Williams Co. Airport, PO Box 488
Bryan, Ohio



1. Drill 3/8" bucking bar holes in side of ribs.

2. Drill #3 holes for drive pin locations with ribs numbered and taped together in pairs.

3. Tap pin holes in one rib for 1/4 - 28 bolt.

4. Drill holes in other mating rib to 1/4".

5. Dab zinc chromate into threaded rib hole and install 1/4" bolts. Jam threads on end of bolt to prevent unscrewing. Saw off heads with hack saw and file chamfer around end.

6. File 1/4" holes lightly in mating rib so that rib will slide onto pins of other rib and permit articulation of flaps when they are down 90 degrees and wing flexes. Holes must not be sloppy in driving direction.

7. Place each rib in proper end of flap. Mark rivet centerlines 1/4" in from edge of skin on all 3 surfaces.

8. Drill with No. 41 drill into center of rib bucking hole.

9. Countersink upper and lower skin rivet holes.

10. Dimple upper and lower rivet holes in flap skin. Use a steel bar with a countersink hole to back up the skin while hammering a 426 - 3 rivet into the skin if you donít have a dimpling tool.

11. With rib installed in end of flap section, insert rivets, drive and buck with a bar which has a 3/8" pin mounted in the bar. A flat spot ground on the side of the pin will make room for the rivet shank and will permit movements of pin as head is formed.