CROSSED STRUCTURE BINDING EXPANDER
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Some people like to write a travel journal during their holidays. Not only do they write, but they also keep bits and pieces as souvenirs: cuttings from tourist brochures, dry leaves, photos, tickets etc.. This extra material causes the book to expand beyond the capacity of its spine depth and, eventually, the book falls apart. The CSB Expander has been devised for such 'in progress' books, allowing potential for expansion when you do not know in advance how much material may be added. This kind of structure can also be useful to gather series of monthly publications.

CSB Expander
I will assume that the book is ready to be bound and that all prior steps have been carefully carried out. The description refers to a full-leather binding with clean-cut edges. I will not work to any particular dimension, assuming the template to be clear enough for each person to adapt it to a given size.
CSB Expander binding works in such a way that the two covers remain unchanged while the spine expands to allow new sections to fit into it. You must keep this in mind when making a dummy to calculate the extra length of the sewing straps and the inner flap, which are the two features which enable the book to expand.

Cutting the back cover
To see the cutting of the straps, go back to Cutting the straps in the index. The two sides of the cover are cut separately.
Cut the back cover following side a of the template with three or more sewing straps according to the size of the book. The sewing straps should be longer than they usually are: they must take into account the book block's thickness plus the estimated swell of sections which will be added in the future, plus approximately 60mm for the out/in anchorage to the front cover.

Cutting the front cover
Cut the front cover following side b of the template. The two parts are linked together before sewing, so you have to guess the approximate thickness of the spine after sewing. The front cover consists of the cover itself, the spine and the inner expansion panel (which will be hidden under the back cover). When calculating the width of the expansion panel in CSB Expander you must take into account the hypothetical future expansion of the spine.
A series of 'windows' should be cut in the spine area for the sewing straps to go in before sewing and out after sewing. The dimension of the windows are: the same width as the sewing straps and the approximated thickness of the sewn book block. It is extremely easy to invert the parts and cut the windows in the wrong place - making a dummy could help to establish their exact position.

The linkage of the two parts
Before sewing, the straps of side a go into the windows of side b. In this way the two parts of the binding are linked before sewing.

Preparation for sewing
To see the fixing of the cover to the sewing frame go to A sewing frame in the index.
During the sewing, the book block will be lying on top of the flap over the back cover, while the front cover hangs loose before you. For a better view of the position of the windows while sewing see sewing 5, at CSB sewings.

The sewing
Each of the sections of CSB Expander is sewn individually. To see sewing 5, go back to CSB sewings in the index.

The expansion
Once the sewing is finished, the straps come out through the same spine windows they came in before sewing. A row of slots is cut on the front cover 10mm away from each window, for the straps to go in and under the front cover.
Each time you decide to add a new section, enlarge the windows by cutting away a segment of the inner expansion panel which is equivalent to the thickness of the new section. The two parts of the cover are carefully pulled apart: the straps slip back and the new section can be sewn either side of, or even in the middle of, the book block.
Pull out the straps to sew the new section with more ease, then put them back in their previous position.

If you want to download the text, templates and sewing of this binding go to Download CSB in the index.