We present a tight-binding theory to analyze the motion of electrons betwee
n carbon nanotubes bundled into a carbon nanotube rope. The theory is devel
oped starting from a description of propagating Bloch waves on ideal tubes,
and the effects of intertube motion are treated perturbatively on this bas
is. Expressions for the interwall tunneling amplitudes between states on ne
ighboring tubes are derived which show the dependence on chiral angles and
intratube crystal momenta. We find that conservation of crystal momentum al
ong the tube direction suppresses interwall coherence in a carbon nanorope
containing tubes with random chiralities, Numerical calculations are presen
ted which indicate that electronic states in a rope are localized in the tr
ansverse direction, with a coherence length corresponding to a tube diamete
r.