Spar/Rib Match Drilling

Time: 8 Hours

I have to tell you I was pretty excited to get out into the Hangar this morning. I was thinking about assembly all night. I figured I would start with the right wing. So I grabbed the main spar and the rear spar from the house and laid them out on the workbench and began to clecko the ribs. You really need to keep an eye on the correct ribs as they face several different directions in relation to inboard and outboard.

It’s pretty cool to see a wing, ok a minimal sub-structure of a wing, in the Hangar!

Before I started match drilling I have seen several builder take the next photo so I did too!

For match drilling I bought a couple of reamers, a #30 and #40 just for the wings. From what I have read they will leave less of a burr on the metal over a drill bit. The process is still the same just with a different tool. On the 4 inboard ribs there are 8 holes that don’t match up. Not sure why Van’s does that but I have read that these ribs are from another aircraft model in the Van’s lineup. So you have to drill these, matching the rear spar and creating a set of new holes in the rib flange. You just abandon the others according to the plans.

Here you can see the 7/8″ hole that will carry the CPVC pipe from the root to tip for the lighting wiring.

Once the top was done I flipped the wing on its end and drilled the bottom.

As excited as I was to assemble I was just as sad to take it all apart! That is the fun part of this build is you work, assemble, disassemble, work and the re-assemble. Lots of fun! Once I had it all torn down I started working on deburring all the holes that I just matched drilled. I started with the rear spar so that I could put it back inside the house for safe keeping with the main spar. Then I grabbed the 14 ribs. They were pretty easy and I figured while I was there I would hit all the holes on the flanges. These holes will be for the skin to attach and will be dimpled in a future step. What I noticed was that the machining process had left a pretty big and wide burr or lip in many if these holes. Too big for my deburring bit to attack with out drilling into the metal. So I grabbed my die grinder and put a soft 3M 1″ wheel in and “buffed” all of these down. They will still get a deburring treatment after match drilling to the skin but that will be light. Here are a before and after photo of that process, the first shows a large lip on the third hole from the left (by the way these are those double holes that Van’s has you drill).

The left wing went just the same and was assembled fairly quickly. I’m glad I took the advise to build both wings at the same time. The learning curve on the second wing is a lot quicker than the first. I’m sure this will help out in the future.

Here is a good view of the 4 inboard ribs, they are doubled up to create a beefier area as this is where you stand when getting in the aircraft.

One thing that I did on both wings was to fabricate the angle aluminum that will be the attach point to the wing stands. Van’s has you use a 5″ piece and drill two 3/16″ holes in the last outboard rib. You use these two holes to bolt the angle piece to the rib, the holes will be abandoned after the build and cause no harm. I figured that this would be an easy enough time to build these.

So as with the right wing I disassembled the left and started deburring the rear spar. It was hitting just over 8 hours in the Hangar so I decided that was a good time to call it a day. I moved the left spars back inside and stacked the left ribs. The Hangar got a good seeping and all the tools found their way back to the drawers. Tomorrow I will finish up the deburring on the ribs and work on the final scuffing and cleaning for their eventual priming, hopefully tomorrow and Monday after my morning flight to Omaha. The rest of my week is pretty busy so I will get to riveting next weekend. That will give the primer a little set up time.

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