Good question
If you are a member of an association my understanding is that you are covered for events as far as insurance is concerned. You then pay the event entry fee.
Check AWA website
www.windsurfing.org/ for more advice
In the past there has been problems when someone arrives late to an event and competes without all their insurance cover in place beforehand
Hope that helps. I wlll check my other notes from the AWA AGM from earlier this year too