A CARGO DC8-73 FLT EXPERIENCES A TAILSTRIKE DURING TKOF ROTATION. LATER IT WAS FOUND TO BE CAUSED BY IMPROPER PALLET WTS THAT AFFECTED THE WT AND BAL TRIM CONDITION FOR TKOF AT SDF; KY.

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TAILSTRIKE ON ROTATION (DC8-73). AT THE POINT OF ROTATION WHERE I EXPECTED LIFTOFF; WE FELT A BUMP. WE SUSPECTED EITHER A TAILSTRIKE OR A LOAD SHIFT. NO CTL DIFFICULTIES OR SYS MALFUNCTIONS; SO WE CONTINUED TO DEST (SJU). REQUESTED A LOAD AUDIT ON ARR AND FOUND POS 15 970 LBS OVERWT ALONG WITH 13 OTHER CONTAINERS OVERWT BY SMALLER AMOUNTS. ACFT WAS LOADED NEAR THE AFT MAX CTR OF GRAVITY WITHOUT THE EXTRA WT. CAUSES AND FACTORS: 1) OVERROTATION -- ALTHOUGH THE CREW (WITH 30 YRS COMBINED EXPERIENCE) DID NOT FEEL WE EXCEEDED ROTATION LIMITS PERCEPTUALLY; WE DID STRIKE THE TAIL. 2) THE EXTRA WT AND CTR OF GRAVITY HAD US OUT OF TRIM FOR TKOF; BUT WERE WITHIN ACFT LIMITS IF KNOWN AHEAD OF TIME. 3) CHANGING WINDS MAY HAVE CAUSED AIRSPD STAGNATION RIGHT AT THE POINT OF ROTATION/LIFTOFF. COMMENT: THERE HAS TO BE A MORE RELIABLE WAY TO CONFIRM THE WTS OF CONTAINERS AND LOOSE CARGO BEING LOADED ON OUR ACFT. EVEN UNDER RUSHED; TIME SENSITIVE OPS; THIS IS CRITICAL TO THE SAFETY OF OUR FLTS. HAVE WE FORGOTTEN 'XY' ACR (MIAMI) ALREADY?