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Saturday, 18 January 2014

Building a wood fired oven - dome form

Today I was doing the preparation work that is needed before I can start to lay the bricks of the dome of the wood fired bread oven.  I have already cut and set the angles bricks that will brace the ends of the dome.  These bricks were cut using a large angle grinder with a diamond abrasive disk.  These bricks transfer the load of the dome to the steel strapping on the outside of the oven.

Dome support bricks ready for pointing and cleaning

In order to create the dome I need a parabola shaped form that will support the bricks until the mortar goes off.  The shape was drawn on a piece of paper to use as a template and then transferred onto a sheet of plywood.  I then cut out the shape a little oversized on the band-saw and then finish on the sander.  Once I am happy with the shape it is used as a template to 3 more sheets of ply, this time screwed together so I can make 3 with one pass.

Cutting out the form supports
 The 4 supports are then screwed to a sheet of plywood on their flat edge.  For the curved surface, as it will need to be quite strong, another sheet of 12mm ply will be bent over the supports.  In-order to make the ply flexible enough, cuts are made 2/3 of the way through the plywood using a circular saw.  I have made these cuts every 2 cm.  If you require a tighter curvature then the cuts will have to be closer together.

Making ply flexible for the form-work

The flexible sheet of ply-wood is then bent and screwed to the supports.  This is best done working from the centre out.  To ensure a strong form, a bead of polyurethane  wood glue is first applied to the supports. Screws will need to be more frequent the tighter the curvature required.

Finished dome form
With the form-work finished I am ready to the start the exciting bit, laying the dome bricks.