After a local maintenance flight the crew returned to St. Petersburg to practice full stop landings. Shortly after becoming airborne during the 2nd takeoff, the right engine experienced a power loss. The aircraft was observed to climb to about 50 ft AGL, then veer right and crash east of the runway. Other than a malfunctioning right fuel tank selector which allowed fuel to bypass to other fuel tanks, there was no pre-impact failure or malfunction. Both right tanks were empty and the left tanks contained about 175 gallons of fuel. However, subsequent tests showed that fluid in the right tank would bypass the right fuel selector and leak into the left tank when the aircraft sat left wing low for about 12 hours. The aircraft was not airworthy in that all the requirements of an approved 91.217 inspection program were not complied with. The PIC had 5 hours as PIC of DC-3 during the last 5 months with 1 hour and 2 takeoff and landings the last 90 days. This was the first flight in a DC-3 for the co-pilot with no record of any training in the DC-3.