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Main Spar Prep Done

April 28th, 2012

Nutplates All Done

Saturday arrived and since I had done the yard work earlier this week, I was ready to have a decent day in the shop. First order of business was to spot prime all the nutplate attach rivet countersinks and rivet on the 150 nutplates to the spars. This took a good portion of the morning to do. That is a lot of nutplates Vans! I was able to easily reach the nutplates near the root of the spar in the center of the web with my 3″ yoke on my squeezer. I only primed the countersinks for the attach rivets because I plan to prime the entire flange once the countersinks for the skin dimples are done. As for now, the nutplates are on and look great.

Tie Down Block Work Begins

Next up on the list were the tie down blocks and spacers. I dressed the edges with my scotchbright wheel on the AEX blocks themselves and then laid out the first holes to be drilled. Van’s has you drill one with the dimensions from the plans, then run a cleco or bolt through that hole and the matching hole in the spar and then match drill the rest. Before you do that, you have to make 4 spacers that will go in between the AEX stock and the spar itself. These are made out of 1″ bar stock. I simply cut them to size with my band saw and then marked the center for the lightening hole. I debated on what to use to cut the lightening holes with. I have a fly cutter, but the 1″ hole is a little tight for it. I ended up running to Lowes Aviation Supply and picking up a 1″ Bi-Metal hole saw. I also picked up a drill press vice to hold parts on the drill press platform. Word to the wise, lube the saw. The next half hour was spent cleaning up the inside radius of the holes with a Dremmel tool with a sanding drum.

One Tie Down Block Done

Once the blocks and spacers were cleaned up, I match drilled them to the spar holes. I taped the spacers down to the spar so they would not move and then clamped the tie down blocks over them. Once drilled, you have to then match drill the spacers AND the blocks for the rivets that hold the nutplates for the aileron bellcrank bolts. After drilling I deburred all the holes and got the parts ready for primer. The parts were then primed and riveted together. Above you see the complete tiedown block/spacer assembly. Van’s designed it this way in case a nutplate had to be serviced. If one is bad, you can remove this block and replace the nutplate. Interestingly enough however, to get to the block assembly, you have to remove the tank on a finished wing. I do not see how you could get to it otherwise. I hope to not need to find out either way.

Nice and Tapped

Before you can install the blocks onto the spars, you need to tap the bottom end to accept the tie down rings that will thread into these blocks. The AEX block is pre-drilled. You have to then tap this to a 3/8-16 thread to about 1″ deep. I do not have this size of a tap, so I called around to those I thought that would with little luck. Finally, I decided to check with my back fence neighbor Jeff, and see if he had one. His is an expert mechanic after all. Turns out Jeff did…and it was a nice one. I promised not to ruin it and he handed it over. After about 5 minutes and some bo-lube, I was able to get these nicely done and they look great and straight. I cleaned up the tap and ran it back over. Thanks a bunch Jeff! (Incidentally, Jeff’s son Pat is an aviation tech for the USAF in Korea, and currently works on A-10’s!)

Both Wing Tie Downs Complete

Here you can see the assemblies bolted on on both spars. I torqued the bolts to spec. It seems so weird to only torque these to 25 in/lbs. Seems light, but it is right.

Aileron Brackets On

Here are the aileron bellcrank brackets bolted on and torqued to spec as well. I torque sealed them too. Turns out, I should have waited as I need to take at least one off to install the autopilot servo bracket. However, I can just clean off and re-torque.

Spar Prep Done...ish

Here is another shot of the tie down assemblies and spacers. As it stands for now, the main spars are prepped for ribs. Next up…rear spars.

Categories: Major Wing Sections
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