NavList:

Thank you those who sent me information about the Appleyard Computer.

Dave Walden, thank you for the link to the photograph.  I’d seen these earlier, but they’d disappeared from the internet before I could make a note of the original vendor’s details.  Fortunately, the link you sent me still had those on.  I contacted them, and, although the computer had been sold, they were able to send me high definition copies of all the photos they’d taken including one from directly overhead.  My son has made colour prints of these, and I think they’ll be round enough to use in the computer.  They also gave me permission to use the photos in any paper I might produce.

Thanks also for tinkering with the Excel spreadsheet to draw the circular logarithmic scale.  With the arrival of a perfect overhead photograph, drawing my own scale might not now be necessary.  I’m going to try and work with colour photos first.

Adrian F thank you for the links you sent me.  I’d already downloaded the NACA 1922 paper, but I hadn’t read it.  When I did, I found it gave a slightly more practical way of using the calculator than the one I’d envisaged, so it rather hit the idea of a revelatory paper on the head.  However, the paper didn’t offer a solution to the problem arguably the most encountered by air navigators and the one which some students have most difficulty with when using the Dalton computer namely, given W/V, TAS, and required track, what heading is required and what will your groundspeed be.  This solution is available using the Appleyard; it just isn’t mentioned in the NACA paper, so maybe there’s still hope for a modern article for Navigation News or elsewhere.

One other piece of information in the NACA paper is that Rollo Appleyard based his computer on the Course Indicator designed by Prince Louis of Battenberg (Father of Lord Louis Mountbatten) in 1892 https://en.wikipedia.org/wiki/Battenberg_course_indicator  and used in the RN until around 1955, so there is other information as to its uses available.

It’s interesting that in 1917 Appleyard restricted the arms to 110 speed units, whereas by 1919 aircraft like the Vimy were already coming close to exceeding those units.

I’m afraid although I was able to download the article from ‘Flight’ magazine, I couldn’t enlarge the pages enough to read them.  Similarly, the Imperial War Museum link said little more than that they hold the item.

At the moment I’m working on trammel methods for cutting perfect discs from 1mm clear PET sheet.  Although this is the cheapest clear sheet material available, cutting it isn’t easy, so I’ve some way to go yet to find the best method.  DaveP