Wow that's awful. How do you know it was a 30 footer. Have you got another source?.
Video shows upturned yacht, indicating keel loss. Clansman has internal ballast keel, so unlikely. However, if the boat was overturned by external forces, maybe the lead ballast could fall out?
Any new details on what happened and why the vessel was hull up?
I'm not sure the vessel was hull up as the video is not of sufficient quality and the girl said that she saw the yacht sink.
People on the Clansman Facebook site reckon they know the guy so apparently it really was a Clansman. As has been noted these have integral long keels and are therefore highly unlikely to lose a keel and invert. If full of water they would just sink right side up as the girl said.
Big waves around Fraser at that time. Also lost a great cat on Yamba bar - Wahoo - with no loss of life, but the cat capsized and broke up. Also tales of hairy Wide Bay bar crossings. Wave rider buoy had peaks of 4-5 m waves, so big conditions out
there. www.qld.gov.au/environment/coasts-waterways/beach/monitoring/waves-sites/wide-bay