Wing Main Spar 13-3-1 to 13-3-3
The next few steps in preparing the spars have you countersinking all the (hundreds of )holes to various depths, and riveting tank attach and access panel nutplates in place.
First off, I reamed all remaining 3/32" holes to #40 (those that I had not previously drilled) as they are all slightly undersized.
I continued by clamping the spar on its side, and taping off any areas where metal chips could enter which would then be difficult to remove.
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| Spar clamped to workbench and any areas where metal chips could fall in are taped off with masking tape |
I then countersunk all the nutplate attach rivet holes for tank attachment and access panels to flush rivet depth. I also countersunk the 7 rib to spar attach rivet holes that were in line with the tank attach nutplates to flush rivet depth on each spar flange (28 holes in total).
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| Countersinking nutplate attach rivet holes to flush depth. I used a rivet to test each and every holes as I drilled to ensure that the countersink cage was not slipping |
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| All nutplate rivet holes countersunk along top of spar |
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| Access panel (x6) nutplate holes also countersunk on both spars |
Next I countersunk all the remaining holes in the spar flanges to accept a dimpled skin (flush +7 notches on the countersink cage). This took quite a while as each flange has around 200-250 skin/rib to spar holes.
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| Subtle difference in diameter between nutplate hole (flush) and skin hole (recessed) |
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| Size difference clearly illustrated with a rivet in the holes. Dimpled skin hole shows a small ring of exposed aluminum around the rivet. |
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| For quicker adjustment, and verification of current setting, I marked my countersink cage for flush and recessed hole depths |
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| All holes countersunk on the right spar bottom flange |
I did switch out the #40 countersink cutter to a new one after having finished countersinking the flange holes on the left spar and those on the bottom right spar flange. I could feel that the original countersink bit was not cutting as easily as it had been (not surprising after having countersunk a few thousand holes), and the new one cuts noticeably easier. I did, however, have to reset my countersink cage again to the correct depth.
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| All holes countersunk on the right spar top flange |
After all holes were countersunk, I deburred every hole along the inside of the spar flanges using the deburring tool with extension to ensure the edges were clean.
Build Hints
- Always tape off any crevices where metal chips could fall in while drilling. These can be hard to remove even with a chip chaser tool.
- Keep a spare countersink bit on hand to avoid delays if the countersink bit in use dulls or breaks.
Time Taken: 12.2 hours
Dates: July 16 - July 27 2023
Wing Main Spar Total Time: 23.2 hours
RV-10 Build Total Time: 434.4 hours
Priming Total Time: 44.3 hours (not included in build time totals)