Reply To: Angle of Vanishing Stability and Capsize Screening Formulae

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Wayne Tripp

    I apologize for my late arrival to this discussion. In terms of applicability of any modern stability methods to 18th and early 19th century vessels, the answer is that yes, we can apply them from a modern view to understand the possible conditions of a period vessel. The answer is also no, it is not appropriate to apply modern formulations to that era.

    Why Yes? We can, with appropriate information concerning the hull form, ballast, displacement and so on, estimate various stability measures for historic vessels. These measures can help in understanding the performance as reported for a vessel, such as whether a vessel handled well to windward, pitched or rolled excessively &c.

    Why No? There are several reasons for the no, but perhaps the most important is that for the period in question, shipwrights of many nations were struggling with the scientific developments that brought a theory to naval architecture. It remained very rare that a ship builder in Britain accurately predicted the draught of water for a vessel when fully burdened before the ship was afloat (that is, the floating level when carrying the intended weight in stores, cargo, crew, weapons, provisions and so on was determined before the vessel was built, and then verified when launched, rather than the common practice of finding the capacity after launch by loading the vessel until it reached the desired draught of water).

    The French, Swedish and other nations were somewhat more advanced in the use of scientific theory rather than rule of thumb, and indeed even into the mid 18th century we see the persistence of a parabolic method of design and construction rather than a due consideration of hull form and shape in British shipbuilding.