  Given a generically smooth stable curve over a discrete valuation ring such
that its special fibre is irreducible with one double point, we construct a
moduli stack over that descrete valuation ring which is a model for the moduli
stack of vector bundles over the generic fibre of the curve. The model has the
following nice properties:
  1. It is regular.
  2. Its special fibre is a normal crossing divisor.
  3. The normalization of its special fibre is a locally trivial KGl-bundle
over the moduli stack of vector bundles over the normalization of the special
fibre of the curve.
  Here KGl is a canonical compactification of the general linear group. Our
motivation is that such a model may help to give recursion formulae for such
cohomological invariants of the moduli stack of vector bundles on smooth curves
which depend only on the genus of the curve.
