I was beginning to think that I was never going to finish the left fuel tank.  I was waiting to make a Van's order to order some Polypropylene tubing to finish my capacitance fuel sender installation.  After some SLIGHT procrastination, I ordered the polypropylene tubing I needed along with some other airplane things since Van's charges a "$5 handling charge".

One of the tasks I still had outstanding on the tank internals was to solder my BNC fitting to the capacitance fuel sender wiring (wire).  Not a great looking solder job (remember, I come from the occupation of "bigger the blob, better the job").  After soldering the BNC connector, I used a Fluke digital multimeter to verify the following:

• That I had electrical continuity between the center pin on the BNC connector and each of the capacitance sender plates.
• The I had NO ELECTRICAL CONTINUITY between any of the fuel tank ribs and the capacitance fuel sender plates.

Everything checked out fine after my highly skilled solder job.....

A pict of the inboard fuel sender capacitance plate.

The outboard fuel sender capacitance plate.

I reviewed the log entry I made for sealing the rear baffle on the right fuel tank and started to assemble all the tools and equipment I was going to need conduct my last (hopefully) sealing session.

Before putting on the rear baffle plate, I finished sealing the BNC connector.  I have heard of a couple of builders who have had leaks around the BNC connector.  I used copious amounts of tank sealant to seal around the BNC connector.  I also encapsulated the wire back a couple of inches so that I didn't get any "wicking" of fuel up the fuel sender wire.  I did this on the right tank as well and didn't have any problems with leaks in this area.

I also put dabs of sealant securing the sender wire(s) to the tank vent tube.

Earlier, I had encapsulated the fuel sender capacitance plate wire that is attached to each fuel sender plate.  This is the inboard rib.

Ditto for the outboard rib.

After putzing with the miscellaneous fuel sender tasks, I coaxed Tami to come out and begin the task of sealing up the rear baffle plate.  Sealing the baffle plate is a BIG JOB.  I didn't get any "in-process" pictures.  If you have done any tank sealing, you know that you stay busy and are usually pretty messy.

One thing that made me really nervous sealing the rear tank baffle is when it came time to mount the 'z-brackets' to the rear baffle plate.  It is really easy to get disorientated and mount these 180 degrees out.  If that happened, I would really be cussing when trying to mount the tank to the spar.  Anyway, I took a few extra minutes to double, TRIPLE, verify that I had the correct orientation for my z-brackets

Just an end shot of the outboard tank rib.

There are a ton of rivets on the rear baffle plate.  It took a ton of time just to do "touch ups" on the rivets, the flanges, etc.

A shot of my inboard rib.

Everything looks okay from the end.

A little messy on the inboard rib, but by this time, I really didn't care.  I was just beat and ready to call it a night.

I am thrilled, if everything on pressure testing goes well, that I am done sealing fuel tanks.  I did make the mistake to seal the rear baffle on a "school night".  I started around 6 pm and didn't finish up until around 1 am.  I didn't even bother cleaning up my mess.  Tami had already cleaned up my clecoes and tools so I didn't have to worry about them.

Not a very detailed log entry.  Check my log entry I made for the right tank baffle plate.  I had much more detail.

Sealing The Baffle Plate Log Entry

This log entry is just a cumulation of several shorter tank sessions.  I spent two separate nights sealing the inboard and outboard tank ribs and reinforcement plates.  Pretty straight forward, just really messy....

I ended up using the fuel pick-up tube that I fabricated a week ago or so.  It was long enough to clear the nutplates on the reinforcement ring.  It is not perfectly centered between the nutplate and stiffener.  What I was really demanding here is that the nothing touched and chaffed.  I tried twice to get a more centered fuel pick-up, but I wasn't any closer than this pick-up.  We are talking 1/16" difference here.  Precision tube bending....

Anyway, after I screwed on the inspection plate, I torqued the 6N fuel pick-up nut to 100 in-ibs.

I also torqued the vent line 4N fitting to 60 in-ibs. 

Notice that there are two wires on the inboard capacitive plate.  One connection goes to the outboard capacitive plate and the other connection goes to the BNC connector on the inboard tank rib.

Tank sealant for the inboard capacitive plate.

I applied sealant to the electrical hardware before I mounted the capacitive plate to the tank rib.  Made it a little easier to goop the tank sealant on and clean it up.

I fully encapsulated the outboard capacitive plate electrical hardware.

To attach the inspection plate, I used the cork gasket and "buttered" it with EZ-Turn lubricant and then placed it between the rib and the inspection plate.  I then attached the inspection plate with some 8-32 x 5/8" stainless steel socket head capscrews.  I wasn't able to torque them with a torque wrench, but I tried to tighten each screw equally by feel.

To finish off the fuel seal of the inspection plate, I topped the whole thing off with some tank sealant around the screws and the inspection plate.  Since I used EZ-Turn on the gasket, I removed all excessive lubricant as I doubt if the tank sealant would stick to it...   This is what I did with the right tank and I didn't have any sealing issues.

The only thing I have left on this tank is to get 1/2" of polypropylene tubing to insulate one of the capacitive plate mounting screws (long story), mount-solder-seal the BNC connector.  Then it is sealing the rear baffle plate and pressure testing.  Woo Hoo....

DRAFT>>>  BLOG ENTRY NOT COMPLETE.
Okay, this log entry deals with the issues of whether or not to install a fuel return line.  I happened to be surfing Dan C's web site and came across a log entry he made while plumbing his purge valve and fuel selector where he stated that if he didn't have his tanks already sealed he would have run a fuel return line all the way back to the tanks.  Alright, now I am hooked I have to figure out if I want to put in a fuel return line and/or if I needed one.  I am not a motor-head by any stretch of the imagination so this was going to take some research.

When talking about fuel return lines, they are used for two, but distinctly different, functions:

1. Fuel Return-  If you are installing a "Subie" automobile conversion engine (Crossflow, or Engenfellner), then a fuel return line is required.  In an automobile, fuel return lines are used to keep a minimum amount of flow through the fuel system and a pressure regulator (or fuel controller) is used to control the fuel system pressure.  It maintains a certain pressure/flow by bypassing some flow from the injector rails back to the fuel tank.  This means that there is always fuel flow through the return line. Engenfellner aircraft engines have their engine installation manual on their web site and chapter 2 details how a fuel return is to be installed to support their engines. 
2. Fuel Vapor Return-  This is a somewhat different function than the fuel return briefly discussed above.  Application to light aircraft is further detailed below.

Allthough, these two functions are different, when researching this concept, I often seen them discussed interchangeably lending to my confusion.

Anyway, the rest of this entry is a little background on light aircraft fuel systems and was taken from the Airflow Performance purge valve installation manual. 
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Airflow Performance Purge Valve Background Info Excerpt
Modern light aircraft fuel injection systems are of the low pressure, constant flow type.  Fuel is metered and is delivered to air bled nozzles which atomize and spray the fuel at each intake valve.  Airflow Performance and Bendix fuel injection systems meter fuel to the engined based on air consumption.  The fuel regulator in both these types of injection systems do not return any fuel to the tanks, therefore only the fuel that is used by the engine flows through the fuel controller.

Vapor in these types of metering systems cause the fuel regulator to operate erratically and poor engine performance will result.  This is usually evident during hot restarts.  Hot restart problems are a typical complaint of pilots operating fuel injected engines.  After engine shut down, heat in the cowling and engine tends to boil the fuel in the fuel control, fuel pump, and related fuel metering components.  Some of the fuel expands in the nozzle lines and gets forced through the injector nozzles and into the engine.  This leaves hot fuel and fuel vapor throughout the complete fuel metering system, engine driven fuel pump included.

During an attempted start under this condition usually results in the engine starting for a moment then quitting.  The pilot is then faced with the decision of how to proceed with the start procedure.  Flooding the engine then cranking the engine until it starts is usually done.  This procedure is dependent upon battery life which sometimes expires before the engine starts.  Engines which use the high pressure diaphragm fuel pump, experience another problem which influences the ease of restarting the engine.  By their design, the diaphragm fuel pump acts like an accumulator when the engine is shut down.  This keeps fuel pressure on the fuel controller, and leakage in the idle cut off circuit of the fuel controller will allow the fuel to bleed off into the engine.  This can cause run on in idle cut off and flooding of the engine initially after shutdown.
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Okay, if I understand this all correctly....  You don't need a fuel return line to have a properly operating fuel system.  Even if you want to have a fuel return line, it does not necessarily have to go back to the tank.  Dan Checkoway ran his to

The map of fittings for my inboard rib is shown in the picture below.  I used the vent fitting for the left tank to plumb my return line.  I will order two more AN833-4D fittings to plumb this the same way in the left wing tank.

The inside of the tank for the return fitting is installed the same as the vent fitting.  I torqued this fitting to 55 in-Ibs and then covered it in tank sealant.  No additional tubing is required for the return line.  Fuel and vapor will be returned to the relatively cool fuel in the tank which will absorb the heat from the circulated fuel.

Today, I didn't have to work as it was my Friday off>>  WooHoo!!!  It looked like a beautiful day outside, so with my usual routine, I came down and checked the weather for today and was shocked to see that the Omaha area had set a new record low temperature.  You know, I just got done installing an air conditioner in the garage because this area is usually so hot and for the last week and a half, the temps have been fabulous.  We are even seeing record low temperatures.

Today's weather was awesome...  It got into the mid 70's, sunny with winds <5 mph.  I just couldn't resist getting the Goldwing out and putting some miles on today.  I cleaned up the garage as it looked like a tornado came through there.  Sealing fuel tanks has taken its tole on my organizational efforts.  By the time I got that all straightened up, Tami came home from work so we took off for a motorcycle ride.  We ended up in Shenandoah Iowa.  We swung by the municipal airport and watched a student practice some touch and go's in the beautiful weather.  I was torn, I wanted to be flying and riding...  To many hobbies, not enough good weather or time.  Anyway, I took my tank sealant helper out for dinner for all of her support so far and so I can guilt her into helping me seal the baffle in place later this weekend.

I did manage to get a couple of odds and ends done on the tank.  I am more or less taking my time making sure that I am not forgetting anything and looking over all my tank sealant "BLOBS" making sure I have adequate coverage.  I don't want any leaks after I seal the baffle plate in place.  I noticed that after I had sealed the rib with the flap door, the door rubbed up against the tank sealant fillet.  I didn't want the door to dig a hole in the tank sealant over time, so I removed the door and took it over to the bench grinder to reshape the flap door on the forward edge.  A couple of seconds on the bench grinder, viola...  I re-installed the flap door and it no longer rubs on the tank sealant fillet (and it still covers the tooling hole).  WooHoo...  EASY FIX!!

To hold the trap door hinge pin in place, I just dabbed some tank sealant over the bent hinge pin.  I made sure that the amount of tank sealant I put on here would not interfere with the rear baffle, when installed.

Next I slopped some solder on the BNC connector for the capacitance fuel sender.  Okay....  I am an ELECTRICIAN and we live by the following creed when it comes to soldering: "The Bigger The Blob, The Better The Job".  Therefore, this is a great job.  No really, my solder work would not impress any electronics guru that has a lot of (or even a little) soldering expertise.  I gave the connection a good tug to ensure it was secure (you don't want a cold solder joint) and then measured the resistance between the center of the BNC connector and the capacitance plate.  I got a value of less than 0.2 ohms.  The test leads alone measure 0.1 ohms so my reading is good.  I then measured from the center of the BNC connector to the rib (to see if I had a ground) and the multimeter indicated over range (OL) which is a high resistance and a good reading.

I covered the back side of the BNC connector with ample tank sealant and I also covered the wire with tank sealant back a couple of inches as the tank sealant also provides some limited strain relief for the wire.  Additionally, the tank sealant covering the wire will prevent fuel from "wicking" up the wire into the BNC connection.  The BNC is a potential source of leakage as it can only be sealed on one side.  Most everything on the tank can be sealed on both sides thereby having more than one sealant boundary.

While doing some research on installing a fuel vapor return line, I came across a short article in a book I am borrowing' "21 years of the RVator" and it talks about the flop tube o-ring coming off the brass pickup.  Van's recommends to proseal this o-ring in place to prevent it falling off after the tank is closed up.

You know, I wished that Van's would just put this information in their instructions or just sell the flop tube with this o-ring already sealed in place.  But then again, they pretty much lack any useful information regarding the flop tube installation so why add this nugget of information either?

As with Van's instructions in the 21 years of the RVator, I put some tank sealant under the o-ring on the flop tube brass pick-up to hold it in place.

I broke down and purchased a Fluke 177 DMM.  Some type of multimeter or test equipment should be used to check the capacitance sender installation prior to closing up the tank.  This would also apply to the resistance (float) sender too.  I figure that this meter will come in handy throughout the project's electrical installations.

My log entries have been kind of slow this week.  Working with tank sealant is not very conducive to taking photographs.  Earlier in the week, Tami and I were able to install 3 tank ribs in one session.  So if you are keeping count, that means I have 5 of the 7 tank ribs riveted and sealed.  That leaves the two outboard ribs.  Therefore, I started working on the vent line and capacitance senders so I could rivet the LAST TWO ribs.
With capacitance fuel senders, you run the wire wrapped along the vent line so the instructions tell you to notch the snap bushing in order to make room for the 18 AWG wire.  It doesn't take much of a notch to fit the wire through the snap bushing.  I just used the Dremel tool and a small cutter bit to remove the small amount of material.

For my vent line, I measured the offset between the root rib and the next outboard rib.  Based on my vent fitting location, I needed to make a approximately a 2" off-set between the vent fitting and the hole in the next rib.  I decided to make this a 60 degree, 2" off-set.  This involved a new skill as I haven't had to use the tubing tools I bought for the project up to this point.  Again, I kind of made the off-set a math (trigonometry) problem to see where I needed to make my bends.  Three tries later, I had my 2" off-set.

After I checked my fit in the tank, I used the flare tool to put a flare in the vent tubing (don't forget to put on the AN sleeve and nut on the tubing before making your flare.)

Here is a picture of the outboard end of the fuel tank, the vent, and the fuel filler flange.  When making the T-714 clip, make sure that it will hold the vent line about where the bottom of the filler flange is (the vent line needs to be at the high point of the tank).  That way, you won't have to do any exotic tubing bends in the tight space to keep your vent fitting secure AND high in the tank.  As you can see, the vent line comes right out of the snap bushing and right into the T-714 clip.  I had to modify the vent clip as it was originally to long (low).  I cut it off, de-burred the end, and re-bent it to hold the vent line.  (If you remember, the rivet that holds the skin, fuel filler flange and vent clip gave me some trouble during installation so I had to hurry and make another clip before the tank sealant cured>>  ARGHH).

This is a picture of where I am trying to correct a tubing length issue.  I did not allow enough room for the AN ELL fitting on the in-board rib.  I had to trim about a 1/2" off, debur, and re-flare.  This flaring tool works GREAT!!!  I had no problem getting it into this somewhat confined space.

I could have just moved the tubing over in the tank, but I had all of my capacitance sender wires wrapped around the vent line and it was just easier to cut and re-flare.

Everything looks good.  When I re-installed the in-board rib, I had near perfect alignment.  WooHooo!!!

This picture kind of back tracks in the actual sequence of how things were actually worked today.  These are the insulating washers that you put between the rib and the capacitance sender plates.  When they were manufactured, the washers were not cleaned up with the excess molding material (in the Navy, we called this "Irish Pennants">>  Don't grade me on my spelling).  I didn't want this stuff to eventually flake off and get into the fuel line.  It is some pretty tough stuff, but I am not taking chances.  Besides, it looks better after the washers were cleaned up.

To clean the edges up, I took an X-acto knife and scraped the edges of the washers.  The bottom two are what they looked like after I was done.  It is all about "piece-of-mind" by trying to ensure some quality of construction.  For goodness sake, it is just an airplane.

Attaching the wire to the outboard sender was a piece of cake.  You have plenty of wire you can pull out to move the plate around to get on the screw and nut to tighten everything up.  When I got the wire/lug attached to the outboard sender plate, I mounted it to the rib so that I could final measure the wire to the inboard sender.
Okay, now the trick...   When you attach your inboard sender plate, the wire from the outboard sender is cut to length.  That doesn't give you a whole lot of room to move the plate around so that you can get on the screw and nut to tighten it up.  Additionally, the inboard sender has two lugs that are attached to the plate.  One from the outboard sender and one from the BNC coax connector on the inboard rib.  What I did to obtain enough room to attach the lugs to the inboard sender plate was remove the outboard plate from the rib so that I could pull a little wire through to the inboard sender plate.  You can get about 4-5" of extra wire on the inboard side to attach everything together.

This is a picture of the inboard side.  As you can see, there are several extra inches of wire that will allow me to attach the inboard plate.

This shows the inboard tank bay.  As you can see, the last thing that I will connect for the capacitance senders is to solder the lead to the BNC connector.  Sequence was important here.  If you soldered the BNC first, then you would not be able to pull any extra through to land the lugs on the inboard sender plate.

Once the inboard plate lugs were screwed on and tightened, the instructions have you put tank sealant over the screw, nut, lugs and wire to kind of seal everything up.  It also has you put a dab of sealant on the head of this screw.  I fully encapsulated everything and made sure the tank sealant was not touching anything on the tank creating a ground path circuit.  These senders will not work if one of the plates is grounded (connected electrically) to the tank.

With the inboard rib hardware almost in place, one last thing I wanted to check before riveting and sealing the inboard rib was the range of the flop tube.   I wanted to make sure there was not any possible orientation(s) that would result in a hang-up of the flop tube.

Normal flight, the flop tube rests in the bottom corner.  It physically cannot get lodged under and between the sealed plate nuts and stiffener.  No problem.

This orientation represents "knife-edge" flight with right wing down.  Flop tube does not rub or hit anything.  No hang-up concerns.

This picture is inverted flight.  The inspection hole strap prevents the flop tube from banging up against the plate nuts as it re-orients to the top of the tank.  I couldn't physically push, pull, or otherwise tug on the the flop tube to put it in a position of getting hung up on any of the plate nuts.  No concern in this orientation...

Just a close up of the flop tube near the inspection hole plate nuts (inverted).  As you can see, there is no possible way that the flop tube can get hung up on the plate nuts.

This orientation is knife edge flight with right wing up.  This was coming from being previously inverted.  The flop tube has not re-oriented itself as of yet.  Again, even if the flop tube moved to the the other side of the tank, the anti-hang-up strap on the inspection hole would prevent it from chafing up against the plate nuts.  When I continued rotation to normal flight, the flop tube immediately repositioned itself to the bottom of the tank.  No concerns here either...

Physically pushing the flop tube over, I could not get it to reach the trap door.  Additionally, it can not get lodged between the end of the stiffener and the rib.  Van's instructions (as vague as they are here) have you put a anti-hang up bracket that is angled down from the rib web to the aft stiffener (where the flop tube is at in the picture below.  I didn't put that anti-hang-up bracket in as it does not seem to serve any real purpose here that I can see.

So far, so good...  No concerns.

Again physically pushing the flop tube over, I also could not get it to reach the rib hole I covered with scrap aluminum. 

I didn't take the next two pictures showing the flop tube anti-rotation device, however, a discussion came up on this in the Yahoo group after I had finished my tank.  One builder was having a hard time keeping the ell fitting from rotating when the flop tube would reposition.  Supposedly, Van's had recommended to other builders with the same problem, to install a anti-rotation device for the flop tube.  I didn't find anything on the prints or instructions that told me to install an anti rotation device, so this must be something that Van's has been recently recommending.

I can't remember who had posted these, but he did a nice job, so I added hid pics to my log entry.  Looks simple enough as long as you don't already have your tank sealed.

I imagine that if the flop tube ell started rotating (if not restrained) that it could result in a tank leak at that fitting.

I borrowed a multimeter from work (I ordered a Fluke 177 from rhinotoolshop.com and it is supposed to be here next week.  They had the cheapest prices on Fluke DMM's I could find on the net).  Before getting to far on the tank, I wanted to make sure that the capacitance plates were isolated from the rest of the tank.  The "OL" is good.  That means there is a high resistance between the tank skin and the capacitance plates.

Next, I wanted to ensure that the two plates were electrically connected together and had a LOW RESISTANCE.  The meter reads 0.5 ohms which is low.  When I checked the resistance of the test leads, they read 0.5 ohms.  So if I subtract the resistance of the test leads from the indicated value, the resistance between the plates is 0 ohms.  THAT IS GOOD.

Today, was enjoyable.  I just took my time thinking things through and enjoying the "building process".  The weather was COOL.

Between other home projects (and chores) this weekend, I was able to get a "6-hr RV-FIX" today.  I started by fabricating the anti-hang-up guide for the inspection plate.  To be honest, I cannot figure out what function this guide serves.  Checking other builder's web sites, it seems that they had the same question.  This guide didn't take long to fabricate, so I went with the flow...  However, I did turn this bracket into a Trigonometry problem (I knew all those math classes would come in handy for something).

I made the anti-hang-up guide out of .025" 2024-T3 scrap aluminum and cut it 3/4" wide (Van's calls out approximately 1/2" wide).  I tapered the ends that are clecoed to the reinforcement ring to the diameter of the large end of my sharpie marker cap.  (Can you see all the precision instruments that are involved here?)

Below is a simple drawing for my anti-hang-up guide for the inspection plate.  The diameter to the outside edge of the inspection hole reinforcement ring was 6.75".  I guesstimated that I wanted the anti-hang-up guide to be an inch high (just a measurement that was higher than the height of the sealed plate nuts on the reinforcement ring).  I was going to make the bend 60 degrees (just another number I pulled out of thin air).  From there, I used a little trig to figure out the hypotenuse of the triangle which turned out to be 1.15".  I marked the aluminum at those points and made my bends.  I used a protractor to obtain my 60 degrees and viola...  I have a symmetrical anti-hang-up guide.

After I fabricated the anti-hang-up guide, I made sure I could get my hand in through the inspection hole.  (I don't know why...  With the capacitive fuel senders, there is nothing in this first bay except the flop tube, back side of the fuel sender BNC, and the nut holding the tank vent AN fitting).  I set the anti-hang-up bracket aside as I will rivet the guide in when I make up my next batch of tank sealant.

I then put the fuel tank back together to finish some other miscellaneous activities.  The first of which was to look at interferences for the capacitive fuel sender plates.  The picture below is the outboard plate.  This plate needs to be notched to provide at least 3/16" clearance between the plate and the fuel tank stiffeners.  I more or less eyeball'd how much material needed to be removed.  To remove the material, I used a hand nibbler I bought a while back.  That thing worked GREAT!!!!  I was able to accurately control removal of material to within 1/16" and the nibbler does NOT distort the aluminum when it makes its cut. 

This picture is of the inboard capacitive sender plate.  It does not require any modifications to maintain the 3/16" between the plate and the other tank components.

Then to finish out the day, I countersunk all the tank skin to baffle holes.  With the tank assembled, cleco in the baffle plate so that the countersink cutter pilot has something to guide the cutter on.  Van's has you countersink the tank skin (T-701) AND NOT the baffle. 

The weather is supposed to turn HOT/HUMID and Jeff hasn't come out to the house to tie in my heat pump refrigerant lines and do the initial freon charge.  I am going to have to get on him about it.  Guess I can't push to hard when he is doing it for free.  If he doesn't come out tomorrow, I will probably be riveting/sealing the tank stiffeners.