Exhaust Wrappin’

Time: 1.5 hrs

Today I wrapped the 4 exhausts running between the cylinders and turbo with Design Engineering 2″ thermal wrap. I had read on the Rotax blog that guys are wrapping the exhausts and haven’t had any negative affects…yet. Also Torrance TAF is wrapping the exhausts on some of the planes their building so it seems safe to do.

The process of wrapping the exhaust was pretty easy. I first cut 2 5ft and 2 6ft lengths (the right side pipes are a bit shorter than the left) of the warp. I did one overlapping wrap to start and then you maintain (or try to maintain) a 1/4″ overlap as you wrap the material around the exhaust. You don’t want to over do it because you could end up putting on too much material and cause too much heat to be retained in the exhaust. I wrapped the 4 main pipes down to where they meet at the turbo. I then did some creative wrapping to try to get the best coverage over this area. It took some experimentation, but I think I got a decent wrap around it. The wrap ends are held down by some stainless steel ties. I’m thinking now about how I will wrap the turbo. The guy at Torrance TAF said he was going to use a 3″ wide piece of wrap to cover it, but I’m not sure how you secure it, I guess you could run some wire through the edges and tie the ends together to form a kind of doughnut. I also saw that you can purchase a boot that is custom made to fit around the turbo, but they’re pretty pricey (like $150) and I saw that some fall apart so I’ll have to think about it.

One tip is if you’re sensitive to fiber glass wear some gloves. It doesn’t bother me so I didn’t wear any, but you’ll definitely get some glass on you if you don’t.

First pipe wrapped. I used a temporary zip tie to hold the end, but it actually stays fairly well with out it. The trickiest part is getting it started after that it goes quick wrapping down the pipe. I tried to hold some tension on the material as I wrapped it around the pipe. It stays wrapped pretty well.

All the pipe are wrapped. Only the area where the pipes all meet before going into the turbo needs to be wrapped. I secured the end with stainless steel ties. I also left the front EGT sensor bolts accessible so if I need to use them I don’t hav the cut the wrap.

This area took some time. I didn’t;t want to over wrap it, but the way it’s shaped makes it hard to wrap it so the wrap wants to stay. I secured it with a few ties.

Close up of the tie. The worst part is that the ends of the material want to fray after you cut it. To do a nice looking job you have to hide the ends. When you start you can do one full wrap to cover the end. When you end you can’t do that so I ended up folding back the frayed part under to hide it.

Avionics Shelf

Time: 2.5hrs

I found got some time to work on the plane. I’ve been so busy with work and then useably tired after that I haven’t had time to do any work on the plane. So today I made two shelves that some of the avionics will sit on. Mainly the GTR20 (Radio), GTX45R (Transponder), and the GMA245R (Remote Audio Panel)… This list might change, but I think this will be the way I’m going for mounting the avionics. Some stuff will mount directly to the rib and then of course a few components mount into the panel itself. The shelves are pretty straight forward. I used some aluminum angle and notched the ends so that it could be riveted to the fuselage stringers. I had to make sure that it didn’t get in the way of the air ducts and anything that will be mounted to the panel. I use .05 6061 aluminum sheets for the shelves themselves and made them removable just incase I have to get in to reach something behind the panel and can’t crawl under for some reason. Now I just need to start buying some avionics, which I will do now that the engine is on and getting close to being done. The nice part about the shelves is it keeps all the avionics out where you can get to them and not buried under the rib section near the firewall which is actually hard to get to when the dash is on.

Shelves are roughed in and mounting holes drilled. Next step is to clean up the parts and install some rivnuts for the M4 screws that will attach the shelves to the angle and rib.

The shelves are mostly installed. I still need to rivet the angle to the stringers and get some shorter M4 screws. I may also make a bracket for the center that attaches the angle to the center console supports or maybe some L brackets to beef up the connection to the stringers on the side. It seems pretty sturdy though so probably not necessary. This will be the basic arrangement of the avionics. I’ll see when I get the actual avionics exactly how everything will fit and how the weight is on the angle piece. I may also be able to cut a little off the end of the shelves to shorten them up for better access behind and less weight. Also I can mount things to the underside of the shelves as well.

Coolant Hoses

Time: 1 hr

I roughed in the two main cooling hoses that run to the water cooler. TAF supplies some custom made hoses that look pretty good, but I’m trying to use the least amount of rubber hoses I can for reduced maintenance. I found some super flexible 25mm silicone hoses that can be used with coolant and meet the specs in the Rotax manual (up to 257º F and 73psi burst). I ordered the hoses from a UK company called Viper Performance which had both reasonable prices and shipping. Shipping via DHL only took a few days so not too bad. I also order a few short bent hoses. The thinking was to use the bent hoses for maybe the tight 90 out of the coolant housing on the top of the engine and then some 45’s into and out of the water cooler. I found though that the super flex hose seems to work better because it’s able to bend in multiple directions so I ended up just using that for now. When I get the water cooler I’ll see how it works on that end. I also found some hose clamps on Amazon that expand and contract as the connection heats up. It’s probably doesn’t matter so much with this smaller hose, but I figured it can’t hurt. The only downside is that the clamps are a bit heavy and bulky.

To get the rear hose in you need to turn the water inlet on the back of the engine to point to the right side rather than the factory install left position. There are actually six different angles the inlet can be position. I ended up using the right facing 70º position (slightly pointing up). The 105º position (slightly pointing down) would have worked as well, but I didn’t like how tight the hose was bent right at the fitting. Moving to the slightly up pointing position allowed the hose to pass through with a bit more space and a better angle. I was kicking myself for not doing this prior to putting on the engine, but it seems like the easiest way to get the hose on the inlet fitting was to remove the fitting and put the hose on then install the fitting. Now that made the hose install easier, but then installing the fitting back with the hose attached proved to be a bit challenging. Though with this in mind I figured it really doesn’t matter if you do this before or after mounting the engine. I suppose if you have the coolant hoses then prior may be better.

The 25mm silicone hose attached to the coolant tank on top of the engine. I was surprised at how flexible the hose was and how well it all fits in the small space there is to run the hose. I thought this was going to be the hard one, but it turns out the hose only took a few minutes to run through. The hose on the back of the engine for the inlet was a bit more involved.

The hose runs down the left side of the engine. I’ll need to find points to secure it.

This is the hose on the inlet on the back of the engine. This took some maneuvering to get in. It’s a bit of a pain trying to get the two allen bolts that hold the inlet onto the engine since there’s not much space to work (but when is there ever?). The inlet is in the 70º position which seemed to work the best.

NOTE (6/8/2019): So a few days ago while I was cleaning up the garage I found a large O-ring on the floor. Guess where that came from? Be careful when you remove the hose inlet there’s an O-ring in there and if it fails out make sure you put it back. Also make sure to use the holes that are across from one another, I almost put it make together with the bolts in different holes and it seemed to fit OK, but it definitely would have leaked.

It’s a bit close to the exhaust, but the exhaust will be wrapped and I’ll put on some thermal wrap on the coolant hose as well.

Just a shot of one of the bent hoses I purchases and the clamp.TAF supplied some fittings to connect hoses together so if I end up using these hoses to feed into and out of the water cooler then I’ll use those fittings.

Air Vents and EGT wiring

Time: 5 hours

I purchase a pair of 2″ AIrKit anodized aluminum vents from Aircraft Spruce. These things aren’t cheap, they’re around $160 each, but seem to be well made and are a good size for what I need to do. I also have AitKit cabin lights so everything kind of looks similar. I made up some fillers out of anodized aluminum (for the front)  and fiber glass sheet (for the back) with a 3 1/8″ hole saw. I then cut a 2″ hole in the middle using another hole saw. The cuts came out well enough. I had to modify the fiber glass ring a bit to get it to sit a bit flatter. The thread on the vents seemed to be long enough, but it was a pain getting the back to screw on. I epoxied the fiber glass ring to the rear of the dash and the front is just held in place by the pressure of the backing nut. I’m happy with the way these came out. They look a lot nicer then the plastic vents and they will seal off much better as well.

I also finally was able to finish up the wiring of the 2 EGT sensors. I had order some K Type  thermo coupler wire which appeared to be exactly what I needed at a reasonable price, but after running the wire and starting to wire it up I found that they had sent the incorrect wire (knew it was too good to be true). They said they will send the correct wire, but it’s back ordered (of course) and they weren’t sure when it would ship out. I decided to go back to my original place called Omega to purchase the wire. Their wire is really high quality but it’s pretty expensive. I purchase 25ft of armored K-Type thermo coupler wire for around $80. It arrived a few days ago and wow, it’s nice stuff. The wire I used (GG-K-20S-SB-25) is a 20 gauge glass insulated 2 core wire with an other glass insulator and then a stainless steel outer sheath. There are other sheathing you can get, but I wanted to use the braided stainless steel. The connection to the EGTs is made by 2 ring connectors, Unfortunately I could only find spade type connectors that are usable with the K-type wire. The spade connectors are made from Alumel and Chromel which is the same material as the K-type wire so the temperature characteristics will be the same. The yellow wire is Chromel so you use the Chromel spade connector on it and the red wire is Alumel so the Alumel connector is used on that. I used a standard open barrel crimper to crimp them on. Working with the K-type wire is a bit of a pain because the wire insulation is like a cloth material and doesn’t cut well with wire stripers. After the wires are bolted together a final length of heat shrink is put over it.

Lastly I roughed in the CEET tubing for the air vents. Because I’m using 2″ air vents I had to find a 3″ to 2″ reducer to tie into the NACA duct. I found some on Amazon for around $6 each and they look like they will work. The NACA duct is a little smaller than 3″ so hopefully it will seal up OK. I’m waiting on my hose brackets to be able to actually connect everything together. The one issue I ran into is that the bar that I’m going to install to hold the avionics shelf gets in the way of the tubing run.

Finer glass backing rung epoxied in.

Vent mounted in the 3 1/8″ anodized aluminum ring. It’s all just held in place with the pressure of the backing nut. The vent moves fairly easy so I don’t think it will be an issue with it coming loose. The fiberglass ring also creates some tension on the nut so it holds very tight and won’t spin loose at all.

EGT wire connection. I could only find spade connectors in Alumel and Chromel, but this all get wrapped in heat shrink so that will keep everything together and offer some strain relief.

Big piece of heat shrink covers up the join.

This 3″ to 2″ reducer looks like it will work. I may cut down the flange a bit to give more room. I need to use 3″ CEET to join it to the NACA duct and then 2″ out to the air vent.

Test fit of the CEET tubing for the air vents.The tight bend may cut down on air flow, but not much I can do about it. I don’t want to put the bar on the other side of the tubing because it may interfere with the fuel selector.