A B737-800 CREW; DEPARTING SLC; HAD A TAILSKID STRIKE ON TKOF.

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THE FLT PLANNED AS NORMAL ACR OP SLC TO IAD. THE ACFT WT AND BAL AND TKOF DATA SHOWED A TKOF WT OF 158.726 LBS AND A %MAC OF 25.5. STABILIZER TRIM WAS SET TO 4.9 UNITS; THE V-SPDS WERE 151; 153; AND 157 FOR V1; VR AND V2. THE ACFT WAS CONFIGURED FOR A 'BLEEDS OFF' FLAP SETTING I TOOK OFF FOR RWY 34R AT SLC. PERFORMANCE WAS LIMITED DUE TO THE HIGH TEMP; PRESSURE ALT AND GROSS WT; HOWEVER; A FAIRLY GOOD MARGIN EXISTED BTWN RWY ALLOWABLE GROSS WT; THE CLB LIMIT AND THE ACTUAL ACFT GROSS WT. WE BOTH CHKED THE DATA IN ACCORDANCE WITH COMPANY PROCS. PUSHBACK AND TAXI OUT WERE UNEVENTFUL. IT WAS THE CAPT'S TKOF AND I WAS TO PERFORM THE PNF DUTIES. WE CONFIGURED THE BLEEDS FOR A 'BLEEDS OFF' TKOF AND TOOK THE RWY. WHEN CLRED FOR TKOF; THE ACFT SEEMED TO ACCELERATE NORMALLY FOR CONDITIONS; BUT WE WERE HVY; HOT AND HIGH. AT V1; THE AUTOMATIC SYS AND I BOTH CALLED 'V1' AND THEN THE AIRSPD SEEMED TO HESITATE IN THAT SMALL GAP BTWN V1 AND VR SO I DELAYED CALLING VR TILL THE AIRSPD GOT TO VR. ON MOT OF OUR TKOFS; VR SEEMS TO COME IMMEDIATELY AFTER V1. I SENSED THAT THE CAPT HAD ALREADY STARTED THE ROTATION PRIOR TO ME CALLING VR POSSIBLY IN ANTICIPATION OF VR. HE HAD SEEMED CONCERNED THAT THE ACFT MIGHT BE DIFFICULT TO ROTATE TO THE TKOF PITCH ATTITUDE DUE TO HVY WT AND THE FLAPS 1 DEG SETTING AND HAD MENTIONED THIS DURING THE BRIEF. ALSO; THE ROTATION RATE SEEMED MUCH FASTER THAN NORMAL. AT ABOUT LIFTOFF WE HEARD A THUD SOMEWHERE BEHIND US. THE REST OF THE TKOF PHASE WENT NORMALLY AND THE ACFT SEEMED TO PERFORM FINE. JUST AFTER CLEANUP; THE FLT ATTENDANTS CALLED TO RPT THAT THEY HAD HEARD THE SAME NOISE AND THE CAPT DISCUSSED THE SIT WITH THEM. WHILE HE CONTINUED TO WORK THE PROB; TALK TO MAINT; FLT CTL AND THE PAX; I CONTINUED THE DEP TO THE E OF SLC OVER THE MOUNTAINS AND UP TO 12000 FT MSL. THE CAPT DETERMINED THE PROB TO BE A POSSIBLE TAILSTRIKE AND HE STARTED THE ABNORMAL PROCS. HE STATED THAT WE NEEDED TO DEPRESSURIZE THE ACFT. I HAD ACCEPTED A CLRNC TO FL230 BUT GOT PERMISSION TO LEVEL OFF AT 14000 FT MSL; THEN A VECTOR BACK TO SLC AND A DSCNT TO 13000 FT MSL WHICH WAS THE MVA DUE TO MOUNTAINS. SOMEWHERE IN THE DSCNT AND TURN MANEUVER; THE CAPT STARTED TO DEPRESSURIZE THE ACFT. I THOUGHT HE WAS GOING TO WAIT TILL WE GOT LOWER AND WAS SURPRISED WHEN THE CABIN ALT WARNING HORN WENT OFF. IT TOOK ME A MOMENT TO REALIZE WHAT THE HORN WAS; BUT THEN I TOLD THE CAPT I WAS DONNING MY OXYGEN MASK; WHICH I DID; AND THE CAPT PUT HIS ON ALSO. SOMEWHERE IN THE MIDDLE OF THIS LITTLE BIT OF CHAOS; I ROLLED OUT OF MY TURN TO SLC; BUT THEN I GOT REORIENTED AND RESUMED MY TURN. WE WERE GIVEN FURTHER DSCNTS TO 12000 FT MSL AND THEN 10000 FT MSL. FIRST WE TOOK VECTORS AND THEN ENTERED A HOLDING PATTERN TO THE W OF SLC IN ORDER TO BURN DOWN FUEL TO BELOW MAX LNDG GROSS WT. THE CAPT CONFIGURED FOR A FLAPS 40 DEG LNDG AND CONDUCTED A NORMAL VISUAL APCH TO RWY 34L AT SLC. AFTER CLRING THE RWY AFTER LNDG; A VISUAL INSPECTION DETERMINED NO DAMAGE TO THE ACFT EXCEPT FOR THE TAILSKID. THE TAILSKID WAS COMPRESSED ABOUT 2 INCHES TILL IT WAS JUST IN THE RED BAND AND THE SHOE HAD ABOUT 1/4 IN GND OFF THE BOTTOM. WE TAXIED IN AND SHUT DOWN NORMALLY. A LOAD AUDIT SHOWED THAT THE ACFT HAD BEEN IMPROPERLY LOADED. THE %MAC WAS ACTUALLY 27% AND THE STABILIZER TRIM SHOULD HAVE BEEN SET AT 4.7 UNITS. THIS ALONE PROBABLY DIDN'T CAUSE THE TAIL STRIKE BUT I THINK THE CAPT HAD HIMSELF CONVINCED THAT THE ACFT WAS GOING TO BE HARD TO ROTATE DUE TO THE FLAPS 1 DEG SETTING AND THE HVY WT. HE GOT A SURPRISE WHEN THE ACFT ROTATED EASILY AND THUS ROTATED TOO FAST. ALSO; I THINK HE ANTICIPATED THE VR CALL. FROM A CRM STANDPOINT; THE CAPT DID AN EXCELLENT JOB OF KEEPING EVERYONE INFORMED BUT ME -- THE FO. FRANKLY; I THINK THE PAX WERE TOLD THE PLAN BEFORE I. DEPRESSURIZING THE ACFT WITHOUT GIVING ME A CHANCE TO FIRST PUT ON MY MASK WAS; AT BEST; RUDE. AFTER THE INCIDENT; HE STATED THAT HE HADN'T FELT COMFORTABLE WITH ME HANDLING THE PROB -- FINE; THEN HAVE ME FLY. ON THE DEP; I THOUGHTHE WAS GOING TO TRY TO DO EVERYTHING HIMSELF -- FLY; ABNORMAL; ATC; COMPANY; ETC -- AND MIGHT HAVE; UNLESS I OFFERED TO TAKE THE ACFT.