Bygrave position-line slide rule

[Richard5]

Who has experience using this?

I am rereading The Lonely Sea And The Sky, by Sir Francis Chichester. He mentions using this slide rule when flying from New Zealand to Australia by way of Norfolk and Lord Howe islands.

As I have a great interest in all types of slide rules I would like to hear of first hand experiences using this tool.

https://timeandnavigation.si.edu/mul...e-slide-rule-1

[Adelie]

Visit NavList. Search the archives there.
The have info on how to build you own and there is a flat version I had printed at Kinkos for about $2.

Brown-Nassau would be better. You can find the stuff to make your own at NavList again.

[Richard5]

Wow, that was fast. Thank you for the NavList site, I hadn't known of it. Well done, Adelie.

I have spent the last few minutes at the website suggested by Adelie. Also, here is a pdf. It seems this slide rule is rare, only a few remain, and most are in museums. I will continue to read up on it and perhaps print out one to play with.

Adelie, do you have any practical experience using your Bygrave?

http://fer3.com/arc/img/PositionLineSlideRules.pdf

[Adelie]

I played around with a LaPook which is the flat version of Bygrave but not seriously.

If I was going to us a mechanism rather than a table I’d go for the Brown-Nassau

In reality I’m very partial to Ageton for sight reduction.

[SeanPatrick]

I have also used Gary LaPook's flat Bygrave quite a few times. Since the scales are on two separate sheets, it's a little trickier to keep everything lined up than I imagine the actual cylindrical slide rule would be. There is also no index line or cursor, so you have to find another way to keep track of where you're at. The accuracy (IIRC) is about 1' in altitude and a little less for azimuth, but this is acceptable for celestial navigation - especially in a boat.


Having said all of that: I think the Bygrave is still a great alternative to tables. Just two sheets and you can do pretty much any sight reduction calculation you need - as opposed to multiple books worth of tables or an overly complicated "concise" set of tables such as those included in the Nautical Almanac. The Bygrave does have its own set of rules for use, but they are relatively simple and once you use it a few times you'll probably have them memorized. And in the case of Gary's version, you simply cannot beat the price.


I tried two different methods of printing mine: having it done at a professional print shop, like Adelie - and using some ink-jet transparencies and normal printer paper at home. Either method produces a perfectly usable slide rule. But, the transparency I used at home is not quite as high quality as the professionally printed version (of course). It has a slight haze to it and I discovered that if it gets wet, the ink is prone to running. Not something you'd want on a boat. I also had the other sheet laminated, so the professionally printed version is completely water-proof.

[sabatini5918]

Originally Posted by Richard5

Who has experience using this?

I am rereading The Lonely Sea And The Sky, by Sir Francis Chichester. He mentions using this slide rule when flying from New Zealand to Australia by way of Norfolk and Lord Howe islands.

As I have a great interest in all types of slide rules I would like to hear of first hand experiences using this tool.

https://timeandnavigation.si.edu/mul...e-slide-rule-1

I used a slide rule in high school (and first year of college) chemistry and physics. You could quickly multiply and divide to 3 significant digits. This was just before electronic calculators first appeared. The slide rule had other functions, but I used it mainly for multiplication and division. I still have two slide rules among my stuff.

[S/V Alchemy]

Every so often, this forum throws out a topic of which I was completely unaware. This is one of those times, and I own both an old rangefinder, three sextants, a Tamaya NC-77 nav calculator and a Walker log!

[Pete17C]

The aviation E6B is the probably the most used slide rule still in use. PVH Weems (Weems & Plath) was involved in it's development. Many of it's functions can be useful for sailing.




https://en.wikipedia.org/wiki/E6B

[a64pilot]

I still think if the course is 180 degrees, you maintain whatever heading is required to get a ground track of 180 degrees.
I don’t think it’s any more complex than that.
The backside of the E6B if cross currents are known will tell you how many degrees left or right you have to steer to maintain course, but it’s really easier than that, just remember to “Push” the head and if your navigating with a radio direction finder, you may need to remember to “pull” the tail.

[Adelie]

Originally Posted by a64pilot

I still think if the course is 180 degrees, you maintain whatever heading is required to get a ground track of 180 degrees.
I don’t think it’s any more complex than that.
The backside of the E6B if cross currents are known will tell you how many degrees left or right you have to steer to maintain course, but it’s really easier than that, just remember to “Push” the head and if your navigating with a radio direction finder, you may need to remember to “pull” the tail.

The point of the E6B was to figure out what course to head in crosswinds for a desired course before the advent of GPS.

[alan2]

RIchard5

When I saw your question, I immediately thought of NavList. Seems as if a number of others did too, getting back to you before I could. Hope you find the site helpful. There is a wealth of information to be found there.

[a64pilot]

Originally Posted by Adelie

The point of the E6B was to figure out what course to head in crosswinds for a desired course before the advent of GPS.

GPS is an after the fact thing.
The point of an E6B is planning, for example do I have enough fuel to get there with an alternate? Also situational awareness, the E6B will tell you you will have to hold a 6 degree course to the left, a GPS will not tell you that, that you can determine by trial and error after takeoff, but it will take time and it will occupy some of your time doing so, it’s a distraction.
E6B back side, the wind face will tell you before you go.

E6B will also compute a fuel consumption check and many other things.
I wore one around my neck for years until the Longbow, which pretty much made it obsolete.

[Scott Berg]

I used a sliderule in highschool and college (a bit) but migrated to an HP45 then. I was on a delivery and the captain was discussing the Bygrave as we did our sight reductions (long before GPS); he said anyone who produced a modern one would be rich. I'm guessing GPS solved that <grin> but I'd love to have a real rotating one... my craft skills aren't up to making it but love the concept!

[Adelie]

Originally Posted by Scott Berg

I used a sliderule in highschool and college (a bit) but migrated to an HP45 then. I was on a delivery and the captain was discussing the Bygrave as we did our sight reductions (long before GPS); he said anyone who produced a modern one would be rich. I'm guessing GPS solved that <grin> but I'd love to have a real rotating one... my craft skills aren't up to making it but love the concept!

Not the hard from what the NavList folks say.

[alan2]

Originally Posted by a64pilot

GPS is an after the fact thing.
The point of an E6B is planning, for example do I have enough fuel to get there with an alternate? Also situational awareness, the E6B will tell you you will have to hold a 6 degree course to the left, a GPS will not tell you that, that you can determine by trial and error after takeoff, but it will take time and it will occupy some of your time doing so, it’s a distraction.
E6B back side, the wind face will tell you before you go.

E6B will also compute a fuel consumption check and many other things.
I wore one around my neck for years until the Longbow, which pretty much made it obsolete.

I assume Longbow is a program of some kind.Information thereon please.Thanks