AC Spark Plug's . . . "Tip Of The Month Contest" By Richard W. Gleason, EAA 3131 hen building my airplane I was W faced by the problem of marking for rib stitching on the fabric of the wings without a helper to hold one end of the chalk line. The idea I hit on worked so well that I am telling others about it. I got a length of electrical conduit long enough to stretch from root to beyond the outboard ribs. About % in. in from each end I drilled a hole, going through one wall only and making sure both were on the same line. The holes were tapped

for 10-32 screws and into each went a machine screw about 1 '.£ in. long, with a plain nut threaded onto each up to its head. The screws were

to get a good, dark mark. One end of the chalkline is lowered onto the rib on the far end from where one is standing, and the near end lowered

turned up tight against the opposite, inner side of the tubing. The chalk line was stretched tight between the two screw heads and the nuts snugged up to hold it against the bottoms of the heads. The result was something similar to an oversize violin bow. The rib spacing was marked on the end ribs with a black pencil

onto the mark at the near end of the wing. Then it is quite easy to snap the line and move on to the next mark. All ribs will be uniformly marked. It is possible to mark a wing the size of a Cub with this gadget in five minutes. To further simplify rib stitching, do the marking on the bottom surface of the wing while it is sup-

CIVIL AERONAUTICS MANUAL 18

PULL TO TIGHTEN

PULL TO TIGHTEN

KNOT FORMED BUT NOT TIGHTENED

KNOT

COMPLETED

Klc.lli: 3-1.

PULL NO

Spile* Knot.

2 -N

COMPLETED KNOT PULL N O . Z - I O L B . TO TIGHTEN KNOT

. fy

PULL NO.I-IOLB.

TO TIGHTEN STITCH

A f T E R PULL NO. I HOLD STITCH TENSION

BY PRESSING HERE

DURING PULL NO. 2

OPERATION NO 2

-EDGE OF CAPSTRIPOIRECTION OF LACING

OPERATION NO. I Ftofu; 3-V

Standard Koot for Rib I.nrinx (Mndlflwl S