If the fin snapped off. you do not want to just butt-glue the fin back together. You may want to use some 1/8" dowels to reinforce the joint. You want to drill a couple or three holes in both the fin and the fuselage for the dowel. cut them about 1-1/4" to 1-1/2" long and glue them in. A plain butt-joint won't have the strength you need. White glue or carpenter's glue is about as good as any for this purpose. Of course slow-cure CA or epoxy would also work.