Chopped reinforcing fibers are sprayed onto a mold and wet with resin.
A yarn of reinforcing material is cut to a set length by a chopper/gun which immediately sprays them onto the mold. Resin and catalyst design must accommodate a spraying process as well.
Single sided, typically composite tools are used for this process
Spray up parts normally have one visible, smooth side. A gel coat can be added during molding to produce cosmetic finished surfaces.