Saturday, October 11, 2025

Panel Assembly!

The day has finally come to put the panel together!  I'd love to be able to route all of the wires before anything is on the panel and there's a lot of space to work with, but it's too hard to know exactly where everything will set.  I screwed the panel to the longeron brackets and then screwed the audio panel tray in (screws/nuts). The tray for the backup battery and comm transceiver went in next.


The brackets for the audio panel tray stiffen the panel up quite a bit, but the top still has a considerable amount of give when pushing on it, like you would do when pushing the buttons on the radio or autopilot panels.  Since the panel is already painted, the last thing I want to do is put more screws through it, so I decided to make some stiffeners out of aluminum angle attached to the subpanel and the top reinforcement of the panel.  I countersunk the screws on top - the glare shield sits down flush on it when the canopy is closed.  This really stiffened up the panel, and as an added bonus it gives me more places to attach wires routed from one side of the panel to the other.  I had to cut off a big chunk of the angle of the stiffener on the right side to allow clearance for the Dsub that goes into the autopilot panel.  Not ideal, but also not really a big deal given that this isn't a part that will really handle much stress at all.


Then the fun part came that I've been waiting months for!  I put everything in place and locked it down with black button head screws.  I have to admit, it looks pretty cool!  It's especially cool to know that I did it all myself, whereas most people these days just pay a shop to make the panel, from cutting to labeling and wiring.  The only thing of note that I'm not sure about is the fit of the audio panel.  It was very tight going into the tray and is canted just a tiny bit, meaning I got the tray angled down just a little bit.  I know it can go in perfectly straight since it was when I first fit the panel.  I may pull the panel out tomorrow and loosen up all of the screws of the tray to see if I can tilt it back to level.

The remaining things to do are to install the headphone jacks (wired into the audio panel by AFS, so I couldn't put them in before installing the audio panel tray) and 3D print a cover to go where the future IFR GPS will go.  I also need to route the cabin heat control from the heater box up to the panel.



Once everything is in place, the space fills up pretty quick!  Routing wires is going to be interesting.









Thursday, October 9, 2025

Exhaust Hangers & Panel Labeling

The exhaust tailpipes need to be supported with rigid, yet flexible, supports to allow the exhaust to move a little with engine vibration (especially on startup) without moving out of position enough to hit the cowl.  This is accomplished by clamping steel tubing to the exhaust and engine/mount and using high pressure rubber hose to tie the two pieces together.  The space in between the two steel tubes is only about 1/4", and the rubber hose spans that space and allows just a slight amount of movement.

The steel tubing that came with the exhaust kit wasn't long enough for my liking, so I got some of the same stainless steel on Amazon and made my own to the size I wanted.  The tubing is scuffed up, and a slight flare is made on the end to help keep the rubber hose from sliding around too much.

The vertical support goes from the tailpipe up to a bolt on the engine sump.  The horizontal support is a little different than what the plans show.  The plans show that you can tie the left and right exhaust to each other in the horizontal plane, but the new nose gear design with the elastomer doesn't have any space to allow a support to go from one tailpipe to the other.  I verified with other builders that the only real option is to go the opposite direction and tie the tailpipe to the engine mount.  That's not ideal because you're attaching a moving engine piece to a mount that doesn't move, but people say it actually works just fine.  These simple connections took hours to do between the two sides - those tailpipe clamps were far from easy to work with!  The setup is nice and rigid, but with a small amount of wiggle room.

The tailpipes take up lots of space and had to be permanently mounted before I could move on to other things.  With those done, I could put the scat tubing in place for the cabin heat box.  The other scat tube going to the inlet of the heat muff will go in a little later since it connects to the rear baffle that's not in place yet.


I switched gears a bit to see if I could salvage the paint job on my panel.  I wet sanded it and then used polish to try to flatten out the extremely uneven surface I had.  I didn't sand it completely flat in all places, mostly because I was afraid of cutting through the paint.  So it's far from perfect, but it's 1000x better than it was.  I definitely see the value of wet sanding!  It's kind of the secret tool of painting, like a grinder is to a welder.  I didn't polish the surface to a mirror finish because my plan is to spray a matte clear coat over it once the labels are on anyway.  The matte clear will also help hide some of the imperfections in the finish.  The gloss finish is what makes every little detail stand out.

I couldn't help but move right on to applying labels!  I had laid out all of my labels in a vector program and sent them off to be printed as dry rub transfers.  The benefit of spending the time getting all of the measurements correct in a vector program was that they could be printed in exact, true sizes.  That meant I could apply whole blocks of labels at one time vs having to do one word at a time and fight with getting them all straight.  The distortion in the photos make it look like some are crooked, but they're pretty straight for the most part.  Of course, I have to leave some imperfections so there's no doubt that I did the work myself vs farming it out!

The panel color isn't quite as dark as the photo makes it look, and the matte clear will lighten it up a little as well.  I'll spray the clear coat on tomorrow, then once that is dry I can get the panel back in the plane and start putting all of the instruments in!










Sunday, October 5, 2025

Heat Muff & Panel Paint

I need to get the exhaust finished up so I can plan out all of the other wire and hose runs for the engine (the exhaust takes up a lot of space, so everything else needs to be planned around it).  I just made a wild guess and made 6 heat sinks to go inside the heat muff.  There is room for more if down the road I find that I still don't have enough heat, but I imagine this will be plenty.  


The heat muff doesn't leave many options for where to put it.  It's about as long as the straight length of pipe it goes on, so regardless of how it sets relative to the engine mount, it's basically going to set where it's going to set.  I'll have to snake the scat tube around the mount.


The weather cooperated today, so I primed and painted the panel and a few other random parts.  I think my HVLP gun has seen better days.  I got it on craigslist for cheap, and while it's a professional gun, the parts it was missing that I scrounged up pseudo fixes for are obviously not ideal.  I will definitely be buying a different gun for the exterior paint.  I think some of my issues with the Stewart Ekocrylic are because the gun can't set a decent fan.  It has leaks around the tip, no matter what I do, and the widest fan that I can get without really messing up the paint atomization is about 4".  That's compared to other HVLPs that can make fans 2-3x that size.  Because of the little fan, it's very difficult to get consistent coverage - easy to go from not enough paint to completely flooding it on.  The gun is fine for primer, but not so great with a finish paint.

It's yet to be seen how the panel turns out.  Since I'm going to spray a matte clear coat over it all once the labels are on, it may not matter how the surface finish looks, as long as it's consistent.




Thursday, October 2, 2025

Misc Wiring & Exhaust

Doing some catch up documentation from the last few days of 10 minute here and there build sessions.

I can't remember if I mentioned before, but my 3D printed fan guards turned out very nice, but when I screwed them down onto the glare shield, they curled up around the screws because I had made them so thin.  3D printed guards are probably not a great solution since I want them to be low profile.  I think I'll probably end up getting them cut out of aluminum instead.  I'm just waiting to see if I have anything else I need cut before sending the design to sendcutsend.com.  I went ahead and spliced the fan wiring together so I could just run one pair of wires to the panel.  Once the panel is in place and the canopy back on, I'll figure out how to deal with the slack needed in the wires for the canopy opening/closing arc.

I hooked the fans up to my bench power to ensure they worked.  I'm glad I got the thicker fans.  They actually move a lot of air!


I had already finished up most of the switches in the panel, but there were still a couple of oddballs left to do - the Pmag and Master switches.  Neither of those go through the ACM.  The Pmag setup took a bit of head scratching.  The use of a three way switch for their OFF-ON-TEST functions is a little confusing to wire (mostly because unlike standard mags, the Pmags have a self powering function, which means they have to be able to be grounded in different ways to allow testing of both internal power and ship power scenarios).  One of the requirements of the Pmag is having either a 3A circuit breaker or fuse in the mix.  Usually a circuit breaker is used when a key switch is used for all of the runup testing, because then the interrupted power test can be done by pulling the breaker for each Pmag.  Since I'm using toggle switches, the circuit breakers ($$$) are not really all that necessary.  Pmag specifies that fuses can be used as long as they are the slow blow type, which allows for the potential initial startup surge.  I don't need access to the fuses in normal operations, so I put them on the subpanel above the ACM.



For my future self - these are the fuses I'm using:


I believe all of my panel wiring is in place at this point (but not routed nicely - that's for after I finally install the panel).  That means I can start creating a new rat's nest of wiring for all of the firewall forward connections.  I started pulling wires to/from the EMS module, as well as continuing with the main wiring of the alternator, starter, etc.  Still more to do there because part of cutting those big wires means figuring out their routing around the engine.  I'm getting there, just mulling it over before committing.


One thing I've procrastinated on is installing the tailpipes on the exhaust.  I was waiting on that because I needed to have an idea of where the lower cowl exhaust exit opening would set to ensure I had good clearance around the pipes.  The pipes have an angle in them, so spinning them in place means there's a huge range of where the ends can exit the engine compartment and what the clearance to the fuselage and cowl is.

After a lot of iterations, I got both tail pipes exiting in a fairly symmetrical way.  Perfect symmetry isn't possible because they both have a slightly different angle where they mate up to the rest of the exhaust.  The tail pipes get connected to their feeder exhaust pipes using a clamp that has a 1/4" pin welded on the inside of it that keeps the pipes from moving out of position.  I drilled a 1/4" hole through the pipes to accept that pin and clamped the pipes down.



The right tail pipe will be where the cabin heat muff is.  I need to get this in place next because the bulky scat tubing to and from it will dictate where I can route some of my wires.  The heat muff is just a thin cylinder that goes around the tail pipe, with fresh air feeding in one side and then going out the other end to the firewall cabin heat box.



One of the complaints about this design is that in cold regions it doesn't provide quite enough cabin heat.  Some people put a second muff on the other tail pipe, but I've seen those installs and it adds a ton of scat tubing to an already cramped area.  Instead I'm going with the increased surface area approach.  A common solution to increasing surface area is to stuff steel wool into the muff around the the pipe, but the complaint with that is that it decreases the volume of air that can get through to begin with.  I saw a builder who instead added stainless rings with fingers to the pipe.  He said it has worked really well, once he found the right number of rings to add on (he had too many at first and was cooked out of the cockpit).

A while back I drew up a design and sent them to sendcutsend to cut out.  The muff sets off center around the pipe, so my rings have to account for that.  One thing I didn't account for is a change in design of the muff from when I first saw it - it now connects the two end caps using steel rods that go inside the muff.  Those would get in the way of my rings, so I'll have to chop of some of the fingers to allow the rods to pass through.

My next step is to do some tweaking of my ring material (I didn't get my measurements perfect when designing them), bend them around the exhaust and bend the fingers up.  I think I'll start with 6 of the rings.  Those fingers should pull a lot of heat off of the tail pipe and still let the air pass through pretty easily...I think.