Injector line reroute

So, I’m pretty happy tonight – I worked out a problem that’s been nagging at me for a while. Previously I’ve mentioned how one of the injector lines interfered with the case top mount for the SDS coil pack, and a while back I took a crack at making a custom mount out of some angle. While the mount itself turned out OK, I discovered while fitting the top cowl that the mount was too tall, causing the coil pack to contact the cowl.

I’ve been rolling around ways to address this for a while. I’d initially thought about making a new custom mount that sat lower, but since the whole idea of that mount was to let the injector line pass below it, there wasn’t really any room to make much of a difference. This week I got back to brainstorming how to handle this, and eventually I decided I only had two real options: either relocate the injector line, or put the coil pack somewhere else. Mocking the coil pack up on the other magneto pad wasn’t encouraging; between the oil pressure sender line and the CS prop oil line, it’s pretty tight back there.

So I went on a research journey on the topic of these injector lines, starting with the intent to buy the materials needed to make a new line. It turns out that these lines can be bought prefabricated, in whatever length you need, and they’re hand-bent to the required routing. That indicated to me that simply massaging the routing of the line I had was a reasonable way to approach this, so I started down that road.

The good news is that this line had enough slack in it to allow for the rerouting I had in mind. A little more bend at the flow divider allowed the line to cross the case a couple inches further forward, in front of the SDS case top mount. I was able to reuse the previous retention mount on the side of the coil mount, thus securing the line just past the case split. Further over, the adel clamps already in place on the pushrod tube still worked just fine.

With the coil pack loosely in place on the mount, we can see the routing. The main area of concern while I was doing this was the spot in this photo – the clearance between that bend and the coil pack mount. I was able to get about an inch of clearance without violating the minimum bend radius specs for this line:

From the other side, we can see how the nice billet mount was reused to secure the line:

This was very satisfying, but it left one more question: supporting the rear baffle. Normally, there’s a brace that goes from the case top to the baffle, but the coil pack mount precludes using that. I’d been planning on figuring some way to brace from my custom mount to the baffle, but hadn’t really worked it out. Since I had the coil pack mocked up in place, I decided to put in the baffles to see how things looked. It turns out that the baffles are close enough to the coil pack that this will be an easy problem to solve – I can just use a small piece of angle to tie the baffle into this mount screw on the coil pack.

I still need to go back and permanently mount all this stuff – for example, the coil pack mount bolts are only hand-tight right now. They’ll need lock washers and torquing as well. I suppose I can go ahead and bolt the coil pack itself in place as well; that way I can double-check the cowl clearance next time I put the top cowl on.

I’m somewhat tempted to quit working on cowl fitting for the time being, and get back to general FWF cable routing and so forth. The whole reason I started on the cowl was to allow working on the baffles, which I guess I’ll still need to resume before I can finish off all the FWF stuff. I think I’m just trying to avoid that whole fiberglass + sweat situation, but there’s not going to be any way around that for probably another four months or so.

Posted in Firewall Forward | Hours Logged: 1

Injection servo mount fix

This was another of my FWF tasks that I’ve been putting off for a while. I discovered some time ago that as provided, the FM150 fuel injection servo interfered with the bottom cowl. I also determined that if I removed the 1/2” spacer between the sump and the servo, the clearance issue went away. Some research indicated that the only reason that spacer is there is because Superior provides really long studs with their cold air sump. That is, it’s just there to accommodate the mount hardware.

Well, as part of a Spruce order I put together last week, I figured out what studs I needed here and got those added to the order. That just left the fun of removing the old ones and installing the new ones. Removing these was a lot more fun than the alternator ones from a few days ago – these were really tight, to the point that my first attempt to remove one using two nuts and some heat failed miserably

I was on the brink of ordering a special stud removal tool, but I decided to give it one more try, this time being more generous with the heat. Turns out that about a 30-second blast with a Mapp gas torch puts enough heat in to break the stud loose, so I was back in business. Most of the fun came from figuring out how to orient the torch to heat the stud without destroying anything else in the area, like the rubber intake boots visible in this photo of the stud-less sump:

This led to a surprisingly long and tortuous discovery session. You see, at a glance, it looked like the studs I ordered were too short to fully engage the sump while also providing enough length for the servo and the mount nuts. I actually came pretty close to ordering another set of studs that were 1/4” longer…oh, and those studs were $18 each.

What made this fun was that I didn’t want to just install a new stud without knowing it was right – so I ended up measuring, re-measuring, reading up on proper thread engagement, and so on. Eventually I decided that these studs would work, to the point that I was confident installing one. But it was also critical that I thread the studs in to a very specific depth, so I ended up using a washer stack on each stud to give me a nice precise stopping point during installation.

After all that worrying, the first stud I installed gave me the chance to verify I had good engagement with the servo, and then the other three went in in about ten minutes. Finally, I got the servo back in place, torqued all the mount nuts, and reinstalled the fuel lines. After being temporarily mounted with a lot of stacked washers for a while, this servo is finally back in place for real:

I guess I can’t really put off cowl trimming any more now. That’s going to be a lot of fun, seeing as how it looks like we’re going to have near-triple-digit high temperatures for the foreseeable future. Sweat and fiberglass dust are not a very enjoyable combination…

Posted in Firewall Forward | Hours Logged: 1

Standby alternator install

So, in sort of an attempt to get some momentum going on this project, I’m pausing on the cowl stuff for a bit, just to get some more fun stuff done. This was somewhat enabled by receiving some parts that I’ve been waiting on for almost a year. Way back when I was trying to get all my accessories mounted before hanging the engine, I discovered that the 90° oil filter interferes with the B&C vacuum pad alternator I’d bought. So at the same time I was ordering a different oil adapter from B&C to work around my engine mount, I also ordered a drive extension kit from them. The extension kit was backordered, but that was OK…I wasn’t in any huge hurry, and worst case the airplane could fly just fine without the standby alt.

Of course, that backorder period was a good bit longer than expected, but it matched up fine with my work ethic (or lack thereof). In any case, last week I got an email from B&C that the parts were finally in, and they showed up here a couple days later. Finally, something relatively simple and fun to do!

The kit consists of a few different parts: first, a longer shear coupling that’s installed on the alternator spline drive, a spacer for the mount pad, and the most fun part: four longer mount studs. So Job #1, after removing the existing blanking plate, was to remove the old studs. In a pattern well-known to any DIY mechanic, the first three studs came off with relative ease, but the last one was a real bear, and required some torching to remove. Really fun trying to heat the stud without scorching anything else nearby…

After that, it went well…new studs went in easily with the provided stud installation tool, then I just had to stack everything together. There’s a gasket, then an adapter with a gear to the accessory drive inside and the splined socket outside, then another gasket, then the spacer, then another gasket, and finally the alternator.

That said, this isn’t 100% done yet. I unwisely used the same mount nuts for the stud removal, and a couple of them got rounded while working on that one stubborn stud. I went ahead and used them to mount the alternator, but I’m going to replace them with new nuts at some point. Oh, and did I mention that I just placed an Aircraft Spruce order today? No matter how hard I try to combine Spruce orders to save on shipping, it seems my efforts are doomed to failure…

Anyway, here’s a shiny new alternator on my shiny new engine:

Posted in Firewall Forward | Hours Logged: 1.5

Lower cowl attach do-over

Yep, I’m back at it. I didn’t do a lot – in fact the stuff I’ll write about here happened over the course of a couple days – but it’s something, right?

I’ve been thinking about this change for a while now. Going by the plans, the cowl attaches to the firewall using piano hinges. The lower cowl has four separate hinge pairs – one pair along the vertical sides, and another on the lower horizontal joint, on either side of the cooling ramp/exhaust exit. It seems that lots of builders have issues with those lower hinges cracking over time – sometimes over a pretty short period of time.

One common fix is to replace the cheap rolled hinges with pricier extruded material, which should hold up better. But after talking to some other builders, it sounds like an even better option is to get rid of the hinges in that spot, and just use screws for the cowl attach. Doing it this way means the hinges are replaced by a couple beefy alclad plates – and the .063” scrap I have lying around is perfect for this.

An additional benefit of this choice is that de-cowling with the engine hot should be less unpleasant. The pins for those hinges are removed on the inboard side – that is, where the exhaust is. It doesn’t take much imagination to envision some really fun burns out of that operation.

So anyway, that’s what I’ve been doing. I cut the new .063” mount plates to size, cleaned up the edges a bit, and match drilled them to the firewall joint. Now that they’re clecoed on, the lower cowl can go back in place, and I can get back to work sanding that cut edge.

Posted in Cowl | Hours Logged: 1

First lower cowl trim

Haven’t had a ton of time for the project this weekend, but I still got some work done. Yesterday I pulled the lower cowl off and got to work fitting the attachment hinges. I actually ended up cutting a new piece for one of the hinges on the bottom of the cowl – because the eyes weren’t lined up like I want. What I want is to always be able to start the attach pin in the fuselage-attached hinge half, before putting the cowl in place – this will make things a tiny bit easier.

After doing that, I just spent the time to clamp each of the four hinges in place on the fuselage and drilling through the rivet holes into the hinges. Today I picked up by removing those hinges and deburring and countersinking the holes as required. Once they were back in place on the fuselage, it was time to move on to trimming the aft end of the cowl.

First, though, I had to finish laying out the trim line. Doing this is a little more complicated on the lower cowl, because it doesn’t sit flush to the fuselage all around like the upper. There’s the cowl exit area, where the cowl itself dips down – there’s no way to easily measure from a guide line on the fuselage to mark this area. What I needed to do was to find some way to take the marked cut lines and extend the plane they represented across the cowl exit area.

The method I settled on for this involved using my laser level again. I just set the cowling on the table on end, set the level diagonally off of the cowl corner, and adjusted it until the line was following my cut marks. At that point, I could be sure it was following the desire cut plane, and so I marked more hashes around the exit area:

I repeated this exercise from the other bottom corner of the cowl, so I essentially brought the cut line in from both sides. It was encouraging to see that the resulting marks joined in the same spot. Next, as with other cuts, I laid masking tape all along the marks to create a continuous cut line, then got to work with the oscillating saw. This was mostly rote work, but the inside corners at the edge of the exit were a little interesting to do…I could just make the cut all the way from the outside, so I ended up making it as deep as I could, then finishing the cut from inside the cowl.

After a bit of basic cleanup sanding of the edge, it was time to hang everything back on the fuselage. I was a little worried that I might have cut too close to my trim line, but as it turns out I did pretty well, and there shouldn’t be nearly as much sanding to fine-tune the cut line as with the upper cowl.

Better yet, it looked like sanding this also won’t be as tedious as I thought it might. Mounting and dismounting the lower cowl in the current configuration is kind of a pain – It has to be lifted in place, the aft end rested on some strategically-stacked boxes, then I hang the front end in place with my cleco + string setup, then I put ratchet straps around the aft end to cinch it in place, then I go back up front and cleco the temporary join plates, and finally the thing is hung.

I really didn’t want to have to repeat that exercise over and over again. But it turns out that with the join plates in place up front, if I loosen the ratchet strap, the aft end will drop down just enough so I can sand it with my little popsicle stick setup. There will still be plenty of trial-and-error, but it’ll be a little more tolerable.

I did start on sanding that edge down a bit today, but there’s still plenty of work to be done…I’ll have to pick back up on that another night.

Posted in Cowl | Hours Logged: 4

Prepping for the lower cowl trim

I started tonight by doing a bit more sanding on the mating points of the forward cowl, but I didn’t really do much. I discovered that waiting a few days made me a lot more accepting of how the gaps were looking now. It helps that in reality, the pieces will be spaced apart (to provide room for paint), which makes the very small variances almost unnoticeable.

Next up was creating a way to fix the cowl halves together at the front. Eventually, there will be screws and nutplates here, and the normal procedure would have been to drill pilot holes for these and cleco the halves together…but since I cut the flanges off, I can’t do that. Instead, I cut some pieces of scrap aluminum and used them to temporarily fix the halves together. On the upper cowl, I’m using two of the three screw pilot holes on each side; on the bottom, it’s just another temporary hole that I’ll fill later on:

Next, I got the cowl halves installed on the airplane, and pulled the halves together at the aft end with a ratchet strap. This allowed me to go around and use that same tape line on the fuselage to draw the aft cut line on the lower cowl:

So now it’s about time to do some more trimming and fitting, though once again I’ll have to pause and fit the hinge halves to the fuselage before I can put the lower cowl back in place. That’ll be work for another day…

Posted in Cowl | Hours Logged: 1

Even more cowl mating

Well, this has been a tedious bit of work so far. After previously doing a test-fit and getting some guidelines to use for working on the cowl halves off the airplane, I’ve been working on getting the forward mating fine-tuned. The first issue was finding the best way to work on the cowl; my previous approach of putting both halves on the floor, aft side down, just wasn’t working for lining them up reasonably.

I decided to try laying the lower cowl up on the work table, and sort of going from there. A jug of checks placed inside the lower cowl, plus some wadded- up old sheets beneath, manages to keep it in a reasonable working position. Then, the upper cowl can sit on top, with the aft ends held together in rough alignment by just a couple cleco clamps. The result actually works out pretty well:

That was the simple part, however. The basic task in getting the forward mating surfaces right is to carefully massage the four points of contact: the two sides of the prop spinner area, and the outboard corners. What I’m going for is having all four points of contact mating once and evenly, while also ensuring that the two air intakes are also the same size. It’s entirely possible to remove material asymmetrically and end up with a lopsided nose, which I don’t want.

The air intake aspect actually made this slightly more straightforward; when I compared the two, I found that the left intake was about 1/4” taller than the other one. Not enough to really be obvious without using a measuring tool, but that meant that I could essentially consider the right outboard corner junction to be my reference point, and do all the material removal on the other three points. This would have the effect of tending to shrink the left intake to make things more even.

The process is simple, but tedious. As long as an unwanted gap exists somewhere, go find the spot where the halves are making the tightest contact, and sand that area until the contact becomes light, or even until there’s a bit of separation for larger adjustments. Then find and sand the new tight contact point, then find the next one…over and over.

At first I was making relatively dramatic adjustments, using a sanding block with 40 grit. As things started to get closer, I switched to using bare sheets of sandpaper, either a bit of the 40-grit – which is relatively thick, cloth-backed material – or some 60 grit I had lying around. The 60 grit is nice thin paper, and works really well for truing up a gap. The approach here is to just pull a strip of sandpaper in the joint to be worked, apply a little pressure to the joint, and work the paper back and forth. An uneven gap will naturally tend to even out, since the tight contact point will put the most pressure on the paper. Once the paper moves with about the same resistance throughout the joint, it’s trued up pretty well.

There’s still a little more work to be done, but overall things are looking pretty good:

Really my only gripe at this point is that the prop spinner joints still aren’t trued up very well – they make good contact on the forward-facing portion, but the flanges have a bit of a gap that opens up towards the back. I’ve about decided that I don’t care about this on the inboard side – this won’t be visible at all when installed on the airplane – but I do want to even up the outboard portion a bit.

Also, the above photo somewhat displays another middle annoying issue I’m dealing with up here – all four points just won’t line up at the same time in terms of the outward-facing areas. If I line the outboard corners up, then the lower cowl sits a little far back on one side of the spinner, and a little bit more on the other side. Note the bit of shadow on the right side of the spinner above. If I close the gap at the spinner, the upper cowl corner overhangs by 1/8” or so, and there’s barely any material left to trim at the back of the lower cowl. On the other hand, if I line up the corner, then I have a similar big gap at the spinner.

In the photo above, I’m basically splitting the difference, which I decided I liked best after trying various approaches. I have to remember that the end goal here is to set the joint on the front of the cowl, so I can then hang them and trim the lower. Sometime down the road, I can worry about fixing the misalignment – I’ll be spending time on the entire exterior of the cowl, and adding some micro up here and reshaping everything will just be part of the fun.

Posted in Cowl | Hours Logged: 2.5

More cowl mating work

So, after the last session, I spent some time reading up on cowl fitting. One particular point I wondered about was whether it might be a good choice to just cut off the overlapping flange around the prop spinner, in order to simplify getting that interface the way I wanted it. I figured it should be fairly simple to add a flange back later on, and when I found a post from Dan Horton, one of the RV fiberglass gurus, suggesting this same path, I decided to go for it.

So I sawed off those flanges, enabling to me to work on that junction as a simple butt joint. This made things easier, but still not 100% easy –  the new issue was figuring out how to fit the portions of the flanges that extended aft. If I just have the cowl halves on the floor, I have to take a pretty wild guess at where they should be positioned at the aft end, and this in turn affect the mating angle at the front. I felt like what I needed was a way to test-fit the halves on the plane to see how the junction was going.

The problem here was figuring out a way to support the front of the lower cowl. Eventually there will be nutplates holding the two halves together, but not only can that not be done until the fitting here is done, it’s really out of the question now that I removed the flange. Eventually I decided to just drill a pair of temporary holes, one below each air inlet. Each hole has a cleco installed, and then a piece of string can go between the checks and over the prop spinner, thus providing a way to roughly hold the lower cowl in position.

With that done, I made my first fitting of the lower cowl on the airplane. The string+cleco idea worked pretty well up front:

…and to bring the rear into alignment, I used the usual method of wrapping a ratchet strap around and using it to pull the lower cowl up against the fuselage:

Doing this allowed me to check the mating angles at the spinner joint, and make some marks to fine-tune them. I removed the lower cowl, sanded it to shape a bit, and hung it once again. This showed that my joints were getting pretty close, but the right side didn’t quite want to pull flush. I suspect that the inboard part of this is interfering, but it’s impossible to see with the cowl on the airplane…which is a new issue with this approach.

But I realized that the main purpose of this was to figure the relationship between the cowl halves when roughly in place. Being on the fuselage was necessary to establish that relationship, but not to maintain it. With the halves pulled together, I just used a Sharpie to trace the upper edge of the untrimmed lower cowl onto the upper…and now I can use that to join them in alignment without being on the airplane, which should allow me to to the last bit of fine-tuning of this interface up front.

That will be for another night, though.

Posted in Cowl | Hours Logged: 1

Fitting the cowl halves together

Today I picked right back up with the fun of trying to hash out the junction between the cowl halves. After looking at some other build logs last night, I worked out a better idea for trimming the forward corners, which in turn allowed for me to make a much better attempt at nesting the spinner area.

This showed me a new problem: specifically, the material thickness in this area on the upper cowl is 1) not consistent, and 2) significantly thicker than the recessed mating area on the lower cowl. So I went to work removing material here; I sanded down the upper cowl mating area a bit, but decided to do the bulk of the removing on the upper cowl. So far, I’ve been through three or four iterations of removing material, smoothing the area out, and trial-fitting the halves together.

Things still aren’t fitting perfectly, but they’re a lot better. I can slide the junction almost all the way together:

But the junction still isn’t quite flush, as a picture from inside the spinner opening shows:

I’ve already surrendered to the fact that this mating area isn’t going to fit snugly at first – there’s just no way I’m going to accurately sand this stuff down to a precise fit. My goal is just to get it to a point where it nests properly, and then I figure I’ll cover one side with tape and mold release, then apply some epoxy-flox mixture and clamp it back together again to fill the gaps.

Similarly, the front corners aren’t exactly meeting beautifully. Maybe they’ll end up looking better once I’m really fitting the halves together, but I’m preparing myself for the possibility of needing to do some significant reshaping there to get things looking good.

Posted in Cowl | Hours Logged: 1

More upper cowl trimming, starting on lower half

OK, so…first order of business today was revisiting the aft flange of the upper cowl. As mentioned yesterday, while I did a lot of fine-tuning of the fit to the fuselage, I still wasn’t completely happy about it. So I spent even more time carefully sanding the flange to further tweak the fit. The good news was that things were close enough that I no longer needed to remove the cowl to sand it. With the spacer between the cowl and the prop spinner, the back of the cowl was pressed snug against the fuselage. That meant that I could wiggle the joint around to figure out where there was contact, then lift that area enough to sand it a bit with some 80 grit glued to a popsicle stick. By doing this, well, a bunch of times, I eventually got things looking really tight:

Since I was finally happy with the fit, it was time to move on to drilling the upper cowl to the hinge halves that retain it. To do this, the holes get laid out and initially drilled in the cowl, then later drilled in assembly with the hinges. As suggested in the construction manual, I laid out the rivets about 1” apart, after marking the ends of the hinge pieces on the cowl. A little work with the rivet fan and I had my holes taken care of:

I also took this opportunity to rough-cut the opening for the oil door; this opening also serves to allow access to the upper cowl hinge pines, so I needed it open for the upcoming work. I didn’t open this up all the way to the plans dimensions; I’m probably going to do something custom with the hinge and latch for this, so I’m leaving extra material for potentially working that out later.

Then the cowl went back onto the fuselage, and I very carefully got it positioned, then started drilling. My approach to managing the gap between the cowl and fuselage is to use that spinner spacer to hold the claw snug against the fuse, then I just manually held the hinge half in the rearmost position while drilling. The intent here was to use the bit of slop in the hinges to allow for moving the cowl forward for final fitting later on. About the only issue here was that while I could easily manipulate the hinge on the right side of the plane – thanks to that oil door opening – the left side was way more difficult. The end result is that I don’t have quite as much room to move the cowl forward on the left side, but I’ll still be able to do even more sanding on that later on to finalize the gap.

Anyway, at the end of all that I had the cowl fully checked to the hinge half: 

And with the cowl off, we can see those newly fitted hinge halves:

There was still more work to be done on these hinges, though; the cowl isn’t as thick as the material stickup in the fuselage, so there’s some shimming needed here to get a nice flush line between the cowl and the fuselage. The plans call for just doing a blanket .032” shim, but I noticed that the gap was more pronounced around the edges of the cowl, and less so in the middle. So I did some trial-and-error with some aluminum scraps; this resulted in using those .032” shims on the outside edges, but then closer to the middle .025” shims made for a better fit.

Once all that was laid up, I got to do the work of cutting the shims, drilling them in assembly with the hinge halves, and finally fitting everything back to the cowl. Once that was done, the cowl went back on – again – to verify that things lined up as expected. The fit still isn’t 100% perfect, but if I want to fine-tune this down the road, I should be able to do it just by adding a bit of micro to the cowl and sanding to fit.

OK, next up – it was time for the rest of the trimming on the upper cowl. With everything else in place, I could use some layout marks I already had just behind the spinner – marking the correct cut point to get things nice and symmetrical with the lower cowl – and lay out the cut lone for the bottom edge of the cowl. My approach for this was to use a laser level to first verify that my reference marks were appropriately level, and then to carry those marks around each side of the cowl.

I started with the fuselage in the level flight attitude – this would have given me a cowl split line parallel to the longerons – but that resulted in the level line dropping off the bottom edge of the cowl at the aft end. So I had to gradually lower the tail until the cut line carried the full length of the cowl. It’ll end up being a degree or two off from the longeron line, but I kind of doubt anyone will notice…

Then I got to go and carefully make Sharpie marks along the level line, along both sides of the cowl… while also making sure not to, you know, lase myself in the eyes:

Then, as with the last trim, I used masking tape to lay out the cut lines all the way around:

Which was followed by rough-trimming, sanding the cut lines close to the masking tape lines, and finally using a long sanding board to finish the entire cut line nice and straight. This was surprisingly not really a ton of work; unlike the aft cut line, which had to be carefully fitted to another part, in this case I’m creating the layout line, so there’s not so much trial-and-error. (That’ll come later when I trim the lower cowl to fit…)

OK, enough of the upper cowl…now it’s time for the real fun, the lower cowl. The lower half mostly butts against the upper cowl, except for the spinner area. Here, the lower cowl has an inset flange that need to fit snugly into the upper cowl…but that there’s no way to test-fit this intersection as provided, because the extra material the outboard cowl edges interferes:

So the strategy here is to carefully and gradually trim the forward outer portion of the lower cowl to hash out this nesting area. The marker line in the previous picture follows the edge of the flange, so that’s hypothetically where I’ll want to trim things here. Thing is, I don’t want to trim any further back than I have to, since I can’t know how what the overlap of the two halves will look until I can fit them together…aka not until I get the front to nest. It’s a sort-of maddening chicken-egg type problem.

The approach so far has been to slowly and conservatively remove material in this area, while repeatedly trial-fitting the halves. Eventually I should be able to creep up on a decent trial fit, but I’m not there yet. I got this far before deciding it was time to call it a night:

So this is where I’ll be picking up next time. I’ll probably need to rethink my localized trimming here to creep up on the fitment…that’s something to mull over for a while. As tedious as some of this is, though, it’s still pretty neat to see the cowl profile coming together.

Posted in Cowl | Hours Logged: 7