How to fix navigation menu bar *only* without logo to top of page when scrolling.

Site URL: https://presenttensebar.squarespace.com

Hi there,

I'm working in the Crosby template, and I'd like to remove the logo from the header when scrolling down past the homepage, leaving only a thin navigation bar at the top. Within the homepage, I've got different sections/links set up with anchor links within the homepage, but when scrolling down the full header with logo is too tall and blocks content. 

I've searched the forum but haven't found an answer yet. I'm trying to mimic the functionality of this site: http://www.lostlakechicago.com/

Site link:  https://presenttensebar.squarespace.com 

Password:  Derek

Thanks so much!