers or draughtsmen is longer and more difficult, but in fact the opposite is true. If you do drawings, whether by hand or computer, you can check this for yourself. Try drawing a few frame profiles using both methods, and for this exercise you may follow Sutherland's instructions shown in this thread. You will find that it is much more difficult and longer to draw the shipyard profiles that were obtained with wooden templates – it's endless fitting by trial and error. In this light, it is clear to me that the designers actually used shortcuts to speed up the drawing. In contrast, it was much more convenient and quicker to use wooden templates in the shipyard. To put it another way, it was a kind of drawing convention, and 'everyone' knew that the floor/hollowing lines would only be finally formed on the mould loft in the shipyard. As is clear just from Sutherland's description. The shape of the ship you posted above gave me a good laugh.... 🙂 What an imagination!

Waterlines and diagonals of the reconstructed hull section of the Danish ship. I have not made any corrections.

Martes, thanks a lot again for pointing me to previously unknown material from 1657. As for this ship plan from the Russian archives (Hermitage), a poor copy of it was first published in the Russian journal Судостроение 1971/08 (Shipbuilding 1971/08) in an article by A. I. Dubravin, Shipbuilding in the age of the Northern War (in Russian). This plan is described in this article as an example of a design drawing from that time, i.e. circa 1700. This is, of course, nonsense. Personally, I think they were simply brought to Russia by Tsar Peter I from his travels in western Europe. I reverse-engineered this plan a few years ago and found many of the proportions consistent with the 1620 shipbuilding manuscript. As in the example illustration below. In the process, I have also made a simple 3D model as a feasibility test.

Thank you very much Druxey. To finish the job one more diagram comparing the design profiles of the Danish ship with the possible profile shapes that could have actually been traced in the shipyard (according to the Sutherland way). I have made no attempt to get these two sets as similar as possible. Now I ask myself: which set would I choose for my model or reconstruction of this ship if such an attempt were made?

Well, I try very hard to keep to the spirit of the age... 🙂 Many thanks to you as well, because through this very exercise I too have become more familiar with the ins and outs of period ship design. 🙂

Many thanks Martes for these links, much appreciated! And you may be perfectly right about the creator of these draughts now kept in the Russian archives. Similarities to the other Balfour's draughts are striking indeed. Once, when examining just a copy of this plan in detail, I also noticed many similarities to the specific proportions, shapes and methods as described in an English manuscript from around 1620. If I had copies of the originals at the time, rather than just this poor redrawing... Anyway, the original drawing, in contrast to its poor copy, show the frame profiles as having the floor curves, so, as a replacement another draught, better suited to my narrative (from the Danish archives). It should replace the first one inserted in post #12:

Firstly, I determined through fitting that all green arcs have the same radius, and all blue arcs have different radii. Then I determined more or less arbitrarily the triangle for the blue curves. The red lines were drawn first, then (inside the triangle) the blue arcs as tangents to the red arcs and the horizontal lines, and finally the green arcs tangent to the previously drawn sections of the profiles. It would even be similar to the conventional moulding method if it weren't for all those variable radii. For greater clarity, I have included another diagram below.

Done. The way the designer of this ship plotted the bottom curves on the plan is not as elegant as the method described by Sutherland. However, this does not matter much in practice, as in both cases these curves were redone by the shipyard workers during the actual construction of the ship anyway. And most likely in an identical manner.

Trying to reverse engineer this plan in a more regular way (btw, the ship's designer is Claus Reimer). The general method is already understood, only those troublesome floor curves remain to be reconstructed...

Nihil novi sub sole. 🙂 To conclude this thread, I also present a design draught of the Danish ship Printz Christian built in 1665, i.e. some 45 years before Sutherland's work was published. A quick check of the frame lines proves that this ship was designed on the conoidal solid principle, so that the cross-sections of the submerged part of the hull have the shape of a perfect arc with varying radii for different frames (Danish archives). Moreover, the shape of the floor curves is somewhat 'suspicious', and I think that these bottom curves are also rather for illustrative purposes only on the plan, to be properly formed on the mould loft in the shipyard, as described in the Sutherland's work.

This rather poor copy of the plan, which I estimate to date from the early 17th century, is perhaps the best visual example of these practices. The profiles of the main frame and the forward 'quarter' frame are not even designed as having floor curves. Only the shapes above the rising floor line were drawn, and the floor curves were apparently 'left to the discretion of the actual builder' by the designer of the ship (Russian archives). And there are other contemporary ships' plans which, for example, show these floor curves only as a symbolic faint line drawn rather for illustrative purposes and/or completeness. Just as on this design draught of the Danish ship Tre Kroner (1604) by Scotsman David Balfour (Danish archives).

And, in this state of affairs, it would not be out of place to ask today's modellers: which model would you like to make, according to the design lines or the real ones? 🙂

Mark, you have made me more precise on this point: 🙂 After reading a number of works on naval architecture, I get the impression that constructing floor curves was a routine procedure used by ship carpenters. And for this very reason the early designers and writers simply did not bother with it. In one of the source works, for example, one can literally read (from memory): "the floor curves are left to the discretion of the actual builder". Sutherland was obviously aware of these common practices as well, and this is the reason for the dualism in his work. On the one hand, it was easier to draw on paper the frames of two arcs and a line, but on the other it was more convenient to use templates in the shipyard. In other words, he knew that the lines he designed would be modified by the ways used the shipyard, so he gave the method to do it more easily and correctly. This is a fortunate circumstance, because through this we learn how these floor curves were practically determined on the mould loft.

Below are the pictures of La Néréïde's model kindly provided by Michele. Now its bow lines can be better appreciated, and it happily seems that they are as perfect as on the contemporary ships' plans, samples of which are shown above in this thread.

Sì, grazie Michele. Ora è molto chiaro che queste linee sono eccellenti e simili a quelle delle altre navi, il che mi rende felice. Yes, thank you Michele. It is now very clear that these lines are excellent and similar to the lines on other ships, which makes me happy.

To be sure: all the above is based on Sutherland's description. It is quite obvious that he must have agreed to such a lack of precision. Wooden floor templates were to be aligned in the following way: they should pass through the point on the keel (or post), be tangent to the frame arc, and the point connecting its straight part with circular part should lie on the auxiliary line (drawn in blue in the diagram). All of this is shown in the third diagram above. Quite tricky, yet unambiguous.

This is perfectly correct. "Connecting tangent lines" should rather be read as "Connecting lines tangent to two arcs". This was just a mental shortcut to keep the description as compact as possible. Sorry. In the diagram below a possible unintentional modification of the frame profiles in the process of actual construction is visually shown, more as a matter of showing the phenomenon itself, rather than its specific magnitude, as this effect could have been reduced by placing auxiliary (guiding) lines in better spots. Either way, the problem of constructing the floor lines was invariably treated in the early works on naval architecture at the most as secondary or not at all, and the Sutherland's description is perhaps the first to deal with it clearly enough.

Bravo!

Grazie per questa fotografia. Le linee di prua di La Néréïde si vedono molto bene. Perfetto. Thank you for this photograph. La Néréïde's bow lines can be seen very well. Perfect.

Why not stop building the model at this stage? 🙂 Such beautiful shapes...

I have the irresistible impression that it is your model that most resembles the originals. More so than those with perfectly smoothed lines from the age of computers and industrial robots.

This is actually a series of publications: The Mariner's Mirror Volume 107, 2021 - Issue 2 A Restoration Yacht’s Design Secrets Unveiled: An examination of a ship model with reference to the works of William Sutherland Effie Moneypenny & David Antscherl Pages 164-187 The Mariner's Mirror Volume 104, 2018 - Issue 2 A Model of the Royal Yacht Henrietta about 1679: Description and identification Effie Moneypenny & Simon Stephens Pages 172-191 The Mariner's Mirror Volume 102, 2016 - Issue 4 The Royal Yacht Isabella of 1683: Identification and principal dimensions Kelvin Moneypenny & Dorin Paul Bucur Pages 400-416 The Mariner's Mirror Volume 100, 2014 - Issue 2 The Royal Yacht Henrietta of 1679: Identification and principal dimensions Kelvin Moneypenny & Dorin Paul Bucur Pages 132-146

Being fresh from reading a very interesting publication on the Restoration yachts of Charles II, I looked again at William Sutherland's work, The Ship-builders Assistant, 1711, focusing on his method of shaping ship hulls. In his work, Sutherland proposes shaping ship hulls so that the submerged part of the hull takes the form of an (elongated) egg. Such a shape is called a conoid. Both the characteristic feature and result of such a form are frames with the profile of a perfect arc (connected by an additional line(s) to the keel and the posts). In addition, the radii of these arcs are different for each frame. The very idea of using variable radius arcs for different frames was not entirely new at the time. Anthony Deane (1670) had already partly used this way to construct the profile of the frames (although not in the textual description, but in his drawings), the way described in the work of Georges Fournier (Hydrographie, 1643) can also be interpreted in this way, and there is a plan of the English origin in the Russian archives, in which the arc of the greatest breadth is based on the principle of variable radius (the plan is undated, but the ship has clear features specific for the turn of the 16th and 17th centuries, in particular the square-tuck stern and the considerable rakes of both posts). Below I have shown my graphical interpretation of the method proposed by Sutherland. It should be stressed here that the original plan has some drawing anomalies and, moreover, does not quite match its textual description, so reverse engineering methods were also necessary to interpret it. As can be seen, the conoid is only the body defined by the upper arcs, while the floor curves (also called hollow lines, bottom curves etc.) were constructed by Sutherland in the conventional way. Here, too, it must be added that Sutherland chose one way of drawing the floor curves in his drawing, while in the textual description he proposed a different method for use in the actual construction of the ship in true scale, but still using a simple template made of only two parts: a line and an arc. As a result, the theoretical shapes (as in the plan) and those of the actual ship had to come out slightly different.

Have just read the paper on the reconstruction of the hull lines of Charles II's yacht. An exciting read, but I must also admit that I would have had a few comments and my interpretation of some important issues would have been different.