Loading and stability of a late 16th century Portuguese Indiaman

The stability characteristics of 16th century ships are not known with certainty, but safety issues related to floatability, stability and overloading were a cause of concern at the time. The aim of the paper is to advance knowledge in this field by developing a set of loading conditions for a typical Portuguese ship of this epoch, for both the voyage from Lisbon to India and the return voyage. This allows testing the reconstruction of the presumable Nossa Senhora dos Mártires as well as to use this reconstruction to bring a better understanding of safety and loading issues on the Portuguese East India route. Given the uncertainties about the loading conditions, several hypotheses are tested, varying the amount of ballast, the degree of overloading and the distribution of weights on board, and allowing the development of a range of plausible loading arrangements. The stability of the ship is then assessed using modern tools to develop the limit KG curve for compliance with a modern stability criterion applicable to large sailing vessels. The case study ship is a plausible reconstruction based on the analysis of nautical archaeological remains, contemporary documents and the use of modern naval architecture methods.