Pin the spar picture

[Bryan Cotton]

Hey guys,
When you pin the spar, do you use the little #40-ish holes at all? Or do you just bolt up the blocks, run a 3/16" bit through, and see how it turned out?

I am probably over thinking this.

[gammaxy]

It's a vague memory, but I think I used a drill bit as a pivot on the center hole and moved the spars until the rest of the holes lined up, then clamped them together.

[Rynoth]

I assume you're referring to the initial rigging/mating of the wing spars? I used some cut lengths piano hinge pin (almost perfect #40 size, clecoes are too short) through the middle 3 holes to secure the alignment of the spars, then clamped the spars together for drilling the blocks.

After drilling the blocks, I went back and drilled up the alignment holes per the plans. The alignment holes are important, as you'll pin them again with spare AN4 bolts during the wing rigging process.

[Sonex1243]

I clecoed the three #40 holes with long reach cleco's, clamped the spars together at the wing attach block ends with "C" clamps, up sized the three holes one at a time to #40, lightly reamed to a little under 1/4" and bolted them together. Then I drilled the attach blocks to 1/4". It worked very well since I did not trust myself to free hand the attach block drilling without egging the holes on the other side. This was in reference to the wing main spar plan, detail "K" which shows how to "mate" the spars and ream the holes out. Plans # SNX-W08, a note after spar assembly is bolted / riveted together, if that helps.

I also cheated a little before mating the spars and removed the two end wing assemblies (only three bolts each) from the spars, jigged them in the drill vise to keep them both the same, pre-drilled them 3/4's of the way through with a piloted 1/4" drill bit in the drill press, then re-installed them. After the three inner bolts were installed, I used the pre-drilled end attach blocks as my drill guide and followed it through the other block, flipped the spars over and repeated for the other end, worked great.

[Bryan Cotton]

I did a poor job of interpreting the plans. Here is what I did. First, from my project thread you will note that I drilled everything in the drill press. After I had the angles mated to the blocks I checked for squareness and found I needed a small tweak.


Fortunately after this tweak all was still square and fit well. Then I transferred the holes into the spar using the block as a drill guide. It lined up pretty good.


Here are my pinned spars. I found I could get a long #40 cleco in the center. The other two holes looked aligned but I could not quite get the cleco in them. The blocks pinned easily.


I must have 0.01 degrees extra or missing dihedral.