# NavList:

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

**Re: Traditional navigation by slide rule**

**From:**Rommel John Miller

**Date:**2016 Jan 6, 21:57 -0500

Some nitpicking by me

The C and D scales on a slide rule take three forms.

C&D Themselves

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.

CI and DI (not 1) Are inverted, which is to say reflection of the C&D scales.

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.

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. Note that I am not lying when I say it is NOT C1 but CI.

Thanks

Rommel John Miller

8679 Island Pointe Drive

Hebron, MD 21830-1093

410-219-2690 (Land and Home)

443-365-7925 (Cell)

**From:** NavList@fer3.com [mailto:NavList@fer3.com] **On Behalf Of **David Pike**Sent:** Wednesday, January 6, 2016 4:40 PM**To:** rommeljohnmiller---.com**Subject:** [NavList] Re: Traditional navigation by slide rule

Bob Goethe sent some photos http://fer3.com/arc/m2.aspx/Traditional-navigation-slide-rule-Goethe-jan-2016-g34055

That’s a mighty slide rule Bob. For one who only ever managed to just scrape through in higher Maths, please confirm what all the scales are. Starting from the backside from bottom up my guesses are:

LL2 = e superscript 0.1x

LL3 = e superscript x

C&D = x

C1 = 1/x

C1F = just a guess 1/pi x

CF = just a guess pi x

LL1 = just a guess e superscript 0.01x

L = log base10 x

Front side from bottom up

Sh1 = just a guess sinh-1 some scale on there? Small angles

Sh2 = just a guess sinh-1 some scale on there? Larger angles

Th = just a guess tanh-1 some scale on there?

D = x

S = sin-1 x

ST = sin-1 x or Tan-1 x Very small angles

T = tan-1 x

A&B = x squared

LL00 = very much a guess e superscript 0.000x

LL0 = very much a guess e superscript 0.00x

Many thanks. DaveP