F3B models are called multitask gliders, similar to F3F slope gliders with a lighter composite layup. The design of the F3B model is especially challenging because of the wide range of operating conditions. It must be flown very slowly to achieve the duration time and create high lift to maximize launch altitude off the winch. At the same time it must have very low drag to fly at high speed during the distance and speed tasks. The launch and turning loads require very strong airframes, composite construction has been in use since the first world championship in 1977. Models are typically constructed from carbon fiber, utilizing more exotic high modulus carbon in the wing spars. The empty weight of the airframes have come down substantially since the early 1990s when competitive aircraft weighed 3 kg empty. Many top designs are commercially available from manufacturers such as TUDM, Baudis Model and Samba Model in Europe.