Eating an Elephant
Page 10-19 is one of those pages where you end up spending weeks before you turn the page! In the end, this page (the side skin riveting) took 38 days (started on the 01 July 19 and finally got it done on the 08 Aug 19) and a total of 764 rivets - by far the single largest page in the build thus far.
Order of Assembly
Early on in the planning for the riveting of the side skins, i noticed that there were a few rivets between the various bulkheads and the side skins, which would have been located under the J Channel side stiffners. In fact, this is mentioned in the special tools required section at the start of the section:
Since i had run out of primer, the side skins ended up being primed but the J stiffners did not - so i clecod the assembly together and checked that the J stiffners could be slid into position after the side skins were riveted to the bulkheads - these slid in easily. This allowed me to crack on with the side skin riveting while i was waiting for the primer.
So based on this, i decided to complete the rivets that would be hidden under the J stiffners before i slid the J stiffners into place. At least that was the plan...
The plans call for riveting the side skins starting at the flat sides and working your way down toward the curved portion at the bottom. This was fine, and i got the rivets under the top J stiffner done before it was put in place, but once the stiffners were primed i went ahead and began to rivet all rivets in the aft section of the tailcone, including those on the lower J stiffner... but i forgot to do the rivets on the forward few bulkheads under the bottom 2 J stiffners - you will see the issues caused below.
In summary - for anyone behind me, i would recommend riveting the bulkheads to the side skins first, all the way to the bottom where the bottom J stiffner is located, then slipping the J stiffners into position and doing those. This should avoid the major issue i had below.
Side Skin Riveting
The skin riveting started with the squeezer, by completing all the rivets along the top C channel stiffners. I was careful with the callouts on the plans, and taped over the holes that didn't get riveted. At the same time, i installed the required nutplates for the inspection panel screws and aft fairings, and countersunk the skins to accept the dimple in the cover plates. I made up a test coupon dimpled for a #6 screw (the same thickness as the cover plates). At this same time, i riveted the skins to the aft 2 bulkheads - mostly using a gun and bucking bar, but some rivets on the aft most bulkhead i could access with the no hole yoke on the squeezer.
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| A coupon instlaled with a #6 screw to check the depth of the countersinks - these countersinks are made through the skin and into the C channel. I don't know what they didn't ask me to countersink the C channel stiffner and dimple the side skin - but i followed the plans in any case - i am sure there is a reason. The nutplate was installed before the countersinking, so it provided some support for the countersink cutter pilot. |
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| The contersinks are through the skin and into the c channel stiffner - the nutplate which was already installed gave some guidance for the pilot on the cutter. |
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| All nutplates needed to have their attach holes dimpled, except the ones on the inside of the C channel stiffner (the holes i countersunk above). |
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| Nutplates installed (note the lower J stiffner is still not primed and installed at this stage). |
Upper side skin rivets
Once i had completed the C channel rivets, i used a gun and bar to rivet the aft 2 bulkheads to the skins. all the way to the bottom J stiffner location. I then went along and riveted the rest of the bulkheads to the side skins from the top down, until i got to the top most J stiffner.
Installing the J stiffners / Aft Section Riveting
Next up, i primed the J stiffners and the cover plates, and slid the J stiffners into location. I decided that i should backrivet the J stiffners to the skins, meaning i needed some help from my dad to hold the backrivet bar he made for me. Before i called him over, i decided to complete all the rivets from the top to the bottom (including both J stiffners and also the lower inspection panel nutplates) using the gun and the buking bar. These all went fine - a few drillouts - mostly from not holding the bar completely perpendicular when setting the rivets, or overdriving them.
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| Aft section rivets complete. |
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| Aft section rivets complete |
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| Had a little helper in the shop! |
Note: I installed the "phone cable" along the top most stiffner at this time as the conenctor would not have fit afterwards (the other wiring will be installed later, as i am running my own wires and these don't have connectors). I didn't like how the wires ran under the bulkhead webs and thought they may cut into the wire eventually (if a cable tie broke etc), so i placed some caterpillar grommet along these, held in place with some RTV.
Once the sides were riveted, i broke the edges of the cover plates, dimpled them and installed them. They were removed afterwards, so i could install the little angled stiffners and also the rudder stops, but i needed to see them in place!
Rudder Stops / Angled Stiffners
The plans call for the installation of the rudder stops first, then the installation of the angle stiffners. However, with the rudder stops in place, i felt there was no nice way to rivet the lowermost (aft) rivet on the angled stiffners, so i installed the angle stiffners first (using a swivel mushroom set and a bucking bar on the inside).
Dad then came over to help and we had no issues with riveting the rudder stops - i used the backrivet set with the collar removed on the outside manufactured head of the rivet (aka the suicide method), and dad used a very tiny footed steel bucking bar on the inside - the only one i had that would fit. It took high pressure and a lot of hits as it didn't have a lot of weight, but i think the rivets turned out well. The aft most rivets were squeezed.
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| The suicide rivet set! Note the tiny footed bucking bar dad is holding was used on the inside. |
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| The rivet to the lower left hand corner of the rudder stop belongs to the angled stiffner - i have no idea how that would have been riveted if you had already installed the rudder stops. |
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| The lower 2 AD4 rivert are the ones holding the ridder stops on. |
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| A few scratches to the primer, but not too bad i don't think for a lightweight bucking bar. |
Riveting the J stiffners
Once the aft section was done, Dad and i moved onto riveting the top most J stiffner, then the bulkheads down to the lower J stiffner. We used a backrivet set on the inside, and the backriveting bar on the outside.
Big Trouble!
Moving down the bulkheads, we realised the error we had made in not riveting the bulkhead rivets that were hidden behind the lower J stiffner - we tried multiple methods to get these riveted, and in trying to use the "footed" bucking bar, i badly bent over a rivet on the forward most bulkhead on the left hand side. In drilling it out, once i broke the head off the rivet, the skin popped away from the flange.
This should have been a "STOP RIGHT HERE AND THINK" moment; the rivet didn't pop out using the centre punch (i believe becasue it had expanded between the skin and the flange), so i continued to drill. Unfortunately, i drilled perpendicular to the popped out skin, which was not perpendicular to the flange. This made the hole oblong somewhat, so i updrilled to #30 in the hope i could remove the oblong and put an oops rivet in the hole, but this was the result - not good:
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| The hole is now oblong, and damaged. |
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| This is the rivet location - right behind the J stiffner. If i had remembered to rivet these before i slid the J stiffner into location i would have been a lot better off. |
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| The flange has lifted a bit away from the skin - probably as part of the drilling out process, but maybe just because of the shape of the skins. |
1800 Tech Support
STOP WORK! I emailed Van's to seek their advice, as well as asked on a couple of facebook groups. Most suggest that it was not a big issue - make up a dimpled washer, or a doubler and rivet on.
This was the reply from Van's:
Just use an oops rivet in the hole – one rivet is not that important.
Try to push the flange down onto the skin when you buck it – you can put tape on the bar around the rivet head to push on the flange while you buck the rivet.
But a small gap will not matter. It
ain’t rocket surgery.
So the fix:
I started by drilling a #30 hole and marking the minimum edge distance (which turned out to be the same diameter as a dimple die).
This was then dimpled, and primed
I then had another go at riveting with the dammed footed buking bar (i hate that thing) and this was the result. Not super pretty but i think it will do the job. As Van's said (suprisingly) - it aint rocket surgery.
Lower J Stiffners
For the lower J stiffners, i had some good success by laying the whole fuselage on its side and either using a mushroom set on the outside and a bucking bar on the inside, or using my backriveting bucking bar on the outside, and the backrivet set on the inside. This depended on if it was the left or the right hand side - i just don't feel very comfortable using the rivet gun in my left hand as yet.
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| Knife Edge pass! |
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| A bit of love for the old girl (this is a gun on the outside and a bar on the inside). |
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| The backrivet bar my dad made up for me. |
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