Sliderule identification challenge

[BruceH]

Came across this site for Dutch slide-rule collectors. They have a mystery items page. I know you're up for the challenge! :-)

https://www.rekeninstrumenten.nl/Engels/mystery.htm

[rprosperi]

Thanks Bruce, some really interesting tools there, just wish there were more / better photos.

The top item has a clear image of a Lockheed F-104 Starfighter (that was it's real name) so this was almost certainly used, somehow, for navigation (or planning for?) but it is damn odd.

@Max - you're the flight computer guru, what the heck is this about?

[Maximilian Hohmann]

Hello!

(11-03-2024 01:15 PM)rprosperi Wrote:  @Max - you're the flight computer guru, what the heck is this about?

I can only guess that this is a sun compass, probably part of the survival kit that the pilots carried in case they had to eject from the aircraft and needed to find their way home. This one assumes that you know the exact time from your watch.
You can see that it was made for the Dutch airforce, because south is abbreviated "Z" for zuid and when you set the "to Sun" pointer to the "12h" mark, the south-pointer will be a little offset due to the difference in latitude between Greenwich and Amsterdam (or wherever the Dutch reference latitude passes through).
If you happen to carry a watch and a compass then you can use the inner scale to determine how many hours away you are from Greenwich, i.e. you can find out your longitude. What the "Rate 1" and "Rate 1/2" scales are for I have no idea.

Regards
Max

NB: This must be a rare item because the Dutch airforce only had ca. 140 Starfighters.

[Ren]

Thanks for posting the link BruceH!
I have a small tub with maybe 30-40 slide rules in it, not sure if I'll obtain any more.
I do have a Concrete Estimator slide rule (how many yards of 'crete will be needed for x width, y length, and z depth (non-SI units) ). It has the name of a concrete company printed on it.
Sliderules were fading out when I went through high school maths, but at the time 4-banger calcs were over $100 new.
Ren
dona nobis pacem

[rprosperi]

(11-03-2024 04:46 PM)Maximilian Hohmann Wrote:  Hello!

(11-03-2024 01:15 PM)rprosperi Wrote:  @Max - you're the flight computer guru, what the heck is this about?

I can only guess that this is a sun compass, probably part of the survival kit that the pilots carried in case they had to eject from the aircraft and needed to find their way home. This one assumes that you know the exact time from your watch.
You can see that it was made for the Dutch airforce, because south is abbreviated "Z" for zuid and when you set the "to Sun" pointer to the "12h" mark, the south-pointer will be a little offset due to the difference in latitude between Greenwich and Amsterdam (or wherever the Dutch reference latitude passes through).
If you happen to carry a watch and a compass then you can use the inner scale to determine how many hours away you are from Greenwich, i.e. you can find out your longitude. What the "Rate 1" and "Rate 1/2" scales are for I have no idea.

Regards
Max

NB: This must be a rare item because the Dutch airforce only had ca. 140 Starfighters.

Thanks for your insights and comments Max, and good catch, pointing out the "Z" is for South in Dutch, I wondered what it was for (clearly South, but why "Z" and why "O" for East...?).

I had not considered a survival kit item, I guess that makes sense, but not sure how comforting it was to know only your latitude in such a situation... (though perhaps tactically, the longitude was easier to guess?)

Thanks!