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    Re: New compact backup CELNAV system
    From: Andrew Nikitin
    Date: 2009 Mar 2, 06:15 -0800

    > Gary LaPook:
    > ... forming tubes of exactly the right size to fit tightly
    > enough together to provide enough friction so they maintain
    > their alignment but not too tight to prevent easy manipulation.
    I did exactly opposite: I started with available tubes and then
    printed scales to fit them. The tubes I tried to use were PVC
    drain pipe, box of Pringles and box of non-dairy coffee creamer.
    I do not recommend Pringles because of fatty residue that
    eventually finds its way outside.
    As for may comment about keeping scales flat, I did not mean to
    be nagative, just try to relay some personal experience. Here is
    some more -- for those who will try to make an instrument.
    It maybe nitpicking, but the distortions I am talking are visible
    to the naked eye.
    Another unpleasant finding was that same scales had different
    length when printed on regular paper and on the transparency.  I
    guess this is related to the fact that medium is being heated and
    stretched when rolled into the paper feeding mechanism of laser
    printer and paper and transparency, apparently, stretch at
    different rates. Inkjet may be better for this kind of work.
    The stretch is only present along the long edge of the page (the
    direction it is being pulled), so it is better to print both
    scales in the same direction.
    What's worsens things further, the stretch is not uniform across
    the length of the page and does not seem to be consistent from
    page to page (although the effect is minimal, while still
    When stored, transparency with anything printed on it, tends to
    stick to whatever
    Here are is couple more words of wisdom that I acquired by
    lurking into slide rule forum once in a while.
    a) Scales do not have to be slanted if you are not going to wrap
    them around a cylinder. Strictly horizontal scales look way
    better when printed because of absence of pixelation.
    b) You do not have to use transparency and may instead use
    dividers to transfer distances between scales (in fact, this is
    exactly how Gunther scale, the precursor for slide rule, works).
    Some care is required when dividers span several steps of
    multi-piece scale (as in your case) -- they should span same
    number of steps when the distance is transfered to the second
    Trick b) suggests the following development of your method:
    instead of Bygrave formulas, we may switch to Ageton formulas.
    Since Ageton uses  only sec/csc (which are, essentially, the same
    scale) you do not need second scale and can perform sight
    reduction by means of a single printed scale and a dividers.
    Andrew Nikitin
    Navigation List archive: www.fer3.com/arc
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