Re: Question on Rod Design
There are three fundamental ferrule types in graphite rods. In some older rods like Orvis Far and Fine, there is a sleeve ferrule which is a graphite tube epoxied onto the tip which fits over the butt. Scott devised, and along with a few others still sometimes uses, a spigot ferrule. In this design a capped hollow tube is fitted inside the butt and the tip fits over the tube leaving a small gap between the two sections. Many have long believed the spigot offers the smoothest, least interrupted flex in a rod. If loose though they can break. Fenwick (which later morphed into Sage) introduced, in their original HMG, "tip over butt" ferrules that were fashioned as one piece into the fabrication of the blank section. This has become the dominant ferrule and had been refined to be slimmer and stronger than the others and is used by the majority of rod makers.
Whatever ferrule design your rod has, it is wise to check it for snugness periodically as loose ferrules are a leading cause of rod failure. Ferrules that loosen on their own are symptomatic of poor rod engineering.