Match drilled the assembled rudder. I also match drilled a 50×50 mm piece of Aluminium angle to the trailing edge, to use later on during rudder assembly. I’m planning to use the technique described here to set the trailing edge. After match drilling, I disassembled the rudder and deburred both skins. That leaves skeleton debur, R-1006 countersink, and dimpling.
Deburring rudder skin after it has been match drilled
Finished deburring rudder components. Assembled and match drilled the rudder skeleton. Deburred the skins. I cleco’d the skins together along the trailing edge, and used a vixen file to debur both skins at once so that the trailing edge of the skins stayed identical. I then cleco’d the skins onto the skeleton, ready for match drilling.
I’ve started preparing the rudder parts. I may get the rudder to a point where the parts are ready to prime, and do the rudder and vertical stabilizer in the same preparation and paint session. The following set of parts is the result of ten hours of cutting, filing and de-burring over the past two days. Still a few parts (covered in blue plastic) to go.
Finished the wing kit inventory. All parts present, Vans are now 2 for 2. The fuselage kit will have to remain in its box for a week or two while the shed extension gets finished, at which time I can move the vehicle and some other things out of the aircraft manufacturing space”.
The large shelf I built is filling up with parts. The wing skins are safely tucked away underneath what you can see in the photo.
Freight costs are a big deal for builders in Australia. I’m worse off than most because after goods clear customs in Australia and are available for pick-up, my crates then have to do another sea crossing down to Tasmania. Other issues to lose sleep about include importation charges and the vagary of international exchange rates.
Combining multiple items into a single shipment is one way of reducing total cost. Between this, and being dead certain the local currency was going to de-value across the year, I ordered the (slow build) wing and fuse kits about five months ago. Today, after being loaded and unloaded from two ships and at least four trucks, the crates showed up.
One of the wing kit crates had an accident during its travels, the bottom plywood was split open by about half an inch, and some pieces of the crate had been left behind somewhere. Perhaps floating in the Pacific. I opened it up and was relieved to find no damage to the skins. I got most of the wing parts inventoried before calling it a day.
The primer on the practise kit parts dried to a nice tough finish. Flexing the skins had no side effects, to that end rolling the leading edge of the practise kit was no problem for the primer. It was also quite resistant to scratching.
With the primer test now out of the way, I assembled the practise kit. I accidentally used -4 rather than -3.5 rivets in two positions on the spar flanges, and had to drill one out. The last rivet closest to the trailing edge on each side was a pain to buck. Otherwise, the practise kit went together easily.
After finishing the rolled edge closeout, I wiped the completed kit off with some acetone, and then dropped it by accident, denting one end of the rolled leading edge. Moral of the story: an assembly is not finished until it is wrapped up and protected from accidental damage.
Finally, after many months, the workshop is now ready, the practise kits are done, and I can get back to finishing the vertical stab and moving on with the rest of the empennage.
I did quite a bit of reading on the contentious subject of priming, and looked into some of the chemistry. Without further justification, my decision was to prime using an aerospace grade two part epoxy primer. As a result of this decision, I would need to set up some sort of spray booth. Spraying outside is not an option, weather is too variable and this is after all a sheep farm – at times it is hard to tell the difference between the hordes of enormous Calliphora stygia and low flying helicopters. Just doesn’t seem right to be prising insects off parts after they landed on wet primer and got stuck.
I have a reasonable amount of room, so I built a spray booth capable of holding enough parts to make up any of the assemblies. I built it out of structural pine, covered it in builder’s plastic, and installed a mesh table, lighting, an exhaust fan and an intake filter. I put the whole thing on 4 inch castors so I can just roll it into a corner when not in use.
I decided to use the Van’s practise kit parts as a means to test the entire process. This meant the practise kit stayed in pieces while I got the booth finished and waited on some of the sundry items I needed. The process I’m using is:
Clean and degrease with PPG Deso-clean 110
Etch with a 5:1 solution of Alumiprep 33
Spray on an adhesion promoter, PPG EAP-12
Spray on PPG CA7700 epoxy primer
I’m using the EAP-12 in preference to Alodine because I have no way of dealing with toxic rinse water here, anything that wound up on the ground around the workshop would eventually wash off into the main dam, and then get pumped to all of the stock troughs that the sheep (and a lot of local wildlife) drink from. I didn’t want to be responsible for causing some sort of zombie sheep apocalypse in the area.
The practise kit trial went OK. The booth could use some back lighting which I will add one day. Cleaning and etching went off without a hitch. I didn’t mix up enough EAP-12, so the application was a bit thin for one of the skins. I decided to let this go, since it was just a practise piece. I tried a few different air pressure and spray gun settings during the primer application. As it turns out the settings I started with were perfect, and each alternative I tried degraded the result – which is OK, that’s what a trial is for. There was some paint spitting when I dropped the air pressure too low. I also got so pre-occupied evaluating various gun settings I coated the skins too heavily.
Now I get to do it all over again with the Vertical Stabilizer parts.
Still catching up with workshop items. Broke out the router and made a back riveting board from a piece of scrap wood, and made the recommended DRDT-2 dimpler frame from some 12mm MDF that was left over from the workbenches.
I decided to conveniently forget about all the farm jobs today and put in some work on the vertical stab.
I de-burred all the ribs, assembled the ribs and spars, and match drilled. Based on numerous Internet posts about nose rib skin bulge, I thought I would check the fit of the nose ribs into the VS skin as a separate operation. I started with the lowest (widest) nose rib, and sure enough, it was simply not possible to cleco the two inner most holes without causing a bulge in the skin. The general advice seemed to be that material needs to be removed from the front of the nose rib in order to allow it to fit. Some individuals have reported taking as much as 3/8 inch off the front of the ribs, but I didn’t want to jump in that deep. So I sawed around 1/8 inch off the front, cleaned it all up, and tried the fit again. This made zero difference, which makes sense since taking this material off made no difference to the shape and distance between the forward most rivet holes. Further research on the forums brought the solution to light – flute the nose of the rib. I thought about this for quite a while since it seemed like a one-way street, and decided it was either bulges, remove a lot of material from the front, or fluting, so I went ahead with the flutes and this completely solved the problem – no bulges.
For the middle and upper ribs, I didn’t remove any material, I fluted them. There’s only really room for a single flute on the narrow top rib. I assembled the VS this way and it all went together well, with no bulges. I match drilled all the #40 holes, moved every cleco over one position, and match drilled the rest. For the nose ribs, I put a cleco in every hole, and removed them one at a time, match drilled, and replaced.