  We theoretically study the Plateau-Rayleigh instability of a thin viscous
film covering a fiber consisting of a rigid cylindrical core coated with a thin
compressible elastic layer. We develop a soft-lubrication model, combining the
capillary-driven flow in the viscous film to the elastic deformation of the
soft coating, within the Winkler-foundation framework. We perform a
linear-stability analysis and derive the dispersion relation. We find that the
growth rate is larger when the soft coating is more compliant. As such,
softness acts as a destabilising factor. In contrast, increasing the thickness
of the soft coating reduces the growth rate, due to the dominating geometrical
effect.
