Mechanics of Aerostructures - Shear Flow in Closed Sections Full Example

The second time I recorded this, I didn't make a silly error at the very beginning. Be careful, kids. I decided to re-record this rather than going back through my original and correcting the error. Hopefully it'll be more instructive this way. I still make a couple of numerical errors in this solution, BUT I show you how I recognise the fact I've made mistakes and then correct them.