Fuse Side Skins 29-12-3 to 29-14-8, SDS Fuel Return
The next somewhat challenging task in this section is to match drill the holes from the fuse channels into the firewall brackets. The difficulty comes from the firewall bracket weldments not sitting in quite the correct locations next to the fuse channel flanges and web, and the risk of having hole edge distance issues if the weldments are not first aligned properly.
Prior to starting any drilling, I first marked the center line of each fuse channel web and the center of each firewall bracket weldment that lays along it. That would provide a good reference to know when the weldments were correctly centered in the web.
Starting with the upper firewall brackets, and the weldments that lie along the upper fuse channel web, I found that a scrap piece of 1/8" angle aligned the weldment perfectly with the centerline drawn on the fuse channel web. Clamping the weldment in position, I carefully match drilled and clecoed each hole.
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| 1/8" angle holding the web weldment in the correct location, secured with a cleco clamp |
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| Scrap piece of oak used to keep the weldment against the fuse channel web while drilling |
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| Due to the size of the F-1001B flange over the top of the upper firewall brackets and fuse channels, I had to make sure the clamps were secure with no chance of slipping |
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| First set of holes match drilled into the upper firewall bracket |
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| No issues with hole edge distance, and the bracket weldment lay flat and centered within the fuse channel web |
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| Same clamping and drilling process to match drill holes into the left upper firewall bracket |
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| Once again, no issues with hole edge distance |
The same process was repeated for the lower firewall brackets.
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| 1/8" angle again used to push the bracket weldment to center, but this time pushing the weldment down instead of up |
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| Weldment clamped and ready for match drilling. Here I used a mirror to be able to verify that nothing slipped while drilling |
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| Left lower firewall bracket drilled and clecoed |
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| Holes came out great |
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| Same repeated for the right lower firewall bracket |
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| Once again holes came out well with zero edge distance issues |
Next, I fitted the fuselage skins to make sure that all holes lined up with the match drilled holes, and to match drill a few remaining holes elsewhere in the fuselage.
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| Left fwd fuse skin fit well after match drilling the firewall brackets... |
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| ...as did the right fwd fuse skin |
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| Left fuse skins from inside fuselage. No oil canning or warping seen after fitting. |
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| Also no issues seen with the right fuse skin fitting |
While the skins were attached, I match drilled the aft most two holes from the F-1001J gussets into the longerons using a right angle drill. I decided to match drill the remaining two holes from the gussets after removing the skins as it would be easier to hold the drill in correct alignment.
I then match drilled a few remaining holes around the fuselage.
Returning to the firewall brackets, it was time to start match drilling holes into the lower and upper weldments of each bracket. Weldment alignment prior to drilling is equally critical here as it was previously to ensure that correct edge distance is maintained for each match drilled hole.
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| Match drilling the two aft holes from the F-1001J gussets into the longerons with the skins attached to set the correct position of the longeron on the gusset |
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| There was one hole in the skin that did not have a matching hole in F-1018 outboard rear seat rib, so I match drilled that one on each side. The rivet diagrams in the plans indicate that there will be rivets in those holes |
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| I also match drilled the single hole at the forward end of each mid cabin deck into the longeron. These holes were not present in the bending template |
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| The hole in the lower tab of the F-01002 left and right forward fuselage bulkheads was also match drilled into the top flange of the F-1041 lower fuse channels |
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| With the skins removed, I completed drilling of the two forward holes of the F-1001J gussets into the longerons, clecoing as I went |
Returning to the firewall brackets, it was time to start match drilling holes into the lower and upper weldments of each bracket. Weldment alignment prior to drilling is equally critical here as it was previously to ensure that correct edge distance is maintained for each match drilled hole.
I used a small steel plate to push each weldment inwards to the point where the aft end of the weldment lined up with the edge of the fuse channel flange. This worked well to ensure there was enough edge distance, and I used an additional cleco clamp to hold the weldment firmly against the fuse channel flange.
I then moved on to match drilling the weldments of the lower firewall brackets from the lower fuse channels. Prior to drilling these, I added some tape 3/16" in from the edge of the weldments to help verify edge distance as I was drilling.
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| Firewall bracket weldments pushed and clamped into position against the fuse channel flanges. Here I used an additional block of wood for clamping due to the extended flange of the F-1001B firewall angle |
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| Clecoes and clamps were moved around as needed to be able to match drill all holes from the fuse channel flanges into the firewall brackets |
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| I started match drilling from the aft end of each weldment, as the initial clecoes helped hold the weldments in place, after which I was able to remove the clamps |
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| Left side weldment match drilling in progress. Edge distance looked good. |
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| Right side match drilling complete. All flanges and bracket weldments were tight and all holes had more than enough edge distance (even though the forward holes tended to be slightly closer to the edge of the weldment than the aft holes) |
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| All holes were clecoed during match drilling to maintain alignment |
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| Left side upper fuse channel to firewall bracket match drilling also completed without issue |
I then moved on to match drilling the weldments of the lower firewall brackets from the lower fuse channels. Prior to drilling these, I added some tape 3/16" in from the edge of the weldments to help verify edge distance as I was drilling.
I also cut away the corner of the F-1001C lower channel flange (roughly a 3/4" x 3/4" triangle) to make it easier to match drill the lower forward most holes. The removal of the flange section was not absolutely necessary for drilling, but I also made sure that I had enough room to later buck these rivets.
Otherwise, match drilling the lower firewall bracket weldments was relatively straightforward other than having to get down low to drill from below.
Prior to moving on to countersinking and dimpling the understructure and skins, I had a few more drilling tasks to complete. The first involved drilling an additional hole in the forward fuselage skins for a fuel return line that is required for the SDS EFI system I will be installing.
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| Corner of F-1001C cut away using a cutoff wheel in the Dremel |
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| All left lower firewall bracket weldments match drilled and clecoed. Blue tape helped verify that minimum edge distances were met |
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| Left lower firewall bracket drilling complete |
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| Right lower firewall bracket drilling complete with good edge distance for all holes |
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| Happy to have completed all firewall bracket drilling without issue |
Prior to moving on to countersinking and dimpling the understructure and skins, I had a few more drilling tasks to complete. The first involved drilling an additional hole in the forward fuselage skins for a fuel return line that is required for the SDS EFI system I will be installing.
I followed the instructions provided by Aircraft Specialty Flightlines for SDS fuel line installation and marked the location of the fuel return line holes as specified. I then used a 9/16" punch to create a hole that fits the AN-833-6D fitting required there.
I also match drilled the remaining holes from the forward cabin floor panels into the upper flanges of the lower fuse channels, and deburred all drilled holes in the firewall brackets.
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| Return fuel line hole location marked, and initial #30 pilot hole drilled in the center |
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| Pilot hole upsized to 3/8" (using a step drill) to fit the stud of the punch |
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| Return fuel line hole punched to 9/16" |
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| After punching the return fuel line hole in the skin, I temporarily attached the skin to the fuselage, and transferred the hole location to the F-01004K center section side plate |
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| I then used the same 9/16" punch to create the fuel return line hole in the side plate (left side shown here) |
I also match drilled the remaining holes from the forward cabin floor panels into the upper flanges of the lower fuse channels, and deburred all drilled holes in the firewall brackets.
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| Holes match drilled from the floor panel into the lower fuse channel. The aft most hole barely meets edge distance requirements, but drawing a line at 3/16" from the edge of the lower fuse channel flange helped me verify (and adjust if necessary) edge distance prior to drilling |
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| Lower firewall bracket upper weldment with guide tape removed and all holes deburred |
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| Deburring the inside of the firewall bracket holes was made easier using an in/out debur tool |
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| Right side lower firewall bracket holes also deburred and are ready for riveting |
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| Fuel return line hole punched into right side center section side plate |
Fuse Side Skins Time Taken: 13.9 hours
Dates: August 23 2025 - August 31 2025
Fuse Side Skins Total Time: 48.7 hours
RV-10 Build Total Time: 1135.2 hours
Priming Total Time: 134.8 hours (not included in build time totals)