answer: by my knowledge: NO
BUUUUUUUUT a lot of people crash/crack and break their masts every day so if you go to a few windsurf forums, post a few adds asking for the bottom part of a FS RF 5000 QT you might just find a guy that broke the top part and already replace the mast and wants to sell it to you. Otherwise: get yourself a new one. Like tennis rackets, after a while, masts also simply wear out (and break).
Haiko, AKA crazychemical