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14-03 Step 4 Match Drilling Ribs to Spar

The spar arrives with all the AN3 bolts for rib attachment installed, so the first job is to remove these and stow away safely until later. Once this is done, the ribs are clecoed to the spar, being VERY careful to place the ribs in the correct places … the drawings show which direction the various rib flanges should point.

Match Drilling AN3 Bolt Holes

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I clamped a wood block across the rib flanges to prevent them flexing whilst match drilling.

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And then used a cordless drill to bore the #12 holes. No problem with keeping everything perpendicular on the thicker step bar portions, but more care needed on the thinner parts of the step bars since there was less bar depth to align the drill bit.

Final Drilling the #30 & #40 holes

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Then I used a #30 reamer to final drill the holes for the AN470AD4 rivets.

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And a #40 reamer for the top & bottom AN426AD3 rivet holes.


I annotated one of the wing rib layout drawings in the manual with L1, R1 etc and then marked the spar & ribs to ensure each rib will find its home after painting.

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2 comments on 14-03 Step 4 Match Drilling Ribs to Spar
  1. Matt Whiting

    Do you have to be concerned about what type of marker to use? Does the ink have the potential to cause corrosion over time?

    1. Steve

      Vans recommend a “Sharpie” pen … this is the advice in the manual – “WARNING: NEVER use a scribe to make layout lines or other marks on aircraft parts. Due to engine vibration part failure can occur along these scribe lines. The use of an ordinary lead pencil will cause the aluminum to corrode. We recommend that you only use an extra-fine point “Sharpie” pen. For some unexplained reason the blue ones seem to last longer than other colors. The sharpie ink will bleed through primer so you can still see the ID marks after priming the parts. Be sure to remove any markings in areas that will be visible after completion as the ink will bleed through primer and paint coatings.”

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