RE: FEJ 1/5,5 scale stabilator help required
Here are other formula's I obtained from Aircraft Design: A Conceptual Approach by Daniel P. Raymer
C = (2 / 3) * R * (1 + t + t^2) / (1 + t)
Y = (b / 6) * [(1 + (2 * t)) / (1 + t)]
Where:
C = Mean Aerodynamic Chord (MAC)
R = Root Chord
T = Tip Chord
t = Taper Ratio = T / R and t^2 = t squared (t * t)
b = Span = 2 * Half Span
Y = Distance from root chord to C
S = Sweep Distance
You will then need to use a little trig based on your leading edge sweep angle to determine the 25% MAC from the root leading edge at the root - Pivot Point distance @ Root Chord.
Using these formula's I obtained the same numbers as you did.
t = 17.5 / 46 = 0.38
C = (2 / 3) * 46 * (1 + 0.38 + 0.144) / (1 + 0.38) = 33.88
Y = (67 / 6) * [(1 + 0.76) / (1 + 0.38)] = 14.24
Sweep Distance @ MAC = (S / b / 2) * Y = 28.5 / 33.5 * 14.24 = 12.12
Pivot Point distance @ Root Chord = 12.12 + .25C = 12.12 + .25 * 33.88 = 20.59