Hedderwick: Marine Architecture (1830)



It has been much disputed by builders which is the proper situation on the keel for the dead-flat frame. Some insist that its proper place is at the distance of 2-3ds of the length of the vessel from the stern-post on the line of floatation; others think this too far forward, and that it should be placed only a very little before the middle of the ship. Theory is in favour of the former opinion, and experience in favour of the latter; for it is found that vessels having their flattest floor, or the flattest part of their bottoms, in their middle, or nearly so, are fast sailers, and much superior to those whose bottoms are carried far forward. This may account for the fast sailing of those vessels which have been built by persons who had no theoretical knowledge but what they derived from their observations on the sailing of vessels.

But as to the situation of the dead-flat frame on the keel, I am inclined to think that it is generally placed too far forward, and that it should not be father before the centre of the ship on the line of floatation than 1-15th of her length. Many persons imagine that the form and position of the midship frame will regulate the rate at which the vessel will sail; but this is incorrect, for it is perfectly certain that the sailing depends on the form of the entrance and run. The midship frame may be of almost any shape, but if the bottom of the vessel be in other respects regularly framed, and possess a proper entrance and run, she will sail fast.

Before concluding this chapter, I shall explain the manner of draughting a small vessel, which will make the reader sufficiently acquainted with the various lines, so as to enable him to construct an original plan from the direction and rules to be explained in the following chapter.

Peter Hedderwick: A Treatise on Marine Architecture, containing the theory and practice of shipbuilding, with rules for the proportions of masts, rigging, weight of anchors, &c including Practical Geometry and the Principles of Mechanics; observations on the Strength of Materials, Hydrostatics, &c. with many valuable tables calculated for the use of shipwrights and seamen; also the proportions, scantlings, construction, and propelling power of steam-ships. Illustrated with twenty large plates, containing plans and draughts of merchant-vessels from fifty to five hundred tons, with mast and rigging plans; plans and sections of a steam-boat of eighty-horse power; and eight quarto plates of diagrams, &c., by Peter Hedderwick.
Printed for the Author, Edinburgh, 1830. p 169.

Transcribed by Lars Bruzelius

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