NavList:

Geoffrey Kolbe, you wrote:
"Such watches are usually called a "deck watch". I would be interested to know where the term 'hack' comes from...?"

This is tied up with the ambiguous history of the word "hack". If someone says, "I hacked together a solution to your problem", or if a software engineer says "I have a hack to resolve the bug", they mean that there is an efficient, cheap, possibly clever, and probably temporary and unstable solution to the problem --"it's a hack". This is the sense of the word in the past fifty years or so. A common usage today is in the phrase "life hack" (or the compound word "lifehack" --it's in the OED) which has its own Wikipedia page, https://en.wikipedia.org/wiki/Life_hack, with some basic background and references. There exists alongside this definition the concept of a computer "hacker" who finds pleasure in creating efficient, cheap, and artfully clever, but probably unstable solutions to problems as well as routes around computer security. This has added more negative connotations to the word "hack".

The phrase "hack watch" has been around since the late 19th century (I found a reference from as early as 1888) when it referred to any "portable chronometer" but probably that applied to any good, small watch with a second hand. It is a "hack" in the sense of a "cheap, efficient solution" to the problem of transferring the chronometer time, so it loosely fits within one of the modern definitions, but it could easily have its origin in some other colloquial sense of hack. And by c.1940 a "hack watch" was simply a "less expensive watch," and it could easily look exactly like a common wristwatch. As long as it could be read to seconds and had reasonable reliability for some hours of operation, it could be used as a hack watch. Starting at about this date, the idea of a simple reset for the second hand (a Weems innovation?) seems to have narrowed the definition in some navigation cultures. In addition, everyday watches with second hands became common in this period, so the name "hack watch" followed the feature that seemed unique. Of course, one does not need a purpose-designed hack watch for navigation. Any instructions that require a hack watch could just as easily say "your watch" (with a footnote indicating that it must be readable to the nearest second and adding that a reset of the seconds count is a desirable feature). Note that a common stopwatch fulfills this role, too, if the interval between comparing against the principal time source (main chronometer) and the observation is less than the maximum time displayed by the stopwatch.

Frank Reed
Clockwork Mapping / ReedNavigation.com / HistoricalAtlas.com
Conanicut Island USA