Category Archives: Cowling

Never ending squawk list

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The airworthiness inspection is rapidly approaching and it’s crunch time now. This post is about as fast and deep as all the stuff I had to do.

The awesome guys on based helped me bend my control sticks to provide plenty of clearance to the instrument panel. I still hit the flap switch in the full nose down, right roll position, but if I ever have to use that stick input, I have way more concerns about dying.

I never installed the tips on the stabilizers, so I wiped the decade old dust off of those and riveted them on then laid up some glass to enclose them. Some tweaking with the heat gun was enough to get them adequate clearance and I’ll let Jonathan do the rest of beautifying them during paint.

I crawled in the tail cone. Again. After I said, “Oh, I’m done back there, I won’t need to get back there.” Hell, at this point I can’t even remember why I had to go back there. I’ll flash forward and tell you that still wasn’t the last time. Either way, here’s how I feel about doing that little shit job.

The rest of the interior went in and lights hooked up. These side panels are pretty tricky to slide in without destroying the paint. I’m happy with how they turned out. The stainless screws also look really nice.

I pulled the plane out for a good GPS and comm check. I’ll have another post about the details, but while everything worked, I have some serious interference with the ZipTip lights and my radios. For now, though, no night flying means I’m safe and legal to fly.

The back seats and carpet are all in now. I had to put a lot of velcro down but man, this Aerosport stuff is amazing. The seats are comfortable, the carpet looks great, and I’m really excited about taking folks flying in this plane!

My cover from Bruce’s came in and is freaking sweet. Fits very nicely, has orange, and the tail number embroidered on it makes it so no one can steal it and use it on their plane without me chasing them down.

I put the cowling on for a final fit check and hooked up the new AeroTherm engine heater. I’ve used these on the Diamond we fly and really like it. I didn’t like the idea of cylinder heaters and want to keep the engine heated during the winter to avoid cold starts. I know this isn’t as portable, but I’m happy with it thus far. I did have to get a very thick extension cord so it would keep tripping its internal breaker with my crappy 15 amp service in the hangar.

Finally, I weighed the fat little piggy with all of the pants and random stuff not yet on for good in their approximate place. Folks, with full interior, oxygen, air conditioning, three screens up front, and all the extras my credit rating could buy, I’m pretty happy with her girlish figure. This let me sit down and compute weight and CG figures as well. Everything turned out nicely with an empty CG of 106.4 inches.

Firewall forward finishing

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There is a lot of little projects yet to be completed on the firewall forward section, so I set about tackling them. First off was safety wiring the prop bolts. I thought torquing them were hard. Well safety wiring them is even worse. Because of the limited space, you actually have to loosen them a bit, thread the wire through the hole, then re-torque them. Ugh. Anyway, it’s not pretty but it’s done. I’m convinced this flange design negates the need to safety wire since they’d all have to unscrew in perfect unison for the damn thing to fall off anyway.

Here is a picture of the custom wrenches I had made up using Joe Key’s templates.

Since I was at the front end, I went ahead and finished up the spinner installation. The back plate takes some time to bolt on as well with 1300 bolts used to hold it to the prop hub. The spinner has three plates behind the blades to fill the gaps and it took a bit of dry fitting to figure out where each one goes. WW had labeled them by number and I was wrongly lining them up with blade numbers not just the reference number on the spinner and back plate. The front of the prop hub fits into a bulkhead in the spinner and it took a few iterations of Teflon tape and sanding to get a nice snug fit with no wobble of the spinner.

The air filters were the last step for the intakes and I had been waiting on a different filter with a tilted base, allowing clearance of the tube to the filter assembly itself. This was required because of the blister I had to glass in for the air conditioning compressor. Fortunately a 10* tilt made just enough clearance and it all fit together nicely. I oiled the filters and got them put on for good or at least until the first annual.

The right intake tube is close to the exhaust, so I used some heat shielding that has an adhesive back to protect the tube. I went back and covered this with 3M foil tape and then applied RTV around the edges to secure it. I’ll monitor this during ground runs to ensure enough protection from the exhaust header.

Since I had RTV all over me anyway, I took the opportunity to finish seal up a few spots around the engine and firewall. I have spent a TON of time trying to find any little spot air could leak out of the baffles that it shouldn’t be leaking. Since the hangar is dark with the lights off, I again used a flashlight on top of the engine to highlight any little spots. It worked great and I’m hoping it pays off with adequate cooling once flying. It’s impossible to be super clean and fancy with this stuff, but I kept most of the mess on me instead of on the engine.

So many of my electrical connections are oddly shaped so getting a boot to fit hasn’t been easy or even possible. I used a 3M product to paint electrical tape onto the hot studs just to keep a surprise shock chance low. Not quite as good as boots, but better than nothing.

Lots of zipties up front still being added as I just see spots here or there that could use some extra security. I may add wire wrap that is rated for high heat to clean it up, but not sure if I care or want to spend the time on that quite yet.

Multi-tasking is key at this point so I setup the vacuum pump on the aircon system while RTV was setting up. All of the lines and connections are secured so I could finally vacuum the system to perform a leak test and evacuate moisture from the system. The ports are just behind the baggage bulkhead and pretty easy to get to. I set up the pump and let it run for about an hour and a half to get moisture out then closed the pump off and let the gauges sit all night long. The next day I returned to see a perfect vacuum still holding, so that is a huge win!

The last two projects up front were some additional glass work on the plenum and a ramp for the aircon compressor. The plenum was designed to be sealed to the cowl around the oil dipstick, but I didn’t like the idea of air potentially leaking out of the plenum through the oil door or into the engine area. I cut up a sports drink bottle as a mold and roughed up a little funnel to fit over the dipstick. The dipstick will have some foam tape sealing the bottom of the funnel. It didn’t come out as pretty as I wanted, but it’s functional and I can always clean that up a little down the road.

The air ramp was a little easier than I expected. On the left side intake, the aircon compressor causes the cooling ramp and induction intake to need a cutout and I wanted to create a little blister to help direct all the air possible into the cooling and intake ducts. I shaped a foam block and used packing tape to secure it to the cowl. I used some carbon fiber to lay up a rough fairing then cleaned up the edges after it set up. This is attached via two screws and should provide a nice air flow deflection that is simple to use. I plan to create a final piece of bulb seal to fully seal the cowl to the engine portion helping minimize air pressure loss while providing flexibility for engine movement.

Wipe the cowl off your face, we’re moving!

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Thanks to a great guy on base that has a side business of welding, I had my AFR (O2) sensor bung welded on the exhaust per Ross’s recommendation on location.  I chose the #6 cylinder, but he said it doesn’t really matter.  I chose that one since it fit well there.  The sensor has a controller that I attached to the engine mount just above the battery box.

I never have been able to wrap my head around the nose gear fairing made by Show Planes until I physically put it all together.  The idea is to not only support the lower cowl around the exhaust openings (and air exit) but also smooth the exiting air flow around a turbulent area.  I started by attaching the front and rear fairing together and then positioning it roughly on the lower cowl.

The rear piece has a few lips that fit over the bottom skin to help locate it correctly, so I did an initial fit before starting to trim the nose gear slot.  Bryan shows a very tight opening for the gear leg, but I’m not sure how much it actually moves, especially on a grass or dirt strip, so I’ll leave a bit more room.

Once initially trimmed, I drilled into the bottom fuse and used nut inserts vs. sheet metal screws.  I figured it’d give a better grip long term and less chance of stripping holes.  Once the fairing is on, it reminds me of a duck billed platypus.  Ha!

I chose to use more SkyBolts to secure the fairings to the cowl.  I am also following Joe Keys’s lead on making a cover plate to cover an extended nose gear leg slot.  This will allow the cowl to fit a bit better going on and coming off since I have the dreaded three blade propeller.

I finished up by extending the cowl slot as far as possible while still covered by the fairing and epoxied the front fairing onto the bottom of the lower cowl.  Getting the lower cowl on and off is a bit of a challenge, but it does just fit and the blade sox I have really pay off here to avoid nasty scratches on the prop blades.  

Since the cowling was the last big project left to complete at home, the fuselage is ready to join the wings at the airport!  I was able to complete all of the interior, electrical, avionics, and engine including cowling at home which saved a lot of time and money in the long run.  Now I need to fit the wings and tail surfaces to finish up the build and need the hangar space to do so.

On a sunny afternoon, we rolled the fuselage out and did a good blow job (hahahaha, grow up) to get most of the dust off of everything.  I found a roll back wrecker driver that made me feel comfortable and who wasn’t in a hurry to move it the few miles to the airport.  He did a fantastic job, talking through each step and making sure I was happy with how we winched it and tied it down.  He took his time on the curvy bumpy back roads after managing down our driveway of doom and destruction with ease.  I think I breathed twice during the 45 minutes it took to move it and I only panicked once when I thought tree limbs were going to scratch the windscreen but were actually three feet clear.

We rolled it off the wrecker onto the ramp and quickly had it tucked away in her forever home at IPJ.  Laura helped me roll the wings still in the wing rack down from the other end of the field (a 20 minute walk with those puppies).  Two guys who I know flying the Diamond were kind enough to let me store the wings for almost a year in their hangar free of charge.  Truly great people makes things like this happen, can’t say enough.

About five trips later, we had all of the tools, parts, pieces, dust, and components all in the hangar.  For the first time, everything is together in one space that will be a flying airplane very shortly!

Insert witty title here – baffles, oil door, random stuff

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The baffles are all trimmed up and ready for a coat of high temp engine paint.  Looking back, I wish I had them powdercoated, but too late now.  They’ll get scratched up and at least this way I can touch them up, similiar to my mentality for the interior.  The front ramp area was trimmed significantly for the air conditioning compressor and turned out pretty nice.  I removed the front fence on both sides, as others say there is no point in them.  I can always add a bit of tape later to warm CHTs up if needed.

The rods that hold the bottom of the baffles together were a bit of work, as you have to put some bends in the rods and then thread them.  I’m using these as mounts for the sensor wires as well as a few other wires including the starter wire and alternator b lead wire.  It really cleans up the wiring nicely and keeps everything tucked away.

With each connection at the engine, I get to verify functionality by turning on the avionics and looking for realistic numbers.  For instance, I now have 14 different temp sensors all telling me the garage is in the low 70’s!

I fabricated up a bracket to mount the throttle cable to for the throttle body.  It routes under the bottom of the engine and since it’s not exactly a stock setup, there is not stock cable mount.  It was a pretty simple fix with some angle channel and a few bolts.  I am thankful I ordered a lot of various 1/4-20 bolts for the engine case since they are not standard AN bolt threads.  The throttle cable is now attached and rigged with good travel on the throttle body and throttle lever, so I’m 50% complete with engine control cables.

The prop lever didn’t work out so quickly or successfully.  After I mounted the Show Planes bracket and hooked up the cable, I began to wonder why the governor is sprung to low rpm/high pitch.  Yeah, oops, no, that’s not right.  The governor can be configured a few different ways including rotational actuation and mine is backwards.  I called Whirl Wind and as always, they took great care of me.  I sent the governor into them and they shipped it back corrected the same day they received it.  Now it is sprung to high rpm/low pitch as it should be with proper activation with the cable.

In an effort to reduce the crap on my workbench, I decided to wire the spark plugs and coils to get rid of two big bags taking up room.  I ended up re-configuring the mount for the coil connections on the top case mounted coil and it made running the signal wires cleaner and easier.  The plug wires themselves were pretty easy and quick to run now that I have the MSD crimp tool.  The biggest challenge was deciding how to route and secure the wires.  I’m pretty happy with some Amazon plug wire organizers and a few adel clamps.

Since everything inside the baffle area and the baffles now on for good (thank goodnes, they are a pain to get on and off a bunch), I could test fit the plenum, ducts, and cowling for the first time.  Boom, it all fits!!!  The plenum is just clear and will allow a bit of shake room for the engine within the cowl.  The intakes and cooling ducts clear the inlets by about 3/8″ and I test fitted the bulb seal which I think will work nicely.  Everything lines up nicely and I think it’s going to work out to a clean and effective installation.

I will need to check the oil from time to time (it’s a joke folks) so the oil door needs to be fabricated.  I have the hidden hinge from Cleveland Tool and planned on using Cessna push button releases for the fasteners but decided against them once I got them in hand.  I just don’t like how they work or look.  I want it convenient to pop that door open and thus will sacrifice looks a bit for functionality.  I ended up ordering the winged Skybolts.  The releif area was cut out using the cutting wheel and I realized that I didn’t leave enough of a flange to mount those Skybolts.  I test fitted the top cowl with the plenum on and ensured there was plenty of clearance for access to the dipstick and then fiberglassed on more of the flange to correct the issue.

The door itself is a perfect mold and only required a bit of sanding.  The stiffner was epoxied on with West epoxy and a bit of flox to add rigidity.  Once it cured, man it is super stiff!  I let it cure on the cowl with clecos to get good form.  Installing the hinge was pretty simple, just a bit of adjustment to get the hinge point located properly and the spring will allow the door to stay open easing access to the dipstick.  I’ll lay up a funnel shape to enclose the dipstick tube and seal the opening in the plenum in a bit.

Finally, I knocked out a nagging job with the air conditioner.  The condensate drain wasn’t routed to the exterior since I redid the ducts in the tail so I had to come up with a way to allow that water to drain out.  I experimented with a fuel tank bung that I had surplus and a short piece of tubing.  It equaled a great fitting vinyl tube with aluminum tube insert threaded into the bung and riveted to the bottom tail skin.  I put an angle cut on it to help create a low pressure on the tub which will help suck the fluid into the airstream.  Elegant solution, if you ask me.  I know, I’m incredible aren’t I?  So humble too.

I really foamed that up

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Now the cowling is fit, some tricky bits come up on the to-do list including the engine intake ducts and cooling ducts.  All of these are complicated by my air conditioning and plenum choices.  If I get it right, it’ll be magic and a work of art.  I probably won’t get it right the first time, as some of you may have guessed.  I started with getting the engine intakes started.  These start at the cowling openings and form the bottom 1/4 of the opening.  they curve inward and join a Y that holds two K&N air filters before hitting the throttle body.  The ducts are well molded and nice light but strong fiberglass.  The problem is they don’t fit very well with the exhaust and other accessories on the engine.  The Show Planes instructions leave a lot to be desired, but once you piece the components together, it starts to make sense.

I first had to cut a relieve for the alternator.  Not sure if it’s just the Plane Power or if all alternators will require this, but mine was about a 1/2″ too low impacting the right duct.  Next, I had to trim quite a bit for the exhaust coming from #2 cylinder.  I tried to get a good 1/2″ to 3/4″ clearance and will using some heat shielding to protect it from the close proximity.  

On the left side, the air conditioning compressor dictates a much larger modification.  Gaylon wound up elimintating this duct all together but I want to at least try to keep it.  The problem is the compressor blocks some of the cowling opening and thus reduces not only intake air flow but cooling air flow.  I’m hoping since I have a plenum and will have the cooling intake completely sealed, that the minimum reduction won’t interfere with adequate cooling.  Time and testing will tell.  I also want to keep the left side induction to maximize manifold pressure thus power and performance of the engine as well as keep the redundant induction air supply (think alternate air on the stock setup).  

I had to notch out a few spots to create clearance around the compressor and mounting bracket.  Once I had the areas trimmed away and fit properly, I laid up fiberglass by hand to enclose the reliefs.  I debated on creating a mold or plug type thing but determined it’d be next to impossible for me since I’m not good at it anyway.  Plus I tried one of them and was pretty happy with the results, so why make it more complicated?  I did two layers of glass then a third on the inside.  I honestly don’t know what weight it was, but it’s very thin thus the three layers added up to about the same thickness as Show Planes had with the same rigidity.

A bit of sanding and trimming, and everything with the ducts were finished up.  I painted them black just to hide them inside the cowling a bit and because I wanted to.  The last two sensors to install for the engine are intake temperature sensors that I had mocked up and ran wire to but not yet permenantly installed.  I bolted those on and sealed them with RTV to avoid air pressure loss.  I also drilled the required water drain holes just below the air filters at the lowest part of the intakes.

It all sounds so simple now, but trust me, I spent many hours thinking, debating, looking, thinking some more, and finally working out the fit of the ducts and getting a solution that I am happy with.  These were just a warm up for the cooling ducts!  Show Planes have you modify the stock baffle ramps and provide upper cowling ramps to be epoxied to the cowl to help guide airflow into the engine baffles.  Since I am using the plenum, I need to keep air going from the openings to under the plenum.  I had originally invisioned carving foam and creating a mold, but once I got busy working, carving foam was going to be next to rediculously impossible.  It’d take me weeks just to do the molds.  So, I took another approach, use what I had on hand and don’t reinvent the wheel.

The upper ramps from Show Planes are the same size as the openings, so I started with those as a transition to the plenum.  Part of the kit is some thin flatstock fiberglass that I wound up using to create the cooling ducts.  I used some manilla folders to create templates and basically pieced it all together using the fiberglass and super glue.  Starting on the right side was simple, as there is no modifications needed and it’s a much simpler routing for air to enter the plenum covered area.

Again, I figured I’d use this rough build up as a mold to create a sleek curvy, sexy, duct that would look like it came from a Formula 1 team.  So I got a brilliant idea of filling it with blocks of foam and then using spray foam out of a can to fill in the gaps.  I’d then sand, trim, and shape before using it as a mold.  Well guess how that worked?  Not great, folks.  Not great.  I didn’t realize that spray foam has to be exposed to air to set up.  So me putting the duct in a plastic bag in a box resulted not in a nice firm square, but a grocery bag full of gooy sticky snot.

I then decided I’m making it difficult and should just keep it simple, stupid.  So I decided to stick with the original prototypes and just reinforce the joints and smoth as much as possible.  While I waited for the disaster to finish curing so I could clean all the foam back off, I started on the left duct.  This was much more complicated with the compressor in the way.  Not only do I need to get around the compressor, but also the tensioning arm and v-belt.  Finally, the prop governor is there too and oh, wait, I forgot, the refrigerant line from the compressor.  Again, I used manilla folders cut up as templates and just pieced it all together, maximizing the amount of space and using the upper ramp from Show Planes as the starting point.

The end result is not too shabby, even if it’s not beautiful.  I hope it’s functional.  I finished cleaning the foam and set about reinforcing all of the joints with glass tape left over from tip fairings.  Once cured, I did a final fit and trim to provide about 3/8″ clearance from the cowl openings and evened them up with the induction ducts below.  This clearance allows the engine to vibrate and twist a bit within the cowl without cracking the ducts, as you don’t want the two rigidly attached to each other.  I really debated on how to close that gap, thinking about creating flexible ducts from the start or taking what I have at this point and using a rubber strip to seal it.  In the end, I copied an idea from the DA-40 I fly and ordered some bulb seal from McMaster Carr.  I’m hoping this will keep the air from leaking around the duct but allow the engine to move within the cowling.  Again, some testing during first few flights will tell.

I may go back and cosmetically clean these ducts up before paint just to make them look good, but for now, I shot a coat of black paint on them to mask imperfections.  I still need to fabricate up a small ramp that will cover the exposed face of the compressor and help direct smooth air into the ducts.  If I find high temps on 1 3 5 clyinders during flight tests, I’ll copy Gaylon and pull the left induction intake to open that entire side to cooling.  I’ll be honest, this has really weighed on my mind how to create these ducts.  I’m sure there’s a better or fancier way of doing them, but for me, this is a good start.  If they work that’s great and if not, I at least have a good starting point.  These were the last items needed before cleaning the engine off and sealing the baffles using 3M firestop.

What’s under the hood?

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While I worked on the wiring, I made progress with mounting the engine cowling as I’m really starting the countdown to moving to the hangar.  The cowl had been at the airport for months, so I retrieved it to start measuring and trimming.  With the baffles and plenum initially fit, I started with the mock up prop spinner plate from Whirl Wind.  This mock up has spacers that position the backplate as if the propeller was on, which is then used as the template for positioning the cowl.

I also used the spinner backplate to tac the cowl halves together and do an initial trim on the front joint.  Clecos worked well holding it in place as I trimmed and ensured a good fit resulting in even circular openings for the intakes and prop.

I started with the top cowl, laying it over the fuselage skin and clamping it to the spinner backplate with spacers for a nice clearance gap.  I used the reference line method to mark the edge of the firewall on the cowl overlap and measured twice before cutting it long so I could sand it to fit.

The cut came out well and a few minutes blocking it with sandpaper resulted in a nice fit.  The bottom cowl was next and needed a clearing slot cut for the nose gear leg before even rough fitting.  The Show Planes cowl has a unique fairing that I still didn’t understand quite yet but did know that I need not worry about a finished product at this stage.  I cut the opening as small as I could while giving room to put the cowl in place.

With the two halves fitted and tapped in place, I established the horizontal split line and the Sky Bolt line.  It’s key to establish where the skybolts will go on the horizontal line so that the firewall line can be even creating a nice symetric appearance.  Once the split line was figured out and marked, the bottom was similar to the top for the aft cut and soon the overlap was gone and sanded to fit with an adequate paint gap.

Finally, I trimmed the horizontal split line on each cowl half and used the top as the line to match with the bottom.  A bit of sanding and fitting the bottom cowl 5-6 times, and I was happy with the result.  Next up was to lay out the skybolt holes and install the brackets for the receivers.  The manual gives a target spacing that I was able to hold to pretty closely.  I started from each side’s horizonal split line placement and did a bit of math to evenly space the upper firewall bolts.  I think used the same spacing on the lower cowl each side to confirm no interference with the engine mount bolts.  It’s tight, but it works.  Lastly, the horizontal spacing was calculated and marked.  In the end, the fasteners will be in line and evenly spaced and will look great.

I transfered the locations onto the fuselage skin around the firewall then positioned the tabs for drilling and riveting.  Pretty soon, those were primed, shaped to match the curve, and installed.  Next step is to use drill guides to drill the initial hole through the cowl.  I thought I’d be able to use the light method from inside but with the new grey fiberglass gel coated parts from Van’s, that option doesn’t work.  I couldn’t drill from the inside using the cleco adapters, so I wound up carefully measruing and marking the centerpoint of each tab and making a #40 sized hole to get started.

Once a few holes were in, the adapters allowed the cowl to stay in place and I then used the adapters as sight gauges while progressing drilling the holes big enough to accept the skybolts.  I stopped every few increments on the step bit to check alignment with the adapters in the tabs.  It was a bit time consuming, but the process worked well and I had no issues with all of the holes.

The split line fasteners were the last ones to be installed, as I used some walrus teeth (2×4) to prop the cowl in place and firewall fasteners to secure it.  Laying out the drill holes and then confirming with a #40 hole was the first step.  Unfortunately, you can’t drill progressively since you don’t have a way to hold the clecos adapters in place as sight gauges.  So I installed the tabs and then marked the centerpoint of the hole before taking time to step drill while the cowl was off the plane.  The skybolts have enough leeway to allow a small margin of error, so it worked out fine.

I’m not sure it was really that much more work than the stock method using the piano hinge, but I’m happy with the result.  It’s dirt simple to remove the cowl and I personally really like the looks of the fasteners.  They aren’t for everyone, but they are for me!