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    Re: Traditional navigation by slide rule
    From: Brad Morris
    Date: 2016 Jan 16, 16:19 -0500

    Francis

    I have been following along but your last presented me with an Ah Ha moment.

    With sine and cosine on the inner tube and sine and cosine on the outer tube, we can perform the standard equation of spherical trigonometry on a cylindrical rule.

    Further, because the scale length is enormous, we have accuracy too!!

    Now that was an Ah Ha moment for me!

    Brad

    On Jan 16, 2016 11:48 AM, "Francis Upchurch" <NoReply_Upchurch@fer3.com> wrote:

    Bob,

    photos of my latest miniFuller2 with sines and cosines marked in degrees and minutes and generally accurate to 1' except at the "squashed" ends of the scales. 

    The design format is my own, based on the Otis King which has 2 identical A/B scales(see attached of  both for comparison) Mine has that plus sine scale in black with cosines in red going the other way.

    This slide rule does all the celnav triangle calculations to 4-7 decimal places, so for me is the ideal general purpose CelNav slide rule.This one is robust and seaworthy too.

    I find the simple cylindrical slide rules easy and cheap to build with plastic drain pipe off- cuts and very little precision engineering, other than printing, cutting and lining up the computer generated scales. 

    Build details on request.

    Best wishes

    Francis



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