The F-shell blob model for tethered polymers as introduced recently by Rzehak et al. in Europhys. Lett. 1999, 46, 821 is investigated. In this model, each blob consists of a free-draining outer shell and a nondraining inner sphere in order to describe the partial draining of tethered polymers in uniform flow as found in computer simulations. It also covers the important property that hydrodynamic interaction effects depend on the shape of a polymer, and therefore, with increasing values of the flow velocities the model describes a transition from a partially draining, weakly elongated polymer, to a strongly stretched free-draining polymer at large flow velocities, similar as in simulations of bead-spring models. In the limit of a vanishing free-draining outer shell the F-shell blob model reduces to the model for nondraining blobs introduced by Brochard. It is shown that analytical solutions of blob models as obtained by an approximation of the velocity dependence of the end-to-end distance always have a larger slope than the exact solution which is obtained by numerical calculations. Moreover, a finite penetration of the flow into the polymer, as described by the F-shell blob model, reduces this slope further. This is in qualitative agreement with previous simulations of tethered bead-spring models in uniform flow, and therefore, large slopes as predicted previously by blob models cannot be expected in experiments.