The Keel

The stocks.

“Aldus de Kiel bereid sijnde, is sy bequaam om plaats, op de Stapelblocken, en Stootwiggen, te nemen, die van midden tot midden gemeeten, ontrent 6 Voeten, een weinig meer of min, naar believen, van den anderen mogen leggen. En van Scheepen die men niet voornemens is op de Werf, overkant te laten vallen, gelijk ontrent swaare Scheepen selde werd gedaan, moet de onderkant vande Kiel, om bekwaamlijk onder ‘t Volk te mogen Werken, drie en een halve Voet tot de bovenkant van het Bedding leggen, voor minder, agter wat meerder, na reden dat de Werv meer of minder nedergaande is”. (p. 55, l. 21) (Thus the keel prepared, it can be placed upon the stocks with thrust wedges, who are 6 feet apart, sometimes a bit more or a bit less, measured from heart to heart. Ships who are not falling sideways at the yard, like seldom is done with heavy ships, the underside of the keel is lying three and a half feet above the slipway, fore less, aft a bit more according to the slope of the slipway, so the shipwrights will be able to work decently at the underside of the ship.)

Eventually the keel will rest on the stocks who are placed 6 feet, 1,7 m¹, from each other, heart to heart, varying at pleasure with this distance. On the stocks thrust wedges are placed used to set the keel at its desired height by striking or loosening them. Before launching the ship these wedges can be loosened and/or removed which allows a movement towards the water. With ships who are not falling sideways to be able to reach the underside, the keel is lying 3½ feet, 1 m¹, above the slipway. Cornelis mentions this slipway in chapter 6 of his book and measures approximately 140 feet in length and 12 feet wide (39,6 m¹ long and 3,40 m¹ wide).The last sentence indicates the direction of the keel is steeper than the slipway itself. But how do you establish the direction of the keel with regard to the slope of the slipway because the keel tapers in height? More about this in the section about rocker.

Nicolaes says: “Een kiel stapelt men achter hooger als voor, op dat het Schip te bequamer af loope; waar toe de werf ook wel vast dient te zyn". (p. 110, c. 2, l. 48, 1690) (A keel is lying higher on its stocks aft than fore so the ship will launch properly for which the yard has to provide a stable ground)

“Het grootte Block, daar op dat men voornemens is het Schip, ontrent het afloopen, te laten Evenaren, en gemeenlijk Dompblok genaamd werd, komt meesten tyd, een vijvde Deel van Schips geheele Langte, agter uit de Hieling te leggen. De hier agter-leggende Stapelblocken behoeven met geen Stootkeggen voorsien, om dat in Schips nedersetten van sig selvs los vallen: maar alle die de Kiel voorwaarts onderschragen, mogen deselve geensints ontbreeken”. (p. 55, l. 30) (The ‘big block’, on which the ship tilts forward when launched and usually called ‘Dompblok’ (‘tilting block’), is normally situated at 1/5th part of the total length of the ship measured from the ‘hieling’, the keel aft. The stocks behind this tilting block don’t have to be provided with thrust wedges because when the ship tilts forward when launched they are automatically released but in front of this tilting block these thrust wedges are essential.)

Besides the ‘regular’ stocks one applies a block on which the ship balances during her launch, i.e. on which the ship hinges or tilts in the direction of the water (in those days the Dutch launched their ships bow first). For this reason the stocks behind this tilting block don’t have to be provided with thrust wedges because the ship is released from these stocks by means of the tilting motion forward. These thrust wedges are necessary on the stocks in front of this tilting block to be able to release them at the time of launch. Cornelis indicates the place of this block is usually at 1/5th of the total length of a ship measured from the ‘hieling’’, the rearmost point of the keel.Apparently this was not the only way they could launch a ship because:

“Sommige Bouwmeesters wel een Vast, dog slagtig Blok, en dat sig ligtelijk laat vaneen kloven, ten Einde van het Bedde, onder de Voor-Steeven, leggen, dat zy dan in Schips nederzetten, inde Aarde laten sinken, om dan eindelijk geheel weg breeken. Dog andere doen weder anders”. (p. 55, l. 37) (Some Master shipwrights use a fixed block at the end of the slipway under the stem which was buried in the earth and splitted and removed before launch. But others do it differently.)

Jaap Luiting © 2015

The Keel

A block that prevented the ship from sliding off the slipway into the water could also be placed under the stem buried in the earth and split and removed at the moment the ship had to be launched. Cornelis hints at several other methods but doesn’t mention them.

Cornelis mentions the ‘hieling’, the end of the keel aft but gives no description. Nicolaas mentions the ‘hieling’ or ‘hielingh’ also a few times also without giving a description. In chapter 18, he states the following.“De lip, die achter aen de kiel uitsteeckt, stut het roer, en verhindert dat ietwes tusschen steven en roer in kome te schieten, en zoo onklaer werde”. (p. 331, c. 1, l. 49, 1690) (This ‘lip’ which protrudes at the underside of the keel protects the rudder and prevents something invading between stern and rudder and thus jamming the rudder.)

The word ‘stut’ as a verb usually means a physical strut or support. Here I think it should be understood as a protection of the front of the rudder. If this was meant as a real physical support the rudder wouldn’t be able to make a turn to port or starboard. Nicolaas does provide a picture.

Nicolaes Witsen. ’Hieling’ of the keel: ‘b’ to ‘d’. Plate 48, 1671.

“De Stootwiggen, of Keggen, op datse, haar Werk verrigt hebbende, sig ligtelijk, door een Balk, Ram genaamd, van onder de Kiel, mogten laten weg stooten, nemen dese hier nevenstaande Figuur, by Nummer 2 aan. A het Stapelblok; B, de Stootkeggen; en C de Kiel beteekend”. (p. 55, l. 43) (The thrust wedges are visible in the attached picture number 2. They are, after they have done their duty, thrusted sideways by a beam, a so called ‘Ram’. In the picture the stocks are shown by ‘A’, the thrust wedges by ‘B’, and the keel by ‘C’.)

Jaap Luiting © 2015

The Keel

Cornelis van Yk. Keel on stocks and thrust wedges. Between page 58 and 59.

We have seen this picture before in the section about the joints. A more careful inspection reveals some interesting details. If we extend the visible transversal lines of the stocks it becomes clear the picture meets the laws of perspective: all lines pass through the same vanishing point (allowing a small margin with regard to the exact position of this point). Even the back of the keel is drawn accordingly. This means Jan Luyken and his son Caspar were not only familiar with the laws of perspective but also applied them in their drawings, in this case a drawing which is not an actual representation of reality.

Transverse lines of the stocks converging in one vanishing point.

Jaap Luiting © 2015

The Keel

Also clearly visible: the top side of the keel is completely straight and so is the rabbet. The right end of this keel part is higher than the left end which means the keel tapers in height as can be expected. Because the first stage of the rabbet runs all the way to the end of the keel we may assume this picture is a representation of the keel aft. It is strange though the rabbet runs over the face side from one side to another while the rabbet isn’t supposed to do this.Noteworthy is the fact that Cornelis specifically indicates the wedges in this picture to be thrust wedges. If this part of the keel represents the part aft there shouldn’t be any thrust wedges present.

Something else is the positioning of the wedges. As said earlier the blocks out of which one stock is assembled have to be connected to one another and the stock itself firmly attached to the slipway or ‘bedding’. These stocks vary in height to be able to lay the keel at different heights “voor minder, agter wat meerder, na reden dat de Werv meer of minder nedergaande is” (fore less, aft a bit more according to the slope of the slipway). The actual differences in height between slipway and keel (about 1 m¹) are largely bridged by stacking these blocks while by striking the wedges only a small difference in height can be bridged.What could be the procedure for adjusting these wedges? Do you strike the lower or upper wedge or both?Striking these wedges yields an upward force to the keel. For that purpose they are very ‘lijdzaam’ i.e. the bevel of the wedges is not very steep as is clearly shown in the picture. The result of this gentle bevel is that height will slowly increase while striking the wedges and the friction between the two wedges mutually and the upper wedge and the keel is such they will not easily slide back. (If you want to decrease the height the usual procedure is to hit the upper wedge alternating on the sides so as to work it backwards and thus decreasing the height.) In other words: due to their mild steepness the vertical resultant (tension in load) of the applied force is much bigger relative to the horizontal resultant (tension in sheer). To prevent a simultaneous displacement sideways of the two wedges while striking, you secure the lower wedge on the stock. To prevent displacement sideways of the keel you place the wedges in such a way that you alternately strike at the port and starboard side. When the keel eventually reaches its desired height the wedges are connected to each other and two cleats are applied on the upper wedge against the keel to prevent displacement sideways while in the process of constructing.The highest side of the upper wedge is the place you strike and this alternation of the highest and lowest side of the wedges is exactly what the picture shows. The way these wedges are drawn could be accidental but it struck me as a bit too accidental because I think it represents a procedure an experienced shipwright would choose.

By means of hitting the earlier described thrust wedges one can adjust the curve of the keel in vertical direction. The wedges can be worked upwards or downwards with the exception of the tilting block and the stocks behind this block. To be able to position the keel behind this tilting block in its desired position I think they also would have used wedges but they lacked a function during the launch of the ship.Adjusting the wedges meant checking if the top side of the keel reached its desired shape, i.e. flat or curved. This check can be done with the same line which is strung above the ‘middle scratch’ with which you also check if the keel has the right position in the horizontal plane.

To make a drawing that incorporates technical information like the positioning of the wedges reveals something about a working order or procedure, which is no obvious circumstance for the gentlemen Luyken. Normally Jan and Caspar Luyken were mainly busy making pictures representing everyday life and religious scenes but the production of a technical drawing is a different thing. The information needed for the drawing was to be transferred to them to produce a drawing which shows the essence of the text or to give additional information. Unfortunately, as far as I know, not much is known about the way the two men worked but we may assume this transfer of information was done by Cornelis himself so he must have had direct contact with father and son Luyken. This drawing ‘number 2’ of the keel on stocks contains elements who contradicts and at the same time confirms the information given by Cornelis while the picture also contains information Cornelis doesn’t mention in his book. This raises questions like how reliable these pictures actually are and especially how they were made and this is true for both authors.

Jaap Luiting © 2015

The Keel

“Dese, op de Bloks leggende Kiel, word aan de boven sijde met een Schrap, van vooren tot agteren, in haar Midden, doortrocken, gemeenlijk Middelschrap gezeid; over welke een Lijn gespannen sijnde, men siet of sy niet Krom, of met Bogten, op dese Stapelingen geklampt en gekneeveld werd”. (p. 55, l. 48) (This keel, laying on the stocks, is provided with a scratch from fore to aft, named ‘middle scratch’, above which a line is strung so one can see the keel is not crooked or curved when cleated and forced with ropes on the stocks)

This means that the pieces of wood, out of which a single stock is made, have to be mutually connected and firmly attached to the slipway otherwise these stocks can’t withstand the lateral forces.This cleating also prevented the keel from moving, in Dutch, ‘vergaan’ or ‘verhalen’ (to displace), when erecting the frames, placing futtocks and the planking, which is also associated with the use of force. Nicolaas mentions this in particular:“dan slaat men op elk stapel-blok een klampje tegen de Kiel aan, om dat men die niet zoude verhalen als men in het boeijen is” (p. 168, c. 1, l. 39, 1690) (on every stock one mounts a cleat against the keel so it won’t move during the mounting of the outside planking)

Nicolaes presents two pictures showing the stocks were firmly attached to the slipway and each other.The use of force is clearly visible at plate 50 where the planking of the hull is forced into position with a ‘boeitang’. A ‘boeitang’ is according to Röding ‘A wooden engine formed like a pair of pincers and employed to confine the planks of a ship in their places till they can be nailed or bolted to the timbers”. (p. 296) Also clearly visible is the fixation of the stocks to the slipway and the absence of the cleats which must have been there if you consider the way force is applied at one side of the keel. A cleat could have prevented the keel from hinging toward the place where the lever is placed.Surprisingly in both pictures the wedges are missing. Nicolaes never mentions these in this part of his book nor in the part where he describes the procedure of launching the ship. It is possible one assembled the blocks for the stocks, build them and at the same time align them, horizontally and vertically, so they have the exact required height after which you put the keel on the stocks.

Nicolaes Witsen. Keel on stocks with first hull planks. Plate 50, 1671.

Jaap Luiting © 2015

The Keel

Nicolaes Witsen. Keel on stocks. Plate 51, 1671.

Cornelis also mentions the word “gekneeveld”, a procedure also associated with the fixation of the keel to the stocks. ‘Knevelen’ here means the use of a wooden peg you put in a noose after which you curl up the noose with the peg which shortens the noose. This applies tension to the points the noose is attached to. Apparently this is done to prevent vertical displacement of the keel.If you want to place a noose you need something to put it through or around. The most obvious place to do that are the stocks where you apply for instance a ring or a sturdy nail. I can imagine they used a cleat or an iron bar, put on the keel and protruding at both sides of the keel after which you tie the noose around the nail and the bar subsequently curling it up. The stock is used also to prevent the noose from releasing itself by positioning the peg against the stock. If you want to mount for instance the garboard strakes at that particular point you uncurl the nooses and take them away.I think applying force with a noose primarily had the function of holding the keel in place during the first phase of construction.

Jaap Luiting © 2015