Removing Stem Engraver

[Adam Tee]

I'm wanting to remove the stem engraver form an example that I a setting
but I've looked at the list and what was suggested works on single stave
music but the example I have has three staves.

I've attached the source 

Adam
-- 
Adam Tee
Postgraduate Research Student
Dept of Electronic & Electrical Engineering and Dept of Music
University of Leeds
LS2 9JT
UK
 viol1 = \notes \relative c'' {
        \clef treble;
        \property Voice.flagStyle="none"
        cis4 b fis c ees gis a \skip 8*4;
        }
      viol2 = \notes \relative c'' {
        \clef treble;
        \property Voice.flagStyle="none"
        cis c \skip 8; f \skip 8; e \skip 4; d \skip 8; bes
        \skip 8;
        }
      viol3 = \notes \relative c'' {
        \clef treble;
        \property Voice.flagStyle="none"
        cis4 \skip 4; a \skip 4; g \skip 8; ees \skip 8*3; bes'
        }
      \score {
        \simultaneous {
          \property Score.timing = ##f
          \viol1
          \viol2
          \viol3
          }
        }
      \paper { 
        \translator {
          \VoiceContext
          \remove "Stem_engraver";
          }
        }