Trans RINA, Vol 152, Part A4, Intl J Maritime Eng, Oct-Dec 2010 HISTORICAL TRAILS OF SHIP BROACHING-TO
K J Spyrou, National Technical University of Athens, Greece (DOI No: 10.3940/rina.2010.a4.187) SUMMARY
The article intends to bring back to light old perceptions about the “broaching-to” behaviour of ships. The signature of broaching-to is the sudden loss of controllability. The phenomenon sometimes ends with vessel capsize. The findings of an investigation into old bibliographical sources are reported, spanning more than 300 years of use of the term. Several citations have been identified in texts of nautical or related content, including voyagers’ records, nautical journals, training manuals, old encyclopaedias and even literary sources and leisure magazines. At a time when broaching-to is considered in the currently formulated new ship stability criteria at IMO, this paper provides a historical perspective on a problem that has maintained relevance despite the changes in ship technology and design.
1. INTRODUCTION
“Broaching-to” is an unstable type of ship behaviour, occasioned by steep following/quartering seas. Loosely described, it is the loss of heading of an actively steered ship, often manifested as a tight turn despite the “hard- over” setting of the rudder. A resonant-type build-up of heading deviation from the desired course is another possible manifestation of broaching-to. Capsize on a wave down-slope is a likely consequence as the ship is brought broadside to the weather. Whilst the subject has been alive in the nautical bibliography for centuries, essential advances in the understanding of the dynamical origins of this behaviour have been realised only after the 1950s [1-6]. Reflective of the notable scientific progress achieved is the current consideration of broaching-to prediction methodologies within the framework of the so called “new generation intact stability criteria” which are currently being discussed at IMO [7].
Since modern ships usually carry no sails, research has targeted the physics of broaching-to as exhibited by modern motor ships operating under the effect of waves, with no concern for wind. In the era of boats with sails however, wind represented a key source of excitation and subsequently, it should have played a major role in shaping the perception of what broaching-to is. The arrangement
of sails and the incurred significant
destabilising wind forces should have been very influential for turning suddenly, despite all efforts, a ship broadside to the weather. It must be a fair conjecture that, the combination of wind and waves should have placed more heavy demands upon the Master of the old days.
It
should be interesting therefore to learn how broaching-to was described and dealt with in the past; an era that in fact still survives to some extent, through the modern sailing boats. Whilst for modern ships one finds some, often vivid, descriptions of broaching-to behaviour [8]; the community of ship designers maintains limited recollection of the deep past of the subject. A glimpse into that, long-gone, world when navigation was, in its own capacity, an adventure reveals that, the prevention of broaching-to represented a great concern for the seamen. Several book excerpts and other texts from the
19th, 18th and even 17th century authenticate explicit use of the term “broaching-to” by the old seamen for characterising what they apparently believed to be one of the most dreadful conditions that ships could encounter during their operation. Such a feeling is distilled in an old sailor’s pocket book where one reads that [9]:
“The one great danger, when running before a broken sea, is that of broaching-to.”
According to the Oxford and the Merriam-Webster dictionaries of the English language, the first documented use of the term “broaching-to” is traced to the year 1705 (referring to a book however which, as will be discussed later, had firstly appeared in 1699). Their definitions
of the phenomenon appear quite alike:
according to the Oxford English Dictionary, broach to is [10]; “to veer suddenly so as to turn the side to windward, or to meet the sea”; whereas in the Merriam- Webster it is defined as [11]: “to veer or yaw dangerously so as to lie broadside to the waves”.
The literature (nautical and beyond) was found to offer some captivating descriptions of real occurrences of broaching-to along with deliberations on how to avoid it; attempts of defining the phenomenon formally; rowing and steering practices; and improvised gear devised specifically for dealing with it in the critical hour. From our investigation comes out that,
broaching-to was
mostly feared when a vessel was heading towards the shore; especially when lying very near to a steep shore. Moreover, it was often discussed within a scenario of the ship sailing at a high speed, rushing before the weather (this is the condition identified as “scudding” and discussed more thoroughly later). The experience has apparently survived in the description of broach-to in the Oxford Companion to Ships and the Sea [12]. In there, all emphasis is placed on the effect of wind and the occurrence of the phenomenon is associated with some skippers’ habit of running their ships too fast; further suggesting that, it is dangerous to sail with spinnaker.
The purpose of the current paper is twofold: firstly, to provide a historical perspective and inform about how
©2010: The Royal Institution of Naval Architects
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