Joining Bulkhead F-404 to Rib F-415

The rivets which were used to construct Bulkhead F-404 appeared to be interfering with the attaching of Rib F-415A. Accordingly, I drilled out 3 rivets, one on the bottom (top on jig) and two along the bottom (top on jig) of the aft facing web. This allowed the rib to rest flush against the U-shaped piece surrounding the Wing Spar opening.

Once the rib was in place the critical measurement between the forward wing spar and the aft wing spar was within 1/8". With minor shaving of the forward part of F-415 rib, I was able to get the measurement on both side spot on.

In a discussion on Vansairforce.net I was encouraged by an experienced builder to not focus too much on ribs and bottom assembly until all the longerons and bulkheads were in place. While I believe this to be good advice, the criticality of the measure (as noted in the preview plan book) between the forward and aft wing spars leads me to believe that F-415 should be considered as part of that process.

Without having confidence in the measurements along F-450 (between Bulkhead F-401 and Bulkhead F-404), and subsequently F-415A there is no way that I can see to get bulkhead F-407 in the correct placement. Starting from the front  and working toward the back, I am able to verify both the overall distances at each bulkhead and distances between.

Bulkhead F-407 seems critical to the correct attachement of the mid and aft body longerons.

My next challenge is to figure out why I am about 1/2" too long at the 69 1/8" measuring point (DWG-26) at bulkhead F-407. There are only ribs between bulkhead F-406 (aft wing spar) and bulkhead F-407, so the error must be in the aft of those two ribs. It seems like I remember the previous builder, who up to this point has demostrated an uncanny degree of accuracy in the building of bulkheads, etc., mentioned that rib F-415B needed to be reworked just a bit. The angle at the forward end of F-415B seems a bit off and I believe when reworked will reduce the distance to the junction of bulkhead F-407.

Once that position is acheived then the aft and mid-point longerons can be clamped in position. At this point, I just have the longerons clamped in the approximate position ready for a more accurate placement.

After spending a little more time on F-415A & F-415B, I have concluded that they just needed to be tweaked a little bit and clamped. Once I squeezed everything together I found the measurement at bulkhead F-407 to be exactly correct.

However, it is a little difficult to put the squeeze on these pieces made out of sheet aluminum. So I have decided to place the 3/4" X 3/4" X .125 aluminum angles along the four rib pieces that are pictured. That will give me a solid structure to clamp and squeeze together and prevent movement as I begin to drill and clecoe all of these junction points.

One fringe benefit of getting more of the longerons in place is that it actually is beginning to look like a fuselage!

If you have any insights or can see I am about to make a big mistake - please post a comment.