Its not a friagate or runabout, but a CLIPPER!! You know like an Atco, Calmoan, etc. Doesn't anyone read any Federation recognision stuff??!!
The definition of a CLIPPER is a border patrol craft in Federation tactical manuals. In the Klingon tactical manuals they're defined as something used to align targeting scanners and test weapons on lduring ong, boring border patrols.
A CLIPPER is about the same size as a CORVETTE , such as the Defiant or a Renner Class, for example, but differs in role. CORVETTEs are used for internal patrols and escort duties, CLIPPERS are used solely to patrol and monitor border activities. Both are reasonably armed for their size.
Klingons use SKIFFS such as the J3 or G2 in a similar role.
On crossing the Federation border a hostile vessel or force would first run into the Clipper patrolling that sector. The Clipper's job is to alert Star Fleet Command of the intrusion and attempt to destroy, delay, repel or damage the intruder (s) until point defence vessels like an Akula Class or Agilis Class perimetre action ship can take over.
These will then attempt to destroy, delay, repel or damage the intruder(s) until larger perimeter action ships can join in the fray.
The object is to buy time for the admirals to decide and respond to the hostile action with the main fleets.
I hope that this clarifies how the Federation tactical scheme works. It's all in Ships of the Fleet Volume 3 anyhow.
I downloaded a Sacagawea Class last year but it was a TMP period command cruiser someone had modelled from a book.
Andy.