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    Re: Eight day aircraft clock
    From: UNK
    Date: 2015 Oct 10, 06:26 +0100

    Hi Hewitt,

    Thanks for the that!

    Yes , I got the photos wrong. The Rotary diameter is 38mm or 1.5 inches, slightly bigger than the Citizen. The Rotary is also water proof to 50m. I’ve never used it for diving, but good enough for wet water sailing.(the usual sort in Cornwall!) The Citizen is a proper diving watch waterproof to 300m. ( I hope to never reach that depth!) William Harrison had to nurture H4 like a baby to stop it getting wet. Pity John H didn’t think of o ring seals. That would have made life a lot easier. A simple waterproof box with internal leather seals and some soft padding would have been feasible back in the 18th century.

    Looking through my last posting, actually, most of my longitudes with the Rotary were within  5-10nm,some spot on. The occasional no watch lunar longitude has been within 5nm, (especially if observations taken in calm water/anchorage etc) most probably around 20nm. So you could do a sort of Cook’s first  Endeavour type voyage just using lunars and no watch. (he did use a “good watch” to do his time sights, but you can manage without.)The watch wins for me though at sea. My emergency ditch bag contains a £5 Casio digital which works well to a couple of seconds per month.

    All good fun.

    Best wishes



    From: NavList@fer3.com [mailto:NavList@fer3.com] On Behalf Of Hewitt Schlereth
    Sent: 10 October 2015 00:27
    To: francisupchurch---.com
    Subject: [NavList] Re: Eight day aircraft clock


    Francis, I will write to the boys in the BOL forthwith. You take the prize and the Rotary takes the cake. What is its diameter? The relative scale looks wrong on my email.




    On Oct 8, 2015, at 10:57 PM, Francis Upchurch <NoReply_Upchurch@fer3.com> wrote:

    I have a 6 year old Rotary mechanical (automatic wind) Chinese built watch (about $100 back then) with glass faces showing the internals a la an open H4.( I fanstasize it maybe an H4 while at sea) Harrison would probably have recognised most of the wirly, tick tock  bits except maybe the movement winder and the lack of bi-metalic parts .The Invar alloy, temperature and magnetic insensitive, would have amazed him no doubt and made  some of his inventions, such as bi-metallic strips, obsolete.

    3 years ago, I did a mock "Longitude prize test", 4 weeks (didn't go to Jamaica, just coastal sailing in Cornwall).

    If warn on the wrist 24/7 at sea, it lost on average 20 secs per day.If warn just a few hours and removed, tended to lose anything from 10- 50 secs per day. So presumably the constant wearing reduces variable  temperature and static positon effects and gives more constant winding?

    Anyways, a graph drawn through the 20 secs per day lost, gave me predicted rate which gave me good accuracy  after 4 weeks, well under 2 minutes out.So I claim the prize please, Longitude Board! With inflation, that would be about £3million. please pay direct into my offsore account. !

    My favourite quartz is my Citizen eco drive divers, virtually bullet proof. Generally good for +2 secs per month whatever I do with it, direct sun, sea or dropping.

    Citizen Professional Diver Eco-Drive Mens Watch BN0000-04H

    The pictures are not to scale! Roughly similar size.

    I also like to do "no clock" cel nav using lunars,bit like Slocum, using a towed log to get distance run between observations. I haven't written up my recent few experiments yet, but Longitude by lunars and no clock generally within 30 nm. most of my longitudes using the Rotary were within 5-20 nm. So the clock beats the moon, at least with my lunars at sea.

    All great fun! Greg, I think JS  Letcher used only an 8 day aircraft panel clock in the 1960s, $22 ($170 now).


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