I laid out the holes for one of the side skirts, then clamped them together and drilled both at the same time. The plans show a uniform spacing for each row, but because the rivets are angled back at the aft end to follow the angle of the canopy frame, the plans show a slightly wider spacing for the upper row of rivets. Instead, I laid out all of the rivets on a 1.5″ spacing except for the aft pair in the upper row which are about 1.7″ apart. I also spent a little time trying to plan how I would fabricate the lift handle. I’m leaning towards cutting a slot in the side frame and skirt and installing the angle from the inside.
I remade the exhaust hangers so that I clearance to install the aft SCAT tube on the heat muff. I ended up shortening each stainless tube by about 2″ or so and then re-flared the ends and reassembled each support. Shortening these caused them to splay out more which is what provided the additional clearance for the SCAT tube. Another advantage of this is that there is more lateral stability for the exhaust pipes.
Now that the exhaust pipes are in the final spot, I installed the adel clamp on the breather tube.
The lower end is positioned right over one of the exhaust pipes so that any oil blown overboard is burned off instead of coating the belly.
Since the cowl is on hold until I get a replacement lower half, I decided to finish off the canopy. Next up is to fabricate the side skirts. I installed a few screws on each side to hold the canopy against the canopy frame. This had the unfortunate side effect of pushing out the frame so that the side skirts are no longer flush with fuselage sides. I’ll have to gently flatten out the curve in the frame to pull the sides in a bit.
Since I was alone, I needed to be able to reach the screw on the outside and the nut on the inside at the same time. My arms were long enough to reach the aft and middle screws, but I needed to fabricate a little tool to hold the nut while I turned the screw from the outside.
Since I cut the forward skin back a bit so that the joint lines up with the bend in the longerons, the included skirts aren’t long enough. I used my air nibbler to cut some longer and narrower side skirts. These are 2.75″ wide and about an inch longer that the included skirts. Once these are fit to the canopy frame, I’ll trim the aft end to match the angle of the skin surrounding the rear window.
After exchanging a couple of emails with Joe Blank at Van’s, they determined that my lower cowl doesn’t have a long enough side flange. They’re going to send me a new lower cowl, so I’m going to work on a few other things until then.
Since I marked the cut points on the exhaust pipes last night, I pulled the lower half of each pipe and cut the three longest pipes to match the shortest. I then cleaned up the ends so that there were no burrs and reinstalled the pipes.
I then fabricated the exhaust hangers. These are each comprised of two pieces of stainless steel tubing connected by a piece of rubber tubing. I flared the ends of the stainless tubes so that they couldn’t slip out of the rubber tube.
Now that the exhaust is installed for good, I installed the heat muff around the #1 and #3 pipes. This was a bitch to get on since the fit is really tight. I moved it almost as far forward as possible so that I can get maximum heat transfer as well as provide the most room for the aft SCAT tube. I could have moved it forward another 1/4″ or so, but I wanted to be able to inspect the weld on the #3 pipe during annuals.
Despite moving the heat muff forward, the right exhaust hanger is still going to interfere with the aft SCAT tube. I’m going to have to shorten the exhaust hangers which will have the effect of moving the upper attach points farther out. Hopefully that will give me enough clearance that the SCAT tube won’t rub on the exhaust hanger.
In order to make sure the cowl returns to the same position each time, I drilled a piece of scrap aluminum angle to the top cowl so that it aligned with the spinner. The clecos didn’t really hold in the fiberglass, so I ended up putting some scrap aluminum on the other side and using some wing-nut draw clecos to anchor this firmly.
I also made a series of marks around the spinner to serve as reference points.
With the cowl in its final location, I put a light inside the cowl and put some masking tape along the cut line.
I did the rough cut with the cutoff wheel to within about 1/16″ of the line. After putting the cowl on and off a few more times, I was able to iteratively trim the line with a vixen file so that these edges align with the firewall flange. I’ll trim the exit once I’m happy with how everything is fitting.
While I had the cowl in its final position, I took the time to position all of the exhaust pipes so there was an even gap all around them. Each pair of pipes will be clamped together and then everything is loosely anchored to the engine mount. I also made some marks on the pipes that are even with the shortest pipe. I’ll cut all of these so that all of the ends are even.
Here’s a shot showing how much clearance I have all around. I have about an inch of clearance top and bottom and about two inches on each side. The pipes look like they aren’t vertically aligned here, but that’s just because the lengths vary.
I drilled and installed the pipe clamps. The bottom steel straps needed to be bent to conform to the pipes.
I re-powder-coated the part that didn’t come out right last week. The problem turned out not to be lubricant leaking out between the steel and brass components. In fact, I had simply not cleaned out all of the grease from the inside of the weldment. When it heated up, it flowed out and ruined the finish. I ground off all of the powder coat and cleaned it inside and out before redoing it tonight. Afterward, I assembled all of the components. This will stay on the shelf until the prop comes back off.
I finished adjusting the flange on the front to be perfectly round and then drilled a hole on each side to lock in the position.
The plans specify that you mark a line 2″ aft of the firewall flange as a reference point for trimming. As I’ve seen several other builders do, I used some 2″ wide painters tape.
I laid a straightedge across the top cowl to see how the four flanges lined up. Three were nicely in line…
However, one of the flanges sits about 1/8″ shy of the line.
After doing a bunch of research on cowl fitting, I decided to fit the bottom cowl first. I started by making a paper template for the gear let cutouts.
I transferred this to the cowl and then cut it out with the angle grinder.
After loosely fitting the cowl halves, I just had to take a picture. This is looking pretty damn sweet!
The flanges around the inlets needed a little trimming to get the joint tight. This is pretty close.
After a little further trimming of the gear leg holes, the cowl halves fit together reasonably well. There’s still a small gap down the side, but that should disappear after making the trims along the aft edges.
This is a problem though. Even if the gap pulls tight, the joint along the right side isn’t remotely straight. I can’t cut a straight line here because that would just make the gap even wider. The instructions (as well as other builder’s websites) indicate that the sides should overlap during the trial fitting. I’m starting to wonder if these pieces weren’t trimmed incorrectly at the factory.
The joint on the left side is pretty close to straight though. I’m going to email Van’s tech support and see why these flanges aren’t overlapping and what they suggest I do about it.
I loosely installed the fuel tank support brackets, mostly to get the brackets off my bench and out of the way. These will need to be tweaked to align with the fuel tank brackets once the wings are mounted, so there is no sense torquing these bolts down right now.
Back to work on the upper cowl, I broke out the die grinder and cutoff wheel and cut out the opening for the oil door. This needs to be removed now so that you have access to the inside of the cowl when fitting the upper hinge pin.
I cut out a 13″ diameter disk of hardboard to use in place of the spinner. I also cut a spacer that is the height of the firewall that is keeping the aft edges of the cowl the right distance apart. Even with the joint pulled tight and the flange around the disk as narrow as possible (without looking out of round), there are still small gaps on the outside edges. I’ll end up having to use some flox to make these joints tight. I also laid a straight edge across the center to see how straight all of the joints are. They’re ok right now, but I’ll need to sand these with a long straight edge to get them perfectly even.
I’ve been laid up on the couch for the last day and a half with the flu, but I’m starting to feel better, so I’ll push myself as usual :-). I started by clecoing the forward top skin to the fuselage so that I could file the firewall flange back flush with the skin. This is because the cowl flange butts up against this skin, but it’s quite a bit thicker.
I also taped together some pieces of popsicle sticks to hold of the front of the cowl. This will allow me to adjust the height if necessary. This is roughly 3/4″ thick.
I cut a 44″ long piece of the 1/8″ hinge material. I sandwiched a strip of 0.020″ aluminum between the hinge and the firewall flange and then drilled the hinge to the flange. This was slow going since I couldn’t use clecos to keep the holes in the skin and the holes in the flange aligned.
I biased the hinge forward slightly so that you wouldn’t see the eyelets between the forward top skin and the cowl.
I stopped by my buddy Corbin’s house to use his large powder coating oven. We powder coated all of the tailwheel components as well as the fuel tank brackets that mount to the fuselage.
The powder coat looked perfect on every part except for the weldment that ties the tailwheel bracket to the spring. Our guess is that they used some oil or other lubrication when press fitting the brass bushing into the steel weldment. This oil ran out during baking and caused the finish to fail. I’m going to clean this off and try again.
I was getting tired of having to squeeze under the engine to get from one side of the plane to the other, so I took the tailwheel spring off and tucked the tail up tight against the wall.
This gives me almost two feet between the spinner and the garage door; perfect.
While I had the tail spring off, I took the opportunity to get a bunch of the parts ready for powder coating. Since I’m using the JD Air Parts tailwheel link which only attaches on one side, I sliced off the other arm from the tailwheel linkage and ground the part smooth.
I also stripped the primer from the Bell tailwheel fork so that it can be powder coated. Afterward, I wrapped silicone tape around all surfaces of the tailwheel parts that I don’t want to be powder coated and set them aside. The tailwheel spring is too big to fit in my little powder coating oven, so I’m going to see if I can drop by a friend’s place who has a pretty big powder coating oven and do them there.
I needed to get the joint at the front of the spinner adjusted so that the opening is circular. Instead of measuring, I just put the spinner on the front of the cowl and adjusted the fit until everything lined up nicely.
I’m using 1/8″ spacers between the cowl and the spinner. The gap is surprisingly good along the top.
However, the joint between the top and bottom leaves a lot to be desired.
The left side is a little better, but there’s still a noticeable step. I spent a little time working on the fit, but there is still a lot to do before this will look good. I’ll probably end up making the gap between the cowl and spinner a little larger to start with and I can tighten it up with some fiberglass layups at the same time I’m fixing the fit between the top and bottom halves.
I spent the rest of the night digesting the instructions and plans for the cowl. This is likely going to be one of the tricker parts of the build.