Sailplane wing joint

Bob, did you have problems with the Zuni's spar end pins fatiguing or cracking becaus of cyclic loads?Â* That's a critique of spar end pins, according to Marske's manual.

The particular HP-14 I have in mind has the bottom of the two long knuckle pins passing through an anchor tab which is just forward of the bottom knuckles.Â* That tab is welded to to the top tube of a steel-aluminum bulkhead which makes up the front wall of the landing gear box.

The knuckle pins have cross-drilled holes at their ends.Â* After the pins are pushed rear-to-front through the knuckles and rotated so the small holes line up vertically, a long 1/16" wire is pushed down through both holes (just forward of the bottom anchor tab) to retain the knuckle pins.