  Molecular chirality frustrates the two-dimensional assembly of filamentous
molecules, a fact that reflects the generic impossibility of imposing a global
twisting of layered materials. We explore the consequences of this frustration
for hexagonally-ordered assemblies of chiral filaments that are {\it finite} in
lateral dimension. Specifically, we employ a continuum-elastic description of
cylindrical bundles of filaments, allowing us to consider the most general
resistance to and preference for chiral ordering of the assembly. We explore
two distinct mechanisms by which chirality at the molecular scale of the
filament frustrates the assembly into aggregates. In the first, chiral
interactions between filaments impart an overall twisting of filaments around
the central axis of the bundle. In the second, we consider filaments that are
inherently helical in structure, imparting a writhing geometry to the central
axis. For both mechanisms, we find that a thermodynamically-stable state of
dispersed bundles of {\it finite} width appears close to, but below, the point
of bulk filament condensation. The range of thermodynamic stability of
dispersed bundles is sensitive only to the elastic cost and preference for
chiral filament packing. The self-limited assembly of chiral filaments has
particular implications for a large class of biological molecules -- DNA,
filamentous proteins, viruses, bacterial flagella -- which are universally
chiral and are observed to form compact bundles under a broad range of
conditions.
