On the early Schwinn 27" rims the spokes were 11 15/16" give or take hair. This is with a high flange and four cross. Later 60's they went three cross and the spokes are 11.5". I don't have a 26" S-6 wheel set handy but it may use the 11.25" spokes. Maybe @Miq can chime in on that spoke length.