Install the bags up against the window and door forms as tightly as possible. The forms are an integral part of the structural dynamics of the dome during the construction process. They act as a link in the chain of each ring of bags or tubes. They are not there just to make a hole; they are there to create a whole — a whole double curvature, monolithic structure. Each row needs to think that it is making a complete ring, an unbroken circle, a full connection, mini-tension ring, bond beam, whatever you want to call it. Without the connection of a unifying compression fit on either side of every form, the dome could collapse.
Remember to interlock any tubes with the bags up against the forms, rather than ending the tubes against the forms. We prefer to use bags around window and door forms as they create a much tighter fit than a tube and offer greater compression.
12.17: This diagram shows the approximate lengths to to which the compass arm radius must be adjusted at every one foot of height. You can draw a larger diagram that includes measurements at every one inch (2 cm) or less for at-a-glance reference calculations during construction.
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