Ted's Aircraft Shop
Step 4. Assembling the Wings, page 2
Step 4.   Assembling the Wings

I used Special stamped aluminum ribs for the wing roots from Wag-Aero.  They provide a little more rigidity for the end of the wing. 

 

After repair, I treated the wing ribs and spray them with a light coat of white epoxy primer.  It is much more secure than the old zinc chromate.  The zinc chromate is an olive green and has a nasty habit of bleeding through the fabric covering.   Zinc chromate is soluble with MEK, the base reducer in Poly-Fiber.  Epoxy is not.  I tried any number of products and fell in love with the PPG products I could purchase locally.  To pretreat aluminum, I used PPG DX533 Aluminum Cleaner followed by PPG DX501 Aluminum Conditioner.  

 

After setting the wood spars on the sawhorses, I slid on the ribs one by one from the end of the spar.  Each was aligned with the rib marks on the top of the spar.  The next step was the installation of the drag struts that hold the spars into position.  Because the space was so tight, I made a "spar spreader" to open up the space just enough to slide the drag struts into place.  Following that I glued small aluminum squares on top of the spars in measured locations prior to trammeling.  Trammeling is a process of squaring the wing spars relative to each other.  The spars are held in position by the drag struts (metal tubes with flanges) and drag strut wires.  Using trammel points on an aluminum bar, I measured one diagonal and then its opposite until the measurements were exactly the same.  Then I used a fish scale to balance the tension in the drag wires to that specified. 

 

Next came the installation of the wing tank in the left wing, the wing strut attachments, the wing attachments, the aileron pulley system, and the pitot system tubing.  Then came perhaps the most challenging problems.  First, I had to install the wood wing bows.  Each has to fit the spars and ribs exactly.  The next

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Restoring a Piper Cub J-3
 
1.  Picking a  Project
 
2. Organizing and Planning
 
3. Overhauling the Engine
 
4. Assembling the Wings
 
5. Covering the Wings
 
6. Covering the Tail Surfaces
 
7. Repairing the Ailerons
 
8. Painting the Wings
 
9. Build Out of the Fuselage
 
10. Covering the Fuselage
 
11. Assembling and Rigging
 
12. Flight Testing