How long should the engineering notebook be? Also, are there any winning notebooks I can see online?
There is no limit or guidelines for how long a notebook should be. Here is the rubric for the engineering notebook when being judged for the design award.
Also, check out this document that defines the differences between notebooks and journals.
https://www.roboticseducation.org/documents/2017/07/team-design-notebooks-and-team-journals.pdf
Award-winning notebooks…
https://www.roboticseducation.org/documents/2016/11/vrc-engineering-notebook-team-1575a.pdf
https://www.roboticseducation.org/documents/2013/10/vrc-engineering-notebook-2013-team-5327a.pdf