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At Ab's request, I am currently preparing to analyse the shape of Witsen's pinas, based on extant numerical data. In this context, I am revisiting the contents of the contracts (bestek) for various ships of the era, which only reminded me that in more detailed cases, the shape of the line of greatest breadth can be also strictly defined in those written specifications.
For example, for the ship Deventer 1640 (Witsen 108 II 48), the rise afore is given as 4 1/4 feet, behind 9 1/4 feet; for the ship Elias 1641 (Witsen 109 II 30), respectively 3 feet and 9 1/2 feet. This is quite sufficient to strictly delineate this line in the sheer view, as it is known to have a circular shape (or catenary curve) for probably all ships.
In one case, for the ship Graef Enno 1642 (Witsen 110 I 22), the run of this line in top view is even given (25 feet from the wing transom the breadth of the ship is 13 1/2 inches less than at the midship frame).
To conclude, the elements of these crucial conceptual data can be found as much as possible in the more detailed contracts, one just have to look at them through the eyes of geometry as well.
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