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May 12, 2011


Nose Rib Attach Angles


Well, now that I had jig drilled nose attach angles, I wanted a way to consistently place them on the spar for match drilling the spar. I grabbed a spare attach angle blank and bent the angle to match the spar flange. Next I determined where (vertically) I wanted all the nose rib attach angles to be and clamped one into position. At the the other end from the clamp I slid the blank angle under the nose rib attach angle and marked me a little bulls eye in the bottom hole. This is almost too simple to call a jig, but it does allow repeatable results.

For each nose rib attach angle I would clamp it loosely to the spar and slide the bulls eye jig under it. Move the nose rib attach angle until the bulls eye was revealed, and clamp the nose rib attach angle tightly at the other end. Now remove the bulls eye jig, verify that the nose rib attach angle is aligned with the marked line on the spar and 90 degrees to the spar.

Now clamp the other end and you are ready to drill and cleco as you go

Back Rib Attach Angles


So I figured I wanted the nose and mid/back ribs aligned where it called for such in the plans. I had predrilled the nose rib attach angles. I used these to match drill the spar. Now I wanted to use the spar to match drill the back rib attach angles. But how to align them and keep them aligned?

Again from from a simple mind come a simple answer.

Clamp the nose rib attach angle to the table with the spar side standing up. Here we have a (FR5) flap nose rib angle clamped to the table with a flap back rib angle in the background.

Hold a fine line Sharpie at the normally vertical center of one of the holes.

While holding the Sharpie still, push the back rib attach angle across the back of the nose rib attach angle making a nice straight line demarking the drill line for the back rib attach angle.

OK, I’ll admit it. The front angle is .025 and the back angle is .032 so I am off by .007”. Some people say I’m off by more than that.


Now when you place the back rib attach angle in it’s position, you can align the ink line with the holes in the spar and clamp it securely before drilling.

That took care of the horizontal alignment. To position the back angle vertically, I made a spacer to clamp to the spar flange to consistently space the angle from the spar flange. I ain’t go no stinkin picture of that, sorry!

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