NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Francis Upchurch
Date: 2016 Jan 21, 07:02 -0000
Thanks Brad,
That is not pedantic, that is very sensible!
Actually ,yes I know enough about slide rules to be well aware of that, but you are right to make sure, given my generally backward knowledge of maths which hampers my progress in celnav somewhat ! (I’m slowly getting better at spherical trig and logs though, thanks to all you Navlist numerati)
Am I correct in thinking that the only common scale on a slide rule which spaced out evenly and not logarithmically ,is indeed the log scale!
Please check attached Fuller 2 sin scale (cos scale, same but numbers go in reverse )and confirm for this maths simpleton, that this is what you meant! (Scale and copyright Wayne Harrison. Unfortunately, I seem to have lost contact with him and not sure if he is still active. He provided all my scales for the authentic Byrave and Fuller models.
Thanks again, and keep assuming the worst when it comes to my maths!
Francis
From: NavList@fer3.com [mailto:NavList@fer3.com] On Behalf Of Brad Morris
Sent: 20 January 2016 21:02
To: francisupchurch@gmail.com
Subject: [NavList] Re: Traditional navigation by slide rule
Hi Francis
I don't mean to be pedantic or otherwise review what you already know. But here goes anyway!
The scales must be logarithmic for the multiplication to work. Just having some sine or cosine scale will not work unless it is also logarithmic.
But you already knew that ;-)
Brad
On Jan 20, 2016 3:16 PM, "Francis Upchurch" <NoReply_Upchurch@fer3.com> wrote:
Thanks Brad,
Yes, I thought you meant that. Good ah ha idea. Like all these, obvious to mere mortals like me once you show us the light! (now why didn’t I think of that? Thought the same years ago about monoclonal antibodies. I did actually think of that, but that sneaky Nobel Laureate got there first!).0
I’ll test run a transparency cos scale over the top of the current cos and sine scale on my big Fuller 2 and see how it goes. The current layout allows multiplication and division of sines and cosines. But indirectly via the A (or is it C or D) regular scale, which involves several extra moves. More asap.
Francis
