THE ULTRALIGHT VEHICLE HAD BEEN RECENTLY BUILT & HAD BEEN FLOWN ONCE BY AN EXPERIENCED ULTRALIGHT PLT. HE REPORTED THERE WERE NO DISCREPANCIES IN THE VEHICLE'S ASSEMBLY OR FLT CHARACTERISTICS. THE OWNER & 2 OTHER PERSONNEL MET AT THE FLYING AREA & ASSEMBLED THE VEHICLE. THE ONLY ONE WITH FLYING EXPERIENCE TOOK OFF & MADE SEVERAL PASSES OVER THE AREA. ON THE LAST PASS, HE WAVED BOTH HANDS & YELLED WHAT 1 WITNESS THOUGHT WAS 'I LOVE IT.' SHORTLY AFTER THAT, THE VEHICLE TURNED INTO THE WIND & BEGAN OSCILLATING IN PITCH. THE NOSE THEN PITCHED UP TO OR BEYOND A VERTICLE ATTITUDE & THE VEHICLE BEGAN DESCENDING TAIL 1ST, THEN CRASHED. WITNESSES REPORTED THAT THE WINGS FOLDED, BUT THEY WERE NOT SURE WHETHER THE WINGS FOLDED BEFORE OR AFTER THE VEHICLE ENTERED THE TAIL SLIDE. THE VEHICLE WAS NOT DESIGNED FOR A TAIL SLIDE. AN EXAM REVEALED THAT 1 LANDING WIRE & ALL 4 CANARD BRACE WIRES HAD SEPARATED FROM OVERLOAD. THE WIND WAS GUSTINGTO 20 KTS, A DUST DEVIL WAS SEEN IN THE VICINITY & SVRL MORE-EXPERIENCED PLTS HAD STOPPED FLYING DUE TO THE WINDS.