Grounding Issue

[dumbassbob]

I just finished a Strat build It has a single coil and a Humbucker and a center dummy pup 3 way switch All my guitars have always been Frankys(EVH) one Pup one pot.This guitar sounds great but when I take my hand away from strings or the bridge I get a low sound hum .I didn't use a ground wire because the pickguard has a foil sheild ,.Just the ground to the spring claw.Did I forget something? Ps I run into a 100 w Plexi Volume at 4 on both 1 and 2 channels. FX,boss Delay, OC-2 and a Tube screamer