  In 1963, Shrikhande and Raghavarao published a recursive construction for
designs that starts with a resolvable design (the "master design") and then
uses a second design (the "indexing design") to take certain unions of blocks
in each parallel class of the master design. Several variations of this
construction have been studied by different authors. We revisit this
construction, concentrating on the case where the master design is a resolvable
BIBD and the indexing design is a 3-design. We show that this construction
yields a 3-design under certain circumstances. The resulting 3-designs have
block size k = v/2 and they are resolvable. We also construct some previously
unknown simple designs by this method.
