CHAPTER 39 - Adding the Baggage Sides and F629
The baggage compartment side ribs seem to give everyone some trouble, and I was no exception. I temporarily clamped my F623s in place while debating with myself how I wanted to make the forward attachment. While I was at it, I decided to see how the F624 should fit. Well, with the web at the apex of the 623 (skin side flange facing forward) it was about 3/4" too far aft! At least given the dimensions on plans sheet 32, but sheet 33 clearly showed the web at the apex (no dimensions given, though). A call to Van's the next morning gave me Ken, who was also somewhat puzzled but said that no one else had mentioned a problem. However, the most important part of positioning this piece is that its inner flange had to support the joint between the F649 and F650 baggage sides.
Armed with this fresh perspective, I tackled the problem again. With my F649 and F650 loosely in place, I tried the F624 again. This was worse! Now the web would be about 1 1/4" forward of the F623 apex. Wait a minute! The inner flange should face forward and the outer flange should face aft! Finally everything worked out except that the web of F624 was 3/4" forward of the F623 apex. Clearly plans sheet 33 was in error. It was the aft facing flange of F624 that should be at the apex, and I was only 1/8" off now. Since I had decided to make a forward butt joint for F623 (which was slightly long to begin with, it was simple to take an extra 1/8" off the front, moving the apex forward to meet the F624 flange. Now with a definite picture in mind, I could proceed.
First the F622 was fitted. The flange had to be relieved slightly at the rear to fit over the J-stringer. You'll also notice in the photo that the particle board is no longer attached to the F606 bulkhead; it is merely resting against the jig to support the upper part of the bulkhead. It had to be taken down because it would interfere with the fit of the F629.
The next photo shows the front attachment of the F622. You can see where the flange had to be cut away to fit over the F605 structure and a tab was fabricated from angle to attach it to F605. The following photo shows the F623 attachment to F605, with approximately 3/4" cut off the front and a tab fabricated to create a flush butt joint. The rear of the F623 is simply clamped in place to the F606 and bottom J-stringer for now; they will all be tied together when the skins are drilled in place.
Fitting the F624 was an iterative process. First a measurement was taken from the main longeron to the F623, using straightedges to make sure the F623 would be flush with the bottom skin. The F624 side flanges were trimmed, taking into account clearance for the flanges of F623 and the longeron, then the remaining web was bent to form the top and bottom attachment. F622 was marked where the web of F624 would pass and the slot was cut, taking care to cut away the skin-side flange where the F624 flange would cross. Then the F624 was marked where the F622 web would cross and the slot was made. I deviated from the plans where they showed using a small flush rivet to tie the two inner flanges together; I wanted the junction to be smooth where the inside skins meet. What I did was to relieve the F624 flange on the inside to make room for the F622 flange. If necessary, while fitting the inner skins, I can make a small tab to secure the junction. Otherwise, I expect that the skins themselves will hold everything in place.
After most of a day trying to get this all in place, I felt I had figured it all out. So I tackled the other side with much confidence and quickly had the F623 and F622 in place. I got the F624 trimmed and the tabs bent at top and bottom and the slot made in F622. Then I cut the slot in F624... on the wrong side! Too much confidence. I ordered a replacement from Van's and went on with the F629. The replacement arrived a couple of days later and took about fifteen minutes to get fitted. This time I didn't make a mistake.
The F629 is fairly straightforward, but the F630 was a bit of a problem. The blank is 3" wide, matching a drawing on sheet 47. There are some top and side views of it, but I finally located the face view of the assembly on sheet 33, where it appears to still be the original 2 3/4" wide. Guessing that the extra 1/4" was because the rivets for F619 would run right down the edge of it, I positioned it to be flush with F629 as shown on the plans. You can see from the photos that the other edge is now flush with the F619, but it will overhang the F628 flange by 1/4" or so. Since this will be behind the baggage compartment wall, I can probably ignore it, though I may decide to trim it flush down to the F606 bulkhead. Anyway, I attached it to the F606 bulkhead and used that as a drilling guide, including the cutout for the elevator pushrod. In the first photo of the assembly, I have marked where the F629 will also have to be trimmed for the cutout (why didn't Van make the flange run the other way?) You can also see arrows pointing out two awkwardly placed holes - the upper one in the photo will be very close to the F628 web (the black vertical line), while the lower one will be near the edge of the F628 flange. The second photo shows the other side of the arrangement. For reference, the red mark on the bulkhead flange is the centerpoint, the blue marks are at 1" (F628 and F629 web distance), and the maroon marks are at 2" (F619 web distance). The maroon line on the F629 angle denotes the clearance required for the bellcrank bearing. The attachment of the F629 itself is pretty much like all the other bottom ribs; I used a straight edge and cleco sidegrips to ensure the bottom flange was flush with the bulkhead flanges.
That's it for the basic fuselage structure. The parts are being taken off the jig and cleaned up, holes countersunk or dimpled where appropriate, and taken to the painter for priming. Since this is springtime and many aircraft are being annualled or having other end-of-winter work performed, it may take awhile before I get them back and start riveting them together. Hopefully, it won't be too long before I start the skinning process.
A piece of good news... you may have noticed a definite quality improvement in the photos on this page. I finally made the jump from a so-so film camera to a good digital. This means better pictures and possibly more frequent site updates. I don't expect to do a daily log like Dan Checkoway (I don't work on my project that often), but I'm hoping to update at least a couple of times a month. Keep watching and we'll see you again soon.