Elliptical Wing Tapered Wing Swept-Forward Wing Rectangular Wing Figure 3-14.  Planforms of glider wings. zero, improving aerodynamic efficiency. This wing design is  difficult and costly to manufacture because of the compound  curves in its design. The elliptical wing is more efficient in  terms of L$_{D}$, but the wing’s uniform lift distribution causes  the entire span of the wing to stall simultaneously, potentially  causing loss of control with little warning.  The rectangular wing is similar in efficiency to the elliptical  wing, but is much easier to build. Rectangular wings have  very gentle stall characteristics with a warning buffet prior to  stall, and are easier to manufacture than elliptical wings. One  drawback to this wing design is that rectangular wings create  more induced drag than an elliptical wing of comparable size. The tapered wing is the planform found most frequently  on gliders. Assuming equal wing area, the tapered wing  produces less drag than the rectangular wing, because there  is less area at the tip of the tapered wing. If speed is the  primary consideration, a tapered wing is more desirable than  a rectangular wing, but a tapered wing with no twist (also  called washout) has undesirable stall characteristics. A swept-forward planform is a wing configuration in which  the quarter-chord line of the wing has a forward sweep.  Swept-forward wings are used to allow the lifting area of  the wing to move forward, while keeping the mounting  point aft of the cockpit. This wing configuration is used on  some tandem two-seat gliders to allow for a small change in  center of gravity (CG) with the rear seat occupied, or while  flying solo. This type of planform design gives the glider  increased maneuverability due to airflow from wing tip to  wing root, preventing a stall of the wing tips and ailerons at  high angles of attack. Instead, the stall occurs in the region  of the wing root.  Washout is built into wings by putting a slight twist between  the wing root and wing tip. When washout is designed into the  wing, the wing displays very good stall characteristics. Moving  outward along the span of the wing, the trailing edge moves  up in reference to the leading edge. This twist causes the wing  root to have a greater AOA than the tip, and as a result, stall  first. This provides ample warning of the impending stall and,  at the same time, allows continued aileron control. Swept-Forward Wing Rectangular Wing Tapered Wing Washout 3-7