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 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.

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.

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.

I fabricated the exhaust stabilizer strap tonight out of some aluminum angle that I cut one leg off of.  I primed and painted it and will install it tomorrow.  This ties each pair of pipes together at the back end so that they all move as a unit.

I installed the exhaust stabilizer strap that ties the two pairs of exhaust pipes together.  This significantly stabilizes the exhaust pipes over just having each pair supported by on hanger.

Construction work is slowing down on the plane a bit while I’m working on the electrical system design.  The VP-X is fairly significantly different than the architecture specified in the Aeroelectric Connection.  I’m reworking most of the schematics and still trying to decide how I’m going to handle backup circuits for several devices.

The stock throttle bracket that Van’s supplies doesn’t work with the Superior sump since the attach point is in a different location.  I’m going to fabricate a custom bracket out of some 16 gauge steel (the same thickness as Van’s bracket).  I used some really thin (0.004″) aluminum flashing I had on hand to mock up the bracket.  This puts the cable on a direct path to the hole in the firewall and keeps it well clear of the exhaust and sump.

Here’s a shot from slightly lower in case that makes it more clear.

Here’s what the rough bracket looks like.  I unfolded this and traced the pattern onto some 16 gauge stock I picked up from Home Depot.  Cutting it out will be easy, but I’m still not quite sure how I’m going to bend this.

The throttle bracket that I mocked up a couple of days ago had an extra bend that was unnecessary and I couldn’t figure out how to bend it using the tools I have.  Instead, I mocked up a simpler bracket.  The slot on the end was only to make it easier to fit while mocking it up.

I unfolded the prototype and transferred it to a piece of 16 gauge steel.

I marked out the bends and bent them using this vise brake that I borrowed from my dad.  This thing had no problems bending 16 gauge steel.

I drilled the mounting and cable holes and temporarily mounted it to the engine.  Unbelievably, I absolutely nailed it on the first try.  The 1/4″ mounting holes perfectly lined up with holes on the sump and the placement and angle of the cable hole was spot on.

Here’s a closeup of the mounting end.  This picture makes it look like it comes pretty close to the exhaust pipe, but there’s quite a lot of clearance.

After some adjustment, here’s the throttle in the full open position.  Notice the slight gap between the nut behind the throttle nob and the friction control.  This ensures that the throttle arm hits the stop on the fuel injection servo which ensures that you can reach full throttle.

Here’s the throttle in the full closed (idle) position.  Again, I’m hitting the stop on the fuel servo which ensures I’ve got the throttle fully closed.

This is a poor picture, but it shows the alignment between the throttle cable and the hole in the firewall.  It’s a perfectly straight shot back to the firewall from the bracket and clears the heat muff inlet by a 1/2″ or so.

Now that the throttle bracket fits correctly, I can clean it up and powder coat it before installing it for good.