I found a video from the Academy of Historical Fencing demonstrating rapier vs. longsword. This is relevant to my own interests, since I put a fair amount of sword-fighting in Starbreaker.
In particular, Morgan Stormrider wields a longsword against Imaginos, who favors the rapier when using a blade. Naomi Bradleigh, in the meantime, favors the side sword.
And while Imaginos learned his sword-fighting over thousands of years, and Naomi had experienced teachers, Morgan learned much of his technique from Renaissance fighting manuals like this one.
Sometimes it just isn’t enough to RTFM.