***GOTCHA ALERT*** - This post contains a few items that confused me and required careful read-ahead in the plans, as well as one particularly nasty "gotcha" that appears to have tripped up more than one builder, including myself. The latter is also mentioned in the last entry on Tim Olson's site under "Fuse Tips" (as well as a few other build blogs) but I never saw them until it was too late.
Continued with the deburring tasks today, this time starting with the four Fwd- and Mid-Fuse R/L skins. It took about 4-5 hours to complete all four pieces, which involved tasks including deburring, edge-finishing, scuffing, and dimpling. Then it was time to see what was left to do. I've divided the finish-work into three categories: (1) loose metal parts, (2) skins, and (3) partially-riveted parts already installed in the fuselage structure. At this point, #2 is done and #1 is almost done except for countersinking and a small number of parts to dimple. Then, the focus will shift back to the fuselage for #3, for parts such as the bulkheads and center section side plate that need to be countersunk. I have to admit, countersinking is one of my less-favorite tasks, especially when there is so much of it do to. I guess I don't really *hate* it, but it does make a giant mess of shavings and doing the same thing eleventy-billion times gets a bit tedious.
For the longerons and fuse channels, I set up the microstop and #40 countersink on the drill press and went to town. I had to clamp a 2x4 to the drill press table for the longerons to glide over so that they could be fed through in the proper orientation:
The longeron countersinking process
Otherwise it actually went pretty well, and after a while I had a neat stack of countersunk metal parts, and a pile of metal shavings reminiscent of the pistachio shell scene in The Naked Gun.
One last thing I did before focusing back on the fuselage structure itself was to attempt to solve two mysteries I had running in the back of my mind (little did I know I was about to uncover a third mystery, too).
The first was what to do with the five 3/32" holes directly above the step in the side skin:
The 5 mystery holes above the step in the F-1070 side skin
The plans make no mention of what these holes are for, and there are no drill/dimple/rivet callouts, and no parts attach here at this stage in the plans. I had to dig pretty deep into the plans to discover that the F-1023B-L/R Baggage Floor Angles will attach here as shown in Section 33-2 Step 8 (and Fig. 4). That step mentions that these pieces need to be dimpled, presumably to match the side skins. One problem, the side skins had never been drilled or dimpled here yet! If I hadn't become curious, these holes would have remained untouched and I would have probably ended up in trouble later on. So, I clecoed these F-1023B angles to the skins, match-drilled, deburred, and dimpled them so that things go well in section 33. If you ask me, the steps between these processes should be presented/ordered a bit differently, and there is no reason I can think of that they shouldn't have you take care of this now. Dodged a bullet here for sure.
The second mystery I wanted to solve was the three nutplate holes along the upper flange of each of the F-1040 fuselage channels. The plans make no mention about installing nutplates here (or at least I couldn't find anything), but all the way in Section 35-7 Figure 2 they reveal what they are used for-- retaining the F-1042G wire cover. Looks like they specify a #8 screw, so I'll have to final-drill the nutplate holes #40 and #19, and countersink the #40 holes flush, and then install K-1000-08 nutplates into place. This is just another example of "missing" detail in the plans that I guess they just expect you to know to do it. This could all be done later, except one #40 hole for the aft-most nutplate is awfully close to a gusset attach point, and I think it would be pretty tricky getting a countersink in there at a later time. Better to do it now, I think. (EDIT: This turned out to be a "known" gotcha originally submitted by Chris Johnston and can be found on Tim Olson's GOTCHA page here... glad we ended up at the same conclusion!)
With all that behind us, we put the fuselage structure back into center stage and began countersinking the center section side plates. Before too long, I discovered another issue, this one being a real doozy. The F-1015A Outboard Seat Rib:
The F-1015A-L Outboard Seat Rib
I just talked with a friend and fellow builder Jon, who's building an RV-10 of his own and is pretty much at the exact same stage as we are, to double-check on something. A subsequent google search revealed that Jon and I appear to be the latest two victims of a nasty oversight in the plans. The #40 holes in the outboard face (or "web") of these ribs need to be dimpled. The plans *do* say to do this for the F-1018 ribs, which are part of the next section to the rear (partially visible at the right edge of the photo above). They make zero mention of doing this to the F-1015A ribs, however.
Additionally, there are some #30 holes that get match-drilled from the side skins into the F-1018 ribs, and the three aft-most of these holes need to be dimpled for a CS4-4 rivet according to Page 29-15 Figure 1. It would probably be best to do that match-drilling now in order to get the dimpling out of the way, because it will be very difficult later on.
In summary, here's what I believe really should happen during Section 26-5, somewhere between steps 1-6:
- For the F-1015A-L/R ribs, dimple all of the #40 holes in the web of the piece, excluding the forward-most row that tucks behind the F-1004D bulkhead. Leave the #30 holes alone (careful, they crisscross!)
- Dimple the flanges of the F-1015B-L/R Intercostals to match the dimples you made in the previous step.
- When completing Step 6 on 26-5, the dimple callouts for the #40 holes in the F-1018-L/R are correct; however you should *also* dimple the three aft-most #30 holes that can be seen on the right side of the photo above. Are those holes not there yet? You'll want to fetch the fuse side skins and cleco this rib into place, and match-drill those #30 holes, then deburr and dimple the rib. Trust me, way easier to do now than when everything's all riveted together. As a final clarification on the #30 holes, none should be dimpled EXCEPT for these three. Refer to callouts on Page 29-15 Figure 1.
In order to dimple these holes now, I took a small piece of steel plate and drilled a 3/16" hole near the corner, to fit a female dimple die. Using my rivet gun and die attachment with male dimple die, I carefully created dimples in each location. The dimples aren't the prettiest, but they should be perfectly adequate for the substructure here and I think we're out of the woods now with this particular gotcha... Whew!
Next on the agenda: Finish countersinking and dimpling the fuselage structure for the side skins, and prime all the loose parts and skins. Oshkosh officially kicks off in one week (although we'll be there even sooner than that)... yay!