Generalized Bhaskar Rao designs and dihedral groups

We solve the existence problem for generalized Bhaskar Rao designs of block size 3 for an infinite family of non-abelian groups, the dihedral groups Dn, of order 2n. In our main result we show that for n⩾1 and v⩾3 the following set of conditions is necessary and sufficient for the existence of a GBRD(v,3,λ;Dn): 1. od 2n); )≡0 (mod 24).