Vertical Stabilizer

Earlier this week I decided to hold off on priming parts until I have a few more tools. I ordered a new spray gun, some towels, some spray bottles, and once that arrived tomorrow I should be ready to prime parts. I spent some time tidying up the garage tonight, and installed an air filter on my bench to ensure I have clean and dry air going to my tools. I also took the opportunity to redimple the other side of the vertical stabilizer skin. The dimples are slightly crisper now and I feel more comfortable with the end result. Next time I dimple, I’ll have a better idea of the pressure I need to be using.

In was in and out of the garage today, but managed to get the rear spa doubler counter sunk, and the spar dimpled to match. I started with a practice piece to get my counter sink cage set correctly, and after a little experimenting had it dialed in to where I was happy. With a rivet in the hole, it sits just shy of the lip, by perhaps a couple hundredths of an inch. The reason for the slightly deeper hole is that the dimpled spar needs to sit inside the countersunk hole, which obviously takes up more space than the rivet itself. The challenge is figuring out exactly how deep to go. I’m going to start with what I have, and can always deepen the cut if needed, but I have a feeling it’s right where it needs to be.

As I dimpled the holes and compared to the skin dimpling I did last night, I’m concerned my skin dimples are not crisp enough. The skin is actually quite thick, thicker than the ribs and spar, and I may need more tension in my dimpled to really form the dimple well. I clecoed the top rib to the skin on one side to see how snug the fit was. It’s hard to see in the photo, but there is slight gap between the rib and the skin. There are larger gaps where I fluted the rib, but the worrying area is where the clecos are inserted. If I haven’t formed a totally clean dimple, there will be a problem when it’s time to rivet to the ribs, the skin will not sit flush with the ribs, and the skin will develop waves. I decided to adjust my DRDT-2 dimpler and to try redoing a couple of dimples and compare the results. With some more tension, the dimple was definitely crisper, and there was more scuffing of metal around the dimple. At one point I put too much tension in the dimpled, and there was a very slight depression formed where the female die depressed the skin. I adjusted back a little and ended up with what I thought was a good amount of pressure. I kept going, re-dimpling one entire side of the skin. It was very hard to tell the difference besides the scuffing marks. Using the reflection test (seeing how reflected light bends around the dimple), there was no appreciable difference. For both the original and the re-dimpled holes, there is no bending of light until inside the ring around the dimpled hole. I did break out the squeezer and redid the tightest 3 dimples on each side. Continuing to the other side of the skin and redoing all the dimples just doesn’t seem worth it. I think what I have is definitely sufficient, and redoing the dimples is just risking a mistake, and probably enlarging the hole as the dimple sets in a slightly different way the second time. The pics below are of the two sides of the skin, one side has been redinpled, the other hasn’t. But which is which? The second pic is of the redimpled holes. You can see slightly crisper edges

With the dimpling all done, it’s time to prime and then start riveting.

In other news, I am hoping to connect with my tech councilor next week before he heads to Oshkosh. And a letter arrived from Vans with my two missing washers. I added them to the appropriate bag and marked the inventory list, which is now complete.

In a couple of sessions today, I was able to debur the Vertical Stabilizer skin, then dimple the skin and all the #40 holes in the sides of the ribs and spars. I taped over the 6 holes on each side of the ribs and skin where the fairing will attach later in the build. The tape to prevent me accidentally dimpling the holes. The skin was a little challenging to manage, but I found I could dimple every hole using the DRDT-2, with a little bending for the holes in the tightest spots on the leading edge. When it came to the ribs and the spars , I needed to use the squeezer to get many of the tighter spots. Tomorrow I’ll tackle the counter sinking of the rear spar doubler, and the last few spar dimples that match. Then I’ll prime all this stuff and get to some riveting.

I finished deburring the spars and doubler tonight, and just have the skin left to debur on the vertical stabilizer. It’s been very time consuming, but I’m striving for a good finish, and doing most of this with scotchbrite by hand. I’m also going beyond just deburring and actually scuffing the surface. This will be required when applying primer anyway, but it’s more that iMm using the scotchbrite to debur the holes, rather than other tools. I don’t like the idea of accidentally counter sinking while deburring, and this approach seems to be producing good results. Hopefully the skin will be a quick debur project that I can complete tomorrow, so I can move on to the next steps; dimpling and counter sinking. Once those steps are done, I’ll prime all parts (including the inside of the skin where parts will be touching), and then I can start riveting. I can see why the parts of the kit with already-final sized holes will go together so much faster. I also spent some time reviewing hints for home builders videos and reading through the digitized plans with links to Vans forum posts. Extremely helpful.

Just an hour or two tonight, and only managed to get through deburring the rear spar. Scotchbrite pads for the most part, across the drilled holes and in the corners of the harder to reach spots. Edge deburring tool and the Scotchbrite wheel took care of the edges. In the process, I found three holes that I hadn’t drilled in the spar and doubler. Will need to drill and deburr those tomorrow night. Hopefully one more evening and I’ll have everything deburred. Then it will be dumpling and counter sinking, then I’ll prime, and then start riveting it all together.

Spent a couple of hours tonight deburring parts for the Vertical Stabilizer. I started with the ribs and focused first on VS-705 which had been scratched from the press. This took the longest time as I tried to completely remove any trace of the scratches. It came out looking good, as did the other pieces. My main tools were scotchbrite pads, and the scotchbrite wheel on my bench grinder. I also used a small flat file in a couple of hard to reach spots. Hoping to get the spare done tomorrow night, and then the skin, so I can start priming all of these parts. Tonight’s effort seemed very time consuming, but this is due mostly to the scratch removal needed on the ribs, which shouldn’t be a problem with the spas and skin, which don’t (currently) have scratches.

The same piece before deburring:

Tonight I spent 3 hours going through the next few steps, ultimately getting all of the match and finish drilling done on the vertical stabilizer. I started by final-drilling the spar to rib holes, #30 size. There was a call out in the plans to match drill the middle holes in two of the ribs, but I found there to already be holes in the ribs, so it was really a case of finish drilling them.

With that done it was time to fit the skin! It was neat to get the skin on and to see a real airplane part taking shape. I was pleasantly surprised at how well everything fit together. Everything lined up nicely, and I was happy with the fit.

At this point I was contemplating calling it a night and going to bed, but I decided I wanted to get the drilling done and the piece disassembled if possible. The drilling went fairly quick, and within an hour I was done and starting to disassemble the parts.

I found one hole I had neglected to drill, so I drilled it and then finished disassembly. Next step is to deburr all parts.

Reading ahead, the plans suggest priming after deburring, but before counter sinking and dumpling. I’m going to ask my EAA chapter members tomorrow how others went about this. It seems like priming should happen after counter sinking, but perhaps there is a good reason.

Spent a few more hours this evening working through the next few steps. First, I final drilled all the rear spar holes for the doubler and the rudder hinge attachments.

With that done, I spent most of the next couple hours reading, researching, and doing some rib flange radius’s, and fluting the ribs. By radiusing the leading edges of the rib flanges, I hope to avoid the possibility of skin deformities once I start riveting. Hard to know how much to round the edges, but given the thickness of the material, I think I did a good enough job.

Fluting the ribs straightens out the rib “web”, which can come out bent from the press. I watched a few “hints for home builders” videos tonight, including one of fluting, and was happy to see the results once I got started. The ribs straightened right out with just a small set of flutes down each side. Then it was time to cleco the vertical stabilizer frame together.

I wanted to move to the next step and drill the holes where the ribs and spars mate, but it was too late and I was too tired. Quite while ahead, I figured.

Spent about 3 hours today going through the first steps in building the vertical stabilizer. The step by step instructions and the diagrams are excellent, it is very clear and easy to follow. I started by final-drilling the forward spar doubler, trimming the bottom of the spar, trimming the doubler, deburring the doubler and the bottom of the spar. Then dimpling the spar and the doubler plate. I held off on riveting, as I want to prime those parts first. Then I started on the aft spar; final drilling the rudder hinge brackets, and clecoing the doubler and brackets together. But before I could cleco these parts I needed to straighten the doubler which was bowed to the point that each end sat about 1.5 inches off the work bench. It took much trial and error to straighten, but ended up with within the 1/16 tolerance.