Finished laying out the outboard nose skin. This area has a double row of rivets along the spar line into the wing tip end of the spar:
Also drilled the main spar out to A5. The amount of aluminum swarf created by this project never ceases to amaze me - I can't imagine how much debris is created by the match drilled factory kits!
Ron and I went to visit with Henri, a local builder and master welder that Ron knows and who is also an aviation guy. His shop is next level - he is building a six seat CompAir 6 which will go on floats. He too is doing an "auto conversion engine" which is an 8 cylinder twin turbo diesel with 6 bladed propeller. Unlike my Corvair which has a proven method, he's doing all this design and testing himself. His work is amazing and has to be seen to be appreciated.
After much tongue wagging over his shop and project, we had a look at my fuel tanks. Although Henri says welding my fuel sender assemblies would be no issue, he wasn't comfortable attempting to weld my fuel tanks. The concern is the thin 025 aluminum will most likely warp beyond easy correcting with the heat of welding. Based on this, his suggestion was to seal and rivet the tanks and after a bit of research, that process is equally effective without the risk of warpage. Kit builders get their tanks from the factory pre-welded but they are expensive to order as individual parts especially the long range versions I want.
When I was forming the tank sides, I followed the same method as the wing ribs which included relief holes at the corners. I originally thought these wouldn't be a issue as welding the tanks would fill in these spaces easily. Sealant isn't capable of covering this big of a gap between parts, so I needed to come up with a way to "fill" the holes that wouldn't also change or interfere with the assembly of the tank.
A piece of 025 "L" can be formed to back the outward facing corners of the tank side panels. A 45 degree notch in one leg of the L allows the angle to be bent to the same angle as the corner, and some light brazing welds the angle into a corner:
This picture shows the concept better. This is the same angle in the vice prior to bending the second corner:
The completed angle backer, brazed closed and sitting in place. This will be treated with sealing compound before being riveted with the tank skins. This will effectively close the corners of the tank sides:
The front corners of the tank side. By placing on the outer side of the the tank wall, it doesn't change the geometry of the corners and the tank skin will still fit correctly.
When sitting in place, I marked where the ends of the corner backers would be, then transfered that mark to the outside of the tank skin so I could lay out the rivet lines:
On the bottom side of the fuel tank, there is one flute in the side wall and several on the top side. I made a mark to remind me that I won't be able to rivet here:
Laid out the rivet line. A3 rivets on 2omm spacing worked well and avoided the aforementioned flute mark. I shortened the rivet spacing at the corners to account for the corner backers.
Cleco clamps hold the skin in place on the side wall. Line up the wall and drill A3 holes along the rivet line:
Same process for the front of the tank:
I didn't drill near the tank outlets. I'm going to drill and tap the outlet fittings for stainless screws. With sealant between, the screws will tighten the fittings against the skin for a leak proof outlets:
Repeat the process for the inboard lower side (shown on the right):
Very pleased how the bottoms and front turned out. They will be the first to be sealed once I get the sealant from Aircraft Spruce in a couple of weeks.
Flip the tank over, and repeat the process, starting at the rear of the tank (3 rivets on 15mm spacing) and working forward, bringing the top tank skin down tight. There are 5 flutes to avoid here, but the spacing at 20mm continued to work out well:
Then the inboard side:
Cleco clamps are very handy here!
The front edge was originally going to be welded, so edge size wasn't a concern. Now however, I'll need to bend a 025 L and install it.
I've read many concerns from kit builders that their factory made tanks are slightly out of square, but this rivet/seal method seems to keep the tank much more square and straight.
Next up, adding the front edge angle, fit the corner doublers and drill/tap/fit the outlet fittings. Very happy this complicated assembly (welded or otherwise) is coming together. I also heard back from the fuel cap manufacturer, I need to order the threaded flange for the tank that interfaces with the threaded tank neck. Not expensive, but wish there were better instructions or explanations as I would have ordered them with the caps and picked them up at the same time from Aircraft Spruce.
As always, thanks for following along.
After a week away for work, it was good to get back to the shop for some build time this past Sunday.
I received my adapaters that go between the fuel finger screen in the tank to the hose end fittings:
Loosely fit in position inside the wing bay:
Next, I needed to drill the large hole in the rear wing channel for the fuel line to pass through into the trailing edge. Laid out the location as per the plans, but moved the centre of the hole down a bit to allow the grommet to sit flat away from the doubler above:
It didn't take as much effort to create the hole with the bi-metal hole saw as I thought it would. This hole goes through the 040 rear channel and the .125 root doubler plate. A bit of sanding and it cleaned up nicely.
I primed the hole on both sides to prevent any corrosion between the channel and doubler:
Next up was adding the Swivel-Seal hose ends to the braided line. The process starts with the threaded collar. I protected the nice anodized finish by covering the vice jaws with tape first.
The cleaned end of the braided line is inserted into the back of the collar. It's a tight fit, but if you twist the line as you push it inwards it goes smoothly:
As per the instructions found online, the line gets inserted to just shy of the inner threads:
Next, the fitting gets mounted in the vice:
Push the collar centred and forward onto the fitting until the threads can start engaging:
Tighten the collar down on the fitting using a wrench while turning the braided line until tight:
It's a bit of a pain to get this large grommet in and sitting flat, but it is the perfect size for the braided line to pass through:
The braided line has a limit to it's bend radius, but I'll be well within the allowable limits once the trailing edge of the wing is in place. I will need to protect the pitot/static lines from abrading against the fuel line.
As I completed the fuel line for left wing, I fabricated the one for the right wing in prep for install once my tanks are ready. These fitting aren't cheap, but this is important for safety and they look good too:
Also got my flush fit fuel caps in from Aircraft Spruce. The factory finish on these is excellent, very pleased. Just need to figure out how to make the threaded flange fit the tanks. Email sent to manufacturer for guidance.
Prepping for the wing nose skin to be rolled up, I marked out the slots needed for the slat support brackets where they pass through the nose skin, using the same method as I used on the other wing:
Wing nose skin ready to roll over the nose ribs using ratchet straps. This went easier without the trailing edges in place:
Inboard nose skin drilled out to A3 at the spar once all squared up with wing:
Both inboard and outboard nose skins now rolled and attached. Still need to final rivet the slat attach brackets to the nose ribs, but at least I'm closer to closing up the wing.
Once the nose skins are final drilled and deburred, I'll add in the fuel tank angles to the back of the spar in the fuel tank bay. I'll need them welded up before doing that. Hopefully I'll have answers back about the fuel caps by then.
More to come, stayed tuned :)
New here? Try starting at:
Husband, father and 911 dispatcher. Long time pilot with a licence that burns a hole in my pocket where my student loan money used to be. First time aircraft builder. Looking to fly my own airplane.