a method for joining fittings to a composite sandwich shell edge includes laying up an inner facesheet and positioning a wrapped flute mandrel on top ; applying a layer of adhesive on the inner facesheet and positioning spacer - supported fittings on top ; applying adhesive over the co - bonded fittings and laying up an outer facesheet forming an assembly ; curing the assembly under heat and pressure ; removing the fittings by first collapsing the spacers and removing the flute mandrel ; placing an adhesive layer on the fittings with collapsible spacers inserted therein ; reinserting the fittings between the inner and outer facesheets and effecting bonding and curing ; and removing the spacers from the fittings by collapsing the spacers .