A Dutch 17th century pleasure vessel by Ab Hoving - CARD

[Roger Pellett]

Prior to the Late Nineteenth Century there was no useful theoretical body of knowledge regarding hydrodynamic performance of ships.  Even after that (up to the 1970’s) it was empirical; make a model, tow it in a tank and see  how it performed.  Ship and boat boat designers worked largely by intuition and experience.  

 

There was, therefore, no reason for shipbuilders, Dutch or otherwise to worry about whether there was a chine at the vessel’s bilge.  They were concerned with structural integrity, seaworthiness, tonnage requirements, and as always, ease and cost of construction.

 

The hull forms developed by the Seventeenth Dutch shipbuilders also provided some Naval Architecture advantages.  The more or less rectangular midship sections would have provided excellent initial stability, would have maximized usable hull volume relative to tonnage accessed by various authorities and the chine possibly reduced rolling by acting like the much later developed bilge keel.

 

All of this allowed Dutch shipbuilders to provide low cost, efficient, tonnage to support the Nation’s commercial expansion.  It also allowed them to expand their fleet faster than their enemies in wartime.

 

Roger

[Ab Hoving]

I agree Roger. Not only the hydrodynamic performance of ships is relatively new, even the matter of stability, seen from a theoretical point of view was left alone for a long time. I spoke to an marine engineer who was (on his own initiative) working on the stability of our post-war Navy ships. Nothing about their stability appeared to be worked out in math. On the other hand, there were shipbuilders in Rotterdam around 1750 who performed tank tests on shaped planks. Chapman came to visit them and published a very identical set-up in 1775. Bouguer, Euler and Bernoulli discovered the physical laws for stability, resistance and displacement in the 1750's but is took ages before their discoveries penetrated into the shipbuilding world, especially for as far as private yards are concerned. But whatever they invented, the real problem was our shallow waters. But indeed a handicap can change into a useful design, even if it is based on limitations instead of on ingenuity. 🙂

[Roger Pellett]

Tank test results were either meaningless or misleading until Froude figured out in the 1870’s that frictional and wave making resistance acted differently in determining the resistance of a floating object moving through a fluid.

 

Once he understood this he was able to develop the tank testing procedures used to this day where frictional and wave making resistance are separated for the model and then scaled up differently before being added back together for the full sized ship.

 

Stability calculations are based in integral calculus a subject probably not understood by most practical shipbuilders.  Even with electric- mechanical calculators (1960’s era) the calculations were tedious. The calculation also requires knowledge of the vessel’s displacement and although shipbuilders in the 1600’s knew how to approximate the submerged volume of a ship’s hull, estimating the weight in various loaded conditions and accounting of the weights that went into building a ship was difficult.   

 

Computers of course have revolutionized ship design with the ability to produce full hydrostatic calculations directly from a CAD generated lines drawing.

 

Roger

Edited March 15, 2021 by Roger Pellett

[Jules van Beek]

Hello Ab,

It is amazing how even we Dutch seem to forget about the tank tests that were done by Huygens in 1669, and about Witsen describing tank tests in his book of 1671, p.274:

"In the past all sorts of shapes of ships were tested by pulling them through the water by the use of discs, to determine which ones sailed the best; the ones that moved fastest over the water, over these blocks, were considered to be the best sailers."

 

But there is something else, something I do not understand. I hope you can help me.

You say in one of your last posts: 

"The fact that Dutch ships showed an angle between bottom and bilge was not the result of a choice the builders had, it was simply the consequence of the method of construction."

 

If I understand correctly, and please correct me if Im wrong, you say that the chine was an inevitable result of the building method the shipwrights used, the bottom based building method, the method Witsen describes in his book. And this would of course imply that all ships that were built using this method would necessarily show this chine.

And here comes my problem: the technical drawing of the 'statenjacht' from Witsen's book I posted earlier, does not show this chine.; it shows a round transition of the bottom into the bilge. This yacht was built by an Amsterdam shipwright in Amsterdam, using the Witsen building method, but it has no chine.

This, in my humble opinion, contradicts your statement. What is your explanation for this?

 

Kind regards,

 

Jules

 

[Ab Hoving]

Hello Roger,

Of course you are right stating that Froude turned tank-tests into scientific rules. But in an empirical way shipbuilders did tests which, according to professor Gerritsma from the Technical University Delft were absolutely valid: for instance in the 1750's Pieter van Zwijndregt built a 186 feet long test track in the Zalmhaven (Salmon Harbor) in Rotterdam, with weights to get an even propulsion and a pendulum to measure the time.

 

Planks were sawn into waterline shapes and of all tests the results were compared and translated into waterline shapes in his designs.

 

Chapman shows an almost identical set-up in his book from 1757.

 

 

 

As for the matter of the hard chine: I don't think I ever stated that ALL Dutch ships had a chine. What I said was, that if a ship's bottom is completely straight in section (it may be rising, but still in a straight line, because that's the way the builder controled his design), the transfer to the sides is marked by a chine. 

 

Of course the builder is free to diminish the angle by lifting the outmost bottom plank a bit, just like Witsen declares) but the transfer from straight to rond causes a visible transition. It might be worthwhile for anyone who doubts that to try it at home, like I did.

 

 

The fact that the few 'hard' designs we know of 17th century ships (for instance in van Dam's book of 1701 about the history of the East India Company) all give the edge of the bottom as a measuring points indicates that there was a way to recognize this location. And the amount of degrees of that angle is something we simply don't know. We are sure however for smaller ships, like the one I showed earlier and which was made after an archeological find, there certainly was one.

[Ab Hoving]

Maybe a short explanation about the method of building is useful. When reading contracts for building ships (our main source on the matter) we almost always see the width of the bottom recorded, together with the measurement how much it rose. For instance: the bottom is wide .. feet and rises .. inch. To control that measure the planks of the bottom were laid in a straight line. It is obvious that the more the bottom rises, the harder it will be to locate the transfer from bottom to bilge. Much loading traders had an almost horizontal bottom, while fast sailers had a more rising one. So on traders the chine will have been more obvious than on frigates. This is Witsen's drawing of that formula:

The formula states that the bottom is 3/4 of the width of the ship (c). The height of the top of the bilge (b) is 1/3 of the ship's depth, the width  is as many inches less than the height of the master ribband in feet (a).

If the chine in the bilge is an invention, then it certainly ain't mine....

[PietFriet]

Fascinating stuff. The contract I'm basing my design on shows that the bottom has only risen 1.5" at 85% of the ship width. So unless they used small width planks to turn the bilge then indeed the chine seems inevitable. It is when you see other (Witzen) drawings without the chine that you start to wonder though, so your thoughts on this are much appreciated.

 

I think you mentioned in another post already that without design drawings the ship was very much an outcome from the ship master. With no two ships the same we are probably wrong to strife for a single outcome. That's why I am inspired by your approach to try to replicate the process and see what happens.

[Ab Hoving]

I think that is the right attitude PietFriet. You will certainly not find me on your way to state that you done wrong 🙂

Ab

[Jules van Beek]

Hello Ab,

Thanks for the explanations. Much appreciated.

Sorry I am insisting, but I am trying to get this right. You know where I'm coming from; still workin on the reconstruction of Gouden Leeuw, and I have to make a decision. Just like PietFriet.

 

So, if I summarise correctly, you now seem to say that the design of the hull did not depend on the building method. It was possible to build round bottom-bilge transitions while building according to the bottom-based building method Witsen describes. The shipwright was free to choose the shape he wanted, without being limited by the building method. He could choose to make a rounded bilge, or choose to make a chine.

 

And, for me, this is confirmed by what Witsen says about design, for which he uses his figure W. Here is his figure W:

 

 

What do you think?

 

Regards,

 

Jules

 

 

 

 

[Ab Hoving]

Sorry Jules, but I think you have to read better. The method of construction always influences the shape. The borders of the bottom can always be seen, if only by the run of the planking. The transition from a flat to a curve always produces an angle, but the shipbuilder could at wish diminish that angle. But why should he? Nothing remains visible of the underwater part.

If you want to give your model a smooth transition, who am I to say that it's not allowed. If you want to read in what I say (or better, in what Witsen writes) that there is no transition, who would fight you over that? I won't. But I cannot agree with you, simply because you want to place words in my mouth. I showed you the literature. Read in it what you want, but don't say that I said you are right. Besides, who am I to judge that? I only have read literature which is accessible to everybody.

Good luck with your model.

Edited March 15, 2021 by Ab Hoving

[Roger Pellett]

Your description of the falling weight test tank setup are interesting.  Thanks for posting them. 

 

I believe that results from these these tests were useful because with the thin waterline shapes used, they were actually measuring frictional resistance that is a linear function of area.  Furthermore, at the slow speeds involved for merchant vessels of the times wave making resistance was much less of a factor.

 

These falling weight test tanks were used here in the USA well into the 1900’s by several of the smaller institutions.  The two large tanks in the US are the 400+ft tank at the University of Michigan and the 1300? Ft David Taylor Model Basin at Carderock, MD.  

 

The model testing facility in the Netherlands is highly regarded.

 

Roger

[Jules van Beek]

Hello Ab,

We are all using the same sources, but it's the interpretation of these sources that can differ. I think it is a good thing to compare our different interpretations. And that's what we're doing here, I think.

This is not an attack, I am just asking you to share your interpretations. But I hope you are willing to accept my interpretations as well.

I am not trying to put words in your mouth, I am just giving you my wording of what I think you are saying; just to make sure that I get your meaning. If you do not like my wording, just say so, and correct me, please.

 

I think I know what you mean with the chine that is a result of using straight planks to build a round bottom-bilge transition. I think an excellent example of this can be found in one of the wrecks found in Copenhagen. Here is a drawing of wreck B&W5 from Lemée's book:

 

 

It was found that this ship was built with the bottom first building method Witsen describes.

 

I think, and, again, correct me if I'm wrong, that the design intend for this ship was a round transition from bottom to bilge, and that building this round shape with straight planks led to that faceted look.

For me that is something else than the chine we were talking about earlier: the clear distinction between the bottom and the bilge, the bigger angle between bottom and bilge.

 

The key question for me is if the building method influenced the design.

When we look at the figures V and W from Witsen's book, which I posted earlier, for me, it is clear that figure W shows that the design intend was a round shape, and that figure V shows that this round shape could be built. After all, if that round design could not have been built by using Witsen's bottom based building method, it would make no sense to make a round design in the first place. Who would design a round shape, if that round shape could not be built on the shipyard?

And that it was possible to make these round shapes while using Witsen's bottom based building method, is, according to me, shown by Lemée's wreck B&W5, but also by the E81 wreck, which remains are now in Den Helder.

 

Could you please give me your thoughts on this?

 

Kind regards,

 

Jules

[Ab Hoving]

Dear Jules,

Interpreting written sources is always dangerous. I don't have to remind you of the numerous deaths of people who were victim of different interpretations of religious written sources. The nasty reason is that people tend to select the interpretation that suits them best and completely ignore different signals.  A nice example is the Witsen drawing you show in #159 (V), where the bottom is planked and the bilge is not (yet). The next drawing in line is the one I showed in #155 (X), where the bilge is planked and an angle does show up. That's pure logic: before a shipbuilder starts planking, he flattens the frames to give the plank a solid landing, as you can see here on this picture, taken at the Statenjacht Utrecht shipyard:

 

I did not write Witsen's book, I am only comparing it to wreck finds and experiments with models and replicas and over and over again Witsen proved to be a trustful source. If you don't agree with my conclusions, that is alright with me. You are completely free to choose your own interpretations. Better even: write them down and publish them. Different ideas are often useful.  The only hesitation I have with your perseverance is a suspicion that you don't want to be convinced. I remember a former sort like discussion, in which you came into a forum as a fresh new member, stating that you had proof of 17th century Dutch shipbuilders designing their ships on paper, referring to a painting by Rembrandt. All the evidence of the contrary was denied and the discussion ended in a chaos. I am afraid this is a repetition. 

Again, I don't care if you think differently than I do on some matters. You are free to do so as you are also free to make your beliefs public. I don't feel attacked, but please stop bothering me, more or less demanding to agree with you in matters where we think differently. We are here to enjoy our hobby and some people like to hear opinions about the roots of the full-size industry. I pass through what I think I know (which is in fact very little) and if you have problems with what I say, I deeply apologize. Life is complicated enough without useless discussions.

Again I wish you all the best with your model of de Gouden Leeuw. Maybe you should post your work here. That would give a good basis for discussion. Better than this one, I'm afraid.

Best,

Ab

 

[Jules van Beek]

Hello Ab,

I think you would be truly amazed about how easy it is to convince me. A couple of good arguments can shut me up in no time. But that's not the case yet.

To get back to the subject one more time: did the building method influence the design? And, again, you stated that the building method does influence the design: building ships by using Witsen's bottom based method, would result in ships with chines. I showed you an example of a drawing from Witsen's book that shows the contrary (the statenjacht drawing), I showed you that Witsen, while talking about design, shows that round shapes were wanted (figure W), and I showed you that these round shapes could be built in actual ships from that period, referring to the wrecks B&W5, and E81. It seems to be of little consequence to what you think. But, let me continue.

 

So, here is part of the reconstruction drawing of E81, presented by Oosting at the1988 'Carvel Construction Technique' symposium. The same symposium where you presented the results of your tests with the two building methods of the 'pleasure vessel':

 

 

Here it is again: a ship built with Witsen's building method, and a round shape. Mind you, this is an actual ship from the period, not a reconstruction model you made, or a replica ship that was built while you were in the advice committee. We do not need to build models or replica's anymore to determine how ships were built while using Witsen's bottom based building method, we can simply study the wrecks.

 

And another one of these wrecks is of course the most famous one: Vasa. Jan started this topic off by saying that he heard that Vasa was built by using Witsen's method, and that it shows no chine, and he asked: "are chine and shell-first one-to-one connected"? You chose to answer this with: "It shows how little we know". Well, in the case of Vasa we actually know a lot. Recent studies have showed that Vasa was built with Witsen's building method.

Here is Batchvarov in 2012:

"The research has proven that Vasa was constructed in accordance with the Northern Dutch method of shipbuilding described by Nicolaes Witsen, rather than the Southern as has sometimes been suggested."

 

And here is Kelby Rose in 2013:

"Construction features of the hull confirm that the ship was built according to 17th-century Northern Dutch methods of naval architecture."

 

And here is Fred Hocker in 2014:

"In Dutch ships, the plugged nail holes from the fastenings are the best clue to the construction method (we see these all over Vasa), ...".

 

I think there is no more doubt about how Vasa was built, it was built according to Nicolaes Witsen's building method. And, as Jan rightfully says, Vasa's hull shows no chine. Making it clear, once again, that the chine and shell first are not one-to-one connected.

 

To get back to the remark Batchvarov made: 'rather than the Southern as has sometimes been suggested'. I do not know who Batchvarov meant when he wrote this, who had suggested that the Southern method was used, but he could have meant you. Because this is what you published back in 1986:

"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."

 

The question now is, would you still write that today?

 

Kind regards,

 

Jules

 

[Kevin Kenny]

Ab i am trying to get in touch to see if you can help me find a model that may have been sold from the Science Museum in 2012.

kevin Kenny

[Ab Hoving]

Hi Kevin,

I really don't know anything about any model from the Science Museum. Sorry.

Ab

[Kevin Kenny]

Thats fine Ab, someone suggested that you might be have been in touch to source models for your collection in the Rijksmuseum when the Science Museum  was closed and the collection sold. I think  i may have found where it might be. 
 

keep well

 

kevin

[wefalck]

Where did you hear that the collection has been sold ? It happened that certain items have been sold in the past, but I understand that most of the collection has been put into storage. 

[Kevin Kenny]

You are correct, some were sold, some were returned to the persons who had loaned them to the museum and the balance are now stored at dedicated storage at an old airfield near Swindon. So i will get one of my UK friends to get in touch and see if they can trace the model of the St Patrick.  Its very exciting to be on the hunt for a possible piece of my countries history. 

[wefalck]

Some years ago I tried to trace the builder's model of a German ship build in the 1840s on a British yard. The model had been donated by the builders to the museum in the late 19th century, but then in the 1930s the museum apparently decided to offload items that were not of immediate relevance to British cultural history and they sold the model off. Together with the museum we found an old auction catalogue that listed the model, but the auction house folded in shortly afterwards, so that I could not find out, who the buyer was ... the museum staff were very helpful at the time, I hasten to add.

[Kevin Kenny]

Update. Just thought i would update you all who have so kindly offered to help. I have located the model and more importantly the curator of the Science Museum who has agreed to help me locate all the possible information the museum has on the model and its builder. She has also offered to help locate the original plans that the model builder must have used to build the model of the SS St. Patrick.  The models will become available for viewing some time 2022-24 so that good. 
 

this has been a wonderful exercise with so many offers of help from so many quarters. The hobby is alive and well. Thanks everyone for participating.

Best regards

kevin

[Meriadoc Brandybuck]

On 6/27/2020 at 5:35 AM, Ab Hoving said:

my colleague suggested 'voile cotton' was one of them, but there was another, called 'Navara fine lawn white', which seems even slightly better. It is slightly less transparent and very closely woven.

 

Hello, I was peeking through this thread as it is such a treasure trove of information for scratch-building, and I asked my wife, who works in the apparel industry, about the fabrics you mentioned. Voile cotton is a soft cloth used in blouses and pajamas, and Navara fine lawn is used in men’s dress shirts, or at least ones that have soft fabric. Perhaps the future supply chain for scratchmaking becalmed sales goes through a used clothing shop, or one’s own closet. 

 

Meriadoc 

[Ab Hoving]

That would at least be a lot cheaper, but alas, the fabric of my shirts is a lot cruder than Navarra Fine Lawn White. I'm just a simple man....