Sea Tango, is a Beneteau 393 with a roller furling mast, manufactured by US Spars. The boat was commissioned in Texas in the year 2007. In May of 2012, I purchased Sea Tango in Charleston, South Carolina and brought her to Annapolis, Maryland. During the winter of 2012-2013 she experienced freezing temperatures for the first time.
The winterization protocols that are available from Beneteau and US Spars do not highlight the importance of or the location of mast drainage holes. The US Spars furling mast system consists of a cylindrical tube for the furled mainsail, inside the mast extrusion. Essentially a mast within a mast. The sail slot for the mainsail to roll in/out, also allows water and debris to accumulate inside the mast. The drainage holes provided to allow this water to escape are minuscule and easily blocked by debris (see photos in "Mast Step").