..... Would you happen to Know about how many gallons of water
the Mast Float will displace ?
I can't afford a new one so i'll need to build my own.
I Don't "Want" to flip my 21-SE but Do Want to be ready
if/when i do......
I've filled masts with "bean-bag" styrene foam balls
Not for floatation as such, but to displace the water when its goes over, lots less worry than how good is the mast sealed up !!!
Another one I saw many years ago was a bag made from sailcloth that was velcro'd to the top of the mast and had a short rope that was shackled to the very top of the mast, the bag lay reasonably flat against the mast for normal duties.
A soda-stream CO2 cylinder was setup at the mast step in an over-centre catch system, simply lift the lever and the bottle was forced up into a bursting chamber that had a small plastic hose that then ran up to the bag...
When inflated the bag was about 1' in diameter and 3' in length...
this setup was on a yvonne 20' timber catamaran back in the early 80's, as a teenager I remember seeing the mast near jump out of the water when it was deployed, you wouldn't want to be in the wrong place !!!
Yvonne data sheet 
