On September 24, 2017, about 1715 eastern daylight time, an experimental amateur-built Vari EZ, N830S, was destroyed when it impacted trees and terrain near Ambler, Pennsylvania. The private pilot sustained serious injuries. The airplane was registered to and operated by the pilot as a Title 14 Code of Federal Regulations Part 91 personal flight. Visual meteorological conditions prevailed at the time of the accident, and no flight plan was filed for the flight that departed Wings Field Airport (LOM), Blue Bell, Pennsylvania, just prior to the accident. According to a witness, during takeoff, the engine sounded like it did "not reach full rpm" and it took the entire 3,700-ft-long runway for the airplane to lift off the ground. Then, about 200 ft above ground level the engine "stopped." Another witness reported hearing the engine "sputter." The airplane was "wobbling," descended, and impacted trees prior to coming to rest near a house. Initial examination of the airplane by a Federal Aviation Administration inspector revealed that both fuel tanks were ruptured, and fuel was leaking from the wings. The canopy was separated from the fuselage and the forward section of the fuselage exhibited crush damage. The engine remained attached to the airframe and the propeller remained attached to the engine. According to FAA records, the airplane was manufactured in 1984 and registered the pilot in May 2017. It was equipped with a Lycoming O-235-C series, 100-horsepower engine that drove a Sensenich propeller. According to airplane maintenance logbooks, the most recent condition inspection was completed on April 1, 2017, at 691.0 total aircraft hours. The engine was removed from the airframe to facilitate further examination. The rocker box covers were removed, and rocker arm movement was noted on all cylinders when the propeller was rotated by hand. Compression and suction were noted on all cylinders. All spark plugs were removed and exhibited normal wear when compared to the Champion Check-A-Plug chart. The magneto was removed, operated, and spark was noted on all towers. Corrosion was noted throughout the engine. It was noted at the crankshaft end of the No. 2 connecting rod and all gears in the accessory section of the engine. The gascolator was removed and water was noted in the fuel. Also, debris was noted in the fuel that restricted the flow of fluid from the gascolator. The carburetor was removed and disassembled. Water was noted in the carburetor when tested with water finding paste. The left fuel tank fuel cap was impact separated and the tank was breached. The debris noted in the fuel was consistent with a substance that was dried on the interior of the left fuel tank. The right fuel tank contained fuel and tested negative for water. When water was poured over the right fuel tank cap while it was seated, then the cap was removed, the fuel in the right tank tested positive for water with water finding paste. According to the pilot, as a result of his injuries from the accident, he was unable to recall any of the events leading up to the accident. However, he stated that it was routine practice for him to complete a thorough preflight inspection and does not believe there would be a reason that a thorough preflight was not completed on the day of the accident. He also stated that the airplane was kept outside.