  Type I rapidly fading supernovae (RFSNe) appear to originate from
hydrogen-free stars with large radii that produce predominantly shock-cooling
light curves, in contrast with more typical nickel-rich SNe Ibc. However, it
remains to be determined what types of stars would produce bright shock-cooling
light curves without significant contribution from radioactive nickel. Bare
helium stars in the mass range ~2-4 solar masses are known to hydrostatically
develop radii as large as 100 solar radii or more due to strong He and C shell
burning outside of a core with a sharp density gradient. We produce several
such stellar models and demonstrate that, when exploded, these helium giants
can naturally produce RFSN light curves. Since many prototypical SNe Ibc should
come from large-radius stars in this mass range as well, we predict that these
RFSNe may be distinct from SNe Ibc solely due to the absence of substantial
nickel.
