Right Fuel Tank - Dimpling

Not a lot of pictures to share today.  I'm back at prep work stage.  Today I deburred all of the edges and holes of the right tank skin, ribs, and stiffeners.

Then of course the next step was to scuff all of the areas that proseal will go, followed by dimpling.  All of the dimpling is finished, so after a brief rest from the proseal goo, I get to jump back into it again, starting with back riveting the filler cap mount, drain, and stiffeners.

Left Fuel Tank - Sealing (5)

I convinced Rose to try her hand at the rivet gun today.  We finished up the handful of rivets remaining in the nose, and then I mixed up some more proseal and sealed all of the rivet heads as well as a few more areas along the rib flanges.  Fingers crossed that it'll be leak free!

The access plate got a few nutplates where the fuel level sender will attach.

The fuel level gauge comes as a float attached to a straight piece of wire that gets cut and then bent to match the depth of the fuel tank.  The wire then slips into a plastic slot in the sender that moves with changes in the fuel level.  Basically, the resistance changes as the float moves the arm.  Once it's installed, I will ensure it's accurately placed by measuring the ohms at the full and empty positions (the manufacturer lists what the correct readings should be).

Next I need to install the vent lines, but I had to order a flaring tool for that, and it won't be here until next week.  So I think in the meantime I will attach a few of the fittings that go through the access plate (for the vent line and fuel pickup line), then start working on the other tank.  It'll be interesting to see how much quicker the next tank goes together.

Left Fuel Tank - Sealing (4)

The inboard and outboard tank ribs were the last to seal.  These were much easier than the rest simply because of the fact that I could use the squeezer for them.  Because of that, I just set the rivets wet instead of waiting for the proseal to partially cure like on the rest of the ribs.  It wasn't nearly as messy as the other ribs regardless, since the only leak path is on the inside portion of the rib.  That means that the proseal doesn't really have to be spread on the entire rib flange to where it squeezes out the outside edge and through the rivet holes.  I know a lot of people do that, but as long as there is sufficient proseal on the inside edge, it shouldn't really be necessary and just causes more mess.

The outboard rib has a tooling hole that has to be covered up.  I just made a small aluminum rectangle, spread proseal on it, and riveted it over the hole (then put proseal over the rivets of course).  These ribs also have an extra piece in the nose that gets riveted on the inside to help cover up the notches in the flange.  I don't know if they're structural or not.  I think they may purely be there to be a more solid barrier to help with better sealing.

The inboard rib was much the same, except that it doesn't have the same tooling hole to cover up, and it also includes the big angle attach bracket that eventually connects to the fuselage.  That attach bracket is the only part I had problems with.  The -4 rivets are really long and take quite a bit of force to set.  I got all of them done just fine except for one where the rivet set bounced off and really made of mess of the rivet head.  As soon as the proseal sets a bit I'll drill that rivet out and reset it.

I still have about a half dozen rib/skin rivets to set that I need some help with.  After I'm done with those I will do a final internal sealing of all the flanges and rivet heads and move on to installing the rest of the tank hardware before I close it up.

Left Fuel Tank - Sealing (3)

Almost done with the inner fuel tank ribs!  I played around with my air pressure on the rivet gun tonight and found a pressure that keeps from bending over all of the rivets.  I have no idea why the change was necessary since I had been using the exact same pressure I've always used, but for whatever reason it helped to lower the pressure slightly.  I do still have a half dozen rivets to do on the upper surface at the leading edge.  Those are really awkward to do alone because of the curve, so I may enlist some spousal support there.  Next I will proseal and rivet the inboard and outboard ribs (first have to seal and rivet on some support brackets and a few other random items that get attached to those ribs).  At least for those ribs the riveting will be pretty easy since it can be done with the squeezer.  They'll be a little less messy as well, since you really only have to seal the inner side of the rib flanges - no reason to seal from the rivets outward as long as the inside portion is well sealed.

With all of the ribs in, I'll move to the tank guts - fuel level senders, vent tube and pickup, etc.  Then lastly, close out by putting on the rear baffle (where the vast majority of leaks end up).  The second tank will definitely go far, far faster than this one.  It was a significant learning curve!  I will for sure leak test this first tank before starting on the second one though, just in case I find something I need to modify when doing the next one.

Left Fuel Tank - Sealing (2)

I attempted to rivet the two ribs I prosealed yesterday.  Emphasis on attempted.  In the end I got them done, but it was definitely not my best showing.  For whatever reason, I had an awful time setting rivets today.  Especially when I got to the extreme curvature of the leading edge, I kept clinching them over.  I had to drill out and redo more than I care to admit.  I was planning on prosealing another two ribs today, but ran out of steam because of all the riveting difficulties.  I found a number of places where I need to spread a bit more proseal, but I think I'll just wait until I'm completely done with the ribs, then seal all of the rivet heads and put more on the light spots.

Left Fuel Tank Sealing

A few days ago I started the nasty process of sealing the left fuel tank.  I'm sure by the time I'm done with the second tank I'll have figured out how not to get proseal on absolutely everything, but in the meantime, what a mess.  There is just no controlling that stuff!  I did one rib with the intention of wet riveting it like Van's explains, but that turned out to be a nightmare.  For a novice, it's just too hard to get a good shop head when the rivet is buried under slime.  You can't see the rivet head after it's set either.  That made me really uncomfortable, since I could never really be sure that the rivet was good.  I'm guessing that it doesn't really matter, considering the proseal would probably hold things together even if half of the rivets were bad. Still, I like to be able to see the rivet heads and know that they are acceptable.  So, after a half dozen rivets in the wet proseal, I abandoned that approach in favor of the dry riveting technique that I've read about.  For this method, instead of putting proseal on and riveting everything together while it's wet, you simply cleco everything together (clecos in every single hole to try to pull things together as tightly as possible), let the proseal cure for at least a day and then rivet.

The dry riveting technique proved to be much easier and a much less stressful.  Even though it's slightly less messy, I'm still glad that nobody will ever see the inside of the tanks!  As neat as I try to be, proseal is next to impossible to keep tidy.  I'm sure if I taped everything off I could make it look a lot nicer, but I don't really see the point.  The sealing works the same whether there's a straight line of proseal or if it looks like a toddler did it.

After I riveted the first rib together, I moved on to putting proseal on two more ribs.

The last step for the previously riveted rib was to encapsulate each rivet head in proseal.  That sounds easy enough, but once again, it's impossible not to make a mess doing it.  By the time I was done, my neat little blobs on each rivet head were smeared all over the place.

So now I wait a day for the proseal to cure on the two ribs I just did.  You can see how much proseal the clecos push back through the holes.  Imagine that being a rivet.  Luckily, after a day of curing, the proseal is just dry enough that you can take the clecos out and just pull the tacky proseal out of the hole.

Aileron Attach Bracket to Spar

I attached the outboard aileron bracket to the rear spar.

The inboard bracket didn't go on quite as easy, mostly because I found out I had swapped a left and a right piece of angle during assembly (holes were not exactly symmetrical between the two, but since they weren't labeled parts, I didn't realize it while I was putting it all together).  So I had to drill out a number of rivets and switch the angle pieces before I could attach everything to the spar.  There is a service bulletin for this attach bracket because apparently some people have found cracks.  The fix is to put two doublers in place during assembly.  Easy enough to do now, but sure wouldn't be fun to try to do it on a flying plane.