Chapter 28: Post Phase I - Improvements
Why This Chapter?
My Cozy has completed Phase I testing and I love it! But I also know I can make it better in a number of ways that don't change it's overall flying qualities. In one case (fuel site windows) the update was required because I run MOGAS and the original fuel site gage backing plates were only designed for 100LL fuel. The main other area is fixing a few things to reduce drag in the custom cowlings, and overall smoothing to prepare for painting the plane in a year or so. Other updates are just replacement of functionality with something a little better or more compatible with the way I fly. Browse the sections below if you are curious.
My Cozy has completed Phase I testing and I love it! But I also know I can make it better in a number of ways that don't change it's overall flying qualities. In one case (fuel site windows) the update was required because I run MOGAS and the original fuel site gage backing plates were only designed for 100LL fuel. The main other area is fixing a few things to reduce drag in the custom cowlings, and overall smoothing to prepare for painting the plane in a year or so. Other updates are just replacement of functionality with something a little better or more compatible with the way I fly. Browse the sections below if you are curious.
Fuel Site Gage Replacement:
I knew from Vance when we worked on First Flight that eventually I'd have to replace the standard Cozy fuel sight gages, because the polypropelene backing plate would soften over time (using MOGAS) and the inlet and vent holes would close up. Once I completed Phase I, and all flight qualities were known to be good, I started to see that the sight gage on the co-pilot side wasn't registering accurately. This was an immediate grounding issue. Vance had already sent me new gages, so I just needed to replace them with the Aluminum backed versions. This should have been rather simple, but as I dug the old gages out, I noticed some softness in the fuselage fiberglass underneath the backing plate. I removed a little bit of this glass very carefully and found a problem. Way back in Chapter 5 when the fuselage sides were fabricated by the the previous builder (before I bought the project). He'd made a mistake and left duct tape in this area between the inner and outer fiberglass. It is supposed to be a glass to glass interface! I then went into major surgical mode and removed all of the interior glass and the duct tape, sealed the area with EZPoxy and glass and tested the result with fuel in the tank to insure I had no leaks before re-applying the backing plate and sight gage bubble. It was really fortunate that I needed to perform this upgrade as it enabled detection of this flaw (which was hidden under the interior fuselage skin). Flight testing show new sight gages are easy to read (day or night) and leak free. Yes! Just need to clean up perimeter and paint to match interior... |
Reducing Drag on Lower Cowling:
During Phase I testing I did a flight with yarn tufts all over the turtleback and upper and lower cowlings as a part of improving flow into the NACA scoops for cooling. In the process I found from a few of the yarns that there was a flow separation on the right side of the lower cowling just ahead and below the exhaust outlet. I didn't see similar separation on the left side. I also noticed some separation near the inboard aft edge of the lower cowling where I'd curved the cowling too aggressively to keep the engine opening in the back as small as possible. And finally there was a big separation region aft of the oil cooler outlet because this area had not been shaped right. Remember that I developed the cowling without knowledge of the flow with this engine, so I always considered this Cowling 1.0 and I'd make improvements as needed. Frankly, the flow characteristics were pretty good for this level of guessing. My intent here was to smooth the narrowing transition on both sides forward of the exhausts and to create a slight boat tail behind the oil cooler to eliminate the separation and also more gradually angle the aft portion of the cowling. Note that I'm also going to improve the exhaust pipe flow outside the cowling but that's addressed in the next section. I also found at the end of Phase I testing with the improved oil cooler diffuser that the opening through the cowling was probably too big and that modification is also covered separately below (but influenced the cowling adjustment). Step 1: Mark and fill the areas where I want to eliminate separation with pour foam. I used pour foam because it's light, easy to sand, and has great adhesion properties with the sanded finish of the primer. I'm not expecting this new shape to carry structural load, it just needs to be smooth and well attached. Step 2-5 were shaping the foam, pouring more, and shaping until I got the shape I wanted. As I improved the R side, I noticed where the L side could also be improved (even though it didn't show visible separation, the transition of flow could be more gentle). Step 6: Micro the shaped foam in "hard shell" and smooth further. Step 7: Glass the surface in overlapping UNI and smooth edges Step 8: Check fit with new exhaust tube tips and updated oil cooler exhaust diffuser Step 9: Install flow separation measuring yarn tufts and Flight test Step 10: Remove and primer coat I fitted 2.5" yarns all over the lower cowling in the regions where I'd made modifications and performed test flights including max speed testing and then examined the yarns for damage (separation will fray the ends of the yarns). The flow is now fully attached everywhere on the lower cowling accept right behind the extended lip on the oil cooler NACA. This is great news on the cowling modification, and I can now smooth/fill/sand and prime the cowling at the next opportunity. For the oil cooler NACA this testing suggested that the sectional area is too large now and the flow is choked and spilling over and around the lip extension. In response, I've cut off the lip extension as it was a bad idea. It was not increasing oil cooling and was creating more separation drag. |
Angling the lower edge of the Oil Cooler Exhaust Diffuser "up" a Little:
Another improvement I wanted to make while working on the lower cowling was to angle the new oil cooler exhaust diffuser bottom surface up a little. I had an angle like this on the original diffuser and had been really aggressive in opening up the exhaust area as well as curving it under the oil pan to get better cooling performance. Curving of the upper surface helps align the diffuser flow with the external flow around the cowling. I did't want to have any smaller an opening as in the original diffuser and decided to make it 20% larger, which set the angle of the lower edge of the diffuser. Note that I'm also adjusting the cowling shape behind the diffuser with slight "boat tail" to encourage more high momentum mixing and drawing of the exhaust into the hopefully non-separated flow. As noted in the flow vis study above, the shape appears to be much better and I'm not measuring any increased oil temperatures compared to previous configurations. |
Turning Exhaust Flow Aft:
In addition to improving the shape of the lower cowling, I wanted to simultaneously have the exhaust of cylinders 1, 4, and 6 turned more aft to align with the flow on the outside of the cowling. The expectation is that this might make a small improvement in drag reduction by not blasting plumes of gas at an angle into the flow passing over the cowling. This involved measuring where I wanted to generate the turn in the exhaust so that it's aligned with the external flow and just outside the cowling. I had a good example that this worked well with the Cylinder 3 exhaust pipe that I configured this way in the original iteration (somewhat by accident). I used curved pieces of exhaust tube from the original cutting down of the stock ULPower exhaust headers, and again had Janelle to the welding. Reinstalled the pipes and needed to do a little surgery on the cowling aft of the #4 pipe to create 1/4" clearance between pipe exit and cowling skin. As noted in the previous section, the flow visualization suggests that the flow is much better all over the lower cowling. I see a little bit of soot on the lower cowling behind #4 exhaust exit, but eventually will plan to paint this area grey or incorporate it into the paint job so it's not noticeable. |
Jet Hot Ceramic Coating:
After running for a bit with this exhaust and feeling I'm not going to make any more changes to the pipes, I was ready to get them ceramic coated. The motivation for this was primarily to reduce radiation heating on the oil pan (you can see how close they are) which may be playing a role in oil temp rises at full throttle (particularly in warm weather). See above pictures added for the pipes after received from Jet Hot, and after install. |
Canopy Seal and Aft Drains:
The original soft window seal I used for my canopy is working well accept at the aft edge of the IP cover on the Co-Pilot side. I have a side hinge canopy, and at one spot where the seal line curves down towards the longeron, the seal gets some tangential force in closure, which it tough on the bond with the canopy. I'm playing around with options so far with the same seal that involve moving it to a point that doesn't see this seal rolling force, and using 2 different seal angles. I'm just now starting to deal with a way to drain water that collects in the trough of the TB/canopy seam down and away from the cockpit. I've done a first draft of this as shown in the photo. More on this once I get something I'm happy with... |
Replacement Landing Light:
I bought a relatively inexpensive off-road LED spotlight originally for my Cozy landing light and it fits and makes a pretty bright beam. Unfortunately it gives off a lot of interference to the radio system. I've not flown the Cozy at night yet, but have purchased a replacement purpose designed for aircraft landing application to hopefully mitigate this interference. The new one is AeroLEDs MicroSun 1170. It's smaller and a much smaller and powered by 12 LEDs in 3 lenses with 2600 lumens and only 20 Watts. I had to design and make a new bracket to mount it, but a benefit of it's smaller size is that the bracket and the light fit in the lower portion of my forward nose cone compartment. This enables me to carry a little more ballast in this area to reduce ballast further aft in the nose when flying solo. The installation went well, and I had no problem landing with it at night, even though it still needed to be adjusted to aim a little more forward. After getting some more night landing practice I'll report on whether I recommend it for others. In the mean time, I modified my pitot tube to become a heated pitot tube (described here) and changed the nose shape to be more pointed (also described in "Fairing" on the same link page pitot tube heat). By moving the landing light lower and only using the lower 1/2 of the window, I could provide more volume for fairing in the sharper nose shape. There's a picture to the right of this smaller window opening, even though the fairing is not done. It's tight getting fingers in there to put the light/pivot into the bracket... |
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Modification to Wheel Fairing for New Tires:
I had a spare set of tires already purchased when I started Phase I testing because I wasn't sure how good the original tires would be after many years sitting and supporting the static project. They turned out to be fine and I did the wheel fairing fitting with them about 3/4 way through Phase I. However, the right side tire had worn more than the left in the early stages of testing because I didn't have the wheel alignment perfect yet. See here for the alignment work I did to correct it, AND the photos of this fairing fix. scroll about 1/2 way down to find the relevant information described below.
When Phase I was over, this R tire needed to be replaced and the new Tire (Goodyear 5x5.00) though the same "size" as the old tire had a slightly different shape and was a bit larger in tread diameter. It was only a small amount and it didn't rub when I pushed the plane around, but after the first flight test and a couple of landings I checked the fairing and noticed that it was rubbing only when the wheels were spinning very fast just before liftoff and on touch down. I could not feel any problem taxiing. I needed to provide a little more clearance and rather than post on it here, I've put that work on the page that shows the fairing creation. Note that not long after, I had to do the same procedure to provide clearance on the pilot side wheel fairing for the same new tire replacement. Much easier the 2nd time around...
I had a spare set of tires already purchased when I started Phase I testing because I wasn't sure how good the original tires would be after many years sitting and supporting the static project. They turned out to be fine and I did the wheel fairing fitting with them about 3/4 way through Phase I. However, the right side tire had worn more than the left in the early stages of testing because I didn't have the wheel alignment perfect yet. See here for the alignment work I did to correct it, AND the photos of this fairing fix. scroll about 1/2 way down to find the relevant information described below.
When Phase I was over, this R tire needed to be replaced and the new Tire (Goodyear 5x5.00) though the same "size" as the old tire had a slightly different shape and was a bit larger in tread diameter. It was only a small amount and it didn't rub when I pushed the plane around, but after the first flight test and a couple of landings I checked the fairing and noticed that it was rubbing only when the wheels were spinning very fast just before liftoff and on touch down. I could not feel any problem taxiing. I needed to provide a little more clearance and rather than post on it here, I've put that work on the page that shows the fairing creation. Note that not long after, I had to do the same procedure to provide clearance on the pilot side wheel fairing for the same new tire replacement. Much easier the 2nd time around...
Fuselage Cover:
As I start to use the Cozy for cross country flights I'll be leaving it on airport ramps at the destinations. My canopy locks but it still has a small gap on the pilot side with the longeron when not latched down from the inside. To reduce the likelihood of getting water in the cockpit as well as potential tampering, I'd like to fit a cover for my Cozy that overlaps down to the strakes. I've gotten great feedback from the builder's group from others who either had a cover made for them or designed and built one on their own, and have decided that based on the longer nose/custom cowling/Texas sized canopy/extended strakes/etc that I should custom fit one for N78CZ. Moreover, I'm going to experiment with a really light silicone coated 1.1oz polyester like tents are made with. It's waterproof and extremely light. Here is a 7 yard piece of the material draped on my Cozy and I'll need to add a little material on one side to accomodate the Texas canopy size. I've got to learn how to handle and sew this stuff as it's really slippery, but I think it will be fun to figure this out. More on this once I get started... |
Upgrade ADSB-In from Scout to Sentry (for Foreflight):
I've been using Foreflight since very early in Phase I testing with a Dual 160 GPS puck and Scout ADSB/Weather IN capability. It's a great compliment to my Dynon system and allows me to use the Dynon Display for Primary Flight Instruments and Engine Monitoring. Yes, I have the bottom area also available for engine monitoring but with the great Foreflight display, I prefer to keep the engine monitoring nice and big in the right side of the Dynon. I've had some issues however with the iPad periodically loosing Wifi signal from the Scout, and switching to the Dynon Wifi network (which I use to upload flight plans to Dynon from Foreflight, typically before the flight). Getting ADSB-In requires going back to iPad Settings to re-set it's Wifi to the Scout, then returning to Foreflight. This takes a little time, but the bigger bother is that I don't get a warning that I've lost ADSB-In until I return to Foreflight, so I can sometimes fly for a bit not seeing traffic and not knowing whether it's actually clear or not. I'm pretty good at sensing when I'm missing traffic, but I'd like to not be concerned about this particular condition. At the same time, I'm flying farther now and like the ability to backup my Dynon system with Foreflight. It can't do everything the Dynon System can do, but it's very powerful. One way to improve this backup would be to incorporate ADAHRS sensing for the software. |
By upgrading from the Scout to the Sentry system I got a more robust ADSB-In and an integrated WAAS GPS and ADAHRS sensor. There's also a Carbon Monoxide sensor for safety. I've flown with the Sentry and had zero drops so far. I flew with it a few times in different positions until I figured out where I really wanted to place the Sentry. I chose to mount it on the fwd edge of the strake extension (which in N78CZ is almost to the Instrument Panel) as shown in the picture. This gave the the following benefits:
a) easy access to power it On/Off, b) easy supply of USB power from behind the IP, c) visual monitoring of GPS/ADSB/Sensor health via Sentry LED's, d) Keeping Sentry out-of-the-way and not interfering with joystick use |
Iphone Mount in IP:
I had planned all along to mount my iPhone in the instrument panel to the left of my EFIS. I use the phone for a number of things and I think this may grow in the future, and I essentially wanted access to it without digging it out of some storage area. I built a fiberglass holder out of 3 BID with a lip on the lower edge to hold the phone weight and a velcro patch epoxied to the upper back area. I then bonded a small velcro patch on the back of my cell phone protector back. The bracket is mounted with 2 AN3 flush screws into floxed hard points in the stock IP. I've flown in pretty heavy turbulence for 45 minutes and the mount shows no sign of releasing the phone. The velcro releases the when pulling straight back from the upper portion of the phone. This position makes it easy to monitor the phone and use apps like a digital stopwatch/timer. Most of the time, the phone display is just OFF to save battery. I may eventually run a USB power cable here, but I need to develop a reason. Mostly I'm trying to give it a known location that I can reach. |
Builders and Pilots are often curious about how each other's cockpits are set up. Here's a picture of mine after Phase 1 Testing. It's pretty modest with Dynon HDX 10" on the left and iPad running Foreflight on the right. Foreflight is being fed by Sentry on it's right. My Radio/Intercom is a Garmin GTR200. Room to grow in the center area below the radio. Note that I've not yet set up the electrical loads for cabin heat, cabin light, seat heaters, and 2nd Battery, so their switches are labeled "INOP". My joysticks are custom shaped and very comfortable and provide trigger push-to-talk and thumb autopilot disengage. I fly with very comfortable foam in the seats (removed here because they have not been upholstered yet).