MD90 CAPTAIN ASSERTS RNAV DEP FROM SLC FAILS TO TAKE ACFT PERFORMANCE LIMITATIONS INTO ACCOUNT.

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SLC ARPT HAS RECENTLY IMPLEMENTED MANY TROUBLESOME DEP PROCS (SID) THAT ARE MORE COMPLEX THAN NECESSARY; CONTAIN SPDS REQUIRING UNUSUAL FLAP MGMNT AND MANY CHANCES TO MESS UP. I PERSONALLY THINK THEY SHOULD ALL BE VIEWED AND DECERTIFIED FOR SAFETY REASONS. A CLASSIC EXAMPLE OCCURRED ON THIS FLT. WE WERE IN A HVY MD90 CLRED FOR TKOF ON RWY 16R ON THE TWIN FALLS 1 DEP PROC (TWF 1.TWF). THE PROC REQUIRES A LARGE R TURN AT 500 FT AGL DIRECT TO PPIGG INTXN. AT 400 FT AGL (THE LOWEST OUR LATERAL NAV WILL ENGAGE AT) WE SELECTED NAV; AT 500 FT AGL I STARTED THE R TURN; GOING TO 15 DEGS OF BANK; AS WE ARE LIMITED BY MINIMUM MANEUVERING SPD (MINIMUM CLEAN SPD IS REALLY HIGH 251K; SO KEEPS THE SLATS AT EVEN PASSING 1000 FT IS REQUIRED). AS SOON AS WE WERE AT MINIMUM MANEUVER SPD FOR SLATS OUT; I WENT TO 30 DEGS OF BANK. THIS REQUIRES FLYING AGAINST THE FLT DIRECTOR! I AM VERY EXPERIENCED ON TYPE; BUT AFTER A FLAPS 5 DEG TKOF WHICH RESULTS IN A LIFTOFF NEAR THE END OF THE RWY; THERE IS NOTHING ELSE YOU CAN DO. DESPITE BEING IN THE TURN; TWR ASKED US TO VERIFY THAT OUR FIRST WAYPOINT WAS PPIGG. THE FO ANSWERED THAT IT WAS AND THAT WE WERE IN THE TURN. OBVIOUSLY WE WERE OVERSHOOTING THE GND TRACK THEY DESIRE (WE DID CROSS PPIGG; THOUGH) BUT THERE IS NOTHING ELSE WE CAN DO ABOUT THE SIT. THESE SID'S DESIRE YOU TO MAINTAIN BOTH LOW SPDS AND UNREALISTIC GND TRACKS (JUST LOOK AT THE WAY THE TWF 1 IS DEPICTED ON THE KSLC CHART) ALTHOUGH THESE ARE STARTED AT POINTS WHERE SOME ACFT WILL NOT BE AT A MINIMUM MANEUVERING SPD; NECESSITATING ONLY 15 DEG ANGLE OF BANK. THESE SIDS/DEP PROCS HAVE BEEN VERY TROUBLESOME FOR OUR OPERATOR; AND I IMAGINE OTHERS. THEY SHOULD BE WITHDRAWN AND REDESIGNED. THEY ARE UNREALISTIC; HIGH WORKLOAD; AND ULTIMATELY UNSAFE.