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Courtney,

Give me a couple of days to hunt around our warehouse, and see if I can find
a castoff to remind myself how it comes apart. It should be similar to the
Freiberger which I described in detail earlier.

While you're waiting, you can run some water through the cylinder. Turn the
sextant over so the underside of the arc is exposed.  Sometimes it pays to
remove the aft leg which will allow the index arm to move backwards off the
arc. There maybe some kind of a stop which has to be removed. Take the index
arm and move it all the way to the back of the arc. In a SNO-T the underside
of the cylinder in which the tangent screw is housed has a slot which is
wide enough to see the teeth of the screw. That is where to run the water or
WD 40 or if serious, Blaster.

Jared Sherman is the resident expert on chemicals, maybe he will give some
advise to what to use for the eye cup other than Armoural which I abhor.

Joel

----- Original Message -----
From: "Courtney Thomas" 
To: 
Sent: Tuesday, August 03, 2004 10:52 AM
Subject: Re: on washing sextants


> Joel,
>
> I have a SNO-T with the barrel enclosed tangent screw.
>
> How do I properly gain access to the tangent screw ?
>
> Also, what should be done to preserve rubber eye cup pliability ?
>
> Appreciatively,
>
> Courtney
>
>
>
> Joel Jacobs wrote:
>
> > Peter,
> >
> > The most damage that befalls a sextant is due to living in a salt
> > atmosphere, particularly when used from small craft where they are
subject
> > to frequent spray. Salt water, left unattended will first attack the
> > mirrors. The backside of the mirror's frames have a trough which
collects
> > more of this spray then elsewhere and this starts to erode the
silvering. In
> > time, it also will eat into any chrome parts, cause the paint to bubble
and
> > lift on the frame. It will do major damage to a sextant with an
aluminium
> > frame as salt water is a strong electrolyte.
> >
> > The prevention is to rinse the sextant in fresh water after each use,
> > whether its been subjected to salt spray or not. If the sextant has its
> > tangent screw encased in a barrel or cylinder like the Russian and
> > Freiberger sextants make sure to run a lot of water through it which
will
> > keep the screw from freezing. Then of course wipe down with a soft
cloth.
> >>From time to time, you may also add some lubricating oil to the tangent
> > screw for protection on those that are housed. This is not necessary on
> > sextants with open screws. Doug Royer recommends NYOIL.  Jared Sherman
> > recommends DuPont Krytox. I use what I have handy which is Vaseline and
> > Never Seize. The latter only on a tangent screw encased inside a barrel
or
> > cylinder because it does stain.
> >
> > Doug some time ago wrote a message which went into great detail of how
he
> > and others on his ship took great pains to clean their instruments and
> > protect them. One of his recommendations was the use of RainX on the
> > mirrors. Hopefully he saved that message and can re-send.
> >
> > I also would like to hear what Jim Thompson has to say. He has one of
the
> > most comprehensive sites on the internet devoted to CELNAV.
> >
> > Joel Jacobs
> >
> >
> >
> > ----- Original Message -----
> > From: "Peter Fogg" 
> > To: 
> > Sent: Monday, August 02, 2004 10:45 PM
> > Subject: on washing sextants
> >
> >
> >
> >>Quoting Joel Jacobs
> >>..where I
> >>
> >>>was talking about washing a sextant after use.
> >>>
> >>Would Joel, or anyone else, like to go into a little detail about this
> >>
> > sextant washing idea?
> >
> >
>
>
> --
> s/v Mutiny
> Rhodes Bounty II
> lying Oriental, NC
> WDB5619

   

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