Maine State Spelling Bee winner Tristan Singh, standing in his mother’s fourth grade classroom at the Rose M. Gaffney Elementary School in Machias, tells others who want to ace the academic competition to “have rocket fuel motivation.” Photo by Jessica Brockington.MACHIAS — A Machias eighth-grader turned his passion for academic competitions into a trip to Washington, D.C. to represent Maine in the Scripps National Spelling Bee in May. Tristan …