A method of winding fibers on a mandrel, the wound fibers being in tension, includes providing a source of fibers, imposing a torque on the source that resists dispensing the fibers from the source to exert a tension on the fibers, adding ultra-violet sensitive material that is polymerized by exposure to ultra-violet light to a resin matrix, impregnating dispensed fibers with the additive containing resin matrix, rotating a mandrel to wind the impregnated fibers on the mandrel, the rotation of the mandrel acting to overcome the torque on the source and putting the fibers in tension, and in situ, quasi instantaneously polymerizing the additive containing resin matrix on the mandrel by means of exposing the additive containing resin matrix to ultra-violet light for a selected period of time, such polymerization acting to lock in the tension in the fibers at the time of polymerization. A rail gun fabricated by means of the above method is further included.