There is more on this topic at viewtopic.php?f=4&t=639
However I have a 20l secumar that I can hoist to the top of the mast. I know my in sail ‘cushion’ is less than 20l, indeed it is possibly nearer 10l, but it does the trick as described above.
It is not just the weight of the mast that makes inversion likely, it is where the forces occur. Andwun is right that a woodie is lees likely to invert because its bouyancy is fore and aft – so creating no turning moment. Whereas the more modern Wayfarer, with bouyancy under the floor, has a strong turning moment when on her side – underfloor bouyancy pushing up and mast down creates a turning moment about the centreline (nicely counterbalanced by the model here!).
[attachment=1:18slicft]world high float.JPG[/attachment:18slicft]
this moment is further reinforced because a World floats higher than other types:
Where I personally disagree with Andwun is that Woodies are not the only marks safe for cruising. We all have our own preferences and for many of us a wooden boat is not practical, but the other marks are just as safe and an inflatable device hauled to the top of the mast is hardly an extensive and ridiculous modification (even less so with in sail bouyancy). I suspect there are more GRP boats out there than woodies and we should not discourage people from cruising in them.
I am very content to cruise in my World and I consider it perfectly safe and feel she is not disfigured by masthead bouyancy.