[Insert Clever Title Here]

Usually as I'm working on the plane, there's a background process running in my head trying to come up with a clever title for the ensuing post. Nothing really came to me this time. I'm still working on the lower half of the firewall, but I'm very nearly done with it. Unfortunately, I need another little dollop of firewall sealant. It's a shame that I had to throw away about 200 times the amount I am now in need of. This time I'll order one of the little one ounce bottles.

At the end of the last session, I had just riveted on the bottom skin. The next step was to rivet in the cooler stiffener, which was the part that gave me so much consternation as to whether holes that seemed like they ought to be countersunk but hadn't been called out in the plans as having countersinking required truly ought to be countersunk. As a reminder, I threw caution to the wind and countersunk them. The fun with this part was not quite over; it had three different rivet types required to get it installed.

Once that was done, a half dozen nutplates were clecoed onto the inside surface of the bottom skin. That was one of those reach-around jobs where it's a chore just to get the things in place.

On the plus side, the reach-around jobs nearly always end up using blind rivets.

With the latest batch of nutplates finally settled into their final resting place, we moved on to installing Cowl Attach Plates. These are nothing more than flat pieces of aluminum that host a collection of (see if you can guess.....) nutplates. There's a little twist here, though, in that the plates can't be flush with the edge of the skin. They have to be recessed just a little bit up into what will be the engine compartment so that the skin of the cowl will be flush with the skin of the fuselage. This spacing is accomplished with the highly technical expedient of... spacers. 

The spacers are simply thin rectangles of thin aluminum. They are to be cut from "AS3-020," whatever that is. It took awhile to find because I thought that it would be a smallish piece of metal shipped in one of the brown paper bags. There was such a piece of metal, as it turns out, but there was only one rather then the two required. I finally found the strip of material over on the parts shelf.

The fabrication is quite simple: measure out and cut a couple of 1 1/2" pieces and round the corners.

The drawing showing how it all fits together is easy to follow.

The little spacer plates get placed inside the flange of the firewall:

The part that will hold the nutplates only has one hole already drilled in it. You use one cleco through that hole and a clamp on the other side to hold the assembly in place. The parts are flat but the flange has a little curvature, so there's a gap:

I took it all apart again and bent a little curvature into the spacer and the Cowl Attach Plate, then clamped and clecoed it back into place.

Once clamped in place, two more holes are match drilled up through the flange and through the spacer and the Cowl Attach Plate. When it's all still attached would be a good time to go ahead and machine countersink the rivet holes for the nutplates. That will keep you from doing what I did, which is to countersink the wrong side of the attach plates. I thought I was doomed, but it turns out that even though the plates were match drilled in different locations from each other, they were still interchangeable side to side. The holes matched up every bit as well as every other hole I've match drilled, which is to say they were approximately aligned.

That done, the last step on the page called for the use of a Uni-Bit to enlarge the hole the gascolator fuel line (I think) will pass through the firewall to 9/16". I got a kick out of this: "To keep the hole centered draw a cross hair out from the hole for reference." Why did I think that was funny? Because I knew that there was absolutely no way a cross hair was going to keep that hole centered. All it was going to do was graphically display just how off center my hole was!

I started with regular bits and worked my way up in size. I was able to keep the hole pretty centered.

When I got to where I needed the Uni-Bit, I marked the step at which I wanted to stop. Uni-Bits have a way of just keeping on going well after the spot where you needed to stop.

I then proceeded to use the Uni-Bit to get the hole off-center.

I'll burn that bridge when I get to it.

The next step was band saw work and I usually enjoy that. It's kind of like going someplace warm on a winter vacation and enhancing the enjoyment of the temperate weather by comparing it to the awful conditions back home. I like to use the band saw because I remember what a pain the hacksaw was. 

In this case, it was the simple separation of four Support Channels. These will sit on the shelf that attaches the lower firewall to the upper firewall. They will support the rudder pedals, unless I miss my guess. The plans call fro the aft two holes of each to be dimpled, but fail to give any written direction as to which end is the aft. Placing them on the shelf shows the aft holes.

That's not the side that gets dimpled, though. You have to turn it over.

Some matching holes get dimpled in the firewall shelf and, as it turns out, so do some non-matching holes. I got lost with the dimpler and put dimples in four holes that didn't need them. It's not hard to un-dimple, but it was an indication that my head was no longer fully engaged in the process. Rather than press on and risk a much more permanent mistake, I just clecoed everything in where I think it belongs. I'll look at it again when I'm fresher to make sure that I have all of the nutplates in the right places. 

Besides which, I need some fuel sealant to run between the shelf and the lower firewall before I can rivet it together.

That "Substantial Penalty for Early Withdrawal"

**** UPDATE UPDATE UPDATE ****

I'm back from the future to tell you something important:

RUN to the phone and call Van's. Place an order for:

F-12125 OVER RUDDER WIREWAY
F-12125C OVER RUDDER WIREWAY BRACKET
FOAM 1/16x1/4 V1110 (4" length, if they ask)
MS35206-248 PANHEAD BOLT
NAS1149FN832P

Then go download Page 31-13 from the Archive Pages on VansAircraft.com. Use that page to install the wireway. You won't be able to install the bracket until you do the rudder pedals, but those are coming soon. You will be happy to have this done when you get to page 31-13, trust me.

Don't believe me? Then take a look at this.

**** UPDATE UPDATE UPDATE ****

You know that substantial penalty for early withdrawal warning you always hear tacked on in the verbal fine print of financial commercials? Well, that's not the only place you'll pay such a penalty.

This morning I finished match drilling and riveting the engine mount brackets to the tunnel walls. The plans have become somewhat cagey with any indication as to which way the rivets should go through the holes. I figure if Van's doesn't care, well, then neither do I. I decide based on the following criteria:

  - Which way is easiest to get at?
  - Which way will hide the wart-like shop head from sight?

If those both happen to coincide, it's an easy decision. Such was the case with the engine mounts. Not only was it easier to rivet through the tunnel sides, it also put the ugly part of the rivets inside the tunnel where they won't be visible.

I then clecoed the tunnel walls, lower firewall, and corner pieces together prior to riveting. 

This was going to be a large enough riveting job to warrant a trip to the hangar. I had to go to Lowe's anyway to pick up a roll of replacement screen (follow that link - it's worth it!) to fix the back porch sliding door anyway, so it was no extra effort to stop by at the hangar on the way. It's something like ten times faster to rivet with the air rivet puller and a hundredth the effort, too, so it was a very simple decision.

What I failed to account for was coffee-speed. Having just finished my morning quart, my brain was firing on all eleven cylinders (most brains only go to ten). That's okay, for the most part, but it can cause problems when attempting to synchronize with the more physical appendages. For example, my hands. My hands, unable to keep up with the blazing speed of my caffeine-addled/enhanced thoughts, tend to either fall behind or rush ahead in hopes of keeping up. This is how I ended up pulling the air riveter away from the rivet in mid-stroke of the internal workings of the rivet puller. I knew something was wrong when I didn't hear the normal "bang" of the rivet mandrel breaking loose and the rivet being set. The gaping hole in the middle of the rivet head didn't look right either. I was sure something had gone horribly awry when the mandrel didn't pop out the front of the rivet puller.

What had happened was that the mandrel didn't break. It actually just pulled through the rivet (without actually setting it - it needed to be drilled out) and jammed in the rivet gun. It wouldn't come out the front because it was still clamped into the inner workings of the rivet gun, and it couldn't come out back either for that reason and because it still had the bead on its end.

I had to disassemble the rivet gun to un-jam it. That wasn't very hard to figure out, although it was something that I was nervous about. You never know if little parts will fall out or a spring will launch itself when the restraining parts have been removed.

It did both.

All told, it took about twenty minutes to get it all put back together and working, Now, you'd think that having learned my lesson about letting my hyperactive brain set the pace, I'd be careful to not let that happen again. As much as I appreciate your confidence in me and my ability to learn a lesson, I have to disappoint you. It wasn't a dozen rivets later before I did the exact same thing.

The last step in the riveting job was to rivet the lower fuselage to the tunnel side flanges. This one was a little tricky. While it appeared that riveting through the firewall and into the tunnel flanges would satisfy both of the decision criteria detailed above, there was the matter of a collection of holes in the front of the firewall that had met whatever arcane criteria is used by Van's to decide whether or not to use their only-when-we-feel-like-it dimpling tool. If those holes needed to be dimpled for flush rivets, why don't the rest of them? But if I riveted from the other direction, they'd be even less flush - the wart heads would be out there for all to see.

I riveted through the firewall. I figure those flush rivets will sit under another part (say, the engine count?) and therefor need to be flush while the surrounding rivets do not.

Sink, Counter-Sink

The idea of starting a new section of the fuselage seemed like it would bring with it some kind of change. New parts, new and exciting stuff to do. Well, not so much. The first steps of Section 22 are countersinking holes and riveting nutplates into place. And not just a little countersinking, either. Lot's and lot's of countersinking!

And that was just fine with me. I only had a brief amount of time available to work on the plane tonight and countersinking a passel of holes was just the right size job. It started out kind of tricky - step 1 offered the not so rare opportunity to easily dimple the wrong side of the part. The dimpling was only two holes, just enough to support one single, lonely nutplate on the lower firewall. I took a great deal of time making sure that I got the dimples on the correct side of the firewall. Once I had it figured out, I was taking no chances on forgetting.

Step 2 was much easier, at first. Both the "sloped upper flanges of the tunnel ribs" and the "nutplate attach holes in the fwd fuse skin" were easy to find. It was the last part of step two that caused me so much trouble. Here, read it for yourself:

The sentence in question (or, more aptly, the sentence that caused the question) says, "Machine countersink the upper most hole in the F-1288 Cooler Stiffener." Well and good, that, but not nearly enough. You see, the hole in that part is being countersunk so that the part will sit flush against the firewall when it is riveted in place. The holes in the firewall underneath the part are already dimpled with Van's now-you-see-it-now-you-don't dimpling machine. They only pull it out on rare occasions; pedestrian tasks such as dimpling are nearly always left to yours truly. Anyway, the problem is that they did not dimple only one hole under the Cooler Stiffener. They dimpled, as even the most casual inspection will show, no less than seven holes under the Cooler Stiffener. Countersinking just one of the seven seemed like it simply would not be sufficient to allow the Stiffener to snug down flush against the firewall. It's always possible that Van's has posted a revision to a page, but a check of their web site showed nothing newer than Revision 2, the very version I was looking at.

This, in a word, was a dilemma.

I looked ahead to see if the countersinking was addressed later. It was not. In fact, in just a few more steps the stiffener gets riveted into place.

Usually the best thing to do when faced with a situation like this is to not do anything you weren't told to do. In this case, though, I can't believe that those holes weren't intended to be countersunk. I went ahead and did them.

The rest of the countersinking was easy.

Step 4 wants the Engine Mount Brackets to be clecoed into place and match drilled. I went ahead and clecoed them in, but the match drilling will have to wait. Thursday is my tiredest day of the week and I had reached my limit.