the plate 280 is relatively near the end 260 one or both these plates may carry fixture elements for holding the individual parts or groups thereof in the illustrated embodiment the parts are blades having airfoils 300 extending from a tip 302 to a platform 304 an attachment root 306 depends from the underside of the platform exemplary fixture elements comprise a firtree receptacle 310 for receiving the root 306 a shaft 312 extends from the receptacle through an associated aperture 314 in the plate 280 the exemplary shaft may freely rotate about an axis 520 so that as the carrier rotates about its axis 500 the parts maintain their orientations fig6 also shows the manifold 56 formed as a pair of tubular sections or conduits 320 e g of a similar material to that of the sheet that forms a body of the hood mounted to the hood e g via welding adjacent the respective edges 162 and 163 an exemplary tubular section 320 has a closed distal end 322 and a longitudinal array of venting apertures or outlets 324 at a proximal end the tube may bear a fitting 330 fig7 which mates with a conduit extending from the source 55 of fig2 for example line 57 of fig2 may discharge to the annular space between the inner and outer sting shafts an additional line 334 may pass from this annular space into.