MD80 CREW DID NOT GO OUTBOUND FROM A WAYPOINT ON THE CORRECT TRACK.

Narrative

I WAS THE CAPT AND PLT AT THE CTLS FOR ACR FLT XXX FROM DFW-CLT. OUR FILED RTE WAS DALL4.TXK.J42.BNA.J46.VXV.SHINES.CLT. AFTER PASSING BNA; I INITIATED A TURN TO PARALLEL THE OUTBOUND COURSE FOR J46 (BNA 097 DEG RADIAL). AFTER PARALLELING THE COURSE; I ALLOWED MYSELF TO BECOME DISTR WITH OTHER PERIPHERAL DUTIES WITHOUT FIRST XFERRING THE PF DUTIES TO THE FO. IN THE PROCESS; I HAD NOT TURNED THE ACFT TO AN INTERCEPT HDG. THE SIT WAS FURTHER AGGRAVATED BY A SOUTHERLY WIND COMPONENT WHICH CAUSED US TO DRIFT TO THE N OF THE AIRWAY. SOME 25 MI E OF BNA; I NOTICED MY ERROR AND BEGAN A TURN TO INTERCEPT THE AIRWAY WITH A 45 DEG INTERCEPT. AS I BEGAN THE TURN; ZME ALSO NOTICED OUR NAV ERROR AND GAVE US A CALL TO INSURE THAT WE WERE ESTABLISHED IN THE TURN TO INTERCEPT. ACFT SEPARATION WAS NEVER AN ISSUE AND THE REMAINDER OF THE FLT WAS NORMAL IN ALL RESPECTS. ALTHOUGH FATIGUE WAS NOT AN EXCUSE; IT DID PLAY A FACTOR. OUR ON-DUTY SIGN-IN WAS SEMI-EARLY (XC45) AND I HAD SLEPT POORLY THE NIGHT BEFORE; RISING AT XA30.