Chapter 19: Wing Jigs


Lessons Learned:

1.      Pay special attention to Chapter 19, Figure #2 and #3 before cutting out the jig templates or the jig boards.  The 17.4 inch reference lines do indeed extend away from the corners of the fishtails.  I thought those lines were "pointing" to the corners of the fishtails, so I screwed up and glued the paper templates with the fish tails in the wrong places (and subsequently cut the jigs wrong…). Norm Muzzy caught my mistake, so I made a new set of jigs.  Better to catch the mistake now than to scrap a thousand dollars worth of wings.

2.      Before you cut out the jig templates from the M drawings, tape all three M drawings together FIRST, being as careful as you can about aligning the match lines. Then take a straight edge and draw in the 17.4-inch reference line the entire length of every template. If you try to cut out the individual pieces first, then tape, the match line is too short and you cannot accurately align the template pieces. A small error here translates into a large error at the trailing edge.  The tick marks are on the leading and trailing edges only -- no tick marks at the match lines of the adjoining middle sections. So it's hard to know when you've got the middle sections of the templates level at the same 17.4-inch mark as the leading and trailing edges. If you're like me and don't want to cut up the original M drawings, go ahead and make copies of the templates, tape all three M-drawings to your big office window, then cut-n-paste the copies over the originals.

3.      Make small holes on the 17.4-inch reference lines about every 5 inches or so. In this manner you can see through the template and ensure you're matching up the template's 17.4-inch reference with the jig's 17.4-inch line as you glue the paper down.

4.      I made my wing jigs (old and new ) from the same type of 3/4-inch MDF boards that I used for the main spar. Home Depot was out of the 14-inch boards, so I used 16-inch boards already available at 49-inch lengths. I chose to leave jigs #1-#4 at 49 inches so that I could run a string across the tops of the jigs to verify alignment. I screwed all the ties into place with drywall screws.  I didn't flox any of them.

5.      For the vertical configuration for core assembly and shear webs, I mounted the jigs onto a 12-foot long by 16-inch wide platform placed onto the hangar floor.  I used additional boards to hold the jigs upright at 90 degrees.  All jigs are also screwed securely to the platform.  Using shims, it was easy to adjust the platform and jigs until everything was level and straight.

6.      I added reference marks at exact locations on the lower jig halves and for the fully assembled jigs.  This helps when using a string to align them properly.

7.      For the horizontal configuration for spar caps and skins, I used the 90-degree brackets and little clips instead of using bondo.  I secured the cores to the jigs with drywall screws through those clips.  Very good for pinpoint control and very useful for accurately jigging the wing straight and level.  The 90-degree brackets were probably overkill, but VERY convenient.  Plus the jigs remained in good shape for another builder or when I build the second Cozy!

 


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