Month: March 2017
Started the Electrical Wiring
Running all of the electrical wiring is a larger task than I anticipated. Figuring out what needs connected to where is easy enough, doing so in a nice tidy, serviceable and long lasting way is what’s hard.
I secured the battery with a battery hold down strap. I had to shorten it significantly and heat weld part of it since I don’t have a sewing machine. A piece of foam is placed under the battery to keep it from sliding around.
I added a ground controlled relay for the master power. When the matter switch is off no power enters the cockpit and nothing electrical is energized. For those unfamiliar with airplanes, the engine ignition system is independent from the electrical system so the master switch will not turn off the engine nor prevent it from starting. The ignition is controlled with the keyed switch, more on that later.
Installed a diode across the starter solenoid. This reduces arcing across the starter switch contacts. Also, ACS service bulletin sb92-01 applies to my ignition switch and requires the installation of the diode. To protect the diode I put it in a small tube and covered it with black heat shrink.
The regulator was mounted to the other side of the fuselage and it’s wire run through wire clamps on the engine just like the EGT and CHT probes.
All of the circuit breakers are on the dashboard so most of the power distribution happens there.
A small ground buss provides a convenient place to connect ground wires.
The keyed switch serves a few functions. When the key is removed the engine magnetos are disabled so the engine will not start, without this simply bumping the propeller could start the engine. The key also has a momentary start position to activate the electric starter, just like a car. It has a run position wherever both magnetos are allowed to operate and a left & right position where you can select the right or left magneto to ensure both are working before taking off.
Still have some other items that need wired, strobe, fuel pump, USB chargers and the radio. I’ll discuss that in a future post.
Modify Exhaust System
The stock exhaust on my airplane was about as attractive as Muppet Gonzo’s nose. The stock exhaust provided by Hirth looks fine on most aircraft with the muffler hanging dead center of the airplane. But the steering bar for my nose wheel would run right through the muffler so that’s not an option. I managed to make it fit but it was ugly.
My engine was purchased from Recreational Power Engineering so I contacted them to find out the proper way to go about this modification. Matt said the total length from engine to muffler needs to be 21″ and the pipe diameter should stay the same size throughout but could be slightly larger just never smaller. Bends are the tricky part, a regular pipe bender will slightly crush the pipe so that’s not an option. RPE sells pre-bent pieces that you can use to build your custom exhaust or you they can build it for you. I managed to make things work without needing any additional bends
The first problem I had was the 90° pipe coming off the engine does not match the angle of the fuselage bringing it too close to the fiberglass and wood. I cut the straight part at the rear of the 90° off and then cut a little off of the bend, you can see the little notch in the left picture below to see the small section I removed. The result is a 65° degree bend. The straight part was also rotated so the springs will be top/bottom instead of side to side. Again this was effort to get more clearance between the fuselage.
The muffler having a 90° elbow welded to it is not going to work so I cut it off.
I don’t have a welder here at my house so I made a template of the of the fuselage shape, marked some key locations and took this to my brothers automotive shop to weld the parts.
He tack welded all the parts so I could take them home and verify fit, if anything needs tweaked the tack welds can be easily cut.
Back home I checked the fit and was satisfied so I created a bracket to hold the muffler onto the fuselage. The bracket was made from some 3/4″ wide steel that I shaped to match the curve of the muffler.
I used a couple large zip ties to hold the bracket in place so I could check the fit. Once satisfied I marked the locations where the new spring hooks need to be welded. Back to the shop for the final weld.
The result is a much better look than the stock system that came from Hirth. The only downside is when it comes time to replace it, all this customization will need recreated again.
I also checked that it flexes properly when the engine moves.
I’m undecided on how I want to paint the exhaust. Black is obvious, maybe I could use red and white to match the fuselage color scheme. Maybe I’ll decide to wrap it. Need some time to think about this.
Wiring Engine Information System
The EIS monitors the cylinder head temp, exhaust gas temp, RPM, battery voltage and air temperature. Each item can have limits set so if something is out of the ordinary the warning light on the dash will illuminate.
The cylinder head temperature probes sit between the sparkplugs and head. I ran the wires through the fins and up the side of the engine where they are held in place with a clamp. The exhaust gas temperature probe wire is also held by this same clip.
The probe wire then run to the front of the engine where another wire clamp was added.
The EIS harness terminates in from of the battery where the probes are connected. I kept the pair of wires for the second exhaust gas probe in the harness even tho I’m not using them. Maybe some day this airplane is updated to two cylinder and then they are needed.
The grey tachometer wire goes to the other side of the engine and connects to the lighting coil. I spliced an extra connector into the voltage regulator wires to connect the tach input. Still need to put an end on the grey tach wire.
The EIS uses a single DB-25 connector for all the wires. I took the connector apart and removed all of the unused wires by pushing the pins out with needle nose pliers. A few of the wires exit the EIS harness just behind the connector such as power, ground, fuel sender and warning light.
The violet wire runs through the harness to the warning light with the other side of the warning light is connected to power. I made sure that the dash is easily removed by disconnecting wires as opposed to having to cut wires to remove it.
The last item to connect is the green wire to the fuel level sending units from the gas tanks. When it gets a little warmer I’ll roll her outside, mount the wings and tanks and then work on routing the fuel sensor wires. I’m not exactly sure where everything ends up so not much I can do with that for now.
Ignition Wire Safety
The manual for my Hirth F-33 engine says that if it is mounted inverted the spark plug wires need to be secured so they cannot fall off from vibration and gravity. After inquiring on the lonesomebuzzards.com forums George and Dick gave me what I thought was the best idea.
Purchased two s-clips and a 1/4″ diameter by 6″ long spring from the hardware store. Added a scrap piece of fuel tubing to prevent the spring from chafing the ignition wires. Drilled a couple of holes in the cylinder head fins and voila, problem solved.
Brakes and BRS Bridles
Awhile back I ordered some black plastic clips from AliExpress.com to hold the bridles for the parachute in place. This weekend I decided to put them to use. When I got started I also decided to tackle the brake cables since it looked like I could route those with the bridle clips too.
The brake cables exit the fuselage near the front of the landing gear on each side, I added a small grommet to this hole to reduce chafing.
To keep the cables from flapping in the breeze I added a couple of rubber lined cable clamps to the landing gear bolts. The cable routed through the clamps then down the landing gear leg along the bridle that is secured with the plastic clips.
The grade cable the runs around the from of the gear into the caliper.
I also used the bridles clips inside the fusealge so they don’t get tangled up with other things. These clips are a little too tall so they don’t clamp the bridle. I put a small piece of foam on the top on in the picture below. Next time I’m at the hardware store I plan to get some self adhesive black foam weather striping to use in the few places where this matters.
I plan to add maybe one or two more clips inside the fusealge but I need to climb in and make sure I don’t place them in a position that my elbow might hit. Right now the seat is covered with parts for electrical wiring so I’ll do that some other time. If the 3M sticky tape does not hold up I plan to secure the clips using a couple of tiny wood screws but so far the 3M tape seems adequate.
Ultralight Builder 