Page 61 - Nicolaes Witsen & Shipbuilding in the Dutch Golden Age

deck would run all the way to the stem and the height had to be extended to the height of the forecastle.
Witsen supplies a formula for the rake of the stem: 28⁄29 of the height, or 96 percent. This is extremely remarkable, as this formula is not to be fou nd in any contract in Wit- sen’s own work or in that of Van Yk. It is not even very logi- cal to provide a formula for this measurement because at this point the shipbuilder c ould influence the sh ape and character of the ship a s nowhere else. With a “neutr al” ship one c ould perhaps state that the r ake of the stem corresponded approximately to its height. But, a s men- tioned before, the r ake of the stem decre ased over the century. According to Van Yk, this was par tly due to the increasing length of the ship s, which would require two expensive curved timbers and force up the price, but also because sailing performance with a steeper stem (and, as a result, a longer keel) proved to be superior.
In general, we can say that, if a shipwright wanted the ship to be f ast, like a yacht or frig ate, he would c hoose a strongly raked stem; a slower vessel, built for c arry- ing capacity more th an speed, would w arrant a steeper stem. Witsen’s formula might well be taken as the neutral middle option. Of the thir ty-four contracts found in the treatises of both Witsen and Van Yk, the average rake in
Figure 2.7. (below) Construction of the stem of the pinas. The measurements were taken from Witsen’s pinas data. (Drawing by A. J. Hoving)
Figure 2.8. (right) Top: Open forecastle; the upper deck
lead through a small foredeck to the beakhead. Bottom: Closed forecastle; the beakhead can be accessed only through the forecastle deck. (Drawing by A. J. Hoving)
relation to the height was 90 percent, with extremes rang- ing from 48 percent to 158 percent.
While trying to draw a number of stems found in con- tracts, I soon di scovered that the points of measurement were not always consistent. Van Yk, giving sketches of the construction of a stem w ith much rake and one w ithout, takes the rabbet of the stem above for the apex of the tri- angle formed b y the height and the r ake. The front and backside of the stem were then s imply “drawn around” the rabbet. For the construction of the stem of the pinas, it is clear that Witsen took the top of the stem for the apex of the triangle, after whic h he “drew in” the r abbet of the stem.
The use of large compasses in the ship yards is very hypothetical. As far as I can see, any curved line needed in the c onstruction of the ship was produced by bend- ing a fl exible batten, the rey (or rij ), and never b y using compasses.
3. The Sternpost.
(73 I 15) Of the Sternpost a prominen t Shipwright says the following:
The sternpost is the most importan t part of the
How Ships Are Built in Holland Today
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