Project Update

Hey Guys,

The perimeter baffle seals are pretty much complete at this point, minus 2 small respective segments near the exhaust pipes.  That being said, I’m moving forward with constructing the Melvill-style exhaust pipe brackets, which the final two segments of baffle seals will attach to (immediately below the exhaust pipes)… then I can declare official victory over the baffle seals!

James rewelded the left outboard exhaust pipe today, so I’m pressing forward in getting the exhaust pipe brackets made and installed before trimming all the exhaust pipes to final length.

Chapter 23 – Exhaust bracket mockups

Yes, it’s been an admittedly slow, iterative process slogging through the minute tweaks to dial in the top and bottom exhaust pipe brackets to get them to acceptable tolerances before cutting them out on the plasma cutting table (at least that’s the plan).

Here is the “final” (always with caveats and alibis) lower right exhaust pipe bracket mockup, hot off the 3D printer press.

And with it test-fitted in place… Version #7 that is.

I also continued on with my tweaking of the top right exhaust bracket as well, dialing in and eliminating (or mitigating?) the gaps between the bracket and the half-tube pipe sleeves and the center crankcase vent pass-thru tube.  Here we have Version #9 (pic 1) and Version #11 shown (pic 2).  As I write this post the latest version is #12.

I’ve also been spending my time on getting the left side exhaust pipe brackets dialed in as well.  Here I’m about round 2 of my 3D printed exhaust pipe bracket mockups for the left side.  I suspect I’ll need a few more versions for both the top and bottom, respectively, before I’m ready to plasma cut these and start welding them up.

Speaking of plasma cutting… since I haven’t used my plasma cutting table in a couple of years, not surprisingly it took me well over 3 hours to get it cleared off and cleaned up in prep for software updates, ops checks and test cuts.  Then I can start making some parts!

As I closed up shop and headed into the house for the evening, I checked the mail to find that I got the PMag spark plug & ignition wire end terminals from the Emag Air bubbas… here those are.  I need to check if I have a spark plug wire crimper on hand from my old chopper building days.  If not, I’ll have to acquisition one of those.

I’ll be spending most of the day tomorrow (Sunday) with Jess down in Wilmington, so no physical (just mental!) airplane building occurring.  I suspect Monday will be final tweaks on the exhaust pipe brackets and working to finalize bringing the plasma cutting table back online.  I plan to plasma cut the top and bottom exhaust pipe bracket plates on Tuesday and get them drilled and tack welded up.

Chapter 23 – Exhaust pipe re-welded

Today was all about “engineering” and design tradeoffs and task redo’s.

I started off with lopping off an angled piece of 3/4″ stainless steel tubing that will serve as the right exhaust pipe bracket’s pass-thru for the crankcase vent tube —that nestles into the top V-groove of the right exhaust pipe pair for about the aft 2/3rds of the overall exhaust pipes’ run.  Since the pipes angle inboard the hole in the bracket plate needs to be less round (pic #1) and a bit more oval (pic #2).

After messing around with the right exhaust pipe bracket crankcase vent tube pass-thru for a bit, rewickering the CAD model and 3D-printing updated versions, I then took a break to go see my race car header welding buddy James to (re)weld up the left outboard exhaust pipe.

James did a phenomenal job as par usual, and below is the freshly rewelded left outboard exhaust pipe back home and in its place on the engine.

Now, that being said: my goal was to position the curved exhaust pipe insert (new piece) to get the outboard exhaust pipe “around the bend” in regard to doglegging it around the vertical slip tube portion of the inboard pipe, to then nestle in and align parallel with the inboard exhaust pipe on the back end.  Unless tack welding these joints and course correcting in situ on the engine, it’s not unreasonable to expect a slight loss in translation when I position it by pressing and taping together in my shop, compared to it actually getting welded up on a bench 40 miles away.

On the left exhaust pipe pair I have a gap between the pipes that is present (no issue as per Klaus Savier… actually preferred!), and after its rewelding the outboard pipe’s curve is probably 0.15″ to 0.19″ (a few degrees) more than I had planned.  This pushes the outboard pipe’s middle out away from the inboard pipe’s vertical slip tube portion a bit more when the very aft ends of the left pipes are kissing.  Thus, to keep the gap line between them more parallel, I need to kick the inboard pipe even more inboard about 1/4″, perhaps even as much as 3/8″ by the end of the day.

Bear with me…. as I told my buddy Dave Berenholtz in an email recently, these pipes are simply not the right ones for my engine and cowlings.  And with that being said, the final curve on the very aft end for all 4 pipes is at about the worst possible position, driving me to cut the pipes’ ends much deeper into the cowling (2-2.5″) than I prefer.

Or so I thought.

The slight unintended kick-out on the just rewelded outboard left exhaust pipe may be a blessing in disguise (in keeping with my motto: “better to be lucky than good!”) in that by bringing in the pipes as inboard as possible —”uncomfortably close” to the prop spinner lampshade— it then better aligns the outboard turning final pipe bend to shoot straighter out the back.  Versus trying to cut off the majority of each aft/final bend and point the straighter pipes inboard.  Roll with the flow and use your opponent’s natural energy against them. 

I looked back at my notes on when I was configuring the top and bottom cowlings in joining them together around the aft cowl opening.  My distance from inboard edge of the left inboard pipe to prop spinner lampshade was 2″.  That distance on the right was 2.5″.  Currently I’m pushing those respective numbers inboard about 1/8″.  Now, that measurement is not the opening exit point of those inboard exhaust pipes, but rather the closest point of the pipe that then curves back outboard with the exhaust exiting either parallel with aircraft centerline (at best), but in reality actually aimed a tad more outboards.

To capture and verify what I had assessed on the left side, I mounted the top cowling in place.  I also wanted to look at the upward angle of all the pipes to see how close the exhaust would get to the actual aft lip of the upper cowling.  Close, but no issue.

Now, the right exhaust pipes are not trimmed at all, so they appear much more outboard in pics than they really are.  I’ll reiterate that without cutting and rewelding, the closest these pipes can come inboard is about 2.35″ away from the lamp shade.  I however was still at 2.5″ away and since I’m bringing the left set of pipes further inboard (and trimming the ends to be about 1.5″ inside the cowling), I needed to bite the bullet and get the right side pipes as inboard as possible as well.

Which of course jacks up all the work I just did on the right side exhaust pipe brackets.  Do it right! (right?!)

Using my known new gaps by driving the right pair of exhaust pipes further inboard by about 1/8″, I then redrew the bottom right exhaust pipe bracket onto cardboard.  Not bad just out of the gate I have to say, and definitely good enough to import into CAD.

I then did the same thing on the top right exhaust pipe bracket.  Again, not too bad at all.

I took my latest top and bottom cardboard mockups of the right side exhaust pipe brackets into the house and imported them both into Fusion 360 CAD and got the initial modeling of those knocked out.  I 3D printed the top bracket mockup and did a quick fit test on it out in the shop.

It was very late in the evening by this point, and with corrective annotations in hand I took the top 3D printed mockup back into the house to tweak it further tomorrow.

Chapter 23 – Exhaust pipe bracket start

I started off today by mounting the bottom cowling to see how my just-installed aft bottom baffle seals fit into the scheme of things.  They look good and functional, so I’m pressing onward, upward and forward!

I spent about 45 minutes going through another few versions of cardboard mockups for the lower right exhaust bracket before dialing the last one in that was good enough to import into Fusion 360 CAD.  After modeling it up I 3D printed a 0.020″ thick version and checked it out in situ.

It’s hard to show all the nuanced gaps and seams that need to be tightened up in pictures, and of course there’s the invariable relational and unintended consequences thing where making one mod negatively affects a different area of the part.  That being said, here is Version 1 that kicked off this very iterative process.

Besides trying to get the seams around the pipe sleeves as air tight as possible, my initial main concern was the “water level” of the bracket itself in that I want it to be very close to covering half the exhaust pipe, lest I get more than a half moon and the installation and removal of the bracket around the pipe would be difficult, if not impossible.  Also, the right outboard “bird beak” needed dialing in, as well as both screw hole positions.

I have a specific position on the lower left where I want the platenut to get mounted, thus the hunting and pecking with each version to get the inboard screw hole positioned correctly.  I still had more finetuning on the curves around the sleeves, and of course more dialing in the “bird beak” on the right.

Version 4 is very, very close to the final configuration I need.  Any more fine tuning at this level will simply be with a file after I plasma cut this bracket half out.  The seams are certainly close enough with the seams that very little extra filler rod material will be required to fill any gaps.  I’m calling this one good!

As a point of interest, here is all the versions of the lower right exhaust bracket in their reverse progression from top to bottom.  These each took about 12-14 minutes each to print, but also required a good 20 minute cool down before removing them from the print plate.  I’d say each one, including the markup and CAD work represents at least one hour each.

It was getting a bit late, but I wanted to get a few rounds of the top right exhaust pipe bracket under my belt before calling it a night.

Here I’m on version 2 (or 3?) of the cardboard bracket mockup (pic #1) before getting one good enough to import into CAD.  I then got the basic outline modeled up and 3D printed a plastic mockup (pic #2).

I essentially worked on filling the same gaps and problem areas on versions 2 and 3, I simply wasn’t aggressive enough on my gap fills on version 2 as required.  I also played around with the top inboard and outboard corner radiuses a bit too.

Here we have the final version (#4) for the night.  I actually kicked off the print and intended to check it in the morning, but curiosity got the best of me and I snuck back out to the shop to see how she fit.  As you can see, I added the mounting screw holes in each corner for this version.

I then marked around the perimeter of this bracket mockup and each of the mounting screw holes to ensure that there was enough meat behind it to mount plantenuts, and to also ensure that the bracket would cover the gap around the exhaust pipes. Looking good so far!

Tomorrow I’ll see how far I can get in constructing this right side bracket… if possible and the plasma cutting goes smoothly, I’ll try to get this tacked up to have James weld this sucker up along with the left outboard pipe.  A long shot, but I’ll try.  We’ll see.

Chapter 23 – Aft bottom baffle seals in

To start off, I spoke with my racecar exhaust header welding buddy James about welding up my once-again-chopped-up left outboard exhaust pipe.  In between his  times being out on the road, he has a couple days back in his shop.  So the Plan is to get the pipe welded up this coming Thursday.

Before I jumped into the baffle seals, I did a little bit of cable management –investigation actually, to get an initial feel for how the bottom PMag spark plug, EGT and CHT wires would run to their respective starting points.  At this brief juncture I just focused on the spark plug wires.  I mounted the cylinder #3 wire into an Adel clamp, and then used zip ties to separate the spark plug wires as per the PMag manual, since these are not shielded cables.  I wasn’t overly happy with how the zip ties dug a little bit into the wire sheathing, so I figured I would try the T-Clips later.

On the right side I merely just mounted the cylinder #2 spark plug wire into hi-temp (white) Adel clamps at the bottom of the rocker covers on both cylinders #2 and #4. I plan on mounting a “K1000-3” platenut on the bottom baffle edge to mount a 3rd Adel clamp near the front corner, just keep the sharp edge of the baffling from gnawing through my spark plug wires.

Back on the aft bottom baffle seals, I started off by securing the middle reinforcement strip in place, determined the rivet spacing and then drilled the holes out for the rivets.

I then did this for both the left and right side reinforcement strips as well.  Obviously I have them tacked in place on the aft side of the aluminum baffles just so I can see them and the relationship of both edges.

This post covers 2 days worth of work, so at the end of the first evening I was on Fusion 360 CAD to make up these 0.032″ thick x 2″ long exhaust pipe sleeve mockups that will be a critical part of the Melvill-style exhaust pipe brackets.  After the ~2.5 hours it took for them to 3D print,  I then quickly set them in place for these shots… more work with them tomorrow/later.

Starting out on Day 2, I spoke with Trent at Emag Air to ensure I wasn’t missing any critical info regarding shortening the PMag spark plug leads (wires currently too long).  After confirming the process, Trent sent me a bunch of terminals for both ends of the spark plug wires.  I just had to pay shipping.

I also grabbed a few T-Clips from the house and tried those out on the spark plug wires, in lieu of the zip tie method… which I tried more out of curiosity, but also in case I run out of T-Clips.  Here’s a T-Clip securing the spark plug wires while also zip tied to the left front corner of the baffling.

Another shot of that from above.  Not bad, but I may very well opt for another Adel clamp here as well.  Assessing.

I then got back to work on the aft bottom “skirt” baffle seals.  After setting the middle baffle seal in place and using paper to create a template for the right side baffle seal (pic #1), I then cut out and test fitted that baffle seal (pic #2).

And then worked the right middle baffle seal and test fitted it in place as well.  Note that the outboard baffle seals on this bottom edge will actually be attached to the bottom exhaust pipe bracket to fill in the gap between this middle seal and the outboard corner.

I grabbed this shot to show how I’m securing the baffle seals with clecos while I fit them into place.

Here we have all the aft bottom baffle seals (minus the exhaust pipe bracket seals of course) test-fitted in place and ready for install.

I then gooped up the interfacing edge of the baffle seals to the aluminum baffle edge, added the reinforcement strips and riveted all the seals into place.

And here’s what that looks like on the inside with the reinforcement strips in place.

Tomorrow I will start work on constructing the left and right exhaust pipe brackets which will entail a lot of CAD work, some 3D printing of mockup pieces, and getting the plasma cutting table back online after its very long hiatus.  Clearly once the left and right exhaust pipe brackets are completed, I can officially finish off the last 2 segments of baffle seals.

Pressing forward!

Chapter 23 – Right baffle seals installed

Today was all about finalizing the aft right corner vertical baffle seals install, and I’m happy to report that I was able to finish that task.

After determining the shape with a paper template, I started off by cutting the top corner aft right baffle seal and fitting it into place, replete with rivet holes drilled and punched.

Here’s the temp install of the aft top right vertical baffle seal segment, held in place by the new and improved 1/16″ thick 2024 angle reinforcement corner bracket (pic #1).  I then mounted the top cowl to test fit the new baffle seal segment (pic #2).  The fit was good and other than trimming down the width a bit, I had no other issues.

The next lower corner baffle seal segment was a little bit trickier, and it took a good number of iterations, both in paper templates and with real actual baffle seal material to get this piece dialed in.

After a few rounds of top cowl on and off, and 2 baffle material segments before finally hitting the configuration jackpot on the 3rd (IIRC), I finally got it dialed in.

As for baffle seals, the final segment was the inboard piece that creates a split seam with the corner piece above to allow for the upper cowl’s right #2 CAMLOC to slide in and out of place when installing or removing the cowling.  In this pic you can see blue painters tape which is what I used for a few rounds of the initial template.

Sitting just inboard of the baffle seal blue tape template is a short piece of angled 2024, which is getting installed in the inside corner to both reinforce the aft right corner, but also provide some meat for the upper outboard K1000-3 platenut that will secure the top exhaust pipe bracket in the upper right corner (I did the same on the left side).

Here we have the aft left inside bracket installed (on the inside corner held in place with the rivet facing aft).  Also note by the copper colored clecos that I drilled out the rivet holes to their final 1/8″ diameter.

After another 45 minutes of cutting and testing the inboard baffle seal segment (blue tape guy from above) I then got to gooping (Hi-temp RTV) and riveting the aft right vertical corner baffle seals into place.

A shot from the inside.

And a shot from right aft outboard.

And a shot from the front “business” side showing the rivet backs and reinforcement bracket.

Yes, it’s a bit of an odd configuration, but here you can see the right side bottom exhaust pipe bracket (mockup) outboard attachment tab secured by a screw, overlaying the bottom inboard baffle seal segment.

And a final shot of the top left exhaust pipe bracket cardboard mockup.

Tomorrow I plan on getting MOST of the aft baffle skirt’s bottom edge baffle seals cut and installed.  However, there will be baffle seals that attach to the bottom edge of the bottom exhaust pipe brackets on each side, so until I get those stainless steel brackets cut out, configured and welded up the baffle seals will not be officially completed.

That being said, I’m pressing onward!

Chapter 23 – Right exhaust pipe tab

Today was all about getting the aft right side baffle seal reinforcement angle strip configuration finalized and installed (the install part didn’t happen)… along with the baffle seals that it will help secure.

Here is the original right side baffle seal reinforcement angle strip (blue) held in place with a clothesline pin.  Note there is very little peaking out on the bottom from behind the actual aluminum vertical baffle wall.  There are 2 reasons for this: A) I was using a length of 0.032″ 2024 that I had leftover from the VANs baffle kit and this length was all I had remaining after cutting out the left side, and B) I had intended to simply copy the bottom edge of the baffle wall to allow for clearance of the #2 CAMLOC while mounting the top cowling.

However, after assessing the aft right baffle corner with the requirements on how the right side exhaust pipe brackets will get secured, I simply didn’t have enough clearance with the right outboard exhaust pipe (from cylinder #4) to make an inward facing tab, as I did on the left.  The tab would have to face outward, so I decided to create a wedge just below the existing vertical baffle wall using the right side baffle seal reinforcement angle strip.  Clearly since the original angle reinforcement strip doesn’t hang below and isn’t long enough, I needed a new one.

After scrounging around I found this length of 1/16″ 2024.  A little thicker than I was looking for, but definitely not too crazy thick.  I temporarily secured it in place to check if the length was good.  It was.

I transferred the outline of the original right side baffle seal reinforcement angle strip to this new stock and then cut out what I could on the band saw.

And finished up some the trickier corner cuts using my Dremel tool.  Here we have the old right side baffle seal reinforcement angle strip along the newly made one.

Again, I did a quick test fit and it looked like it was definitely going to fit the bill in regards to my new requirement.

Somewhat as I did on the left side, and after a few rounds of assessing the aft right corner’s configuration, I mounted a 10-32 platenut to the right side baffle seal reinforcement angle strip onto the bottom edge peaking out from below the vertical baffle wall.

To confirm how the right side exhaust pipe brackets would fit before I proceeded further, I spent the rest of the evening painstakingly and iteratively creating first the bottom bracket, replete with its outboard mounting screw hole (pic #2).

I then did the same thing for the top side, making up the mounting bracket mockup in thin cardboard.

I’ll note that I of course reserve the right to change the design of the top side bracket, in that it looks a little round on the corners to my liking… perhaps I’ll try to match it more with the left side, still allowing for the exhaust pipe clearance opening in the baffle underneath.

Tomorrow is shaking out to be a rather busy day.  I have an EAA meeting in the morning, multiple scheduled phone calls, etc.  but hopefully I can get out into the shop to knock a good bit out.

Chapter 23 – Left baffle seals installed

Today was all about getting the aft left baffle seals installed and done with.  After remaking the larger lower baffle seal segment to extend it outboard, I then redrilled all the rivet holes out to 1/8″.  I also pulled the blue protective plastic off the aluminum parts (all 0.032″ 2024 aluminum scraps from the VANs Baffle Kit) and cleaned those up with acetone before gooping up the baffle seal edges with hi-temp RTV and riveting them into place.

Another shot of the aft left baffle seals installed.

And yet another shot from the forward side.

To do a final check on the aft left baffle seals fit I mounted the top and bottom cowlings, after I secured the exhaust pipes into position with some string… since I noticed that tape wasn’t holding them in place well enough.

I also did another round of sanding and shaping of the top cowl’s aft right trailing edge intersection with the right wing’s TE.

Here we have the installed aft left baffle seals inside the cowlings.  I’m thinking this dog will hunt!  I do see where I may have to pull the very bottom baffle seal into place aft of the CAMLOC, but that may very well be remedied just by putting the top cowl on first and then the bottom cowl on after that, whenever able.

A shot of the left side cowl opening with both the aft left baffle seals installed and the exhaust pipes (note still not finally trimmed to length) secured in position as well.

Here we have a couple of shots of the right side exhaust pipes (also not trimmed to final length) set close to final position inside the cowlings.  I’ll be starting on the aft right baffle seals next.

Moving forward!

Chapter 23 – Left aft baffle seals

Today I started off by cutting out a quick rough mockup of the topside plate for the left exhaust pipes’ securing bracket.  I’ll fine tune it and dial it in as I get closer to actually constructing the bracket.

Here are a couple more shots of the left side exhaust pipe bracket mockup.

I then embarked on the slow arduous process of cutting out templates (here I’m using a paper towel) for the aft left corner baffle seals…

Then placing the baffle seals, drilling the rivet holes, and test fitting the baffle seal segments.

Once I was sold on the baffle seal fit —this is just the top aft corner seal— I would punch the rivet holes in the baffle seals with a leather punch.  These oversized holes allow for more movement of the seal and reportedly mitigates the seals from splitting due to vibration.

Again, the machinations of fitting the baffle seal segments to the aluminum baffle, as well as integrating them to each other, then checking if they close up the gaps with the top cowling installed, is a very iterative process: with cowls constantly going on and coming off, with nearly all the CAMLOCs installed to check final baffle seal vs cowl contour.

That all being said, here I’m checking the clearance of the #2 CAMLOC of the top cowling with the bottom of the aft left corner angle reinforcement strip (blue, red pointer) that is hanging down below the aluminum baffle corner.

Although the reinforcement strip didn’t really create any clearance issues, I trimmed it at an angle to match the contour of the top cowl’s interior lip, and then cut, shaped and created another fascia piece to cover what would be exposed baffle seal material down in that lower corner.  Clearly it also helps reinforce the 2 overlapping baffle segments down in this corner.

Here we have all the aft left corner baffle seals in place, minus one small segment (see next pic).  The V-shaped gap on the side is to allow the baffle seals to seal both above and below the oil door opening cable conduit, respectively.

I then once again mounted the top cowling to double check my work.  As an added layer to seal up any gaps allowing any air through or around the oil door opening cable conduit, the small baffle seal segment (with green tape and red pointer) will be mounted on the forward side of the V-shaped split, filling in that gap.

It was quite late and although I didn’t reach my goal of actually getting the aft left corner baffle seals installed, I thought better of pressing forward tonight in order to ensure that I could double-check my work tomorrow in that all air paths are blocked off.

I’ll add that I ended the evening by taking a good look at my bottom spark plug wires’ routing as well as the EGT cable routing.  I’ve got a good mental plan on how I want those run and will document some mounting tabs that I’ll need to make up.

Speaking of EGTs… Yesterday I installed first the standard EGT probe into the cylinder #2 exhaust pipe and assessed its clearance.  It was quite acceptable (clearly not quite as good as if I used the compression fitting EGT probe).  Today I did the same on cylinder #3.  Same story.  So my plan on EGT probes AT THIS TIME is to use all standard probes and upgrade when able (task complete… for now!).

Pressing forward…. painstakingly slow at this point!


Chapter 23 – Left exhaust pipe tab

Yesterday I used a yard stick with a Sharpie taped onto the end of it to make a mark on the top cowling right baffle & reinforcement rib as a starting point for where it needed some trimming.

Today, after removing the top cowling, I started at that mark going forward to mark the right baffle rib for trimming (pic #1), and then trimmed it (pic #2).

After re-taping the outboard left exhaust pipe back into its proper position, and the left lower outboard exhaust pipe bracket mounting tab, I then mounted the top cowling back into place.

I have to say trimming the right baffle rib seems to have done the trick as all the front right corner fasteners went in fairly easily.  Moreover, the baffle seals are slowly conforming to the shape of the top cowling as each time the top cowling is mounted in place it’s going on just a little bit easier each time.

I also took a few minutes to sand down the outboard trailing edge of the right aft side of the top cowling where it intersects the aft inboard TE of the right wing, of which I’ve also been doing some fine tuning as well (marking while cowl on, then sanding/trimming when top cowl off).  I still need to finalize the cowl TE here, but I’m waiting until all the baffle seals are in and the exhaust pipes are secured internally to finalize this junction.

Of course the left outboard exhaust pipe hasn’t been welded up into it’s final configuration yet, nor have the exhaust pipes been trimmed to final length, but here is a current view of how they sit inside the aft left opening of the cowling.  Not bad, but they do tend to still point outboard a bit more than I want.  I’ll try to mitigate that a bit when I trim them to final length inside the cowling.

I thought I would add a shot of my chicken scratching plan that I drew up last night for today.  Of course while my mental meanderings can take a bit of time to get down on paper, I don’t often make it a practice to include them into these blog posts.

Now, my primary reason for putting the top cowling back on was to check the position of the left lower outboard exhaust pipe bracket mounting tab that is the focus of today’s efforts.  I had measured the proposed exposed drop of this tab to be 0.875″ from the bottom edge of the current aluminum baffle (“skirt”).

However, after both cowls were installed I realized that this measurement needed to be reduced in dropdown depth to just 0.6″.

With that bit of knowledge I then created the actual outboard tab/bracket (still blue at this point) and taped it into place inside the aluminum baffle aft corner.

I then connected the outboard 0.6″ marked line to the inboard bottom curved line of the bottom baffle edge (inboard of the inboard exhaust pipe) to get my downward angle of the tab going inboard.  I (quite cleverly… ahem!) used a magnet retriever to hold a 10-32 platenut in place to give an idea of what this bracket is all about (pic #1).  I then trimmed the corner tab to length (pic #2).

In a way installing this aft corner tab is atonement for another sin of the past, in that if I had had my exhaust pipe configurations truly dialed in, I wouldn’t have cut nearly as much of the bottom baffle corner away as I did.  Thus, I would have still installed an interior corner reinforcement bracket, but the original face (“skirt”) of the aluminum baffle would have been present.

But since it’s not, I had to resort to cutting out a corner fascia piece of 0.032″ thick 6061 to replace the material I had errantly cut away.  Here we have not only the corner fascia piece fitted and riveted into place, but the 10-32 (“K1000-3”) platenut and the corner exhaust pipe tab/bracket installed as well.

And a closer look at all that…

And a look from the left side at the side bracket securing rivets.

With the exhaust pipe bracket corner tab installed, I remounted the bottom cowling to check clearance… not too bad.

But since the lip of the top cowling overlaps the bottom cowling in this area, I had less than 1/16″ clearance with the top cowling mounted in place.  Clearly some trimming was required.

I reached into the cowling to mark the bottom corner of the exhaust pipe bracket corner tab for trimming (pic #1) and then refined the trim line after I removed both the top and bottom cowlings (pic #2).

I grabbed my trusty Dremel tool and carefully trimmed away the offending extra material on the lower edge of the exhaust pipe bracket corner tab.  I then threw a screw into the platenut just to reiterate the point visually that I installed the darn thing!

It was getting late, but I spent another 15 minutes making up a quick cardboard mockup of the lower left exhaust pipe bracket.  There will of course be a bracket on the top side as well that clamps the exhaust pipes into place on each lower corner of the baffles (with welded-in half tube “cups” compressing the exhaust pipes from top and bottom to secure them in place).

Hopefully this should help explain the purpose of the tab I just installed that will secure the left corner of the lower left exhaust pipe bracket, as there will be a screw securing each corner of the exhaust pipe bracket plates: 2 on the bottom plate (shown) and 2 on the top plate (4 total).  Again, as I casually mentioned, these exhaust pipe brackets are based fairly close to what Mike Melvill had on his bird.

And with that, I called it a night.  Tomorrow, after I finish designing and configuring my exhaust pipe brackets, I intend on getting the left aft baffle seals installed.  I’ll then repeat this process for the right side exhaust pipes and baffle seals.