ON 6/26/86, THE PLT & HIS WIFE HAD FLOWN FROM HELENA, MT. TO POWELL, WY, TO VISIT FAMILY & RELATIVES. ON THE DAY OF THE ACDNT, HE HAD CONSUMED ALCOHOLIC BEVERAGES. DESPITE PLEAS FM HIS WIFE NOT TO RETURN TO HELENA THAT EVENING, HE ELECTED TO FLY BACK. WHILE EN ROUTE, THERE WAS A CATASTROPHIC FAILURE OF THE ACFT; THE WRECKAGE WAS SCATTERED OVER A 1460' AREA.THE RGT WING & BOTH STABILATORS WERE FOUND APRX 750' FM THE MAIN WRECKAGE WITH EVIDENCE OF OVERLOAD FAILURE. THERE WAS EVIDENCE OF UPWARD DEFORMATION/FAILURE OF WINGS & DOWNWARD FAILURE OF THE STABILATORS. CAMPERS NEAR THE CRASH SITE RPRTDA MOONLESS, CLOUDY NGT WITH THUNDER & LIGHTNING IN THE AREA, BUT NO RAIN. APRX 60 MI WEST AT HELENA, THE 2350 MDT WX WAS, IN PART: 6500' OVERCAST, VIS 15 MI. ELEV OF THE CRASH SITE WAS APRX 6000'; ELEV OF THE WX STN WAS 3873'. THE PLT HAD ONLY 6 HRS OF NGT FLYING TIME (LAST NGT FLT WAS LOGGED ON 6/29/83) & ONLY 2.8 HRS OF INSTRUMENT TIME (LAST LOGGED ON 7/16/82). A CHECK OF THE PLT'S BLOOD SHOWED AN ALCOHOL LVL OF 0.115%.