Blasa blocks are provided to be trimmed and cut to fit between the ribs – mounted on top of the spar (using epoxy) to then be shaped to form a mounting surface for the top leading edge 0.8mm ply
The blocks are first pre shaped to provide a ‘mated’ key to the top of the spar. A 1″ round dolly is used with sandpaper wrapped around to provide a suitable curved channel in the bottom of the balsa block.
Once dried these can then be shaped on top using a larger hardwood dolly to overlay two ribs so that you sand down evenly to get a flat surface.
The 0.8mm ply is then epoxied to the top if the block and, once dry, Aerolite glue is used to secure to the top of the ribs and the leading edge beech.