Edited sentence: SZD-29 Zefir 3 - With a 19m wing this Zefir was optimised for long distance high speed flight with a min sink of 0.66m/s @ 100km/h and L/D of42 @ 84km/h.SZD-31 Zefir 4 - A further efinement of the Zefir 3 to compete in the Open class at the 1968 World Gliding Championships at Lesno in Poland with simnilar dimensions and performance.The first prototype,(SP-2465), with Stanisław Skrzydlewski M.Three aircraft were built, two of which took 14th and 28th place at the Lesno competition.at the controls flew on 26 A€pril 1965, a second prototype was also built