6-05: Tech Counselor Visit / Vertical Stab Complete

 I decided with my Tech Counselor that it would be a good idea to take the VS and Rudder down to him for him to have a look inside, before i riveted on the trailing edges and closed the structure up forever! Overall, Pete was pretty happy with my work, but identified the following items:

1. 3 rivets on the lower section of the VS spar: In this case, after completing the back riveting of the lower AN426 flush rivets on the VS spar, i moved onto the AN470-AD4 rivets. I used a squeezer for these, however inadvertently picked up a AD3 sized cupped set instead of an AD4 size. I set 3 rivets before i realised. These left a concentric mark on the rivet head, which Pete said could cause a cracked rivet later. So out they came!

A note on removing AD4 size rivets: i have found these pretty hard to remove initially, especially where there was a lot of material. I worked out the best process was to use a #31 (or 1/8") drill bit to drill off the head. This leaves a conical indentation from the end of the drill bit, so i then use a #31 (or 3/32") drill bit to drill down into the shank, keeping it carefully in the indentation, and being careful not to touch the skin. This gives some room for the rivet tail to collapse and it tends to punch out a lot easier. If it doesn't punch out, i use a pair of ground down side cutters to twist the tail of the rivet off (as per Van's Section 5). 

2. Some of the smaller AD3 rivets on the stiffners of the rudder or the VS parts were slightly over driven. It seems i tend to go slightly over, then slightly under. Pete recommended going slightly under is better than over.

3. When i scuffed the rudder hinge brackets on the VS, i inadvertently scuffed off the powder coat on the edges. Pete thought it best that i re-painted these for corrosion protection. For this i just sprayed some rattle can etch primer that i had into a cup, and brushed it onto the edges and the bolt holes.

Here you can see how i scuffed off the powder coating

4. Finally, Pete noticed a couple of fish eyes in the primer on the VS stab and asked about my shop air setup and priming practices. I told him that i had a dedicated painting line etc etc, and i mentioned how i was drying the parts by blowing them off with shop air... doh! headslap! Pete pointed out that i was using the same hose to do this blowing off that i was using for my air tools, which had oil in them! So i need to stop doing that!

Overall the first TC visit went very well, and i took away some good advice. Here is the first TC report:

So after rectifying all those issues, i was able to successfully rivet the rear spar into the VS and finally the VS is complete. 

Overall the VS took 23 shop hours, and 303 rivets. 

6-02:05 - Vertical Stab Priming and Assembly

After a almost 2 weeks away in China at an airshow, I finally got back to the VS, by preparing the VS components for priming, then priming itself.

My choice of primer is Stewart Systems, 2 part EkoPoxy in smoke grey, with EkoClean and EkoEtch prior to painting. I chose this method as i am painting at home, and anything else was simply to hazardous to be spraying around my family and neighbors. More on the priming process in a later post.

The first priming session was the VS forward spar and doubler. Once this was primed, i squeezed the first rivets of the project:

Once this was done, i primed the rest of the VS components:

The priming process is not too bad - i use a DeVilbiss Starting line gun, at 30 PSI at the regulator, and about a 20 foot line. So long as i make sure the centre of the test shot on to the cardboard is wet, the paint goes on well. If not, it can be a little orange peely / rough to the feel (i.e. too dry), but it is only primer: there to protect not to be topcoated. The Stewart systems is fairly thick, and once mixed and thinned sprays fine. I keep it inside to keep the temperature of the paint at 20C, and keep the heater on in the back room. If it is cold, then it won't spray. More on that later.

Once the parts had dried for about 12 hours, i was able to rivet together the forward spar. This went ok with the squeezer with only a few rivets that may be questionable. I drilled out 3 rivets. I back riveted the AD426 rivets at the bottom of the spar. I also chose to put the manufactured heads forward on the spar, up to where the skin starts, purely so the tails of the rivets were all on the same side on the lower portion where the VS is in the fuselage. Van's asks for the manufactured head to be on the aft side, so there is more room to squeeze the spar to skin rivets later. Below the skin though, i didn't see any reason why not put the shop heads aft - plus this put them on the thicker material. Some of the rivets on the lower brackets could not be squeezed, and i used a gun for these.

Backriveting the lower AD426 rivets.

very satisfying

Will get a TC to check these before i rivet it to the assembly and close it up forever

Drilling out - on AD4 rivets, i used a #31 drill initially and break the head off. I then use a #41 drill to drill almost through the stem. They can then be sometimes punched out, but sometimes it is easier to twist them out with a set of side cutters.

I color coded the rivet call out, so as not to make a mistake. 

Once the spar was done, i riveted together the skeleton, using the squeezer. The lower ribs were done using a bucking, and my first go at a 6" offset cupped set, which seemed to work ok. 

Skeleton and skin ready to come together. 

I was then going to give it a break, as i didn't want to start on the skin rivets at the end of the day (and screw something up). I decided to mount the cradles onto a new work platform, and just cleco the skin in place and leave it for the day. Then i figured i would just shoot one rivet. Then i ended up doing them all!!! 

I used a swivel mushroom set, and a tungsten bucking bar, with a wooden offset so i could keep the bar parallel to the skin:

The finished product, showing the cradle dad made up for me, securely clamped to the work platform. This made reaching in and bucking the spar rivets easy, plus allowed me to go back and forth between the left and right side, keeping the rivet pressure even. 

Some rivet closeups:

VS-705 nose rib to VS-702 forward spar rivets

VS-707 mid rib to VS-702 forward spar rivets

VS702 forward spar to skin rivets above the VS-707 rib

VS-702 forward spar to skin rivets, below the VS707 rib. 

First major subsection almost complete! 

I will not rivet the rear spar into place, until a TC can check my work to make sure i am on the straight and narrow. 

6-04: VS deburring

Page 6-04 Step 3 - “Disassemble all parts and deburr”

8 hours of work later..

The process I seemed to find worked the best was as follows:
- Start with the rib flange edges or the skin edges. They all seem to have some “steps”, presumably from the stamping process. I tried removing these with the edge scraper tool, but all this does is scrape the edges and maintains the steps. I found the best way to remove the steps was with a vixen file to flatten the whole edge. Once this is done, for rib flanges I gave a quick gentle pass with the scraper tool and then onto the scotchbrite wheel. For skins (which are too big to take to the scotchbrite wheel), after the vixen file, a smooth file to smooth it off some more. Then a 120 grit flap wheel seems to work better than a 1” scotchbrite. Finally the edge scraper tool gently, and some 400grit and maroon scotchbrite pad - all edges now done. You really need to go easy on the edge scraper tool - it's very easy to take to much and end up with a faceted edge.

Edge Deburring Tool

- After the edges, I found 400 grip aluminium oxide paper wrapped around a square of maroon scotchbrite pad works really well on the gaps between the flanges.

- Finally, all holes are deburred with the countersink tool - either the normal one, extra long one or a small one that I spin in my fingers. After the hole tool, a quick pass along all hole areas with a scotchbrite pad gets any remaining tiny burrs.

- Once this is done, I check over for any large scratches, and if there are any, sand them out with 400 then 600 grit aluminium oxide paper, followed by a rub with maroon scotchbrite.

Below are some images of the front edges of the VS-705 and VS-706 ribs and how I needed to adjust them so they fit the skins.

VS-706 Tip Rib - didn't need too much removed, and it was the flanges which were interfering with the skin. These were initially bent out of the way a little, and then filed to a profile. A small amount was removed with the snips - edge distance was not an issue at all. 

VS-705 Root Rib - this one needed quite a bit removed - it was the flange/web corner which was interfering with the skins. I ended up knife edging the corner of the flange and web, so ended up marking the minimum edge distance, and snipping the end off. After this everything was rounded and sanded to prevent cracks. Came out ok i think. 

VS-705 on the left, and VS-706 on the right. 

Once 6-04 Step 3 was done (took 8 hours!), I moved onto step 4 - dimpling the skins. I started by carefully taping over all the holes which did not get dimpled in both the skins and the ribs, and i recking i checked this 50 times.

Lessons learned here:

- The DRDT2 works better on my large wide worktable, rather than the side bench, as i have more depth to move the side tables around. It works fine even if not screwed or clamped down.
- The folding mechanism on the side tables was poorly designed - i needed to whack in a chipboard screw to secure them so they didn't collapse as they require quite a bit of moving around to support the skins.
- Tape needs to be applied to the top of the dimpling mechanism, otherwise it really scratches the top skin (this needed a bit of sanding to get the scratches out - once i taped the skin, no problem).
- the laser really helps to find the holes.
- You really need to lift the skin when moving it, or you scratch the outer skin surface with the male dimple.
- It takes some creating maneuvering to get to all the inside dimples, but i doable with one person easily.
- The remaining edge dimples, which i could not get to as the skin was too tight near the leading edge, were done with the pneumatic squeezer.

The side bench depth is not enough to successfully dimple large skins here. The side tables work very well once the legs were secured with a screw. 

 

All dimples done - skin ready for cleaning, etching and priming. 

Once the skin was done, all the corresponding holes in the flanges of the ribs were also dimpled. I was using the Cleveland Substructure Dimple Die set to dimple the flanges, but they just didn't look right to me. The dimples seemed under formed. I was scratching my head about it, until i realised that i had the substructure male die mating with the normal female die. All was good once i redid all the dimples with a matching set of dies.

Moving onto 6-04 Step 5 - i used a practice piece and setup my countersink cutter in my hand held electric drill. I considered using the drill press, but the VS-808PP Spar Doubler was a long piece which would need supporting (stands), and i thought i could do it just freehand with the drill. Each hole was half done with light pressure and slower speed, the cutter cleaned out and the shavings removed from the piece, then the full speed and full depth cut made. I think it turned out ok:

This step also included dimpling the corresponding holes in the VS-803PP aft spar that the VS-808PP doubler gets rivet to. (the flush rivets at the bottom of this piece are there so the whole assembly bolts flush to the aft fuselage bulkhead(s). The holes we leave open are tooling holes - later on, the aft bulkheads are cleco'd and aligned to the spar assembly using these holes, then using holes in the bulkheads, bolt holes are match drilled to the spar assembly - effectively aligning the VS with the bulkhead, before it is riveted into the fuse). The holes in the VS803PP spar were dimpled with the pneumatic squeezer and the longeron yoke easily. 

Dimples in the aft face of the VS803PP rear spar, nest into...

... countersinks on the forward face of the VS808PP spar doubler, which is a hefty piece of structure. 

Of course, i didn't work alone - my trusty cleco assistant helped whenever there were cleco's needing removal:

At this point the work ceased, as i am waiting on my order of EkoClean, EkoEtch and EkoPoxy (Smoke Grey) to arrive. Should be here this week. 

Here are all the parts lined up ready to go for cleaning, etching and painting. 

TO DO:

- mark the substructure die pair with some nail polish so i don't get them mixed up again. 

6-02>04: The project begins.

The project has begun! With Section 6 - Vertical Stab.

The first day of building went smoothly - was basically match drilling, with a couple of dimples thrown in for good measure. When drilling the skins i need a more robust system for the drilling of the holes with the clecos in - i forgot on one line which side of the recently moved cleco i should be drilling. Perhaps i'll always move them up one, and aft one (so always drill the hole down from the cleco, and fwd of the cleco). We'll see.

The electric drill is working well, and the pneumatic cleco gun is great.

The obligatory photo of the first 10 holes of the project.

Rear spar of the CS coming together.

Skeleton cleco'd and match drilled.

The skin fit pretty well straight out of the box, however both the tip ribs needed to be bent.

Adjusting the tip and root ribs: The instructions are correct in that the tip rob and the root rib interfere with the skin. I cleco'd them in place and used a sharpie to mark where the final hole in the front of each rib would fall. Looking up the Cleveland Reference Table a 3/32 rivet needs 3/16 of edge distance, so i drew a line on the ends of the flanges at this distance. Once this was done, due to the taper of the skins, i found the lower root rib needed quite a bit taken off the upper corner of the rib, and i knife edged the corners a bit. Concerned about cracks, i clipped off a bit from the flanges of each rib up to my edge distance line, and then filed the corners to a radius. For the tip (upper) rib it was a lot easier. The rib is installed upside down with the flanges facing up, so it was these that contacted the skin - it was a simple matter of bending these a bit to ease the fit, not so much filing. I will take some photos of these tomorrow and put them at the end.

The obligatory first part photo after 4 hours of work - event though it is far from being finished, it looks like part of an aircraft!!!!! Yee haw.