Wing Tie-Down Points
There has been some question about the intended purpose of the threaded holes in the underside of the wings near the ailerons.
These appear only on early editions of Standard Cirrus gliders. According to Helmut Treiber of Schempp-Hirth (9/20/2005),
these holes are intended as tie-down points. Early gliders equipped with this feature were shipped with special, forged
eyebolts that screw into these holes, providing a tie-down point.
The drawing on the right shows how this threaded hole is designed into a bracket on the opposite side of the wing rib
that supports the aileron linkage. For images of these parts, see
Stefan Melber's Project Pictures.
It would be unwise to use these brackets for purposes that stress them beyond the originally intended purposes.
Stefan Melber cautions against using long bolts that could apply twisting moments to the brackets. The original tie-down
bolts have padded shoulders that snug up to the wing surfaces to prevent such forces.