FLT CREW HAVE COURSE DEV AFTER LOADING AND FOLLOWING THE WRONG SID ON DEP FROM GWU.

Narrative

WE WERE DEPARTING GWU. ABOUT 30 MINS BEFORE DEP WE REQUESTED THE DEP CLRNC AND WERE TOLD TO CALL BACK WHEN READY TO START. AFTER THE PAX AND BAGGAGE WERE LOADED WE REQUESTED CLRNC AND START. WE WERE CLRED VIA THE COMPTON 4Y DEP; FPR. I WAS IN THE R SEAT AND PROGRAMMED THE FMS FOR DEP. THERE WERE A COUPLE OF PAGES OF DEPS. ON THE R SIDE OF THE FIRST PAGE THERE WAS A CLN4Y AND RIGHT UNDER IT WAS CPT4Y. I SELECTED THE FIRST ONE WHICH WAS THE CLACTON 4Y DEP. BOTH THESE DEPS START OUT ON THE SAME RTE FOR THE FIRST 8 MI OR SO. I HAD MY NAV DISPLAY SET UPON A 5 MI SCALE SO DID NOT NOTICE THAT AFTER THE FIRST 8 MI THE COURSE WENT IN THE WRONG DIRECTION. ON DEP WE EXPERIENCED A GLITCH IN THE AUTOFLT SYS CAUSING US TO DISCONNECT THE AUTOPLT. THE PF FOLLOWED THE FMS RTE WHICH TOOK US IN THE WRONG DIRECTION AFTER THE FIRST 8 MI WHILE I TRIED TO SEE WHAT HAPPENED WITH THE AUTOFLT SYS. DEP CTL TOLD US WE WERE HEADING IN THE WRONG DIRECTION AND GAVE US RADAR VECTORS. I THEN CHKED THE FMS SID AND FOUND I HAD LOADED CLN4Y INSTEAD OF CPT4Y. CHAIN OF EVENTS: 1) NOT BEING ABLE TO GET THE CLRNC EARLY. 2) RUSH TO START AND TAXI. 3) HAVING 2 SID'S WITH SIMILAR DESIGNATORS; BOTH STARTING WITH THE SAME FIRST LETTER AND ENDING WITH THE SAME 2 CHARACTERS. 4) BOTH THE PIC AND SIC NOT TAKING THE TIME TO REVIEW THE DEP RTE FROM THE COMMERCIAL CHART AND COMPARING IT TO THE FMS.