There are fancy tools out there (lasers, 3D scanners, etc.) to achieve this - but as of this date, those are beyond my budget and not within my reach.
One of the very first steps in this chapter is to set up the jig; while this sounds like a good idea in theory, I do not agree with this at all! Let me explain why:
I spent 3 days setting up the jig below... making sure they were all vertical in both planes and that they were in a perfectly straight line. I pre-drilled holes into the jigs and used aluminum braces to secure everything.
The first problem I encountered was when trying to perform step 4 in the plans to "slide the foam cores into the jig". I had read the plans many times before, and didn't think this would be an issue, but the cores and the templates are a very tight fit. Sliding the outboard core (FC3) through all the jigs seemed irrational.
Not wanting to harm the cores, I decided to undo the jig from one end, and insert the cores directly (rather than trying to slide them through all the jigs).
Just when I thought I was home free, I quickly learned that my "perfectly flat table" wasn't so perfectly flat after all. There was a small gap at the bottom mating surface between FC2 and FC3. I could only think of two reasons why this would occur: 1) the FC sections were not cut properly, or 2) my table was not perfectly flat. Given that these cores were cut with precision CNC tooling by Eureka, I was convinced it was my table.
Here's a close up...
This is why setting up the jig first (without testing it with the cores) is a bad idea. One needs to have the ability to fine tune the jigs to make everything fit perfectly together. To fix this, I now had to undo the remaining bracing on the other side so that it would allow me to shim under the jig.
I want to point out that I wasn't naive to think that my table was 100% perfectly flat. I knew it wouldn't be. The mistake I made was to think that it would be within the margin of noise (i.e., negligible). Well, it wasn't negligible. Another note I want to make is that I wasn't simply shimming the jigs to make the gap go away; I had a straight edge sitting on the top of the shear web letting me know it in fact needed to be shimmed between FC2 and FC3.
I also checked the angle between FC1 and FC2. The top-view drawing on page 19-10 shows the top edge of FC1 at 8.57 degrees and the top edge of FC2 at 18.42 degrees. This means the angle between FC1 and FC2 should be 9.85 degrees. I used a digital inclonometer to verify the angle between my FC1 and FC2 was between 9.8 and 9.9 degrees.
So you can see that at this point, I had spent 3 days of aligning and bracing the jigs for nothing. I wish I would have inserted the foam cores first, and then shimmed and braced accordingly.
Difficult to see in this picture, but notice the shims I inserted under the jigs... I used plastic squeegee cards.
It took quite a bit of work to get all mating surfaces aligned. The hard part is that tweaking one will change the others. When I redo this for the left wing, I will make sure to have the center core (FC 2) higher than the others, and then shim FC1 and FC3 accordingly.
Notice how I also set up a rest stand for FC1's trailing edge. Since FC1 is only supported by a single jig, it was important to have a support for it where it mates with FC2.
FC2 and FC3 all aligned and ready to be bonded as well.
I then slid FC1 out a bit...
So that it would give me room to apply slurry to both FC1 and FC2 mating surfaces...
I then slid FC1 and FC2 together. To make sure they were both perfectly aligned with each other, I placed cling wrap over the shear web section, placed two flat cards and clamped them together.
To make sure the sections stayed aligned along the chord, I inserted toothpicks along the airfoil to act like a zipper.
I repeated this process for sections FC2 and FC3. I slid FC3 outboard (with jigs and all)...
Slurried the mating surfaces...
And joined them together...
With FC1, FC2 and FC3 all bonded, it was time to re-attach the inboard shell section. I started out by applying slurry to the mating surfaces...
And attached it to FC1. I used toothpicks to pin it in place...
I then slurried the top surface of the shell...
And bonded it to FC1...
The last piece was the shear web face...
I slurried the mating surfaces...
And installed the face in place. The shell is now complete... there is LWA6 anxiously waiting to go to its new home. Notice the nails acting like pins holding everything exactly where it needs to be.
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