Fuselage

There sure are a lot of holes on this airplane. I got started in mid afternoon, after did a bit of kayaking in the morning. Pretty much went straight to work on the countersinking, since I’d marked up everything already. First I worked on all the #30 holes, which took an hour or so, followed by the handful of #19 screw holes (mostly in the gear tower cover plates). Then it was on to the bulk of the work, the bazillion #40 holes in all the longerons. I got through everything except for perhaps the most extensive job – all the #40 holes on the side webs of the main longerons. I should be able to knock all those out in a long work session one evening this week. Then it’ll be on to a lot of deburring and dimpling. I don’t think I really have any extensive fab work to worry about before the fuselage starts going back together…

Here are some fairly boring photos. The first is a blurry pile of metal shavings. The second is, you guessed it, countersunk holes. Exciting, eh?

Actually, countersinking is done for the time being. Tonight I took care of all the rivet holes in the side webs of both upper longerons. Not especially challenging, just tedious. After that was done, I decided to do some more hole deburring before calling it a night. Among the parts I deburred were the tailcone bulkheads. I was a little disappointed to find a few spots with elongated rivet holes. The first one I found wasn’t really bad, and can probably just be fixed with a NAS 1097 oversize rivet, but the second spot is much worse:

That’s at one of the rounded bottom corners of the forward most bulkhead. I assume that all the difficulty I had getting everything lined up properly here contributed to this issue. I can’t remember for sure, but I may have been more conservative with clecos than I should have been. Fortunately, fixing this spot should be easy – I momentarily considered replacing the entire bulkhead, but that’s overkill. Instead, I should be able to just cut off this flange and rivet a replacement to the bulkhead web. It’ll be under the fuselage floor anyway, out of sight. Still kind of disappointing, though.

Tonight I set out to repair the bulkhead flange where I found elongated holes the other night. I decided to simply fabricate a new flange unit and rivet it to the bulkhead web. Not excessively complicated, but a little tedious making sure everything fit properly.

Here’s the splice piece after bending and trimming it to fit:

Then it was time to take a really deep breath and cut off the damaged flange. OK, not that deep of a breath, since this portion was ruined anyway, but still…

To fit the repair piece, I clecoed the bulkhead to the aft bottom skin, clamped the splice into place, and drilled it to the bulkhead flange. After deburring all the holes, I riveted it to the bulkhead:

Then it was just a matter of clecoing the bulkhead in place again and drilling the two #40 holes in the flange, using the skin as a guide.

I also went ahead and deburred the aft bottom skin while I had it down from its storage spot. Next up is – I think – more deburring. Quite a bit of it as a mater of fact. I’ve been trying to knock out the deburring a little at a time with other work sessions, but now I think I’ll just have to buckle down and spend a day doing it. We shall see.

Tonight I pulled apart the mid side skin assemblies and deburred the skins and the bulkhead/armrest parts. That’s it. Exciting, eh?

Got back to work deburring tonight. I took care of the last of the parts from the seat pan, then moved on to working on the forward cabin assembly. It took quite  a while to finish that, since not only are there lots of holes, many of them are located in tight spots and require some creativity to get to. It should be lots of fun to rivet in some of these areas.

I need to check all the loose parts, but I think all I have left to deburr are the aft side skins and a couple of bulkhead assemblies from the tail. Then I get to do a bunch of dimpling, followed by a bunch of priming and pairing, but then I can start assembling stuff…I think…

Finally…a weekend without lots of other stuff to do. Last weekend my brother was in town and I helped him with some work on his car. The previous weekend was entirely spent doing suspension work on my car. Before that…well, I guess I was just lazy. We did actually have an afternoon engagement today, but for once I committed to doing some work before and after.

I started out with another bit of cleanup – there were still tools and other junk lying around from the car work weekends. Then I got to work deburring. The only large pieces remaining were the forward and aft side skins, the latter of which are rather large and cumbersome. I also had the two aft most bulkheads and the heavy skin that attaches to them, and the tail spring weldment. I also enlarged a hole in the bottom of the aft bottom skin; this will provide access to the tail spring attach bolt once the plane is together:

On each forward side skin, there were two tabs that needed to be removed. This is another one of those procedures that seems random to me – the instructions refer to these as “indexing tabs,” but I don’t recall using them index anything. I presume this is a leftover bit from the early RV-8 kits that weren’t prepunched or something like that. Anyway, I used a straight edge to lay out cut lines parallel to the lower edge of the skin:

Then I made rough cuts with a cutoff wheel, and finished with a series of files:

And I’m pretty sure that I now have everything deburred, a task I can jokingly say took me three months to do. Next up, I have lots of dimpling to do, as well as priming certain parts. I’m going to try and paint all the interior parts before final assembly, to avoid the obnoxiousness of trying to spray paint inside the confined space of the fuselage. We’ll see how that works, I guess…

Not a lot to report today. Basically I dimpled everything except for the skins, which will require use of the C-frame. For the most part it was uneventful, except for some spots on the forward floor. On each outboard edge, where the lower longeron attaches, there are five spots that require flush rivets for clearance. One of these is at the aft end, which is easy to get to. The other four are right up next to the gear towers, presumably to provide a flush surface for the gear mounts. These are annoying to get to, because the gear tower and the gear weldment make access difficult.

There’s no way to get a squeezer onto the holes to dimple. There’s no room to use my vise-grip dimpler. The skin is way too thick for the pop-rivet dimple tool to work. I eventually worked out a method using the pop rivet dimples dies and a squeezer with a no-hole yoke (to get into the tight area). The resulting dimples aren’t great, but are acceptable. This is a spot where I would have been better served to depart from the instructions and countersink the flow instead of dimpling. The material is plenty thick for countersinking, and in fact the holes at the aft end of the floor, where it mates with the center section bulkheads, are countersunk for flush rivets. Unfortunately, in the case of these holes, I already countersunk the lower longerons at those locations, so my choices were to either dimple the floor or replace the longerons. Oh well.

Next up, I get to roll some skin edges and then do a lot of dimpling with the C-frame, followed by priming. Which reminds me, I need to restock on primer. Hopefully the weather next weekend is good, so I can get some priming done. It should be especially fun to clean and prep the 16’ longerons…

Moved on to dimpling larger parts tonight. Before dimpling any of the skins, I rolled the overlapping edges on the forward and mid side skins, as well as the aft edge of the seat rib/floor assembly. The aft side skins and forward aft lower skin also need to be rolled, but they’re not easily accessible, and so I won’t roll them until I get them out for dimpling. I may even go so far as to hold off dimpling those pieces until I’m almost ready to assemble them; I’ll have to read forward and see how the assembly procedure goes to see if that’s viable. Mainly I’m concerned about the aft side skins; I’ve been storing them side-by side, slid behind some stuff on one wall. I figure they might be more prone to damage and scratching if I try to slide them in there after dimpling.

Anyway, next I moved on to dimpling the forward side skins. These are fairly complex; they include #6 flush screw holes, and -3 and -4 flush rivets, along with some universal-head 04 rivets. So I took care to mark all the location that weren’t getting dimpled, and for good measure I worked my way from large (screw) to small (-3 rivet) holes, just to prevent the possibility of me dimpling a hole with the wrong die.

Hey look, dimples!

Hopefully this week I can finish dimpling and other prep tasks – one of the looming ones is to add notches in the main longerons to accommodate the vertical bars that the horizontal stab will attach to, and to trim the longerons to length. Obviously I don’t want to foul anything up there…

I’d like to be able to concentrate on priming parts this weekend so I can then move on to some final assembly work. I also need to think about ordering a fuel pump and filter assembly, so I can install those while the forward fuselage is still open and access is good.

Actually, that should be it for dimpling for the time being. After reading forward in the instructions last night, I decided that my plan to delay dimpling the aft side and bottom skins was a good one – so that’s what I’m going to do. Tonight I just dimpled the mid side skins, and got Josie to come out and help me dimple the forward edge of the bottom skins on the seat rib assembly. That just leaves notching and trimming the main longerons, and then I get to do a whole bunch of priming before I get to remember how to rivet again.

So my goal for tonight was to get the upper longerons trimmed and notched at the aft end. This seemed like a fairly simple thing, but it was actually a bit tedious, mainly due to me being reeaaallly careful to not damage or otherwise ruin the longerons.

I’d previously marked the notch locations and the aft trim point, but after examining the plans for the aft trim, I realized the cut was a bit more complex than I’d thought. Instead of simply cutting the angle to a certain length, I have to cut the upper side of the angle back to allow for the vertical stab spar to nest against the aft most bulkhead, while the outboard sides protrude aft a bit further, to the aft end of the aft side skins. At least I think that’s how far back they’re supposed to go; the plans weren’t especially clear here. They show the outboard edges protruding past the bulkhead flanges, so I figure the end of the skin is a logical trim point.

Anyway, I wiped off my previous cut marks and clecoed the aft most bulkhead into place so I could draw new cut lines:

The cut line for the upper side is visible here; I measured the aft side skins to figure out where to mark the outboard cut lines. Next, I marked locations to drill holes for the corners of the cuts, to make nice rounded inside edges. I drilled the holes on the drill press, after recruiting Josie to come out and hole the other end of each longeron (they’re 16’ long, after all). Then I roughed out the cuts using a hacksaw, before finishing with files to smooth everything out.

Here are the longerons with both aft bulkheads clecoed in place, along with the horizontal stab attach bars:

A detail view of one of the notches to accommodate the stab attach bars:

And a detail view of the trimmed aft ends:

While I was working on this stuff, I found a number of rivet holes in the longerons that either weren’t deburred at all or were just done badly. So after finishing up the trimming and notching, I inspected both longerons and touched up holes as necessary. This should put me in good shape to get some priming done this weekend – and the weather looks great to boot.