FLT ENCOUNTERED WX DURING VFR DEP CLB.

Narrative

I FILED AN IFR FLT PLAN FROM TRK TO CMA USING A SID TRUCK 1 FROM TRK. TRK IS UNCTLED. I ATTEMPTED COM WITH OAKLAND CTR BEFORE TKOF; BUT WAS UNABLE TO REACH THEM BECAUSE OF TERRAIN. I DEPARTED TRK VFR IN LIGHT RAIN AND CLBED VFR TOWARD TRUCK INTXN VIA THE SID. I REMAINED VFR WHILE CLBING VIA THE SID AND CONTINUALLY TRIED TO CONTACT OAKLAND ATC. I FINALLY GOT THROUGH AND ADVISED ENTERING THE HOLD AT TRUCK INTXN AT +/- 13000 FT. I WAS ADVISED TO SQUAWK IN AND REMAIN VFR. I WAS UNABLE TO REMAIN VFR ALL THE TIME IN THE HOLD AND CONTINUED CLB TO 15000 FT AT WHICH TIME ATC ADVISED RADAR CONTACT. I HAD INTENDED TO REMAIN VFR AND HAD NOT GOTTEN 'RELEASED' BEFORE TKOF EVEN THOUGH I HAD FILED AN IFR FLT PLAN. I SHOULD NOT HAVE ASSUMED I COULD STAY VFR UP TO 13000 FT AND ABOVE; AND I SHOULD NOT HAVE ASSUMED THAT EVEN THOUGH I COULD TALK TO ATC AT 13000 FT THAT THEY WOULD BE ABLE TO GET ME IN RADAR CONTACT QUICKLY - (THEY WERE VERY BUSY WITH OTHER TFC AND COULD ONLY WORK US IN SEQUENCE.) I SHOULD HAVE GOTTEN A RELEASE TIME BEFORE TKOF THROUGH THE FSS VIA PHONE. I WILL IN THE FUTURE IF IT IS NOT CLRLY VFR.