Nov 02, 2023     Starter - (10 hours)       Category: C23 Eng+Cowl

I started by installing the starter previously used on this engine: one salvaged from a Honda Civic. It came with a custom mounting bracket milled from heavy aluminum stock, but the fit was not perfect, and at full extension the starter gear engages only half the surface of the ring gear. I was happy when another Cozy builder had a spare starter and took him up on the offer. It's "new old stock", meaning its been on his shelf for years. It's an ElectroSystems MZ-6222, which became part of Kelly Aerospace, then Hartzell. It has a 12/14 gear pitch, the one I need for my 149 tooth ring gear. This model starter is the same one used on the Mooney M20J, the original installation of the Cozy engine.

One bit of good news - using aircraft starter and B&C alternator means I was able to make a good fit for the reinforcing link between the two. Now to find the correct bolt! 5/16x1.25 - 18, drilled head. Add it to my SnF shopping list.

  Mar 20, 2022     Cowling - fasteners - (4 hours)       Category: C23 Eng+Cowl

Piano hinges join to the wing, Dzuz fasteners for the top and bottom arches. See attached write up.

The stronger extruded piano hinges are pricey - $37.50 each, but they are stronger, lighter, and look better than the alternative of Camlocs. Now I'm paying the price for a deviation from plans + the custom cowl. _Lots_ of tweaking has happened. Constantly moving above and below the cowl proved to have its own risks - three weeks of wearing a bandage after I barked my head against a cowl edge.

  May 24, 2022     Cooling - (5 hours)       Category: C23 Eng+Cowl

I've been concerned about cooling since the very first time I saw a Cozy. Pre-flight, I intend to make two tweaks to the air intake at the stock NACA vent and one to the air exit. If post break in I see climb out CHT's over ~420, there more things to try.

At start, I'm using
a) corner tabs on the NACA duct. This is no more than a bracket added to the rear corners of the NACA, aiming to keep in flow the turbulent air that wants to spill out and away from the air intake. See detail on attached.
b) cooling large scale VG's, creating turbulence at the intake. See detail on attached.
c) small scale eductors. Eductors are said to use exhaust pulses to draw air out of the cowl. Maybe. I need to protect the cowl from the exhaust heat, and I made stainless-lined eductors from CF-Cormat-CF using high temp epoxy. I'm not thrilled with the impact on fit of the upper and lower cowl, but I'll give it a go.

As a backup, I made armpit scoops which I can use to force air iinto the oil cooler. See below a Long EZ example of how such a scoop is part of the lower cowl. In my case the scoop-cowl attach point is to be a square the same size as the face of the oil cooler. Nothing off the shelf can plug and play, so I have to either modify an after market part or scratch build. A Bingelis standard says says I need an additional ~30 in2 of inlet area to handle a 200 hp engine. I can do that with a scoop dedicated to the oil cooler. I created a 2-part mold using 4 lb pour foam, and used my new favorite CF-Coremat-CF. No fancy bell mouth. The stem / support was left long for final trimming after I finish the cowl and install the oil cooler. I made one for the right and one for the left - I don't know which side I'll use for the oil cooler, so one of each.

  Nov 03, 2023     Cowl #5 - oil door Category: C23 Eng+Cowl

Procedure for cutting into any composite panel....

Nick,

Perhaps I am misunderstanding in which case forget the following.

It appears that you want to cut a hatch in an already existing front area and you want to be able to have a door that opens and closes and seals on a flange (that fits it) you also want a drip rail for moisture (which of course you want to drain somewhere.

If I am correct, the way that I have done it was:

Before cutting the panel out:

1. draw the outline of the purposed hatch
2. Place one layer of duct tape over this line extending about 1" OUTside the line and approximately 1" inside of the line (this will be adjusted later
3. Make a 3 layer or so BID layup over this duct tape. (creates the flange which will be foxed inside of the fuselage)
4. Peel ply the layup.
5 When cured, separate it from the duct tape and totally cut out the shape. (I don't have to add the word carefully.
6. Neaten up the outside of the layup produced in step4.

7. If you want a drip rail put a round shape of foam on the layup (on the side that was touching the tape) at the inside edge sand and make a layup over this with enough overlap to secure it. if you do the drip rail, you will have to first trim the inside of this layup and let cure
8. Remove the foam and refine

9. sand the inside of the fuselage approximately 1.5" from the cutout hole around the entire hole left after the cutout (for bonding.)
10. make a few layups of BID around this hole the thickness that you want to use for your gasket material
11 Using a relatively thin flox (but still thixatrophic) butter the inside of this fuselage layup
12. fit the new piece that you created in step 9 and or 4 with or without the rail through the hole orientated in the same way in which it was made.
13. Press it into place (upward) (from the inside) and using multiple clamps hold it to the periphery of the hole allow cure and get rid of the goobers
14. When cured create a flox corner in the outside skin, a flox fillet at the junction of the inside skin and the now affixed flange and use some light bid to seal the foam and create a stronger joint.
15. clean the layup and slightly radius the outer skin flox joint
16. Reduce the size of the cutout panel to fit its new flanged hole (remember you will have to address the raw foam edges which will, of course take up some space)

Hinge and lock.

  Apr 19, 2023     Engine mount       Category: C23 Eng+Cowl

The engine mount was bought from Cozy Girrrls, and responds to the early concern over cracking by adding extra bracing. Cleaned with alcohol and acetone,, then painted iwth a zinc chromate primer and appliance epoxy.

The engine is secured to the mount with Dynafocal mounts made by Lord Manufacturing (a division of Parker Hannifin). For the build / dummy engine phase I used the mounts that were used in the build phase for Andrew Anunson, then build phase for Hugh Farrior. As near as I can tell they are the heavy duty mounts sold by Aircraft Spruce for the Acro and Christian Eagle - aerobatic biplanes. I've had them on and off a few times and see no distortion. On 5/26 I corrected an earlier error and moved the large diameter washer to the compression side (for upper Dynafocal cups, the firewall side, for lower cups, the engine side). Moving the washer had the effect of raising the prop. With tires inflated to 60/60/55 and all 4 thick washers on the firewall side, the bottom of the prop extension was 45" above the floor. The new measurement is 46".

Prior to fitting the cowl I wanted to switch over to new mounts. I bought a new-in-box set of the mounts specified for the Cozy: the J9613-40 originally spec'd for the IO-360-A3B6D. When the inner gel capsule burst I used the customer service email at Lord, sending in a description and pictures. That was Memorial Day. Now it is 7/13. I called again (877-275-5673) and left a message with technical support.

I may or may not change over to the new mounts - the old ones have not deformed in any way. In January 2019 I spoke with customer service at the Lord mount division of Parker Hannifin: I described the pusher configuration and mentioned that it was common to use a prop extension. That news made her recommend a stiffer mount, and to avoid the ones with the gel capsule dampers. I infer that the mount is dealing with the vibrations created by the prop as much or more than the vibration of the engine. A prop extension is a longer arm to the prop vibration, and merits a stiffer mount.

  Jul 02, 2020     dummy engine for the build - (12 hours)       Category: C23 Eng+Cowl

January-March I had an O-235 engine overhauled at Zephyr Engines, in Zephyrhills, FL. I happened to be in the right place at the right time and was loaned a dummy IO-360 engine which they had stored in a back room. (Seems they used it in recruiting for a local technical training institute.) The dummy is the IO-360-C1E6, where I have an A3B6D. Both are wide deck / angle valve engines, and the dummy is an appropriate tool for the build. Based on an online version of the Lycoming engine codes (http://www.meyette.us/LycomingEngineNumbers.htm) both have
- Bendix fuel injection, tuned induction
- a prop governor on the left side of the crankcase,
- the Bendix D4LN-3000 impulse coupling dual magneto,
- counter-weighted crankshafts

Note that I will be moving over to electronic injection and electronic ignition, so I avoid the single point failure mode of the one magneto shaft.
A big difference is that the dummy engine has a rear-mounted air intake. It's a feature I would like to have, since it means ram air when mounted on a canard. Converting my enigne to rear air intake is something to look into.

  May 16, 2023     reference - torque values       Category: C23 Eng+Cowl

Below are reference tables for torque values. Where reasonable I write the torque value next to the fastener.

  Apr 03, 2023     Notes - Cautions - Warnings Category: C23 Eng+Cowl

From the Cozy Builders Group, a recommended secton of the manual:

Notes, Cautions, and Warnings

WARNING – This aircraft uses an electrically-dependent igntion system. With any electrical failure, reduce electrical load and land as soon as possible.

WARNING: Takeoff and land with both boost pumps on. After takeoff, either boost pump may be turned off.

WARNING: Brake lines are to be replaced every 5 years at the Condition Inspection. Brake fluid (5606) is to be replaced no less frequently. Brake fluid absorbs moisture which lowers the boiling point of the fluid and contributes to caliper corrosion. Bottom-filling of brake lines is recommended. Suction old fluid out of the reservoirs with a large syringe and place the extended nose gear on an elevated platform. Pump new fluid in at the brake caliper until fluid appears clean and free of bubbles.

CAUTION – If the nose inadventently rises more than a few inches, a tipback can happen quickly which will damage wheel pants and prop. When parked on three wheels with the cockpit empty: i) insure the 25 lb weight is hung in the nose gear; ii) lower the nosewheel if parked pointed into a strong wind or on an upslope. Apply the parking brake when parked on a downslope.

CAUTION: The nose gear mechanism must be fully extended over-center or fully retracted. If weight is placed on the nose in any other position, it may strip the gear in the mechanism. A stripped gear can be reversed for one more usage.

CAUTION: For safe stall behavior, this aircraft requires 16# of ballast placed ahead of the rudder pedals with a 225 pilot. Cast lead weights fit in the compartments under the nose hatch.

CAUTION: To prevent nose gear damage, avoid taxiing into potholes or ground-wire depressions on the ramp.

CAUTION: Keep the swiveling nose gear adjusted so that that a hard blow with the fist against the tire does not freely deflect the tire, otherwise, the nose gear may shimmy and destroy the nose gear.

CAUTION: There is no warning of an unlocked canopy in this aircraft. Insure that the canopy emergency catch is bent so that it engages when the canopy is lifted.

CAUTION: Leaning during ground operations is recommended, however, lean so that if the throttle is inadvertently advanced for takeoff with the engine leaned, the engine will die.

CAUTION: In the event of alternator failure, lowest current drain will be achieved by selecting E-bus power, then turn off the master switch, then selectively turn off any E-bus-powered equipment that is not needed (i.e., com radio, transponder, D-10A, one fuel pump). Turn off Lightspeed Ignition #2 to save the backup battery for last use.

NOTE: Before removing fuel tank caps for refueling, attach the fueling ground wire to the step. The step is bonded to each fuel cap ring via internal wiring.

NOTE:: For normal operation, maintain Ignition 2 Pwr Select in the “aux batt” position. This checks the condition of the aux battery.

NOTE: Lightspeed ignition #1 is powered directly from the main battery and #2 is normally powered from the aux battery, each through its own switch. If alternator failure occurs, reduce any other electrical load and turn off one igntion (normally turn off #2) until the main battery is exhausted, then turn on ignition #2

NOTE: Spare fuses are stored in a red bag in the right strake hole.

NOTE: If the fuel valve binds, position the aircraft nose-high, disassemble and lube the spool with a tiny smear of Fuel Lube. If too much Fuel Lube is used, bits of it can lodge in the gascolator screen (where it will not desolve!).

NOTE: Tire pressures are 50# main wheels, 65# nose gear. It is particularly important to keep the nose tire inflated to avoid turning on the rim at touchdown.

NOTE: This aircraft uses DOT3/4 brake fluid and EPDM o-rings in brake hardware.

NOTE: The Dynon D-10A EFIS and uMonitor are powered via the E-bus and will indicate approximately one volt less than battery voltage due to loss in the E-bus diode.

NOTE: Water is seldom found in the tank or gascolator drains but if any water is found in the tank drains, then also check the gascolator for water.

NOTE: At high cruise speed and wide-open-throttle, the throttle may need to be retarded slightly for smooth running and peak RPM.

NOTE: This Ellison carburetor set-up exhibits a slight engine surge at medium RPM.

NOTE: For instrument access: remove the canard cover, remove two long pins securing the instrument cover, remove instrument cover and disconnect the connector for cockpit lights.

NOTE: To remove the canard, remove the instrument cover as described above, remove the footwell access hatch, disconnect the elevator control rod quick-disconnect (starboard side), loosen two screws holding the trim spring wires in the trim mechanism (port side), disconnect Dynon remote compass box, unscrew & remove two screws through the canard incidence-setting tabs, unbolt the canard lift tabs, lift the canard up and out.

  Mar 05, 2022     IO-360 sumps & the Cozy - (50 hours)       Category: C23 Eng+Cowl

My Cozy was built using the engine I had on the shelf - an IO-360-A3B6D. The codes mean my engine left the factory as
I Fuel injected
0 opposed-
360 360 cubic inches of cylinder volume –
A type A sump
3 propeller locating bushings rotated 120 degrees clockwise
B with an accessory section using Bendix accessories
6 (1) sixth and (1) eighth order crankshaft counterweights
D (1) Bendix D4LN-3000 impulse coupling dual magneto

Attached is a write up of modifications made to fit this engine to the Cozy.

The angle valve wide deck sump is above the induction chamber, with wings to the right and left. Both wings are tapped 1/2" NPT for oil drains. The standard Lycoming plug has a square head. On one side I installed a stainless plug that uses a recessed hex head / Allen key. On the other I installed a Fumoto engine oil drain valve (p/n T202N) with the lycoming engine thread of 1/2-14 NPT. Spring loaded and brass, vs the standard springloaded and aluminum. This is brass going into aluminum - a strong hand tight is sufficient! Use safety wire for peace of mind. I also have a 1/2" id plastic tube and a solid plug. To drain oil, roll the left wheel onto a ramp, attach the hose, put the drain end in the pan, remove the hose plug, and flip the switch.

  Mar 31, 2023     Exhaust - (2 hours) Category: C23 Eng+Cowl

I bought the standard exhaust for the Cozy.

Here are tips for the flanges (I use the ones made by SDS), studs and nuts.

“While conducting GA and Experimental airplane inspections, I have found many exhaust leak(s) at the interface of the cylinder flange and exhaust stack. Here's some bullet points for your consideration:
1. Ensure the nut that you choose has a High temperature lock device. The Continental part number is a plated-high temp all metal stop nut. I've seen corrosion issues with this particular application and this is not my first choice.
2. Find a system that is corrosion resistant. G#^*'s aero used to send back OH'd cylinders with CAD steel stop nuts and CAD plated washers. In a very short period of time, these would corrode away and allow the stack to loosen and the gasket to be breached by hot jets of exhaust.
3. If a washer is needed, use a stainless or corrosion resistant option.
4. Ensure your studs have a proper interface with the cylinder. If a stud comes out with the nut corroded onto it; Don't be tempted to simply
screw it back in. Replace the stud and ensure you have proper rotational resistance during the process. Oversized studs are available and there's an ID marking on the end of the stud alerting the Mechanic of the existing stud size/oversize.
5. I favor the large profile Continental brass exhaust nuts - like the ones you find at Spruce. The lock is a "stake" or slightly out-of-round scenario. These nuts work very well and are corrosion resistant. Also, they tolerate re-torquing. However, they are NOT reusable. Once they're removed, the threads will be severely compromised.
6. I recommend spending a few extra bucks and getting the No - Blow gaskets. They will last the life of your engine and can even be reused on your next engine.
7. Lastly, address any erosion issues in aluminum flange of the cylinder before assembling your exhaust stack. If it's a used engine, there's a good chance you will find erosion from a previous exhaust leak.
Dave Ronneberg (Berkut designer) prefers - using Stainless 12 sided nuts which are lower profile and easier to put a socket to and seem to resist backing off. No more corrosion that so many exhaust nuts exhibit – sometimes locking onto the stud which results in the stud coming out of the head. He agrees on the blo-proof gaskets being the best – many home-built Lycoming pipes start their "turns" close to the head, restricting space for tools.

  Feb 06, 2021     cowling - Boat Tail or No? - (8 hours)       Category: C23 Eng+Cowl

On 2/5/21 I heard Klaus Savier endorse the boat tail lower cowling. Changes to the plans burn up time, but the cowling is already a custom feature. Here's an explanation and picture of a "boat tail", then a discussion of baffling. I'll be cautious in planning, but it's where I'm headed.
__________________________________________________

The plans version of the cowling involves a large curve that results in separated airflow. Somewhere along the way, someone came up with the boat tail. The idea is that by adding a tail to the back the slope of change can remain at or under the 3 to 1 ratio (for every three inches of length the curve only changes 1 inch or less). This allows a more gradual change in the contour which keeps the airflow connected - see the tuft testing photo below. Then someone went further and moved the exhaust to this location as there was space there and it smooths airflow over the cowling.

Nick Ugolini used an eductor in a standard cowling, and perhaps that can be used with both exhaust and with air exiting the baffles.
_____________________________________________________

Air through the cowling - tractor vs. Canard. A typical tractor-form airplane (think Cub) has pressurized air come through the nose and held tightly over the cylinders before exiting to the lower cowling and out a large and generally neglected exit at the bottom of the cowl. In a canard the air enters at the bottom of the cowl pressurized with intake air from the NACA. That air flows up through the cylinder fins, constrained by baffles, which guide around the cylinders and into a pressure box open at the rear. The air exits the cowling through largely unrestricted openings

Background - plenum & eductor. To increase pressure differentials, a lot of time and trouble goes into constructing tight baffles, with rubber / neoprene strips pressed tight against the cowl to hold air in and increase pressure differentials. When that approach is exhausted, people use plenums - see the BD-4 plenum below. A plenum is a pressurized chamber containing cooling air and forcing it over the cylinder fins. But I have an updraft cooling Cozy and it is darn hard to shape a plenum for the bottom of an engine - the induction pipes and oil drain, are hard to work around. Is there any benefit to a top side plenum with an updraft engine?

I have never seen one on the hot side, but perhaps it could be called a modified eductor. (Wow, straight from the Latin educare, "to lead out"!) Below is a picture of the Nick Ugolini "eductor". He used the eductor to exit exhaust gases, with the cylinder heated air exiting through ducts on the top of his cowling. (There is a slightly more detailed description of eductors at https://groups.google.com/g/cozy_builders/c/-YRfovdF1-E/m/j-1-d7pkOUUJ.) Could an eductor be used in a boat tail cowling - the cooling air exits through the eductors on the right and left side of the prop, while the exhaust pipes exit below.

In this approach the NACA is as well done as possible, pushing into the cowling as much air as possible and losing as little as possible to anything not cooling the engine or oil. The air escapes up past the cylinders into the plenum and out through an eductor exit. In the real world it is hard to pressurize anything, so I'm simply closing off big air exits other than through the baffles. Regarding exhaust, the pipes are kept fairly short, and 4 pipes exit below the prop hub. I'm going to use a 8" prop extension. That should give enough dissipation area for the exhaust not to focus heat on a given strip of the prop.

In summary,
- boat tail cowling
- plenum atop cylinders
- cylinder cooling air exits through eductors either side of the prop hub
- exhaust exits through eductor underneath prop hub

___________________________________________________


And here are the half-done ideas on making cowling and cooling easy to live with.
• The top cowling “plate” should come off with nothing attached to the engine, so I get to see and service most things from the top. Dipstick hole in the top plate.
• The bottom cowling piece includes a ground adjustable lip to the NACA air intake, done via a metal lip on some screws. That lip includes the “fences” that keep NACA air from spilling out the corners.
• Exhaust pipes are pulled in close to and under the propeller – probably without a 4-into-1, just 4 pipes pointing aft. The exhaust exit is framed with an aluminum plate / mask, so airflow can leak around the pipes, but less than otherwise.
• Baffling will be high temp composite - I've ordered a half gallon of "Max HT", being the PCI product for high temps. It looks difficult to work with - at room temp's it can get to gel stage, then put it out in the sun for a "glass" stage (where it can shatter), then cook at 200 for 5 hours to get a hard cure that keeps strength up over 350 degrees.
• A hole in the forward baffle gives a dedicated air exit to the oil cooler, which is mounted on the spar with a 2” or 3” SCAT hose into the baffle.
• Cabin heat will be the EAA standard aluminum sleeve around a door spring around the exhaust pipe, with a bilge blower drawing air forward.
• With Dual EFI I won't need to blow air on a mag, so I don't need a cool air pipe.
• I have a prop-facing induction. I'd like air intake to come with the blessing of intake pressure, but the replacement systems all focus on making a vertical intake into a prop-facing intake (for instance, https://www.aircraftspruce.com/catalog/eppages/superior_sv78950.php). I'll keep looking for something that might work. Right now I expect to end up at an elliptical lip air filter box feeding a fiberglass connection to intake. I can use the Freeman modeling wax sheets to make the complex shape locking onto the induction box.

  Feb 26, 2023     Cowl #4 - (48 hours)       Category: C23 Eng+Cowl

I shaped one half of the cowl mold, then cut profiles (see below) and used them to shape the other half. There were multiple checks against the profile taken from the airplane (pink foam cutout shown below). After plaster and final shaping, it was two coats of epoxy to seal the plaster dust, then 3 coats of mold release wax and two coats of Part All spray mold release (polyvinyl alcohol). Note - you get better results with sealed plaster + packing tape.

I then layered the form with peel ply. I'm making cowls with layers of 6k h5 twill carbon fiber, Coremat 2mm XM and a second layer of carbon fiber. The headache with cutting CF is that it slips like crazy on the peel ply - a shot of spary adhesive fixes that. The headache with the Coremat is that until wetted it is much less flexible than the CF. I ended up with 3 pieces in each CF layer and 8 pieces in the Coremat layer. It all gets topped with more peel ply. Attached is a picture showing the inner CF layer sitting on the inner peel ply, with the next 3 layers on the strake in the background.

The layup was West Systems slow for the inner layer, then Raka + Non-blushing hardener for the Coremat and outer layer. I continue to be wildly impressed with the Raka epoxy - so long as I use their high end hardener I get a superb layup. The tradeoff is a short pot life... The layup day was 6.5 hours of scramble, but I have well wetted layers and it all tied together. The Coremat got a lot more flexible when wetted, so perhaps I could have cut corners in fitting that layer. After a 18 hour cure the mold+cowl went into the Florida sun. 4 hours at 120-140 surface temp finishes the 2nd cure.

Below are pictures of the piece before and after removing from the mold and cleanup. The inside was coated with fuel proof epoxy, and the photo shows the areas I again masked with peel ply. (Note for others - I mixed 300 cc's of epoxy and could have done the job with 210. I hate wasting the good stuff.) Once I had a clean lower cowl I started iterating test fit + trim. The lower cowl was on and off ~10 times, aligning it front and back, marking the edge, back to the table to trim off a bit, then repeat. Picture 10 is a milestone where the front and rear edges work and I still need to trim both top & bottom for good matching surfaces.

  Dec 12, 2022     Cowl #3 - (60 hours)       Category: C23 Eng+Cowl

I can accept the quality of the top cowl (CF + Coremat + CF) but I was sure the commercial ones must be better. In KY, Greg Cross had one he ended up not using, whcih he said was for a wide deck 360. It was a 3-day 2000 mile round trip but I went up, socialized and brought it home. Then I found it is actually a poor fit - !@#$!. The commercial cowl has the oil door too far forward and the exhaust openings are too tight and incorrectly oriented. The upside is that my Coremat cowl is about 60% of the weight of the commercial product and a lot stiffer. Time to double down on making the lower cowl....

This has proven to be a much bigger task than expected, and perhaps it would have been more direct to flip the plane again. But I persevere. Here's what has proven successful.

I need a tight fit at the firewall/wing root, and then at the trailing edge, particularly around my exhaust eductors.
- Lower profile. I used square cross section aluminum to bridge the NACA duct, providing a shelf/lip for the forward edge pf the lower cowl. The lower cowl needs to wrap around the air intake, alternator and starter, reaching up in front of the ring gear to fit behind the (extended) prop hub. I like having at least a 1.5" gap for the lower engine baffle. I used building sheet foam (purple!) to profile the lower cowl - it ended up looking like a hockey stick. I copied that foam shape onto luan plywood and fixed it in place using 5 minute epoxy. The plywood ends up as a keel for my boat tail lower cowling.
- Wing root match. Using the same wing root profile as used for the upper cowling, I built on the plane a foam block lower cowling. The wing root blocks were held in place with bamboo skewers passing thorugh the wood profiles into the foam . At this point I have gone through a _lot_ of foam insulation sheets, and the cost approaches buying something from Velocity. Moving on...
- I did a rough carving of the foam while in place on the plane. I then (carefully!) supported the cowl while I sliced the foam away form the wing root profiles and firewall. I removed the cowl and reinforced the inside with pour foam and building foam. At the sides I added an additional 3/4" wing profile, copying the wooden ones. The block was then moved to the bench, ending the messiest part of the upside down work. Note that with the interior of the foam core now reinforced with pur foam, this core can no longer fit on the plane.
- Firewall profile. I trimmed a piece of foam board to match the exisiting firewall lip. Fitting it to the foam core I saw that it was not a great fit to the new foam template. !@#$!. After 3x checking the template I used both foam and plaster to get a darn good match. I then re-shaped the cowl to smoothly flow from the correct firewall profile.

[Sidebar: Spray foam was an uncontrolled horror, but it took only 2-3 hours to clean that up. Pour foam is much easier to sand, but expensive and it's hard to predict how it flows before it swells, gells and hardens. I was happy to find a pour foam source even less expensive than my bare bones boat supply distributer - Amazon has some, and they sent me 1/2 g containers of A&B when I had paid for only the quarts. Doing it again I would build on the airplane with blocks of foam, remove and add a thick pour foam layer, shape with rasps, then use plaster to get a smooth surface. Model one side, then cut templates and shape the other.]

  Dec 12, 2022     Throttle Cable 2 - (12 hours)       Category: C23 Eng+Cowl

It took a darn long time to 4x measure the correct length and winnow vendors. See attached. The cable is treaded from rear of the instrument panel, a U-turn to run alongside the pilot side of the aircraft, and throught the firewall just left of the fuel. 3 new clickbond studs were added to further secure the shielded, armored throttle cable.

At the engine end the armored throttle cable goes into a steel tube with external threads, then a small dimeter smooth steel tube, from which emerges the moving 10-32 threaded solid rod. To the end of that threaded rod is an engine-rated clevis with a 3/16ths pin, matching the hole in the throttle arm. I modified of piece of aluminum angle so that it bolts (two 1/4-20 by 3/4" high strength bolts, with split washers) to the existing tapped holes in the oil sump. That bracket holds two engine compartment - rated Adel clamps. The forward one is secured around the steel tube with external threads. The one further rear is secured around the small dimeter smooth steel tube.

There was a fair amount of measuring and re-measuring, which meant 1st try success in cutting and drilling the bracket. There is full throw of the throttle are with no conflict with any structure throughout the travel.

  Oct 26, 2022     Cowl #2 - (100 hours)       Category: C23 Eng+Cowl

My first pass at an upper cowl weighted in at 7 lbs, right on target. But I can see the errors. I had rough edges where CF strips bridged across my 3-part layup. I had not lowered the nose and layers slipped to the rear and down the sidewall, leaving me with edges without the Coremate center. My edge was not smooth where I met the firewall. Clearance of the starter ring gear was only 3/8". The right and left looked symmetrical, but measurement says they are not.
Smoothing the surface and prepping for paint added too much weight. Crap... I decided to do better with the next effort.

I again started with the top cowl. Top cowls are straightforward - start at the firewall and go smoothly to the prop, while staying clear of the cylinders and starter ring. I modified the mold to get a better outcome.

Building a core for the cowl:
- I changed the profile at the firewall to get a smooth line around and across the (wide deck) cylinders
- over the ring gear and rocker covers, add a clearance spacer
- starting from the wing profile and firewall, make a foam core/mold that fits around the engine installation,
- define the exit for cooling air. In my case, a box with the lower horizontal tangential at the lower edge of the prop extension, the rest defined by the shape exiting the wrap around the cylinders.
- rough shaping, then fine shaping, I used foam blocks, foam strips, plaster and micro. For plaster, use the quick set that comes in the 18 lb bag. A 5 lb bucket of plaster will dry too slowly for any practical use.
- fill-sand-fill-sand the mold, then epoxy wipe. Now that one side is perfect, copy that profile to the other side.
- box tape on the mold (you need the epoxy wipe before tape will stick to the plaster)

Layup schedule, top cowl
- Prepare airplane – lower nose so cowl is near horizontal
- Prepare mold: 3 layers wax, buffing between each + 2 layers PVA, using spray bottle
- Using Raka slow cure non-blushing epoxy, paint mold and affix peel ply
- Using oil & gas resistant (GRE) epoxy, carbon fiber tape on edges that will hold Dzuz / Camlock fasteners
- Using GRE epoxy, place and wet out the inner layer of CF
- Using AeroPoxy, place and wet out the 3 pieces of Coremat 2mm XM
- Using AeroPoxy, place and wet out the outer layer of CF
- Afix peel ply and roller, hoping to draw out excess epoxy
- Plastic sheeting for spreader work – draw out excess epoxy and aim for smooth finish

[This task will use a lot of scrap foam, Gorilla Glue, and cheap boat epoxy. On pricing, note that the best epoxy made by Raka (900 resin + 350 hardener) was 75% the cost of West Systems and 50% the cost of Aeropoxy.]

The bottom cowl is a lot harder than the top. I am wildly disinterested in flipping the plane, so I explored making a removable mold. I began with a bridge across the NACA duct, then a "keel" piece to form the center profile (first in foam, then in luan ply). The keel also facilitates a boat tail cowling, which race winners say is more efficient. THe forward edge is glued to the aluminum bridge, the trailing edge glued to a wood disk between prop flange and prop extension. I then filled in with styrofoam 2" board insulation.

  May 22, 2022     cowl       Category: C23 Eng+Cowl

The engine is a wide deck angle valve. The plans call for buying the cowl - with no cowl available for my engine scratch build is a reasonable deviation from plans. Below I show that this is _not_ efficient or cost effective; if you can use the Aero Composites / Featherlite cowl, by all means do so.

I had to start with the requirements. The cowl has to
- provide a streamlined shape to the fuselage,
- have a stiff and resilient surface durable enough to handle the proximity to prop wash and engine vibration,
- be secured with reliable and easy-to-remove fasteners and
- facilitate engine cooling, with efficient and properly sized intake and exit areas.

Shape and Fasteners. Cowls should have minimal drag and ideally complete an airfoil shape over the fuselage. I've chosen to have a) an upper - lower join that matches the wing trailing edge, b) a boat tail on the lower surface, and c) exhaust exiting through an "eductor", an effort to have exhaust gases pull air through the cowl.

I secure the cowl to the attachment flanges built into the wings and fuselage. I will use Dzuz fasteners every 4 inches on the top and bottom arch, and piano hinges at the wing-cowl mating surface. This is contrary to the builder group discussions, which prefer Camlocks. I have 85 year old Dzuz still working well in a PA12, and I'm comfortable with the simpler install - I'll go with Dzuz and use more of them. For the long straight joins I'll use my RV experience and go with piano hinges. I'll pay up for the extruded hinges, just in case it's a strength issue.

Construction method. The shockwave of prop passage will hit the cowl surface at 2700 rpm x 2 blades = 5400 times a minute, 90 times per second. The closer to the prop the harder the hit. To handle that force I decided to make this cowling from carbon fiber cloth with a Coremat center. This is consistent with a presentation for the Cozy builders group. The presentation is at https://docs.google.com/presentation/d/1vTyFMM8RQ9PijpZ07AT6vDHU164KCHXY/edit?usp=sharing&ouid=111349802257488370268&rtpof=true&sd=true

Intake area. Per _Tony Bingelis on Engines_, the rule of thumb for inlet areas is .35 x engine hp (p.87). At 200 hp, my IO-360 should have an inlet area of 70 in2. The cross section at the end of the ramp of the NACA inlet is 15 x 2.75 = 41.25 inches. Unless the NACA in nutty efficient and has an effective area 1.7x the cross section, I need another 30 in2. My oil cooler has a face of 30.8 in2 - if I feed the cooler with an armpit scoop sized to match the inlet area is 72 in2 and on target with the Bingelis guidance. But most Cozy fly without the armpit scoop feeding the oil cooler. I will build and make initial flights with no armpit scoop, knowing I can add one. I will focus on having an efficient NACA intake, using the corner tabs that keep air from tumbling out of the intake.

Exit area. I have not found a standard for outlet area. Per Bingelis the outlet is at least equal to the inlet. Per the Vans forums it should be around 1.6x the inlet area. Above I plan for 72 in2 of intake, so I target an outlet of 115 in2. The area around the prop flange is a diamond of total area = 119, less the area of the extension prop flange for a net 80. My exhaust pipes exit through the lower cowl; I am shaping my exhaust pipe exits as eductors, hoping they will pull air out of the cowl. The area of the eductor is 23.8 in2, less the area of the exhaust pipes is a net of 17 per side = 34 total. Total exit area is 114 in2. On target.

Construction steps.

1) Install the (purchased) exhaust on the dummy engine, and any eductors. If not done already, install the cowl mounting flanges, keyed to the expected thickness of your cowl. Wrap the engine.

(Eductors are a lower cowl feature, and need to be fitted and secured before the lower cowl layup. I determined the target radius and pop riveted stainless steel shim stock. I then wrapped this in a sandwich of fiberfrax, CF+ Coremat + CF. I let the epoxy set in a frame that gave me a targeted oval shape, matching the exhaust pipes.)

2) Mount the prop extension - the cowls will need to converge and terminate 1-3 inches forward of the mounting flange. The front face of the extension is the back face of the prop.

3) Mount the wings and copy the edge profile required at the cowl-wing join. Securely attach the profile to the spar, but knowing it will be removed after final cowl casting. Remove and store the wings.

4) Surround with foam STRIPS. The cleaner the curves of the foam strips the less time and money you will spend on filler. [A better approach is to build a cardboard shape, then fill around that with the foam.] The cowl is laid up on a casting surface, and the better the surface the better the cowl. Plaster and sanding, epoxy squeegee on the plaster, then packing tape. After all this work I finally have a good casting surface.

5) An armpit scoop was laid on a core carved from a block of pour foam. CF + Coremat + CF for the scoop. This will be held in reserve for use if required.



Materials:
4 sheets of foam sheathing @ $28 each = $112
6 cans gap fill = $24
2 gallon kit of pour foam x 2 = $125 x 2 = $250
1 quart PVA = $26
1 tin miracle glaze mold release wax = $22
10 yards 3k 4hs carbon fiber (needed 7, bought extra) = $182 (Soller Composites)
5 yards CoreMat XM = $0 (the manufacturer sent a free test roll)
1 gallon West resin + extra slow hardener = $120 + $60 = $180. I buy this as I run out, and it was time to get more.
1 gallon acetone to clean arm hairs of gap filling spray foam = $25. As with the epoxy, buy it when in runs out.

Total ~ $825. Chris at Aerocomposites offers a full set for $650 - if you can use a purchased cowl, it's the smart way to go! https://aerocomposites.aero/

  Mar 05, 2022     air filter - (2 hours)       Category: C23 Eng+Cowl

The A sump locates the throttle body between the sump and prop. It was convenient to directly connect the air filer, putting it at the aft end of the cowl. Per other builders, air "piles up" at this location for a relatively higher intake air pressure. The plans say the air filter is to be "Fram 3647 or equivalent". That filter has a surface area of 66.9 in2 (2.5" height & 8.52" diameter) before counting the pleats. I went with a K&N filter connected to the SDS throttle body with a section of 3" reinforced hose. (I hear rotten lab tests for the K&N air filters, but I think it is the most common make used in amateur built aircraft.) This filter has a pleated surface with an average diameter of 5.44" and height of 5.0". C= pi x d = 17. A = C x H = 85 in2. This is before counting the inner cone, estimated at 40 in2 for total area ~2x the plan filter. The additional area will offset the difficulty of breathing through an oiled filter.

  Mar 06, 2022     Throttle cable - (1 hour)       Category: C23 Eng+Cowl

Before buying a cable I made sure of the length at full throw. That required knowing the throw. I measured the distance from arm to a known point (here, the throttle body base) at full open and full closed. The distance is 2.75 inches.

The throttle body mounts on studs inserted into the sump, forming a square 2.5" on a side, The throttle body was installed in the temp engine using the o-ring and a film of lube.

  Feb 20, 2022     Baffles - composite w high temp epoxy       Category: C23 Eng+Cowl

Talking to experts built my confidence - I'm going to try for composite baffles, done with high temp epoxy. Klaus uses an aerospace product I can't access, so when pressed for a recommendation he offered:
- make sure it's a laminating epoxy and test the sample with a scratch test. There will be a transition temperature where it goes from a hard ceramic-type scratch result to something like a rubber sheet. That transition is the measured temperature for this use.
- The outer edge of a cylinder fin will be a lot cooler than 400 degrees - closer to 200.
- An epoxy with a two-stage curing cycle has a chance of meeting the standard. He likes MGS.

I have West, Aeropoxy, Max HTE (high temp), Max GRE (fuel resisistant) and a number of general purpose epoxies. Only the Max HTE comes anwhere close to the target temperatures, so I'll make a test blank with it, then stress test a toaster oven!

Here's the write up on Max HTE: MAX HTE A/B is a two-part epoxy based system especially formulated to provide structural strength at temperatures of up to 200⁰C or 390⁰F under pressure or load. It is formulated as an impregnating resin for fiberglass, Carbon Fiber, Kevlar, Spectra Fiber and other specialty materials that require heat performance. MAX HTE A/B can also be utilized as an adhesive, encapsulant or potting compound, tooling resin for high temperature applications. MAX HTE exhibits exceptional toughness and other mechanical properties such as adhesion, compressive strength and flexural modulus at high temperature exposure. MAX HTE also provides excellent chemical and water resistance. Fillers and colorants can be added to modify it for a specific use. MAX HTE provides a long pot life at room temperature suitable vacuum assisted resin transfer molding or VARTM, fiber pultrusion, pre-impregnation process with a relatively short heat cure time. It is specially designed to withstand continuous high temperature service, high impact resistance and exposure to harsh conditions. MAX HTE A/B is 100 % solids, low odor and toxicity and does not contain Ozone Depleting Chemicals (ODC).

  Jun 09, 2020     Picking an IO-360-A3B6D & SDS electronic ignition - (10 hours)       Category: C23 Eng+Cowl

My biases. My preferences are shaped from my own flying, decades of reading a lot of aviation press, and 20+ years of chatting to other EAA members. My rank ordered preferences are Lycoming, Continental, Rotax. I rank the auto conversions alongside the the exotics commonly seen pre-1950: Hirth, Gombe, Ken-Royce, et al. If I were building something with low wing loading I would have high confidence in my ability to find a survivable landing site. But the Cozy is built for travel between hard surfaced runways over 3500'; it makes sense to stick to the reliable makes, which I see as Lycoming & Continental.

Buly Alieve is a respected Cozy builder. Following are his biases plus some of my own.
1. Dual electronic ignition from the start.
2. Updraft cooling
3. Dynon sensor harness from Stein Air
4. baffling kit from Vans Aircraft
5. red Silicone valve cover gaskets
6. push-pull marine control cable for throttle with vernier fine tuning
7. 90 degree oil filter adapter
8. Kavlico 3 wire OP and FP sensors
9. B&C Starter
10. 2 wire Oil Temp sensor
11. Steve's gas collator

Engine on hand. As noted in "research", the selection of a Cozy IV was partly around its ability to fly well with an IO-360. I have an IO-360-A3B6D, originally from a Mooney, then used in a BD-4 until removed for overhaul. The engine was never reassembled, so I have a full set parts ready to assemble with aging yellow tags. When I last flew this engine, it had the dual mag on one side firing one set of spark plugs, and a Klaus Savier Lightspeed ignition (generation 1!) firing the other set. This gave 90+% of the benefits of spark advance with the simplicity of a traditional magneto. I never liked the dual mags on one shaft, and that stops with the dual EI. From the engine pics you can see that the A3B6D has a prop-facing air intake. Since I'm going to a pusher configuration I'll see if I can rotate or swap the oil sump - I'm pessimistic but its worth asking the question. And this is a wide angle / angle valve engine. While that's a better geometry for the valves, the stock engine for the Cozy is narrow deck / straight valve. I get to do a custom cowl, and probably a custom exhaust.

There has been some progress in the 30+ years since the Lightspeed ignition. For a few of the manufacturers I am comfortable going with dual electronic ignition. SDS has the most installed systems, has been the manufacturer behind other EI brands, and has a good reputation on the Cozy builders forum. As a result, I plan to build the engine with SDS EI and FI, and hope to sell off the mechanical FI and the dual magneto originally used on this engine.

Attached are photos showing some of the SDS components and installs in other aircraft.

  Nov 18, 2020     Throttle - (20 hours)       Category: C23 Eng+Cowl

I never knew picking a throttle cable was going to be so complex! Buly Alieve recommended that I go with marine grade cables, so I first I had to buy the right cable (15 foot vernier style), then the vernier-style throttle control head. Turns out that there are lots of small differences that I care about in the look and feel of the throttle, so I ended up with a "Seastar Solutions" cable and control head. Well, what they show in the pictures is not what they ship. Also, there are a fair number of crooked vendors for marine parts, with at least one just a few miles from me. Sigh.