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    Re: Traditional navigation by slide rule
    From: Paul Hirose
    Date: 2016 Oct 19, 22:00 -0700

    On 2016-10-18 14:33, Bob Goethe wrote:
    >
    > I am attaching a 100%-scale copy of the current design that should be 
    sufficient for folks to make cardboard prototypes.
    >
    > Attached File: http://fer3.com/arc/imgx/2016.10.18-Full-Scale-Paper-Version-Letter-sized.pdf
    > Attached File: http://fer3.com/arc/imgx/2016.10.18-Full-Scale-Paper-Version.pdf
    
    I wonder why the trig scales don't include a small overrun to the next
    convenient graduation at each end. For instance, at the top left of the
    rule, is there some reason T0 cannot extend down to 33′? The practice of
    chopping off trig scales exactly in line with the C and D indices is
    widespread on slide rules, and has long been a sore point with me.
    
    In some cases this is necessary. Many slide rules have no C scale on the
    "trig side." Scale S is on the bottom of the slide, so it must have a
    graduation on the left to match the D index. But that's not the case
    with your rule. Its C scale indices can serve that function for all the
    trig scales on the slide.
    
    Keuffel & Esser got it right on their flagship rule, the Deci-Lon. Note
    the generous scale extensions. These make reading and setting noticeably
    easier when working near the ends of the scales.
    
    http://www.sliderulemuseum.com/KE/KE_68-1100_Decilon_sn318318_DonatedByRichardPlastino.jpg
    
    You have 80 and 90 numbered on scale S, but the Deci-Lon omits 80. Most
    slide rules do.
    
    Is the alignment of the top and bottom of the body adjustable? If so, it
    would be nice to include a couple marks on the top of the slide to match
    the left and right indices of scale A. If the body is aligned properly,
    these should coincide when the C and D indices coincide.
    
    

       
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