The Main Column is constructed of 10 foot long fabricated half sections. These comprise most of the mast column. These half sections are the only part of the fabrication, which needs to be formed in a press break by a sheet metal shop.
Since the quality of the mast starts at the beginning of the fabrication, the sheet material must be cut squarely, dimensional correct, formed with the proper top and bottom tooling, with the finish half section being to specifications.
The corners of the mast are of a determined radius and bent to a 90-degree angle, although in practice, a bend of 1 or 2 degrees over 90 degrees is more workable when fabricating the mast.
The starting half section is usually five feet long - it begins the mast construction. Its purpose is to stagger the mast half sections to guarantee that no two seams fall across from each other.
The last sections at the top of the mast vary in length to achieve the desired mast height.
The transverse divider is an aid in fabrication that gives the half sections shape during construction. It is a flat piece of material, the same gauge thickness as the half sections. Holes are punched along the length leaving approximately 1" of space at the edges, with 1" of material left between holes. These holes save weight, as the divider itself serves no structural purpose.
Also shown in the drawing is the teak sail track spacer, the sail track, and machine screws. The machine screws are used to secure the sail track to the mast. They are drill and tapped to the mast.
The center divider is also shown. Note the alignment of the center divider to the mast sections. They are aligned corner to corner. This allows for full weld penetration of all the pieces.
Mast Column Details, back to Sailboat Mast Building
About the 12.5 Design
