Navigation and other Marine Applications for SRs

[pabrides]

I'm not sure how many here remember the slide rule (SR).  if you were in high school in the 60s then you would probably have some experience.

I went to HS in the 70s and never heard of the SR.  Only 10 years ago did I discover them as a source of enjoyment.  it feels pretty cool to know how to use some of the scales, and the more I use them the more I like SRs.  Just yesterday I bought a full sized 10in SR used from a guy in manila.  My new toy will be here in 2 days.  Up until now I've been using a 5in model.  I can hardly wait.

Anyway, a couple years ago I found this PDF book about how to use SRs for marine and aviation problems; from simple time, speed, distance calculations to cargo handling and trim.  I wrote about it here at the time.  However, maybe some of you missed that post.  Just goes to show I'm still excited about the subject.

I'm thinking some of you might like to review the book, a free download, and discover how fascinating and ingenuous the SR really is.  You don't need to have the same one they use in their example; any SR with similar basic scales will do.

http://www.survivorlibrary.com/library/t...n_1974.pdf

This site is put together by a very nice man who assembled a collection of old books that keep my mind occupied.

Check it out and tell me if you don't agree that SRs are still useful... and they don't require batteries.

Cheers

[Fred_B]

I have 2 of them and still use them. It's often easier to use a sr to see various answers quickly or approximate comparisons. Sight Reductions can be done but there's a need to be very careful since I'm no expert in mathematics or slide rules. There are many different types of slide rules and some that are specific to celestial navigation if I remember correctly.

Survivorlibrary is very good.

Fred

[pabrides]

Yes Fred, the SR does that which the electronic calculator can't do, that is to display visually a range of ratios or proportions at a glance. M:N :: O:P or M/N to O/P

ex: 2 is to 3 as 4 is to 6; 2:3 :: 4:6

For instance, if the ship is running at 8 knots the SR will tell you how far the boat will travel in one hour, 3.5 hrs, 6.25 hrs, or any length of time, and at the same time tell you how long it will take to travel any distance. Or it can tell what speed to travel for a certain distance in a certain amount of time. How cool is that? Using an EC would require many operations.

Many other ratios besides time, speed, distance are just as easy such as fuel consumption over time, fuel over distance, fuel over HP, battery rates of charge or discharge, conversions of weight, length, volume, and a ton of other stuff. This is all besides the ability to perform more interesting complex operations like current vectors and the sailings.

Glad to see another SR user on the site.

Thanks for the post

Cheers

[pabrides]

Good day shipmates,

I got my new slide rule the other day: Hemmi 259D   <  $14 + $3 shipping

It was so unused and pristine I needed to lubricate the slide and do a general alignment.

What a pleasure it is to use.

The 259 has a good range of log-log scales as well; something my other SR lacks completely.   I spent a day just learning how to use them.

You don't have to love math to enjoy an SR.  They make navigation functions so much more fun and interesting.

Cheers