Nothing. The sheet and sail force loads are much higher while sailing then any loads that tipping the boat over on the beach can put on the mast. So if the mast is designed to hold up under sailing then it will do so as well when tipped over.

Phill has not specified what kind of mast he will be using exactly (none of us know any specs of that Blade 12 as a matter of fact) but the F12's that use a similar unstayed mast have taken the design of class 5 landyachting. These landyachts sometimes tip over at speed (think 30-60 mph) with the crew remaining in the seat and the mast survives without any issues. I did this two weeks ago in my own class 5 landyacht and I was almost at full speed (50 mph). These masts are pretty strong and dependable.

Tipping over landyachts over on the beach when we go for a break or a drink is standard operating procedure. Tony, if you ever want to do some landyachting just contact me and I'll take you along sometime.

Wouter