

Home > Articles & Tips Index > Model Design > Quick VTail Sizing [Courtesy of Mark Drela, drela "at" mit.edu, March 2000] The issue of Vtail size and angle came up several times at the last meeting. Below is a short blurb on converting a conventional tail to an equivalent Vtail and vice versa.  Mark To convert a conventional tail into a Vtail: A_vtail = A_vertical + A_horizontal angle = arctan[ sqrt( A_vertical / A_horizontal ) ] Notes: "A_vtail" is the area of both halves together, rotated flat. "angle" is the Vtail's dihedral angle from the horizontal. To convert a Vtail into a conventional tail, use the reciprocal formulas: A_horizontal = A_vtail * [ cos(angle) ]^2 A_vertical = A_vtail * [ sin(angle) ]^2 These formulas are strictly correct only for large tail aspect ratios, since they do not account for the local interference and lift cancellation at the Vtail roots during yaw or "rudder" application. But they are much better than guessing. 
