Obtaining the correct distance between wing spars

After adding F-415a/b ribs (R&L) to the fuselage I measured a slightly longer distance between the main wing sparand the rear wing spar attach point previously built. Inasmuch as this was a clear warning in the builders instructions I set out to discover why and correct it.

Turns out that the intersection of floor rib F-415a, bulkhead F406, and rib 415b was a bit sloppy. This added about 1/2" of distance that needed resolved. So I attempted the clamp the entire assembly and put the squeeze on it.

That did not work because F415a/b on boths sides began to buckle under the load. Without the 3/4 X 3/4 X .063 aluminum angles attached, there was no way to compress the whole After adding F-415a/b ribs (R&L) to the fuselage I measured a slightly longer distance between the main wing sparand the rear wing spar attach point previously built. Inasmuch as this was a clear warning in the builders instructions I set out to discover why and correct it.

Accordingly, I cut and fitted the four pieces of aluminum angle which were then drilled and clecoed onto the webbing and provided sufficient strength to compress the assembly and achive the 25 7/8" distance.

Your distance may be slightly different, but as mentioned in the builders manual - this distance must match the distance on the wing or you will be unable to mount the wings to the fuselage when the time comes. 

Once these strenghtened ribs were clamped to bulkhead F-406, it seemed apparent that ribs F-418 needed to be placed next. They determine the distance between bulkhead's F-407 and F-408.

Although one could as easily just use a simple measurements to place the bulkheads; it seems helpful to use the F-418 ribs (with aluminum angles attached) to confirm this distance.

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.

Bulkhead F-402 Dilemma

The previous builder claimed to have built all of the bulkheads, so I wondered why F-402 was still in four pieces. It turns out that F-402 intersects with two ribs (F-413) which attach to the F-401 & F-404 Firewalls.

My biggest problem was that I could not find brackets F-442, which are  attachment points that fit on either side of F-413 ribbing. Eventually the engine mount connects to these F-442 brackets through the firewall.

Furthermore, I could not locate an aluminum angle piece that connects the two ribs via F-442L & R. Are these angles, when not specified by part number always fabricated by the builder?

Eventually I found brackets F-442, but it appears that I have made my first mistake, which corresponded to the first holes I drilled in them and the angle piece between them. I did not allow for the additional angles which run along the top of F-413. This added 1/4" to the called out dimension of 7 1/2"

The plans are very inadequate in constructing this rib assembly. You have to search through three or four drawings to figure it out. I also found two 3/4 X 3/4 X .125 aluminum angles that run the length of both F-413 ribs. Unfortunately one of them is about 7 1/2" too short now as I used part of it to create the angle piece that connects the assembly together.

Although this assembly could have been made much later, I hope it will be useful in verifying the distance between F-401 & F-404. Although I need to complete it before I can place it in the fuselage. Here is a side view of the same assembly.

Probably going to need some help from Van's on this one. I cannot interpret the drawings.

I have the following questions  on this assembly:

1. Are the 3/4 X 3/4 X .125 angles which run along the top of F-413's precut or do I cut them from the stock angle material on hand? How much extra is in a typical kit?
2. Is there any better detail about how the angles attach to F-413 ribs, F-442 brackets, and F-443 brackets? (I am also missing spacers called for in the plans as F-444)
3. Do you attach the vertical angles on the F-401 Firewall first to accomodate this assembly?
4. Am I getting way ahead of myself? Should I be focusing on longerons, bulkheads, etc before tackliing this?

Any help would be appreciated.