Second Leak Fixed

The day started with spraying the white primer for the paint coat on the last stack of parts before the fuel tank. That was quickly done and the parts were left for drying.



Warning from the future!
Here I am traveling back in time from 2.5 years after I created this easter-egg to warn you NOT to follow my steps in how I tested the fuel system for leaks. While I was successful in finding and eliminating the leaks this way, I also created a serious problem in the fuel system that could have caused quite some more pain than it did in my case (which was luck alone!). 
The water in the system will cause the fuel pump to rust and decrease its performance significantly (or make it fail). This will lead to low fuel pressure issues on long WOT runs and will require a fuel pump replacement to fix (I am not sure if also the transducer might have been damaged by the water).
My suggestion is to use air alone at this point and to ensure that the temperature is the same when comparing PSI values from over-night runs. The alternative is to use actual gas but do recommend against it as it is too dangerous to mess with gas when there is a safer option.

Then it was back to the pressure test. The thread sealant should have had enough time over night to cure enough to withstand a few pounds.... I set everything back up again and set the pressure to around 7 psi. It didn't show an immediate drop so I let it alone and installed the servos for the autopilot.


That was kind of awkward to install first I thought I had to break my hand to get the servo in position with the pushrod already installed, then getting at the hex nuts to screw the servo in place was hard too. My hand seems a bit on the large side compared to the average Oregonian. I finally got all in only to realize I had forgotten to put the Loctite on. Argh! All out and back in. The second time was easier it appeared. Either my hand shrunk or I got used to the tight space. Anyway, I think installing the pushrod on the servo arm AFTER the servo has been installed would have been easier.

Back to checking the pressure.

Ouch!

It dropped half a pound while I was installing servo one. What the hell is this?

I pulled my soap water gun out and threatened those fittings but it didn't help. The leak must be a small one and hard to see with soap water. I used the flooding method and finally found another fitting that built up a foam collar although much slower and less impressive as the one I found yesterday. This time it was the forward fitting on the fuel valve. I drilled out the rivets holding the valve assembly to better work on it, removed the fitting and cleaned the threads as well as I could. Washed everything off with alcohol and smothered it with Rectorseal No.7 and put it back in. I gave it about 15 minutes to cure as I felt like I really had it with this cr*p. I pressure tested the valve assembly while still on the work bench and confirmed it was good to operating pressure of the fuel pump (about 5 psi). The difference was that I must have been worried about stripping the threads last time I put it in. Only the first 5 threads where in the valve and now I've screwed it almost completely in.
I put it back in the line but didn't want to give it my usual 8 psi test yet as the sealant was all fresh and I didn't want to blow it out with too early of a test. So I worked on the second servo.


(Comment from the past: You see this roll servo neatly installed at this point. DO NOT DO THIS! This is too early as it will prevent you from inserting the very long flaperon pushrods through that opening in the aft bulkhead that is blocked by the servo. Wait with this step until the pushrods are in place.)

Much easier to install although I don't know how to torque the forward two nuts. There's no way you can put a socket on them AND get a torque wrench connected to it. I torqued by feel instead.

Back to the pressure test. I filled the system with 8 psi and waited a little. I noticed a very small but noticeable drop.

Jeeeez!

What else can I do? Oh, I know! No more air! I need a liquid to see were it drips. I decided to hook up a small pump I have to fill the system with water (while the pump is on you have to push the gascolator drain to allow the air to escape).



Once the system is filled with water, I squeezed the water hose to stop the back bleeding and the I could add water through the Schrader valve to set it to the pressure desired. My gauge, Schrader valve assembly is above the water line, so this is the only part of the system that is not flooded.


Back to 8 psi again and waiting.

I went in the paint booth to check the parts and they were dry enough to get sanded with SB pads. So that's how I spent the waiting time, getting the parts ready for painting.

After half an hour I checked the gauge again.


I grabbed the work light and checked for leaks in the tunnel. Everything was perfectly dry. Not even moisture.
I sprayed the parts above the water line with soap again and couldn't see a blip. I checked the drain valve, not even moisture.
At this point I was considering selling the project.

Breath, Breath, Think!

I checked the water hose.


And there it was! A few drops of water were coming out of the large hose and resting on the clear line. As you can see I had a diameter issue here and no converters. This hose-in-a-hose thing with a clamp was all I could come up with. And that's were it leaked.
I clamped it a bit more and in different places and finally saw the bleeding stop and the pressure staying where it was.

Now the only unanswered question is: Why does it work with water but not with air? It looked like I had a very slow drop before doing the water test and I didn't have that hose hooked up then. I had a plug sitting on that end instead.

So was this test successful? Hm, I don't want fuel leaking into my plane. If I'd be flying with water I think I'd be good now. Unfortunately, that's not the case, is it?

Pressure Test Failed

I didn't get up as early as I had wanted to and so the early morning priming session had to wait. Just as well, as I had later found out that I hadn't really prepared all the parts correctly yet.
I started in the shop by cleaning and scuffing the parts I had missed and setting up the paint both to accommodate the large canopy frame, allowing me to walk around it when painting.


These are some of the parts that will get painted.

When this was all done the friendly USPS postman came by and dropped off the parts I had waited for from Aircraft Spruce to get the pressure test done. So, I quickly pulled the tarp off of the fuselage and set up the fittings to connect return and supply line at the tank area to pressure test the whole fuel line at once.
Oops, that didn't work out at all. The pressure I put in with a ball pump didn't even hold for a few seconds. And I was wondering if I could really hear a hissing sound or if this is a sign of developing a tinnitus... Well my ears are ok. It turned out the ball pump is so cheap it wouldn't hold pressure slowly leaking air unless you kept on pumping.
I removed the ball pump and hooked up the tire filler gauge to the compressor.
Ah, that was better!
Oh, wait, wasn't this 0.1 psi higher a moment ago?
Sure was!
So there was a leak! At least one, I should say ...

I used the fuel valve to shut off everything behind it but I till lost pressure. That could have meant that either the valve is leaking, or the leak is in front of the valve, or the valve doesn't perfectly shut off.

I first wanted to make sure my test setup was leaky itself, so I removed and tested the pressure gauge and Schrader valve assembly. It turned out to be perfectly sealed.

I didn't trust the valve and started removing flared tube connections one by one. Cleaning them, greasing them with fuel lube and putting them back on. Still a leak.
When I got to the valve I decided to stop and see if I can locate the leak with soapy water as I was starting to believe the valve did indeed cut off the aft line.

After cleaning the whole forward tunnel with soapy water I finally sprayed it on the fitting end of the aft connection of the fuel flow sensor. Aha! That's how a bubble bath in the making looks like. It was leaking not at the flared end but where the fitting screws into the sensor.

I removed the fitting, cleaned the threads as good as I could and put a thick layer of Rectorseal No. 7 on it and screw it back in. While I was doing that I was thinking that this could have all been easily avoided by getting the pressure test equipment before even starting on the fuel lines. That way I could have tested every component before putting it into the plane. Now I'm thinking about pressure testing the brake system before putting fluid in it as well!
I assumed that an immediate follow-up pressure test could jeopardize the seal and so I decided to stop there and let the sealant cure before I add pressure to the system again.

I went back to prep and prime and finished the priming part. I decided that the steel parts as well as the parts that get into contact with the elements should get primed green as that stuff is the better corrosion primer. This would include the flap handle, the flap guide assembly and the canopy and the canopy skirts.


After some two hours the stuff had turned green.


Somewhere in between, I forgot when, I also primed the servo pushrods. Because of that dreaded fuel line leak I didn't get to the installation of the servos today.

Servo Crimp

Didn't do a lot today but managed to crimp the wires on the servos.


With pushrods done as well I can now install them in the fuselage.
I hope to get up early tomorrow morning to escape the heat and get some prep and prime done on the remaining parts as well as the servo installation.

Almost forgot to mention that my plexiglass rear window arrived today. This will be fuel proof and the tint will help keeping the fuel cool.


And this is how it arrived here. Please notice the integrated carry handle!!!

Vacuumed a Thread

Again I did a million different things in as many different chapters. It's really hard to see any progress working like this. The reason is still that I couldn't complete the pressure test due to missing parts and this is holding me off from really starting the wiring section yet. So I try to stay busy picking up easy and limited tasks in preparation of other steps.
Tonight I worked on parts of the canopy that will hold the plexiglass in place on the sides of the canopy. These little angles will have to get painted, so I prepared them as much as I can at this point for getting the Sandlewood sprayed over it.


I marked the drill spots according to the instructions, pre-punched them and used the drill press to drill through them. Put some wood behind it as the metal is thin and could warp if the drill just sees air behind it.

The next step was some preparation for the actual wiring section. I had read on VAF that a lot of people spent hours to get the guide thread through the control stick to eventually pull the wire for the microphone switch through. It appears that the shape of the tube with a 90 degree turn and some additional obstruction in there and the sharp edges inside the control stick is catching on to the thread and preventing it from following the tube to its other end. People used lead bobs, and pressurized air to push the thread through. One guy suggested vacuuming the thread from the other end.
It works!
Here's my modified version.


I used an ordinary thread. Nothing slick or a nylon line or anything. On one end I attached a 100 grain .32 wadcutter bullet (just some plated lead I had in stock) by drilling a #40 hole through the bullet and tied the thread to it. The reason is that the thread could try to fall into the tube while I am painting it. The bullet is too big to pass the obstruction in the tube and so I can shake the bullet back out on the desired end and hopefully the thread will still be attached. To increase my chances of the thread being still attached I added some glue to the knot. The bullet also helps to prevent the thread getting sucked into the vacuum as the bullet can't pass the obstruction.
Then I put a few inches of the thread into the tube on the side where the mike switch will go and put the end of the vacuum cleaner on the other end and turn it to maximum power. The thread gets sucked in best if you obstruct the opening on the mike switch side with your thumb to increase the speed of the air in that area. When the bullet is about to get sucked in, STOP :-).
It might be that the thread is not hanging out of the lower end of the control stick at this point but it should be really close and probably caught up on one of the burrs inside the tube. Get some tweezers and pull the string out, Voila!
It took me 5 minutes on each stick to get that string sucked through and tape it to the tube.

With so much time left after finishing way ahead of average time on this task I started some prep work on the servo installation which will follow right after the wiring is completed. There is a small mechanical task in section 44 and that is manufacturing the pushrods for both servos. It's not really difficult but took a about an hour to finish it up. Cutting the tube lengths, deburring, pre-drilling, taping the rods on both ends and cleaning up the mess where the subtasks. I think the challenging part here is the pre-drilling as the tube is quite thin and a canted drill could probably render the piece as trash. So I used a technique learned in one of the earlier chapters. I used an undersized drill bit that just barely fir into the tube. In my case the best I had available was #12 bit. I used this to adjust the position of the tube in the drill press. Then I replaced the #12 with a #3 bit and drilled that side. Remove, replace, repeat until done. I think the holes turned out pretty good.


Finally I put the bearings in there as well and adjusted the pushrods to about the right length using the 1:1 drawing in the manual.



Now I am waiting for the missing parts to do the pressure test and the only other thing I might be able to do is some surface prep and to spray some primer and paint on the last parts.