Welcome to the NavList Message Boards.


A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Add Images & Files
    Re: Traditional navigation by slide rule
    From: David Pike
    Date: 2016 Jan 7, 02:54 -0800

    Rommel you wrote:

    CF and DF where the  F signifies the line is folded over.  That is to say C and D both begin and end with Pi.  Of course! The penny drops.  F meaning Folded means moved along a by 3.142 or effectively multiplying by pi.

     CI and DI (not 1) Are inverted, which is to say reflection of the C&D scales.  Inverted, yes!  How blind of me.  I've taken another look the 1s and the Is are completely different.

    CIF is a funny scale in that it is inverted and folded and the left index is 3.5 and the right index is 3.1  on the K+E Log Log Duplex Decitrig 3.1 is thus the right index in that it extends past what would be the traditional place of terminus for the C or D scales.  If you have a slide rule that has an inverted and folded C scale (CIF) look at it.  Interestingly, looking at Bob Goethe's photos, you can achieve this scale in two ways.  Upwards, by taking CI and F ing it, or downwards by taking CF and I ing it.  The laws of algebra I suppose. You need to keep a careful track of the decimal point though.

    This site http://www.sliderules.info/a-to-z/scales.htm  Does a pretty good job of describing the scales on a just about all scale rules out there.  You'd think I'd have learned by now.  If you have a question, Google it first. 

     That's the great thing about this site; you learn something new everyday.  Conversly, you realise you don't know anything like as much as the tiny amount you thought you did know.  DaveP 

    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.

    Email Settings

    Posting Code:

    Custom Index

    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site