Cross section of slide rules

Data:

• Production of slide rules started with a solid massive cross section of (boxwood).
• Quality was improved by adding both horizontal as vertical stiffener strips. They were mostly of metal, but also plastic (Astralon or PVC) was used.
• Sometimes the horizontal strip was split in longitudinal direction. An example of Faber Castell is added.
• Sometimes this strip was used for numbering, but it was also kept virgin (see example of an unknown SR).
• Mahogany (very dark compared to boxwood) was used from the moment plastic was invented. The numbers could than we printed on bright plastic.
• An excerpt from “Rechenschieber - eine Dokumentation” by Dieter von Jezierski is added to help you with the discussions about the different types of timber
• An excerpt from “The Slide Rule, Technical Cultural Heritage” by IJzebrand Schuitema shows some typical cross sections of ARISTO. But there are many more in the book.

Questions:

1. Who can explain more ins and outs of the stiffeners used by the different manufacturers?
2. Was plastic stiffener used for printing numbers, or was it (also?) used for stiffening. In this case is the thin sheet op plastic stiffer than the thicker mahogany? Who knows more about this subject.
3. Does somebody has data (bending) about the effect of the (metal) strips? Is the slide rule really stiffer?
4. Some slide rules have screws. Was that really an improvement? Are data available?
5. Do you know of other ways or other purposes the strip was used?
6. If there are no data available about the improvement of the different types and directions of stiffeners, is somebody in the audience willing and capable of doing bending tests? You need to have or to set up some testing facility for it. It would be nice if we — as collectors — can qualitatively provide testing results.