  We analyze the dust attenuation properties of a volume-limited,
optically-selected sample of normal star forming galaxies in nearby clusters as
observed by GALEX. The internal attenuation is estimated using three
independent indicators, namely: the ratio of the total infrared to
far-ultraviolet emission, the ultraviolet spectral slope beta and the Balmer
decrement. We confirm that normal galaxies follow a L_TIR/L_FUV-beta relation
offset from the one observed for starburst galaxies. This offset is found to
weakly correlate with the birthrate parameter, thus with the galaxy star
formation history. We study the correlations of dust attenuation with other
global properties, such as the metallicity, dynamical mass, ionized gas
attenuation, Halpha emission and mass surface density. Metal-rich, massive
galaxies are, as expected, more heavily extinguished in the UV than are small
systems. For the same gas metallicity normal galaxies have lower L_TIR/L_FUV
ratio than starbursts, in agreement with the difference observed in the
L_TIR/L_FUV-beta relation. Unexpectedly we find however that normal star
forming galaxies follow exactly the same relationship between metallicity and
ultraviolet spectral slope beta determined for starbursts, complicating our
understanding of dust properties. This result might indicate a different dust
geometry between normal galaxies and starbursts, but it could also be due to
aperture effects eventually present in the IUE starbursts dataset. The present
multiwavelength study allows us to provide some empirical relations from which
the total infrared to far ultraviolet ratio (L_TIR/L_FUV) can be estimated when
far infrared data are absent.
