Today I added a couple more blast tubes to cool the battery, and the voltage regulator on the back of the alternator. I also reconfigured the fuel lines in the engine compartment and moved the fuel flow sensor to the engine mount.
The Earth-X battery gets a lot hotter than the standard battery, and benefits from a blast tube to direct cool air at the battery while in flight. I used a length of 1 inch SCAT tube, some hose clamps, and an aluminum flange to make the blast tube. I used a step drill to upsize the hole to the right size. I also added a lock washer on the back side of the flange, along with RTV to make it secure to the baffling.
I had bought a 3D printed fitting for the back of the alternator that directs air at the voltage regulator, but never installed it. Today I mounted it and hooked it up with a blast tube from the air inlet ramp on the right side of the engine compartment. Lots of RTV, another lock washer, hose clamps, and it was done.
Then I moved onto the fuel lines. I had previously loosened some of the fuel lines to test that my new routing would work. By switching the fuel lines either side of the fuel flow sensor, the sensor moves aft several inches, placing it right above one of the engine mount struts. Today I removed some of the old fittings, added new ones to streamline to fuel line routing, and mounted the red cube to the engine mount. It’ll be much more stable, and cooler, in this location, which should hopefully make for a longer useful life.
Battery blast tube, forward side of bafflingBack side of the baffling showing the new blast tube Blast tube directed at the battery. The safety wire is holding the tube steady while a blob of RTV driesVoltage regulator blast tube entry on the air rampUnder side of the blast tube flange on the air rampThe 3-D printed fitting for the back of the alternator. Note, this is high-temp material with Carbon fiber blended inThe new blast tube The new location for the Red Cube (fuel flow sensor)The fuel lines aft of the fuel flow sensor. I removed the 45 degree fitting from the red cube inlet, as this is not ideal. The straight fitting I replaced it with will allow for a smoother flow of fuel, and is actually the recommended configuration by the manufacturer. A single adel clamp is holding the sensor.
Today Donnie helped me with a weight and balance. The airplane weighed in at 1257 pounds, which is right about what I expected. The center of gravity is a very important datapoint too, and after crunching some numbers the empty CG was 81.54 inches aft of the datum. The datum is a point 72 inches forward of the wing leading edge.
The process started by loading up the airplane with all the panels, screws, interior panels, carpet, literally everything that will be part of the airplane. I didn’t bother installing everything, in some cases I just placed the parts in their correct position.
With that done, the next task was to level the airplane. The weight needs to be calculated on level flight condition, so I needed to raise the tail up about 3 feet. To facilitate this I brought my standing desk from home, and was able to easily raise and lower the desk to find level. Using a desk instead of a saw horse allowed room for the scale to sit under the tailwheel. A digital level on the canopy rail was sufficient to identify level.
With that done, I moved the desk out of the way and Donnie set up the scales – one under each wheel with a WiFi controller giving a digital readout for each scale. We then rolled the mains up onto the scales. Then we raised the tail and positioned the desk and scale under the tailwheel. With that done we wrote down the weights, and the weighing exercise was complete.
To get an accurate arm for each scale, I used a plumb bob to make a mark on the floor identifying the wing leading edge. Then I carefully measured the distance to the center of each wheel. The plum bob came in handle at the tail too so I could measure the distance while the tail wheel was still elevated.
With those calculations done, I created a spreadsheet to plot W&B and played around with a few scenarios.
Configuring the standing desk to attain level flight attitudeThe numbers. Interestingly, the right main wheel is a quarter inch aft of the left main wheel, relative to the wing leading edge.
Following Dan Horton’s recommendations, I set the engine advance to a range of 19.6-28 degrees…
The process is very easy, just power up the electrical system, set the prop to the appropriate position, and blow a puff of air into the Manifold Pressure port on the mag. Conveniently I already have flexible rubber tubes connected to these ports, so it was a trivial task.
The black mark on the left was my reference point for setting the timing. The p-mag will operate ~30 degrees from this point.Using a mirror was the only way to see the LED light on the mags. Green indicates the timing process has completed.
Last night I drained the engine preservation oil and added 6 quarts of mineral oil. I ran out of time to set the engine timing, but that is a quick job I can accomplish next time I’m at the hangar.
While I was changing the oil, I took the time to replace the oil drain plug with a quick drain fitting, and put some RTV between the starter solenoid and the snorkel.
I started by removing the snorkle and inspecting the fuel servo. Sure enough, some preservative oil had drained down the intake pipes and collected in the bottom of the servo. Rather than removing the servo, I was able to suck the oil out using a small piece of flexible plastic hose, and the wiping up the residue. There’s still a film of oil, but no pooling of oil at all.
View down the fuel servo’s air inlet. A small amount of oil had pooled at the back of air intake
Then I removed the bottom set of spark plugs, and rotated the prop a few times to push out the remaining oil. A lot of oil came out of cylinder 2, and just a small amount from the other cylinders. I leveled the airplane to help drain as much as possible. I also used a borescope to check the cylinders and take a few pictures, just because.
A small amount of preservative oil leaks out of the lower spark plug hole on one of the cylinders Oil from the spark plug hole ran down the exhaust pipes and dripped all over the place. The red bucket caught most of it
With that done, I removed the oil drain plug and let the rest of the oil drain out the bottom.
The original oil drain plug, safety wired to the oil screen cover
After consulting a number of threads from Vansairforce, I left the oil filter alone. This is a new filter added by Lycoming, so I’ll just keep it on for the first 10 hours of engine time. At $40 per filter, no need to waste a new one.
Once all the oil was out, I cleaned and installed the quick drain fitting. I used some loctite to seal the threads, and torqued it to 14 foot pounds, per the table of limits for a 1/2-14 pipe fitting. The quick drain should make future oil changes a lot easier – just push on a drain hose, and push the fitting up and rotate to release all of the engine oil.
Preservative oil draining from the sump. By the time I thought to take a photo, most of the oil had drained outOil pan and a bucket collected most of the oil.The quick drain fitting (finished in blue)The underside of the quick drain fitting showing the safety wire securing it to the oil screen cover
I then cleaned and reinstalled the spark plugs. After wiping off all the oil, I used some acetone to clean the threads and carefully wiped the spark plugs down. I added some copper based anti-seize and reinstalled, torquing to 35 foot pounds per Lycoming’s spec.
Then I put the snorkle back on, adding a bead of RTV to help protect it from the starter. There’s plenty of clearance, but the RTV will help reduce any chance of rubbing and damage as things heat up, shift around and vibrate etc.
With that done, I poured in 6 quarts of straight mineral oil.
I’m adding Aeroshell 80 straight mineral oil which is SAE-40 oil, and is good for a wide range of outside air temperatures Oil change complete
Tonight I finished safety wiring the prop attach bolts. I had previously wired two of the 6 bolts, but had left the others so I could move on with other tasks. At the time I was working towards a deadline – moving the fuselage to the airport – and didn’t want to spend more time on the task. The first two bolts had been a real pain, and I had redone the wiring several times before I was satisfied that it didn’t suck too badly.
For the remaining four bolts, I started by practicing with the thinnest safety wire I have, which is much easier to work with. After figuring out the routing, the length required, and any other relevant details, I switched to the large diameter wire and completed the task. The bolts are wired in pairs, and each bolt has a hole through the center where the wire passes. Because of the varied orientation of the bolts, each one presents a unique challenge in getting the wire through the hole. I was lucky that only one bolt needed loosening and reorienting, and I was able to get all the others to work without adjustment.
In the end I was quite happy with how it turned out, and found that a little practice and lots of patience definitely helps.
A pair of wired bolts. The wire acts as a fail safe in case the bolts vibrate lose and start backing offAnother pair of wired bolts
Before completing the aircraft wiring, I decided to switch to a Lithium battery, and EarthX seems to be the most popular brand for RV builders. The difference in weight between the original lead acid battery and the Lithium battery is substantial. I didn’t have the original battery specs, but it must be 3-4 times heavier than the Lithium battery. There are some other benefits too, such as a longer period of output, longer store of charge, and a battery health indicator output wire.
The EarthX 1200 series is an almost exact match in size. It’s slightly deeper, slightly narrower, and the top is shaped differently. The battery came with some foam to help make up for the narrower shape. I added a washer on each side to account for the wider shape, and added some aluminum strips with foam to the hold-down bar to ensure a snug and secure fit.
The battery terminals are basically the same, so once I had modified the hold down bar and charged the battery, it was ready to go.
Original Vans supplied battery. This is a few years old now.Side by side comparison of Vans batttery (right) with EarthX battery (left)Test fitting. Not the gap under the hold down barAdded some aluminum strips and foam to the hold down barFinal installment. Note, the ground is disconnected since I’m still running on ground power at this point
I took the time to address a minor issue with the tail fairing, where it was trimmed a little too much. Right under the leading edge of the horizontal stabilizer the fairing is designed to cover the gap between two sections of aluminum. I had trimmed it slightly too much and a small 1/8 gap had been created.
I took the fairing home and added some fiberglass and micro-balloons to build up the edge about 1/4 inch. A quick sand and spray with primer and I reinstalled the fairing. I used some more micro balloons behind the fairing, using tape to prevent it sticking to the fuse, and it came out with a perfect fit on the aluminum.
The original gap. This was the same on both sides.After building up with glass and filler, this was a final step to ensure a clean fitTidied up and primed
My original plans with the control sticks was to use Infinity Aerospace stick grips. Unfortunately, no amount of trimming of the stick base was enough to create clearance from the throttle and mixture controls with these stick grips. If I had installed a throttle quadrant instead of the standard vernier controls, they would have worked out.
So I went with plan B and bought the standard Vans stick grips. These provide *just* enough clearance from the throttle and mixture controls, and they clear the bottom of the panel. There is still interference if the cabin heat vent is on and the stick is in the full forward and left/right positions, but there really isn’t anything I can do to avoid that.
The sticks just needed to have their base holes drilled, and the wire harness connectors replaced with my setup, and they were ready to install.
Holes drilled and connector replaced. I bought a spare stick base to serve as a drill guide for drilling these holes. I wasn’t going to try to drill them in place, and didn’t want to take the stick bases out of the airplane.There are fewer switches on this stick, but enough for what I need.
This morning I finished out chapter 41 (wing attach) by installing the fuel vent lines. I opted for Aircraft Specialty vent lines, just to save some time and effort, and I also installed the JD Air fuel vents.
The standard Vans fuel vent design has a fuel line passing from the tank down through the wing fairing, where it’s chamfered at 45 degrees. I’m sure this works great, but there are a couple of downsides. The line has no screen, so there’s a risk of insects or dirt making its way into the fuel line, or even the tank, and causing an obstruction. There’s also a chance I’ll snag the vent on something and damage it. JD Air makes a streamlined vent with a built in screen, so I installed these instead. Aircraft Specialty makes a fuel line that fits the JD Air vent, so that was very convenient.
The vent itself attaches to the bottom wing root fairing using a bulk-head fluid fitting, so it simply screws into position. I was then able to loosely install the fairing, position the fuel line, final torque the fairing screws, then torque the b-nuts on the fuel line to secure it in place.
Everything went well, the only bummer is the gap at the aft end of the fuel vent, caused by the curvature of the fairing. It’s no big deal, it’s just cosmetic, and no one will see it unless they look for it specifically.
I also installed fuel placards and some grip tape on the pilot side of the wing walk area.
After a weeks off for the holidays, I was able to make some more progress this week.
I finished the wing root fairings, and installed the wing root fuel lines. These are the lines that connect the fuel tanks in the wings to the fuselage.
The wing root fairings were fairly straight forward. Getting the right shape on the bottom fairing was probably the biggest challenge.
Soon after getting the shape right I realized that I needed to countersinking the holes on the tank attach bracket. And then I noticed I had more containing to do on the wing top skin, so that the top fairing could be installed.
I brought all my countersinking, drilling, dimpling and riveting equipment to the hangar today and knocked it out. The countersinks are a little tricky because the nut plates are already installed, so a #8 countersink (the correct size) doesn’t work because the pilot interferes with the nut plate threads. I used a #21 count sink bit which seemed to be just the right size to fit into the nut plates. The countersinks are fairly deep because the fairing has #8 dimples that need to nestle down into the countersinks. The aluminum stack up is several layers deep, so there is plenty of material to support the counting depth. The only tricky part was the top, inboard countersink on the tank attach bracket. This was too close to the fuselage to get the counting cage to sit vertical, let alone the drill. I rigged up a long extension, about 18 inches long, a drilled those countersinks without a cage. It was quite easy to see the depth and I just went little by little until it was done.
There are some holes that need to be match drilled, and then 3 nutplates installed on each size. I drilled, dimpled and riveted these.
I found some proseal and used it to glue down the wing spar spacers, after giving them a little shape to conform to the wing skin.
The fuel lines were next on the list. These were pre-bent by Aircraft Specialty, and they fit exactly right. The time consuming challenge was finding a way to get them into position. The line is short and quite inflexible, and the flared ends, which are easily damaged, mate to the aluminum fittings on each side.
I loosened up the fuselage side fitting so I could flex it inboard and create enough space to insert the fuel line. I had to use a wedge to push and hold the fuselage fuel line out of the way enough to insert the new line. Once the line was in position, I torqued everything up and it all looked good.
The three nutplates that I installed, this picture is of the right hand side, it’s a mirror image on the leftClose up of one of the nut platesCountersinks on the top of the tank attach bracket. The one at the top of the image is close to the side of the fuselage and hard to reach. The spacer glued into position on top of the wing spar. This hard plastic block supports the upper wing root fairingTop fairing installed on the left sideThe underside of the bottom fairing. The screw in this position grazes the end of the wing spar. Rather than installing a full length screw, I plan to order and install some shorter screws that will stop short of touching the sparThe fuel line in place. The wing tank is on the left, and the fuselage is on the right. B-Nuts are not torqued yet.Looking down at the left hand side fuel line After torquing the B-nutsEarly morning at Ramona after a rainy night
