Spar Mating

 
 
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The first step in mating the spars is to make the wing attach blocks. These are made from a serious hunk of aluminum bar (1" x 1.25"). Here, all four blocks are drawn out prior to cutting and drilling.
I chose to drill all the holes prior to cuting each block appart. This would simplifly the handling required for each block.
Next, the bar is taken to the band saw. Go slow and use lots of wax on the blade.
Completed attach blocks and spacers. You can see 4 spacers here, but reading the plans carefully will show that you only need two. This is one place that the plans could be a bit more descriptive.
The attach blocks are clamped to the angles in preparation for drilling.
Lastly, the blocks are bolted to the angles and then to the spars.
With the attach blocks in place, I lined the spars up and supported them on the saw horses. I had originally planned to drill the holes on my drill press, but after considering how much rearranging of my shop would be required, I decided to go with the saw horses. Beside, I've drilled nearly all of the holes in the spar by hand, why stop now!
After aligning the spars based on the holes already in the attach blocks, I realized that I needed some 3/16" rods, bolts, dowels, or something. Looking around my shop, the only thing I had on hand was some R/C control pushrods. They were perfect: stiff, slick, and sized just right! I cut sections for both blocks and pinned and clamped the spars together.
Before committing to drilling the blot holes, I wanted to ensure the alignment was accurate. There was a chance the attach block holes were in the wrong spot. I shinned a light from the bottom side of the spar to check the three pre-punched rigging holes (these are also the pilots for the bolts I was getting ready to drill). The holes matched up perfectly. Light passed through like there was only one continuous hole! I was impressed!
The three pilot holes were drilled out for 1/8" long-reach clecoes.
Then, on by one the holes were drilled progressively up to 1/4" and bolts temporarily installed.
Close up of the center section showing the left and right spar overlap.
Finally, the spars are mated!
Here is a good shot of the curve in the spars. Believe it or not, it really does take very little effort to straighten this spar back out. Don't worry about it!

 

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Updated: 24 Aug 05