Does anyone here know what the dimensions of Wyatt Mangum's topbar hives are?
I googled extensively and found an image of one of his hives taken directly from the side, with a reference measurement in the form of a queen cage, which I was able to identify and get the measurements for. From this I was able to deduce that the Mangum hive's dimensions are approximately as follows:
top: 400 mm
bottom: 200 mm
height: 260 mm
angle: 69 degrees
This means that Mangum's hive has the most vertical sides of the latter-day big three (compare Chandler 65 deg, Crowder 61 deg), though still quite a bit less than those of old timers Hardison (77 deg) and Berube (79 deg).
To get the same comb area as 20 Illinois medium frames, you'd need the following number of bars from each one's hive: Crowder 18, Chandler 24, Mangum 22, Hardison 22, Berube 19. Put differently, a 24-frame hive from each of these designs would yield the following volumes (in litres): Crowder 75, Chandler 57, Mangum 62, Hardison 63, Berube 70.
I compared 14 top-bar hive sizes (my criteria was that the person's plans must be mentioned in several places, and/or he must have run several hives for several years, or he must have published and have been quoted to a reasonable degree). To get a 60 litre volume, the top-bar hive design that would require the highest number of frames is Corwin Bell's "golden section" hive (28 bars), followed closely by Chandler (27 bars). The least number of bars required for 60 litres comes from Dennis Murell's design (14 bars) and the 50-degree oddity called the Kumasi "Ghana" hive (16 bars). Gibb's Zambian hive design needs 18 bars for 60 litres.