how 2 do scale calculations:
first, convert feet into inches (multiply the # of feet by 12)
then, divide that number by the denominator of ur chosen scale
(in ur case , that would b 35)
13.5 feet times twelve =162 ( prototype dimension in inches)
take that # & divide it by 35....
162 inches divided by 35 = 4.62 inches in 1/35 !
c'mon, u can do it !
frosty