Mid-Fuselage Parts Assembly, Part 3

As mentioned in the Service Bulletin post, I eventually decided to go ahead with my initial plans of making the Landing Gear Covers, F-1275G removable with the addition of nutplates and rivnuts.  I also opted to proceed with the attachment of the bottom fuselage skin.

First, the removable gear covers.  Pictured below is the installation in progress of installing miniature nutplates into the flanges of one of the fuselage bulkheads.  Of special note, is the rivnut installation to the immediate right of the cleco'd miniature nutplate.  After breaking loose one of these critters from turning a somewhat tight #8 screw, I decided to abandon rivnuts in favor of the nutplates.  I drilled it out and carefully managed my edge distances and positioned it diagonally on the bulkhead flange.

While I have not yet replaced the two rivnuts on the cover plate, it is only a matter of time before I order the corner nutplates, remove the rivnuts and install them.

This shot shows both bulkheads that the cover plate spans with their accompanying nutplates and rivnuts.

And finally, a couple of pictures of the finished product - a removable land gear cover.

 

As previously mentioned, I had decided to postpone installation of the bottom mid-fuselage skin, as I was concerned that I would have clearance to install the landing gear assembly doublers and any other items as yet unspecified in the unresolved service bulletin.  After Van's published the details of the modifications imposed by the bulletin, it became clearer to me that I could indeed proceed with the install of the bottom skin.  Unfortunately, I never shot any pictures of that installation process and will have to show the bottom fuselage skin with the forward section already installed.

Prior to the mating of the forward fuselage section with the mid-fuselage section, the forward bulkhead and forward floor skins had to be riveted into place.  Below are two shots of the final riveted forward section of the mid-fuselage.

Next, came the fit-up of the forward fuselage section to the mid-fuselage section.  A separate table supported the forward section, while it was shimmed into accurate position.  After a multitude of clecos and some slight wrestling with the two assemblies, riveting ensued....and the result was quite pleasing.

Next, the fuselage cross brace is cleco'd up and placed into position immediately prior to riveting.

 
Side bulkheads are riveted to the horizontal fuselage bulkheads with the armrests attached.

 
The longeron/canopy deck is cleco'd into postion next as a final prerequisite for sizing and fitting the side skins.

 After a long session of work, I had to put one of the seatbacks into position to see what it would look like.
 

Fast forward to the week before Christmas and Van's has delivered some of their last service bulletin kits, of which I am a fortunate recipient.  Following are some shots of the work installing the fuselage side parts - the upper channel stiffener and the side skin doublers.

The shot below illustrates the upper channel skin stiffener, which has already been primed, top coated and riveted into place along with the original, lower stiffener.

Next came the process of match drilling the side skins, using the side skin doublers as a template since my skins were not yet attached to the fuselage.

After the relevant detour from the service bulletin work to install some nutplates on the side skins, prior to their installation onto the fuselage.

The final preps for installing the sideskins on the fuselage.

Next is a couple of close ups of the side skin doublers.

 

One of the previous steps that I believe I failed to document with photos, was the assembly of the fresh air vents.  This was another sub-assembly that was installed after the side skins were attached. Below are the requisite interior and exterior shots of the vents installed into the fuselage side skins.

Finally, the lower firewall/cowl hinges were fabricated and installed.  First is the passenger side.

Pilot side...

A final view of both hinges.

And the almost-finished canoe!
 

Longerons

As previously mentioned in the Service Bulletin post, I decided to undertake the longeron assembly, while awaiting the outcome of the main landing gear alterations.  I was able to borrow a set of longeron dies from a fellow builder in Missouri.  Shown below are the dies clamping the longeron while tightening the assembly in the vise.

The dies are very efficient at setting a curve into the clamped section of longeron.  In fact, I was easily able to "over-bend" the longerons with only a couple of squeezes with the vice.  It was definitely a learning process that I am still uncertain I have mastered.

Once clamped, the longeron could be pulled or pushed to pre-load and set a significant bend.

After setting several bends, it was time to compare the curve in the longeron to the canopy deck or "template" as it is referred to.

Another issue for me with the longeron bending process was my uncanny ability to induce a twist into the cross section - very frustrating!  How can that possibly happen with use of dies?!  Most everything I had read on the subject of this project reflected the author's opinion of from "very easy" to "almost impossible".  Invariably, I approached this project with my natural optimism, but was quickly humbled by the daunting task.  I would have to say that I am currently in the latter camp....not impossible, but you can see it from here.

Pictured below is the most curved section of the longeron, exhibiting the battle scars of the dies.  Once I was mostly satisfied with the shape of the longerons, I proceeded to buff out as much of the surface abrasions as possible.  They actually came out looking pretty good after scuffing, priming and top coat.

Now as I approach the process of match drilling the holes in the canopy deck to the longeron, I am questioning the accuracy of the .025" overhang (lack of uniformity) along the curved edge of the assembly.  The overhang of the canopy deck is to serve as a butt joint for the upper edge of the fuselage side skins.  I have probably .035 - .045" inch variation at the worst points along the length of the assembly.  The issue then becomes will the inconsistent overhang affect the assembly. Obviously, I can rivet the longeron to the canopy deck as is and then file away any excess overhang of the canopy deck.  My greatest concern is that I induce a wrinkle in the fuselage side skins because my longeron curvature does not exactly match the original shape of the canopy deck.  As I compared the longeron curve to that of the arm rest member, which is parallel and located several inches below the canopy deck, it appeared that the differences in curvature were minimal and the risk of skin wrinkle or warp improbable...but that is definitely a guess!

Several days later: Okay, after finally positioning the canopy decks on to the longerons, it quickly became clear that my concerns over the variation in the overhang was a non-issue.  Once the match hole drilling/cleco-ing process began along the length of the longeron, slight thumb/index finger pressure applied to the longeron brought the overhang into a very consistent margin as prescribed by the manual.  Problem was way over-analyzed!

Though not possible to tell from these views, they do show the longeron cleco'ed into place with the canopy deck.  First picture shows the longeron/canopy deck temporarily cleco'd into position.

 
Final picture in this blog shows the longeron/canopy deck resting in place after the side skin holes were match drilled.  More to continue in the Mid-Fuselage Assembly Part 3 posts.