Wills Wing Sport 2 155, Owner'S Service Manual

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Sport 2 Stability Systems
Several design features of the Sport 2 determine the glider's degree of stability in pitch:
a. The combination of wing sweep and spanwise twist.
b. The alignment of the sprogs, and the height at which they and the transverse battens support the
trailing edge.
c. The length of the bridle cables and the height at which they support the trailing edge of the sail.
d. The shape of the preformed battens and the internal fabric ribs, and adjustment of the internal
velcro attachments which define the airfoil.
e. The setting of the tip wands.
Correct attachment and proper adjustment of the sprogs and reflex bridles are critical to providing
adequate stability at low angles of attack, particularly those below the normal operating range.
Sport 2 Sprog and Bridle Adjustment and Flight Testing
The Sport 2 uses two internal sprogs, one per side, in combination with one transverse batten on each
sprog. Each transverse batten spans two top surface battens, so a total of four top surface battens are
supported by the sprogs. In addition the Sport 2 uses one reflex bridle cable per wing to support one
additional batten per wing. The sprog and bridle systems are the primary components that provide
pitch stability at low angles of attack outside the normal flight envelope. The function of these sys-
tems is to support the trailing edge of the sail at low angles of attack, and thus provide a nose up
pitching moment. The bridles also provide structural support in a manner that reduces the loads on the
sprog system. The sprogs and bridles are adjusted at the factory to their proper settings. You can
check this adjustment as follows:
Sprog and Bridle measurement
1. Fully set up glider on a reasonably level surface and set the VG to full tight.
2. Place the rear end of the keel on the floor. The wing tips should be just slightly off the floor. If
they are not, place something under the rear keel so that the wing tips are not contacting the floor.
3. Tie a lightweight thread tightly across wing from the left #4 batten to the right #4 batten, and from
the left #5 batten to the right #5 batten. (These are the third and fourth cambered battens, count-
ing in from the tip - counting the shortest cambered tip batten as the #2 batten).
4. Press firmly on the top of the sail at the center of the transverse batten at the end of the sprog and
then release. Measure the height of each thread relative to the top of the keel tube. The results
should be as follows:
Outer (Sprog) Thread Inner (Bridle) Thread
Sport 2 155 at least 6.25" (158 mm) above keel at least 6.25" (158 mm) above keel