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    Refilling Mk IXA Bubble Sextant - Lessons Learnt
    From: Zvi Doron
    Date: 2004 Mar 6, 07:53 -0000

    Hello,
    
    Having been told in no uncertain terms "Don't be so problematic" for asking
    too many questions (Deming said once that there was no substitute for
    knowledge) I set about to do the job based on the confident instructions
    given to me in previous correspondedence. A few days later I received the
    original Frank Bartlett Instructions PDF file from Steve Grobler and could
    see how it was supposed to be done as written and drawn by an expert.
    
    Lessons learnt:
    
    1. Cutting the top of the filling tube WAS A MISTAKE. As solder penetrated
    into the tube in the original manufacturing process it took several cuts to
    reveal the opening, by which time the filling tube was much shorter and as
    we all learned at childhood it is easy to cut things but pretty difficult to
    put them back together. I should have either unsoldered it or better still
    used Bartlett's way of gently drilling through the solder with a
    watchmaker's screwdriver holding the unit upside down to prevent swarf
    falling into the cylinder.
    
    2. Yes as I suspected IT WAS very important to fill exactly the correct
    amount of Hexane. Too much and you cannot form a bubble, too little and you
    cannot get rid of it or reduce its size.
    
    3. As I could not find a 5ml syringe I bought a pack of 10 1ml syringes used
    by diabetics. THIS WAS a very fortunate move as when you fill the syringe
    with Hexane and start injecting it the Hexane reacts with the synthetic
    rubber pistone inside the syringe and by the time you empty it in the
    pistone seizes and you have to throw it away and use a new one. In my case
    3ml were needed and the 4th was an overfill which had to be squirted out to
    get to the right amount of liquid. I made sure a window was open and the
    bottle was well stoppered between fillings - the staff is highly volatile
    and flamable and can ruin your whole day if it goes "Poof".
    
    The sextant now works like a dream. I am taking series of 12 individual
    shots and averaging the results to determine its combind error at various
    altitudes. It appears to be in the order of 4.5' - 4.7' between 15-35
    degrees
    
    Hope this info might help somene's future endevours.
    
    Best regards
    
    Zvi
    
    
    

       
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