Step 7  On-site: plinth, lower section of the bell, installing the core


Once on site, determine the location of the Roquetinho. The rear edge of the bottom slab should be placed at least 160 mm from the rear wall (to allow space for connecting the flue). Mark the footprint of the plinth on the floor according to the chosen overhang. Note well when aligning the plinth that the flue does not exit in the centre of the Roquetinho. The floor can be protected by sticking lengths of masking tape 10 mm outside this footprint.

    Installing the lower section of the bell

Construct the plinth using concrete blocks and normal mortar. Ensure it is square and level. Butter the top face of the plinth with an even layer of mortar and lower the bottom slab onto it. Positioning is made easier if two concrete blocks (standing on end) are placed on the floor so as to mark the locations of the two rear corners. Tap the bottom slab down gently so that it settles into place firmly (and level) on the mortar.

   Installing the core

Remove the battens from the transport board. Carefully slide a pair of lightweight winching straps under the core to use as lifting handles; this is best done by sliding the core slightly off the end of the transport board and lifting it up a few degrees, making sure to take the weight on the middle of the bottom.

Use a few concrete blocks to form a platform in front of the bottom slab. Lift the core, still on the transport board, onto this platform. Ideally the core will now be at almost its installed height.

Prepare some cob and spread it in three lines 3 mm thick from front to back of the bottom slab where the core will be placed. The two outer lines will go under the sides. When the core is settled onto this cob, it will spread slightly. It is important that there are no sealed air pockets; air should be able to escape forward between the lines of cob.

Gently lift the core using the straps. Two people are needed to do this, with a third to ensure proper positioning of the core on the bottom slab. Lower the core such that there is a gap of 12 mm to the left wall of the bell; this space will be filled with superwool. The front of the core protrudes exactly 30 mm in front of the bottom slab.

Ensure that the core settles into place level and without going out of position. It can be tapped gently with a rubber mallet. Fill the 12 mm gap with superwool. At the front it needs to be as airtight as possible.