The shinai is the main gear piece in Kendo and Kendo practice. A bad shinai is the most probable cause for accidents hence it requires regular maintenance and extensive checks on a regular basis (before, during and after practice). Below there are two links to some good resources we found on the Internet about this topic:
http://www.halifaxkendo.org/articles/Shinai.pdf
http://kendo.union.rpi.edu/Shinai%20Assembly.pdf
See you at the Dojo!
Marius @GSKC