Section 10 - Aft Fuselage Begins

The aft fuselage began with some cutting of parts and deburring. As per the previous sections, i decided to deburr the edges of parts as they were called up in the plans - rather than have a huge pile of parts needing to be deburred at the end. Edge deburring can be soul destroying and really burn through the podcasts.

First up was to separate and deburr the aft fuse J stiffners, and also the battery angles (which have nothing whatsoever to do with the battery! I believe this comes from the RV-10, where the battery is mounted in the back). A couple of bellcrank brackets were removed, drilled and deburred, and these get kept until the fuselage later to hold the elevator bellcrank.

Next up, some J stiffners were modified, then i edge deburred the C shaped aft fuselage longerons, which showed me how large the aft fuse section actually is!

J stiffners - the ends closest to the camera were removed - so they fit past the aft 2 bulkheads on each side.

The aft fuse C channel longerons are massive (and thick) - deburring took ages.

Next up was the fabrication of the aft fuse attach support brackets-

Laid out as per the very clear plans

Rough cut on the bandsaw (i used a #30 drill for the inside cornera). 

Filing to the lines...

Finished - looks like a bought one

Next i fabricated the rudder stops:

Marked out..

2 wooden blocks were used to support the work under the bandsaw (as it was much easier to mark it up on the outside of the part, rather than on the inside). This also kept the work square (check the blocks are square!)

The blocks were trimmed... 

To allow for the cuts at an angle through the thick material. 

I had to go very slowly here - and i used some candle wax on the blade. 

Rough cut, ready for deburring and hole countersinking.

To countersink the holes, there as no way i was able to do this using the cage, so i put the countersink bit in my hand debur tool and went into full suicide mode.

Done! 

A new tool - sort of

I found that the small file i was using to finish off the above parts was constantly getting clogged, despite using chalk etc. So i made up a little tool, with the only copper i could find laying around (water pipe) - this is scraped across the file and removed the build up easily.

Of course, it was an excuse to use my new reversible lockwire pliers.

WHANG!

Next up, i straightened, final drilled and then deburred the HS rear attach bars:

The payload increase procedure in progress - the Vixen file has been worth its weight in gold on this project.

A reamer was used to final drill the holes for the rear HS attach bars.

VS out of storage

I took the VS out from under the sheet it has been hiding under, in order to drill the VS to the aft 2 bulkheads (which go back to back). I had to go and buy a 17/64" drill bit because i didn't have one, but needn't have bothered, as this is just a systems hole for the rudder taillight wire to go through.

Aft 2 Bulkheads

The aft 2 bulkheads, which go back to back at the very tail, were deburred and the edges were filed to remove any "facets", and they were test fit with the rear bottom skin. I ended up using a hand seamer to bend each tab slightly so it conformed to the skin a bit better - as i didn't want any gaps for the rivet to squeeze between later.

Each tab required quite a bit of encouragement to bend to fit the skin. 

"facets" removed and deburred

After removing the "facets" and bending the rib tabs to fit somewhat. 

Next 4 bulkheads

The next 2 bulkheads forward, are also fit back to back, and these received the same treatment as the aft bulkheads - massaged into position and deburred etc. Same for the 3rd bulkhead sandwich along, however on this one, I noticed that the holes in the forward 2 HS attach bars (the little ones) were very rough and looked like they needed final drilling. However, nowhere in the plans i could find, mentioned final drilling these. I checked to see if a rivet would fit, and it did not, so i cleco'd the whole assembly together and final reamed to #30.

The holes on these parts were very rough and were undersize

The '3rd last' set of bulkheads - or the forward most HS attach bars.

Hitting the prime time

At this point i decided i had had just about enough of edge deburring, so decided to split this section into smaller chunks, by priming then dimpling and riveting the aft bulkheads before getting back into deburring again.

Back into the fun bit (and a mistake)

I find the really fun part is the dimpling and the riveting - unless you make a mistake!

This warrants a bit of explanation - there are 2 inspection plates on each side of the fuselage, under the HS. These are on the outside of the skin, and require nutplates to hold them on. See the image below. As you can see there is an option to install the cover plates with countersunk screws which i decided to do (at my detriment!)

As per the (pretty confusing) image above, the 4 horizontal nutplates are installed inside the longerons - and the rivets that hold them on, also hold on the skin. The vertical nutplates are installed on the flanges of the 2 bulkheads (both of 2 parts back to back) we will rivet together shortly - this means that the screw holes for these need to be dimpled to accept a dimpled cover plate (and a countersunk screw). This means the skin has to be dimpled, as so does the underlying bulkhead flange (and a special dimpled nutplate is used). For the aft bulkhead, the nutplates are installed on the flanges of the bulkhead which has its flanges facing forward (as this is a 2 bulkhead sandwich, we will rivet together shortly).

If you look at the image above however, there is an additional nutplate on the bulkhead flange that is facing backwards - this needs to have its rivet attachment holes dimpled (as it needs to fit a dimpled skin), however NOT its screw hole (in this case because the skin will have a countersunk fibreglass fairing over the top).

What did i do then?

So, in my dimpling excitement, i picked up the aft most bulkhead and dimpled the screw hole that i just mentioned above (the one which should not be dimpled). No big deal, i will just get the hand squeezer out and flatten this dimple out!

Multi levels of stupidness

Now here is the big error - instead if picking up the bulkhead with the wayward dimples, i picked up the forward most bulkhead and flattened the top 2 screw hole dimples on that - THE ONES THAT SHOULD HAVE REMAINED DIMPLED! ARGH!

So against all advice, i got out the squeezer and re-dimpled these 2 holes. This worked out fine, except now i had a bunch of tiny cracks all over the lip of each dimple, however no cracks going all the way through the material.

You can clearly see the cracks around the screw hole dimple

1800-SUPPORT

I sent an email to Van's to ask if i needed a new part, and thankfully got this response from Sterling:

Given this area is just for attaching a nut plate for the cover plate installation sanding these cracks out should not be a problem.

So, that's what i did - the sanding left a knife edge on the material, so i updrilled to #19 to take away the knife edge. In the end, this will have a skin dimple nestled into it so i think it should be structurally fine; the skin will be held using the nutplate attach hole rivets (and you won't see the larger dimple under the skin).

Cracks filed and sanded out

The hole ended up being enlarged to a #19 drill by the end. 

Prior to riveting, all the other bulkheads were also dimpled where this was required (mostly along the flanges). 

Riveting stuff

Moving on the rear to bulkheads were riveted together with the squeezer:

Happy these same out well and i didn't need to order a new bulkhead.

The 2nd bulkhead sandwich was also riveted together - i put the manufactured heads on the bulkhead material as it was thicker, and the shop head on the thick bars (shop head ended up being forward). All rivets were set with the squeezer.

Finally, the 3rd last bulkhead sandwich was riveted together. The small AD3 rivets are cute next to their big brothers - again the shop heads were put on the thinner material, and i kept the rivets in this direction for the whole bulkhead. All rivets were set with the squeezer.

These were AD4-8's - the larger rivets are a pleasure to squeeze and almost never tip over. 

Big brothers watching over their baby brothers.

Now that all the fun was had, back to deburring.