26-21: Riveting Baggage Ribs to Lower Skin and Finishing Chapter 26

In order to rivet the baggage ribs to the bottom skin, i decided the best access was to stand the assembly up. I used the low bench to do this, and used a safety rope and various clamps and straps to secure the assemble for riveting. 

I thought that i might be able to set the rivets using the gun on the skin (and the swivel mushroom set) and reach into set the rivets with the small tungsten bar. While this was doable, there was a high risk of slipping with the gun and stuffing up the skin. Also, it just doesn't produce as nice a finish as backriveting. So i did a few, then decided to wait for my Dad to do the rest. 

This is a rivet which was backriveted. A nice, almost optically flat surface (no gap under the ruler). 

This was set using the gun and bar on a low psi (30Psi). There is a depression caused by the gun that you don't get backriveting. 

You can see the unevenness in the skin due to using the gun (the wavy reflection). 

In the video below, you can see how there is a small amount of deformation around the rivet set with the gun - you can see the reflection of the cleco can bending. 

So i waited for Dad to come over, and on Christmas Eve we backriveted the skins using the long double offset backrivet set, at 50 Psi - much happier with the result, and much faster too. The whole of the baggage ribs only took a couple of hours, and Dad brought a ham over too!

We clamped and secured the assembly very well to the bench - it helps if it doesn't wobble. 

Baggage ribs to bottom skin, done! 

Chapter 26 Final Steps

The last step was to clean, etch and prime the baggage floor stiffner and install it with pop-rivets. I also riveted on the power-outlet bracket, which i had not done earlier. 

Once this was done, the outboard baggage rib could be installed. Since i was by myself, and the assembly was already laying down, i backriveted this using my small backrivet plate. Only took 15 mins - the hardest part was getting the rivets to stay in the holes while i put the tape on (as the assembly was right way up). 

Baggage floor stiffner in place. 

Simple task to pop-rivet in place. 

Outboard rib ready for backriveting.

The hardest part was putting in the rivets, then quickly covering with the tape before they fell out.

This is my original backrivet plate - comes in handy for things like this. I just slipped it under the section being riveted. This needed 60Psi to backrivet using the double offset backrivet set - i guess because the plate had less mass, i needed more pressure.

Chapter 26 - done!

Put in storage while i move into the firewall. 

26-20->21: Riveting Baggage Ribs to Seat Rib Bulkheads

Now the step attach assemblies are done, everything can begin to be installed to the lower skin / seat rib structure. This was all setup using the workbench extension on a pair of stands - and i used a sawhorse with some 2x4's to support the lower skin. This allowed space for me to cleco each rib in place before riveting.

The first ribs to to be riveted were the 2 rib flanges in each step attach assemblies, as well as the flanges on triangle ribs which sandwich the seatbelt attach lugs. To get to these rivets, i chose to use the manufactured head on the forward side - as the only real place i could fit the rivet gun was on the seat rib side. I ended up using the short offset rivet set for the step attach assemblies and 60 Psi! 

I used a small wooden shim for the lowest of the rivets, due to the curve of the skin - to make sure the bar was perpendicular to the bulkhead.

I then moved on to riveting all the other baggage ribs to the seat rib bulkheads. These were also done at 60 Psi, however since these baggage ribs had some flex in them, i was able to use the long straight cupped set. When setting the last pair of ribs (the F-01426 ribs), i had to really lean over the assembly - but this worked fine. The order in which the rib riveting was called out worked really well for access. Thanks Van's.

The long straight cupped set worked well here - especially due to the lack of access next to the seatbelt lugs.

All ribs riveted to the seat rib bulkhead

Really had to lean over for these ones, due to the direction of the flange on the rib.

Next up, is riveting the baggage ribs to the lower skin.

26-17->20: Baggage Ribs - Step Attach Assemblies

In a previous session, i had completed most of the baggage ribs. In fact, all that was left was 2 baggage ribs, along with the components used to attach the steps (and including the F-00016 Step Attach Weldment - powder-coated steel rib), as well as the aft side angles. 

So in this session, i prepped all these parts, cleaned etched and primed them. 

The first task was some work on the steel step attach weldments - i needed to enlarge the holes for the step bolts to 1/4" and also countersink for some nutplates. To enlarge the holes, i setup the 1/4" reamer in the drill press. However, i obviously didn't read the instructions properly (RTFQ) - if you look carefully, there are only 2 holes in each weldment which need to be enlarged. However, on the inside plate of the weldment, the part has 4 holes - 2 are covered by the outer plate. I did not notice this and tried to ream the blind hole (which obviously did not work). I realised i was doing something wrong in time, and re-checked the plans. I had damaged the powder coating in trying to ream the wrong hole, so primed these holes (along with the nutplate attach countersunk holes). 

Here i tried to ream a blind hole - i thought it was just full of powdercoat! It was not - there's a piece of steel behind it. You are not supposed to ream 4 holes on each bracket - only 2. 

This is the back side - as you can see only 2 holes here. 

Here you can see how there are 4 'holes' on one side of the parts - however, you are only supposed to ream 2 of them. 

I started these countersinks using the piloted countersink cutter, then switched to the hand deburring tool.

Holes primed

I also primed where i had damaged the part slightly when trying to ream holes which were not holes!

Next up i was able to start riveting the step attachment assembly. You start by riveting some angles to the steel weldment. You then rivet the steel weldment to the outboard rib. The plans call for CR3213-4 rivets in a couple of holes in the end flange of the weldment and optionally in all the holes - i used cherry rivets in all the holes - i could not see how i was supposed to get a squeezer into the tight corners of the weldment, and i would have had to use the gun / bar. I saw the video (below) on lubricating cherry rivets - however i had no issues setting them as they came. 

My first proper structural cherry rivets of the project.

A squeezer would not fit in here - i might have been able to use a gun and the bar, but went with the optional cherry rivets.

No bueno!

I used the optional cherry rivets in all the holes. 

Next up was to continue the assembly of the remainder of the components, including doublers on the step attach ribs, the step attach ribs themselves and the side angles. 

Doublers riveted to the step attach ribs

Step attach ribs riveted to the outboard baggage ribs

These cute little clips - perhaps the smallest parts in the build so far - are used to connect the side frames to the main side longerons.

There were also some little clips riveted to the bottom of the side angles.

The next step was a little more difficult - up until now it was an easy session of riveting using the pneumatic squeezer. However, the time came to rivet the aft flange of the outboard seatbelt lug ribs to the step attach ribs. There was no way to get a squeezer in here at all - the rivet tails were in-between the step attach ribs and the steel step attach weldments - so out came the long offset rivet set and the tungsten bar. I clamped the whole assembly to the table to stop it moving when riveting. These rivets were ok - not the greatest but acceptable. 

Not shown, but i drape a rag over the rib so the gun body doesn't damage it when i pull the trigger.

The little AN470AD3 rivets between the little side angle clips and the seat belt lug rib were done with the squeezer through a lightening hole.

Once this was done, the next most inboard baggage rib is riveted to the step attach rib and steel step attach weldment. These were all done with the squeezer. The plans asked me to use some cherry rivets on the steep attach weldments, however i was able to reach them easily with the squeezer so used solid rivets.

I used the squeezer and the longeron yoke here.

On the steel weldment, i used AD4-5 rivets in place of the 2 cherry rivets highlighted in orange.

The completed step attach assemblies.

The nutplates on the steel weldment are left until last - i assume for access while riveting. I think they could be installed before the weldment was riveted onto the structure - but putting them in later was easy with the hand squeezer.

That completes the step attach assemblies - they are ready, along with the rest of the baggage ribs, to be installed onto the lower skin assembly.