Carbon tube is hollow carbon fibre stock, and in stiffness per gram it is the best material a modeller can readily buy. Because a section in bending works mostly at its outer surface, taking the core away saves weight at almost no cost in rigidity.
It is used for tail booms, struts, shaft housings and the load-bearing tubes of lightweight structures. A short length also makes a convenient socket, since a wooden or plastic plug can be bonded inside it as a bushing. Lightweight airframes built around a tube boom and a tube spar are in hand-launch glider kits, and the straight stock a modeller reaches for where carbon is not called for, brass and steel rod, plastic tube and piano wire, is in wires and rods for models.
