A Dutch merchant vessel of 1664. The Stem, part 1/9.

May 28, 2017 | Author: Jaap Luiting | Category: 17th Century Dutch Republic, Dutch East India Company, Dutch shipbuilding, Nicolaes Witsen (1641-1717), Cornelis van Yk
Report this link


Description

The Stem

General. After the description of the keel in chapter 12 Cornelis continues with the stem:

“De Voorsteven, of zo andere willen de Voorstyven, om dat ‘t Schip daar door sijn stijv, of sterkheid bekomt, een vande voornaamste Scheeps-deelen, geplaatst, ten deele staande, ten deele voor overhangende, voor in ‘t midde van ‘t Schip, en is gelijk als een Schild, welke alle harde ontmoetinge moet afkeeren. De Einde van Schips Huid, of planken worden in deselve vergaderd, en vast gemaakt. Is onder aan ‘t Einde vande Kiel gelast, en aldaar na Schips Grootheid, met verscheide ysere Bouten t’ samen geklonken”. (p. 56, l. 12)

(The stem or ‘sturdy’ others would like to call it, because the ship obtains its stiffness or strength through this part, is one of the major elements of the ship, partly standing, partly hanging over, standing fore in the middle line of the ship, and is like a shield which should return every severe encounter. The ends of the planking of the hull are gathered in this part and mounted. It is joined at the lower end at the end of the keel and there, according to the size of the ship, mounted with several iron bolts.) Nicolaes gives a general description of the stem at two places in his book but, surprisingly enough, again, like with the keel, not at the pages where he discusses the shipbuilding in his time. The first place is in chapter 7 where he discusses shipbuilding in the Netherlands around 1520.

“De voorsteven schoot meest altijt uit, met een kringsche rontheit, en een derdendeel van de kiels lengte na vooren toe; zijnde de hoogte van het schips bovenste overloop. Uit het hooft van de kiel wierd een linie opgehaelt, tot de gegevene hooghte: het derde van kiels lengte, weinig min of meer; welkers toppunt voor het middelpunt dient, daer de steven werd uitgetrokken. Dees middelstip, doch, wierd een weinig hooger of laeger genomen, na gelegentheit van het gebouw; om dat zijn hooge of laege stant het stevens vallen bepaelt. Zwaere wijde schepen vereischen lange stevens; maer smalle schepen wierden met lange stevens zeer verswakt; naer het oordeel der Bouwmeesters van dien tijt. Het middel-punt evenwel, daer de steven uitgetrokken wierd, behield men altans in een recht opgaende linie, van wat gestalte de schepen ook mochten zijn. Een vaste regel was het, dat ’t uitschieten van de steven noit min mochte zijn, als vijf zesten van de hoogte tot d’ overloop, en noit meer als dees hoogte, en een zesten”. (p. 47, c. 2, l. 7, 1671)

(The stem almost always protrudes, with a circular roundness, and at one third of the keels length towards fore; being the height of the ships upper deck. From the head of the keel a line is taken, up to the given height: one third of the keels length, a bit more or less; which top is the center, from which the stem is derived. This center, will be taken a bit higher or lower, according to the size of the structure; because this determines the stems rake.

Heavy wide ships require long stems; but narrow ships with long stems will be severely weakened; according to the judgement of the Master Shipwrights of the time. The center however, from which the stem is derived, was kept on a perpendicular line, no matter what shape the ships have.

A fixed rule was that the protruding of the stem may never be less then five/sixth of the height to the lower deck, and never more then this height and one/sixth.)

In chapter 15 Nicolaes describes the stem as constructed by the French just like he did with the keel:

“Aan het eindt van deeze kiel, (die omtrent 21/2 voet vierkant moet zyn, na hun stellen op de lengte van 120 voet) na vooren, wordt de voor-steven ingeënt: deeze is rats- of krings-wyze van gestalte. (p. 219, c. 1, l. 31, 1690)

(At the end of this keel, (who has to be around 21/2 feet square at a length of 120 feet) fore the stem is inserted: this part is wheel like or circular in shape.)

The mentioned width and depth for this keel is impressive. Converted into meters, assuming Nicolaes uses Amsterdam feet, this keel measures 0,71 m. x 0,71 m. and if these are supposed to Jaap Luiting @ 2016

The Stem

be the French ‘Pied de Roy’ (0,3248 m.) 0,81 m. x 0,81 m., which is an improbable size. But the stem is described as a circle cut, just like the description in chapter 7. This shape is discussed in the concerned section.

One of the notable things Nicolaes mentions about the stem though is that it is used as a basis for retrieving measurements of all other major ship parts.

“De voor-steven is de richt-snoer daar men alle grootte in een Schip uit trekt: deeze vindt men uit de lengte van ’t schip”. (p. 111, c. 1, l. 6, 1690)

(The stem is the guidance from which all sizes of a ship are derived: this (measurement) one will find from the length of the ship.)

Actually it doesn’t really matter which construction part you take as a basis for the other measurements. Every part is linearly related to the length of the ship over stem and stern as Nicolaes confirms:

“Meest alle de Scheeps-deelen worden, na voorgang van andere, uit de Voor-steven getrokken, strekkende deeze voor grondt-slag en tot maat van de zelve; waar toe men ook wel eenigh ander lidt konde genoomen hebben (…..): zijne dikte zelf vindt men uit de lengte van het Schip; waar van d’ondervinding leert dat de hier voor opgegevene even-maat na den eisch is, en dat de dikte, zoo genoomen, niet te grof noch te licht zy”. (p. 329, c. 2, l. 29, 1690)

(Most ship parts are, in a progressive order, derived from the stem, as this part is the foundation and measure of all parts, for which one could have taken any other part (…..): the thickness one derives from the length of the ship; and the experience learns the given ratio is as required and the thickness, made as proposed, is nor too heavy nor too light.)

Cornelis continues his description of the stem by discussing the shape of the stem and the bow:

“Een goed beloop van een Voorsteven, was het seggen onser Vaders; maakt een mooy voor-Schip: waarom sy dan, om sodanig Hout te bekomen, somtijds ook dapper inde Beurs tastede. En al schoon dit haar seggen wel waar was, soo siet men egter onse Hedensdaagse Bouwmeesters Scheepen bouwen, diemen, alhoewel dese Steeven, de, by haar vereiste Hoedanigheden ten grooten deele komt te ontbreeken, geensints de Naam van leelijk geven kan”. (p. 56, l. 20)

(A fair profile of a stem makes a beautiful bow as our fathers used to say; why they, to obtain the right pieces of wood, sometimes had to dig deep into their purse. And although these sayings were true, one sees the present-day Master shipwrights build ships one can’t call unsightly although the stem lacks for the most part these qualities.) Cornelis states the shape of the stem as constructed by ‘our fathers’ yielded a beautiful bow but although the stem in his time is not built according to the rules of those days, the resulting ships can’t be called unsightly.

This change of shape occurred in the course of the 17th century which is, as we have seen in chapter 3, confirmed by the tables concerning the rakes with regard to the length of the ship. These tables show a decrease of the rake as a consequence of this change. Cornelis continues his description:

“‘t Gevoelen van dat de Scheepen, om vaart te maken, niet het Water mosten van een kloven; maar het selve gelijk als inslorpen, of daar over heen loopen, en alzo onder de Kiel doorjagen, was de reden waarom sy dese Steeven dapper over ‘t Water lieten hangen. En nademaal de veelvallende Steeven, egter de vereiste Hoogte diende aan te brengen, zo heeft zy noodsaaklijk heel lang moeten wezen. Daar benevens, deze Steeven, moetende, ten naasten by, aan ‘t boven Einde lootregt op komen, heeft seer veel Bogt moeten hebbe, en, by gevolg, heel groot en kostlyk vallen. Sulks dat om dit Schips-Deel alleen, den meesten Tyd, twee raare, en zwaare Bomen, die dan van ter zyden met lange Lasschen wierden in een gesloten, hebbe sterven moeten. Heden werd dese Steven veel steilder gesteld, waar door veel Langte, en Bogt ontgaan werd. Ook vintmen de Scheepen hier Jaap Luiting @ 2016

The Stem

door, aan haar onder Water sijnde Deel, veel Langer, en (gevolglijk) om by de Wind te zeilen, veel snediger geschikt. De Ervarentheit leert ook daaglijks, dat Scheepen sodanig gebouwd, datse van alle kanten het Water gemaklijk konnen van haar afwijsen, en alzo in haar natuurlijke Zwaarheid blyven, veel meerder Weg afleggen, als andere, die door hare platte, uitgebrookene, en over ‘t Waterhangende Boegen, haar selve uit haar Gewigt, en ter smoor, Zeilen”. (p. 56, l. 28)

(The opinion that ships, to be able to make speed, do not have to split the water but merely absorb it or run over it and chase it beneath the keel, was the reason they made the stem with a significant rake above the water. Because the stem also needed to be high enough this large rake caused it to be very long. Besides that, this stem needed to be as close as perpendicular at the top which is why it has an enormous curve and as a consequence be very large and precious. That is why only for this ships part often two peculiar and heavy trees, connected to each other with sideways made long joints, had to die. Today this stem is made steeper for which one doesn’t need that much length and curvature. Because of this, the part of the ship which is under water will be much longer and, as a consequence, is much more suited to sail windward. The experience shows daily, ships built this way, are easily capable to rebuff the water by using their natural weight, covering much more distance than others who, due to their flat protruding and over the water hanging bows, are too heavy and smothering their sailing qualities.) One remarkable thing Cornelis mentions here is the relation between the length of the ship’s hull which is submerged and the sailing properties. The stem standing steeper is apparently connected with a load waterline which is longer compared to a ship with a stem with a larger rake. This can only mean the hull fore is becoming sharper which causes the ship to sink in deeper compared to ships with a bluff bow. The qualities he mentions is the ability so sail faster and better windward.

In chapter 36, which is completely dedicated to the sailing properties of ships, he states:

“Onze Vaders, die haare Scheepen met zeer veel vallende Stevens, en over ‘t Water hangende Boegen bouwde, en over sulks getragt hebben, ‘t Water eerder onder ‘t Schip deur, als daar buiten om heen te leiden, schynen my in dit geval te hebben mis getast. Dewijl het Schip, hoeveel Waters ook onder de Boegen inslorpende, evenwel sijne zwaarheid niet verliezen, maar sig soo veel te meer versmoord zeilen, kan. De hedendaagse Bouwmeesters, die, alhoewel by Kiel en Steven Schips Boegen, om Bijt, of Bit* te hebben, hoog genoeg opschorten, egter haar Werk buitewaards wederom sodanig laaten neervallen, dat de Wrangens voor op Steven een verkeerde Bogt moeten aannemen, mijns agtens, deselve Feil begaan; want dewijl het Schip om in deselve stand, of diepte te blyven, sig geduurig, aan allen zyden, van soo veel Waters moet ontlasten, als het door desselvs voortgang, voor by de Boegen neer, en onder ‘t Vlak inzwelgd, soo sal dit Water, wegens de Holheid der Boegen, veel meer geprangd, en (by gevolg) vaart-stremmende moeten sijn, als of deselve eenparig rond opgaande, en ‘t Water van alle kanten weg-wysende, waaren gemaakt geweest. Zulks ik besluit best te wezen, ‘t Water op de gemaklijkste wyse buiten om, en niet onder ‘t Schip heen te brengen”. (p. 353, l. 8)

(Our fathers, who build their ships with stems with very large rakes and overhanging prows, tried to lead the water underneath the ship instead of around it, seems in my opinion to have made a mistake in this case. A ship build like this will not lose its weight regardless of how much water it will absorb but will lose the more its sailing qualities. Although the present day master shipwrights build the bow at keel and stem high enough in order to have enough windward ‘bite’* but let the outside of the ship hang over in such a way so the futtocks on the stem are taking up a false shape so making the same mistake because the ship will have to unburden itself of so much water as it through its movement so this water will, because of the height of the bows, much more compressed and inhibitory to the speed than if the bows were made uniformly rounded upwards making the water

Jaap Luiting @ 2016

The Stem

spread on all sides. This as I decide to the best way, to guide the water the easiest way around the ship and not under it.)

)* Nicolaes gives a description of this term ‘Bit’ in the glossary at the end of his book:

“Bit. De scherpte voor aan 't schip: anders, het Snee. Het hout, 't geen buitewaarts voor onder tegen de steven gezet wort, wert mede Bit- of Loef-hout genaamt. Van de scherpte achter werdt gezeght: Het schip is wel, of qualyk, geschort”. (p. 580, c 1, l. 30, 1690) ( Bite. The sharpness of the ship fore, also the cut. The wood used to put outward below at the front against the stem is also called bite- or windward-wood. Concerning the sharpness aft is said: The ship is well or bad joined together.)

The way Cornelis describes the change in shape of stem and bow is intriguing. It seems to be all about enhancing the sailing properties of the ship. Unfortunately he does not tell us exactly how this development took place but about one thing he is unambiguously clear: a ship has to ‘cut’ the body of water instead of ‘pressing’ it downward underneath the ship.

When we read the text carefully Cornelis just mentions the qualities of the stem with a large rake and compares these qualities to the qualities of a stem with a lesser rake.

This change in shape enabled the construction of a sharp bow instead of the round, blunt bow and to accomplish this transformation, the stem is designed much steeper. The stem of ‘our fathers’ had a large curve and was very long for which two heavy ‘peculiar’ trees were needed and as a consequence this stem was expensive. The steeper stem turns out to be cheaper because the wood for this stem was easier to find. The strangest fact though is the fact that if the change in shape of the stem is motivated by a change in shape of the hull, some Master shipwrights still constructed a round bow which nullifies in Cornelis’s opinion the advantage a steeper stem could have on the sailing properties of the hull. To show what this might have looked like we have to reconstruct the shape of the hull which is done in chapter 8.

As mentioned earlier Cornelis stresses that the elongation of the waterline enabled the ship to sail faster and more windward.

Nicolaes also mentions this change in shape of the stem in the addition of his book:

“In ’t jaar 1683 heb ik opgenomen den bouw van een zwaar Schip, genaamd de Ridderschap, en daar aan bespeurt vry veele veranderingen, ten aanzien van Scheepen in onze jeugt getimmerd: zag het galjoen en voor-steven veel rechter en steilder te staan als ooit (…..)”. (Byvoegsel, p. 19, c. 1, l. 61, 1690)

(In the year 1683 I recorded the construction of a heavy ship named ‘de Riddershap’ (the knighthood) and have seen quite many changes with regard to the ships carpentry from our youth: saw the head and the stem standing steeper as ever.)

Jaap Luiting @ 2016



Comments

Copyright © 2024 UPDOCS Inc.