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    Re: Brown-Nassau spherical computer
    From: UNK
    Date: 2015 Apr 1, 08:02 +0100

    Thanks Hanno,

    Yes, I agree. The hav-Doniol + Otis King is my most compact, easy non electronic back-up system.

    This BN was made from polycarbonate sheet off cuts.The printed graphs covered in transparent plastic book cover sheets. Very robust and water proof I think compared to the sextant which is the weak link with respect to mechanical reliability! One little knock/drop/wave soaking and game over!

    We’ll see. Can’t wait to test all these at sea in next few months, health allowing.



    From: NavList@fer3.com [mailto:NavList@fer3.com] On Behalf Of Hanno Ix
    Sent: 31 March 2015 23:17
    To: francisupchurch@gmail.com
    Subject: [NavList] Re: Brown-Nassau spherical computer



    not only "so far-so good" but real nice!

    As you know, I personally like those ingenuous sight reduction slide rules for their sheer ingenuity. However, for actual work on the water I probably would prefer arithmetic methods. Reason: devices will fail one way or the other, and clever ones will fail earlier. I know that from 30 yrs of practical engineering. Sad recent example: electronically controlled doors to the flight deck :(

    I recently discussed to some extend sight reduction with David Burch / Starpath to sell him on the hav-Doniol - no success; he goes with the assumed location, period. Re: slide-rules he recognized openly their utility but he was concerned about their being special devices, a situation not generally acceptable.

    But since you are making your own devices, perhaps taking along two of them is a good solution for you. Inventing and making them has its own attraction - I know!



    On Tue, Mar 31, 2015 at 9:11 AM, Francis Upchurch <NoReply_Upchurch@fer3.com> wrote:

    Just completed my full sized version. See attached. Details of build on request. Used Harri's wonderful graphs based equations in the original papers (thanks Harri). We had to guess the layout of the B/Y side (or dark side) since the only photo of the original in the Smithsonian is of the A/X side. (If any of our US friends happen to visit the SM, I would appreciate a detailed pic of the far side. repeated email requests have remained unanswered.)  However, it works ,so I think it is correct.

    So far , getting mean of 2-3' errors for Hc compared to calculator. Hc only takes about a minute. Easier and faster than Bygrave or even calculator.

    I think it would pass the "Chichester Test".

    More to follow, but so far so good.


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