1. Brush the outside of all rib flanges with a coat of Prussian Blue.

2. Mark all rib flanges with a rivet centerline 9/32 inch from the outside of the web. 3/8" works better on the heavy #1 and #36 ribs.

3. Mark rib flanges that mount to spar web for rivet holes and drill.

4. Check I beam section of spars with a square to insure that upper and lower caps are perpendicular to webs. Bend shear web flanges as necessary before any ribs are mounted to the I beam portion.

If spar web to cap holes are drilled accurately with a hardened drill guide, ribs can be spaced by reference to these holes. Later attachment of the skin and finding of rib centerlines will also be facilitated when a drill guide is used.

Make a gauge that can be used for drawing rib position lines on spar shear webs .perpendicular to web centerline. Draw web lines with a pencil. These lines should be positioned to locate the outboard side of the rib web.

5. Inboard ribs will have to be attached to spar with pop rivets unless one side of shear web in box section of spar is left unriveted for easy disassembly and subsequent rib attachment rivet bucking.

6. Tape rib flanges against shear web so that outboard edge is on locating line and any height variation is evenly split at top and bottom. Drill through rib flange holes into shear web.

7. Remove one web of box spar and rivet ribs in place.

8. When all ribs are attached to main spar, clamp spar to table and nail blocks against bottom spar flange as necessary to got spar straight in chordwise plane.

9. Clamp first section of rear spar to rear ribs at inboard end of wing.

10. Draw a centerline on top spar cap and clamp No. 1 rear rib with a diagonal brace which will hold it securely in position 90 degrees to spar cap centerline.

11. Clamp all other ribs to rear spar so that they are perpendicular to cap centerline in box section and web centerline in I beam section. Rear spar can be spliced together as sections are added.

12. Straightedges held on top and bottom flanges of rear rib will aid in centering rib on rear spar. Rear spar flanges must be adjusted if necessary to match the angle of the rib flanges.

13. Drill through rear spar into rib flanges. A small steel guide will speed up locating of these similar holes.

14. Install rear spar drag plate fittings and rivet rear spar to ribs.

15. Install aileron push pull guides and aileron bellcrank assembly.