The first order of business is to strap the wing skin onto the skeleton exactly where you want it. Take your time here and lay it down smooth and evenly tensioned.

Now mark the spar flanges, rib webs and rib flanges just as you did when making the pattern. Follow Eric’s directions for marking the skin. I copied him and it works well. Make your marks as accurately as possible while in all of those new yoga positions you are learning.

Now remove the skin and it should look something like this. I label the skin so I don’t turn it upside down by accident.

Here you see the bottom of the rear spar flange marked and the thin rib flange marks with the thicker rib web marks.

Here’s a close-up of one of the rib ends marked. Sometimes it is kind of messy when marking blindly through lightening holes by feel.

The rib flange mark is on the left. It is the important rib mark.

The rear spar flange mark runs horizontally across the bottom. It’s important too.

Now place the pattern on top of the marked skin. Center the rear spar flange mark on the skin (red line) between the two parallel spar flange lines (blue) on the pattern.

At the same time align the dashed rib flange marks on the pattern (thin vertical blue lines) with the top and bottom rib flange marks on the skin (also thin vertical blue lines).

Weight the pattern down so it will not move as you punch the skin. I used lead ingots or shot bags. You want to place the pattern accurately and keep it there while punching the skin.

Here’s a broader view of the pattern on a rib location on the marked skin ready to go.

Note that you can flip the pattern over (left to right) to mark rib flanges facing the opposite direction as occurs around the root and fuel tanks.

Now use a center punch to mark the rivet holes. Once the mylar was used the first time, the center punch was easy to locate at a rivet location for subsequent punching because a small hole was punched through the mylar.

Repeat the last step for each rib on the skin. This goes really fast. I’m sure it is faster and more accurate than measuring and marking each rivet location one at a time.

This is kind of like making the lightening hole flanging dies for the ribs. A little time spent making the pattern saves a good deal of time later on.

After center punching all of the rivets locations, drill them out.

When you place the skin back on the wing skeleton you should see the rib centerline through the rivet holes (if you were careful when marking the skin and using the pattern!) It really is not hard.

Again, it works amazingly well. I marked and drilled a bottom skin and the rib centerlines lined up all the way across the skin. Never more than a half off of the centerlines.

Well, that’s my story. If you have any questions feel free to email me. I’ll try to ‘splain it better than I did here.