A320 Captain reports requesting new weight and balance numbers during taxi out due to a gross weight increase. The new V speeds are entered in the FMGC but the flap setting is never changed from 1 to 2 as required by the new weight and balance. The error is not detected until flap retraction altitude.

Narrative

As we taxied to Runway 15R via Taxiway B at BOS; I directed the First Officer to begin the Before Takeoff Checklist. The First Officer noted that our calculated TOG was 148.0; and the takeoff performance FLEX limit weight was 147.5 at FLEX 63 degrees and flaps 1. The First Officer redid the performance weights via ACARS and new numbers indicated same FLEX temperature; but flaps 2. Together we noted the new speeds; inserted them into the FMGC; and then the First Officer continued the checklist until completion. By then we were cleared for takeoff so there was some urgency to finish the checklist. We took the runway and the takeoff roll and rotation was uneventful and normal. At acceleration altitude; as I anticipated a flaps 1 call; I noticed that there was no F speed index on the airspeed tape. We were already at flaps 1! The flaps never got reset to 2 when the new performance numbers were calculated. We took off at flaps 1 with flaps 2 speeds in the box! Rotation and initial climb was normal because the flaps 2 speeds were greater than the flaps 1 speeds. Flaps 1 V speeds were 138; 143; 143. Flaps 2 speeds were 143; 143; 145. The problem would have been if we had to execute a high speed abort; we could have aborted above the flaps 1 V1 with flaps 1 set. Contributing factors were; rushing to be ready for takeoff; not starting over the checklist after a configuration change; complacency. Fatigue was not really a factor for me in that I got sufficient rest. The First Officer indicated that fatigue was a possible factor.