Welcome to the NavList Message Boards.


A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Add Images & Files
    Pilot watch slide rules
    From: Paul Hirose
    Date: 2019 Dec 30, 13:03 -0800

    What a busy watch face:
    If that's the "Co-Pilot's Watch," one can only wonder what the pilot's
    watch looks like. I think the slide rule would initially disorient me,
    as the outer (distance) scale moves and the time scale is fixed. An E-6B
    is the opposite. But I could get used to it, though driving a car while
    wearing my strongest reading glasses and fiddling with the watch is out
    of the question.
    One customer review says, "I had asked customer service how the
    Tachymeter function worked (the outer movable bezel and adjacent rings),
    as there are no instructions for that. I have since researched this and
    have provided them with a document I drafted that outlines how to do
    time, distance and rate of speed calculations with the watch."
    However, I don't see a tachymeter on the watch. There is one on the
    "Flyboy" watch.
    Of that watch, someone says, "Which brings us to the rotating slide rule
    bezel. This is where some improvement is needed. It is a true,
    bi-directional rotating slide-rule bezel, but some of the numbers are a
    little out of place, causing some calculations to be a little
    inaccurate. Treat any calculation results with this slide rule as VERY
    approximate. Plus, the hash marks around the bezel are too close
    together and too similar in size to be useful."
    That sounds like something I would write. One of my favorite slide rule
    complaints is that the graduations are hard to read without making a
    mistake (as on the Pickett N4). In that respect the Co-Pilot watch looks
    much better.
    I have long thought the usual tachymeter format was far from optimum,
    since the numbers just clockwise from 12 o'clock are absurdly high for
    any practical use. But the Wikipedia article explains a method for
    extending the range downward:
    Unfortunately, I find it incomprehensible. It seems to be one of those
    "explanations" which make sense if you already have a clue, which I
    clearly don't. For instance, you time a mile at 65 seconds, so at the
    end of the mile the second hand is stopped at the 5 second mark. Speed
    is about 55 mph, but I don't see how to read that from the tachymeter.
    Of course you could make the calculation with the circular slide rule.
    Rotate the outer scale to set 1 mile opposite 65 seconds on the inner
    scale. Now all possible combinations of miles and seconds — for that
    speed — are opposite each other. To get miles per hour, observe 55.5
    miles opposite 3600 seconds. (Flight computers of the E-6B type have
    special marks at 60 and 3600 on the time scale to help the user's eye.)
    The outermost scale on the bezel is graduated in degrees, but the watch
    description says nothing about a compass function. Even more mysterious
    are two scales on this "Explorer" watch, one graduated up to 15 and the
    other to 165 — ?

    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.

    Email Settings

    Posting Code:

    Custom Index

    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site