Fuel Tanks - Proseal bottle #5

Started off this morning with our fifth bottle of proseal! We installed the T-1005 tank attach brackets and T-1003B aft-inboard ribs on both tanks. This used more sealant than I thought it would, and we actually got pretty close to using the whole bottle on just those four pieces. I used the leftover to install the fuel feed and return fittings, vent fittings, and then drilled out and redid a small handful of rivets we had marked with a sharpie that didn't come out to our liking-- maybe 5 or 6 or so.

L and R tanks, respectively after the last of the ribs had been installed

Close-up of R fuel tank inboard rib. From left to right, you can see the vent fitting, return fitting, and feed flange; as well as custom access panel cutout (bottom) and fuel sender cutout (top)

Close-up of L tank, mirror image of R tank above

Inside of R tank inboard rib

Inside of L tank inboard rib

Once that was done, I got out the coil of vent tubing and realized... doh! We were supposed to install the vent line before riveting the inboard rib into place to facilitate feeding the line through all the ribs. Actually, it wasn't very difficult to feed it through anyway, it just went slower and took a little more care. Next thing to do was get started on a fuel tab. Although it's not in the plans, I figure it would be really useful to have tab sticking down into the fuel tank from the filler neck to mark the 2/3 full point, like you see on some production aircraft. The trick is, how far down from the filler neck is really 2/3 full? Given the angles due to dihedral and angle of incidence the plane sits at on level ground, plus the airfoil shape of the tank itself, this isn't an easy question to answer. I had posted a question on VAF a couple days ago but haven't heard any responses... I suppose it's sort of an odd question and it would take someone to have to go out to their plane and measure. So, I'll have to take a stab in the dark on this. Ready for some Kentucky Windage? Here goes:

Given that the tank is about 9" tall at the baffle, if we were dealing with a square and level tank we'd want our mark to be 3" down from the top. Dihedral causes more fuel to settle near the root than at the filler location, but incidence angle/airfoil shape will affect it also. Best guess, 3.5" down from the filler neck should give us 2/3 full, within say 1/8 tank plus or minus. We'll see how good this guess was in another year or so, I suppose!

The fuel tab, 3/4" wide with lengths of 1/2", 3-1/2", 3/4"

Tomorrow, time permitting, we'll make the second tab and install them to our custom fuel cap flanges, along with the vent line holder!

Fuel Tanks - Proseal bottle #4

Well, we didn't get to do nearly as much work on the plane this last week as we had hoped... I was on travel Mon/Tues, then Wednesday we were both pretty tired and decided to skip a day. Then Thursday our friend Martin offered to give us a ride in his Bonanza to MCW for "Third Thursday" fly-in BBQ and had a blast. It was our first visit to this event, we'll be back next month for sure! Fridays we usually take off from building, and then this morning we went up to IIB for a fly-in pancake breakfast at Walter Aviation. Unfortunately, only Sarah got to actually fly up due to one of the two rental planes our group of 6 was using had a dead battery due to the previous renter leaving the master switch on (aaarrrgh!). Have I mentioned before we can't wait to have access to our own aircraft?!?!? Really frustrating. So we ended up re-shuffling the group and the 4 lightest people still went in the one operational plane. That left me out :-( but I still drove up and re-joined the group for some pancakes and hangar flying. Sadly, shortly before we got there a Cessna 195 had ground looped on landing (~15-20kt direct crosswind) and although the airport remained open, the mood was soured a little bit due to that incident, and we didn't stay and chat as long as we sometimes do.

A sad sight to see, just glad no one was hurt!

No one was hurt thankfully, but it's still a pretty bad day when you wreck a very beautiful and sought-after (not to mention expensive) aircraft.

Anyway.... after we got back home, it was time to shift focus back to the project!

Our friend Alec stopped over again to hang out and witness the "joy" of proseal. We installed the remaining ribs and stiffener into the L tank, which almost perfectly finished off the 3.5oz bottle. So far, four bottles have gotten both tanks to the same stage: ready to install vent line, fittings, and inboard ribs. Hopefully, we'll get to that tomorrow! For now, here's a few pics from Alec, who was on photo duty for the day :-)

Sarah and I posing for a perfect "action" shot building the tanks

Our dogs Dag and Mesa watching the fun

Alec and Sarah being silly... he loves to peel the blue cellophane off the parts, but apparently if he does it too much it gets stuck to his glasses...

Wings

Today Sarah started final-drilling the bottom skins while I was away on travel. No pics, but it's about 3/4 of the way done... that should make for an easy finish tomorrow, along with maybe another bottle of proseal... yay!

Wings

No proseal today, we'll wait until maybe Wednesday or so I think for the next round. Everything in moderation, right?

Instead, we cleaned up the shop a little bit, and I put together a small utility cart we got from HF yesterday. I think it will be nice to use it to hold parts, tools, etc and help keep clutter off the work tables. We'll see how well it works. Certainly, in true Harbor Freight fashion, this thing was... well... "interesting" to put together. The quality of workmanship for the parts in this utility cart were not exactly at the same level as, say, Van's.

Other than that, the only real work on the plane was starting to match-drill the remaining holes in the bottom wing box stiffeners, and preparing for a massive final-drilling event to get both bottom skins complete. That should happen sometime next week, I believe!


***GOTCHA ALERT***
I'm going to start a new tag on this blog called Gotchas, with this being our first installment. On Page 14-6 for the Wing rib assembly (completed by us several weeks ago), there is ONE of the 24 bolts (per wing) that requires two washers stacked on each other instead of the typical single washer. The plans only call this out with a small "2X" mentioned in the parts listing, but it is neither depicted in the graphic; nor is it highlighted, flagged, or mentioned anywhere else in the plans. In my opinion, this is an extremely easy detail for a builder to miss. They call for two washers here in order to keep the nut from reaching the end of the threaded portion of the AN3-20A bolt to be used. I missed this callout when assembling the wing ribs, and the tolerances here are so close that using just one washer will still barely snug up on the two parts (as the nut reaches the end of the bolt threads) just as you reach 25 in-lbs torque on the bolt.

Step 14-6, with the bolt in question circled

You could probably use a shorter bolt instead (like an AN3-17A) with one washer, but I think the reason Van's did it this way is so that the shank of each bolt protrudes all the way through the spar and rib flange, and the threads for each bolt begin past the rib flange. This probably helps with the shear strength characteristics of the fastener.

I doubt I would have ever caught this mistake, and I'm pretty confident it would have never been caught, had my Pitts builder friends Gary and Justin not stopped over to set a few rivets for their project and talk shop for a little while. We got into a discussion about bolt lengths, and I went over to demonstrate the way the spar and ribs had been assembled on our wings, when Gary just so happened to grab the ONE bolt (remember, out of 24) that was incorrectly done and was able to make it twist with his fingers. You can imagine my horror!

It took all three of us a good 20 minutes staring at this page of the plans, and checking our work to realize the problem. After quickly remedying the issue and dabbing an emotionally comforting extra-thick blob of torque seal on the bolt, I showed the plans to another friend of mine who specializes in engineering/installation drawings and diagrams for retrofitting the big jets (Boeing/Airbus) with electrical upgrades. He was appalled by the lack of a flag or some other highlight to point out the discrepancy for that one bolt versus the others, and recommended I contact Van's to suggest they highlight this step a little more clearly. That made me feel a little bit better, and I might just do that... but for now I wanted to at least document this finding here on the blog.

The good news here, folks (read: mom) is that I don't believe this one bolt being out of tolerance would have caused anywhere near a 'real' safety hazard for the airplane itself. With the skins riveted into place, and 23 other bolts and 81 more rivets holding the ribs to the spar, it's not as though the whole wing structure was compromised by this one bolt not being fully snug against the parts. That being said, it wasn't fastened as well as Van's engineers wanted it to be, and that is indeed not a good thing. Care needs to be taken to ensure you don't miss these kinds of details hidden in the plans, and plain and simple we failed with that here. I'd be willing to bet, though, that there's more than one RV-10 flying around out there with a missing washer in this location.

Fuel Tanks - Proseal bottle #3

Woke up earlier than normal for a Saturday morning, feeling energized and ready to take on the world. Nothing can ruin that feeling faster than deciding to dive into another round of proseal :-)

In all seriousness, I guess you could say I'm coming around with this stuff. It really isn't THAT bad, it just takes some preparation and organization to keep the mess under control. Also, we're definitely getting into the rhythm of working together on the fuel tanks, and for the most part the assembly process is going quite smoothly. I'm still pretty nervous about leaks though, and that fear hasn't been diminished any by reading all the horror stories on the forums. I think once we finish with all the ribs and are ready to install the baffle, we'll run another fillet around all the seams and any potential leak spots just to keep our 'i's dotted and 't's crossed.

Today, this third bottle of sealant got us through the remaining R tank ribs, as well as two more ribs on the L tank. I think the fourth bottle should finish off the ribs and remaining stiffener for sure.

L tank ribs 2&3 riveted into place

R tank ribs complete!

R tank outboard end rib with fillet

R Outboard tank bay

R tank outboard end rib, from outside

We then spent the rest of the day making a Harbor Freight run for more disposable gloves, had an afternoon family birthday party, and finished off the day with a quick joyride flight to Platteville, WI and back. It was too beautiful of a day to not go up, even just for a bit.

Sort of off-topic, but had to post this here. Last night we went out for a beer with some friends after work, and Sarah's story of drilling through the tank J-stiffener into her finger came up. In order to re-enact how it happened, she improvised a tank skin and J-stiffener using a napkin and a piece of celery. Brilliant use of props!

Sarah demonstrates her technique drilling through a napkin skin and celery stiffener

Tomorrow, maybe more proseal? We'll see....

Wings

Had a few of the first spring storms roll through the area tonight and didn't feel like chancing it by embarking on a non-stop 3-hour commitment with proseal. So instead, we had a pretty easy night continuing on Section 20 with the wing bottom skins. I had previously clecoed the gap fairings into place, so we made quick work out of final-drilling all the #40 fairing-to-top-skin holes on both wings. Still need to do all the #30 fairing-to-rear-spar holes, because apparently changing a drill bit was beyond our motivation at the time.

Also, we hung the bottom skins and started clecoing everything into place. This is definitely reminiscent of the top skins!

R bottom skin starting to be clecoed into place

L bottom skin starting to be clecoed into place

Last thing from tonight was I decided to cut out the hole for the pitot mast. I have the SafeAir pitot mast from Avery tools (link here) and have also bought the Garmin GAP26 heated pitot/AOA. I've decided to mount it in the #2 bay inboard from the tip, using the outboard-most 3 rivets within that bay. The mast comes with a template that helped position everything and draw a cutout line and two drill holes in the skin, although I feel like the template was at about 95% scale of the real thing. That didn't affect much, except once I had the hole cut out I had to run another pass with the dremel to enlarge it again so the mast would actually fit. I didn't take any pics during the process (oops) but here is the final product, clecoed into place:

Pitot mast clecoed to L bottom skin, second bay from tip

Different angle of the pitot mast installed

The mast is fairly long compared to other models, but I'm not sure if I want to cut it down or not. There is certainly enough clearance to work with, and I'm figuring the farther the pitot is from the wing, the less error will be induced. Most likely we'll leave it as-is.

Probably take Friday off from building as usual, Saturday probably get through at least one more bottle of proseal, and then maybe Sunday do some final pre-baffle installation prep, including plumbing the vent line, rivet QA/redos and installation of my home-brew capacitance probes. Oh yeah, and we still have to prime the external tank parts like the zees, half the inboard support bracket, and a small handful of miscellaneous parts. Maybe we'll throw the wing gap fairings into the batch too while we're at it. I have some work travel planned early next week, but hoping to have the tanks done by the following weekend!

Fuel Tanks - Proseal bottle #2

Well, we're through one more 3.5oz bottle of proseal, which got us through the rest of the stiffeners on the L tank, 5 ribs on the R tank, the inboard nose rib of the L tank, and the L sump drain flange. The 3.5oz bottles seem to be working perfectly-- by the time we hit the end of the bottle it's just starting to become less goopy (technical term) and we can go back and clean up after ourselves before it's really set. We're finding acetone works great to clean up bead lines and erase smudges while it's still pliable. If it's sat a few days and hardened a bit, MEK is the next best alternative, but man that stuff smells hardcore. Lesson here is clean it up as early as possible to avoid needing to use the "heavy stuff".

By the time we got through the first couple ribs on the R tank, we had a system down that was working pretty well. I'd wash the inside of the skin and rib flange with acetone, run a thin bead of proseal on the rib flange and hand it off to Sarah, and then run a medium-size bead of proseal on the inside of the skin. Sarah would "butter" the rib flange with an icing scribe while I would butter the inside of the skin with a popsicle stick. We'd insert the rib and install a few clecos on each side to hold it in place. Then, we'd start on one side (either top or bottom) and install rivets from aft working forwards. Sarah would place rivets, clean the rivet gun and/or anything else needing an acetone wipe, as well as being on cleco duty. Meanwhile, I would only have one gloved hand and be working the rivet gun and bucking bar. In this way, we could get through a rib fairly quickly and move on to the next one, working outboard from the innermost rib.

"Ms. I Love Proseal".... I don't get it. ;-)

"Buttered" inside skin ready for a rib, with a previously completed rib behind it

R Inboard nose rib, with an extra fillet bead around the inside edge

Our setup, with holder vee blocks screwed to the tables. This way, we could get around to the nose of the leading edge without obstruction.

R tank under construction, inboard side

R tank after cleanup for the night

R tank after cleanup for the night, inboard nose rib

R tank inboard nose rib, close-up of fillet bead and mini-blockoff plates riveted into place

Fuel Tanks/Wings

No proseal today either... but I did take care of a few to-do items that I hadn't gotten around to yet. Attached all the nutplates for the fuel level sensors and tank access plates, as well as fabricated 12 small covers for the 12 small holes in the tank end ribs that the factory uses as guide holes when forming the ribs. The plans call out to do this on page 18-5 step 6. I also trial-fitted my homemade capacitance probes in the tank. They seem to fit well using three nylon screws and washers. I'll make a post about this soon, since it's a whole side-project in itself.

Other than that, did some get-ahead work starting on section 20 for the bottom wing skins. This involved mostly staring at the left wing bays and thinking about where the pitot tube was going to mount. Then I clecoed the gap fairings into place, just in case I wake up in the middle of the night and feel like match-drilling, I guess.

L gap fairing clecoed into place, inboard side

L gap fairing clecoed into place, outboard side

Stay tuned for more tank/bottom skin fun!

Fuel Tanks

Easy day in the garage today. Worked a bit later than usual and didn't really feel like embarking on too extensive of a task. So, I cleaned up a bit and started fabricating some retaining brackets for the fuel return line. The fuel return is going to simply be an AN832-6D bulkhead union that will dump fuel back into the tank. I don't have any pics of the bracket but it's pretty similar to the T-1010 bracket designed to hold the AN832-4D vent union (just bigger, and uglier because I made it by hand instead of Vans' pre-punched deal).

Maybe tomorrow some more pro-sealing? We'll see. I think I'm procrastinating on this a bit, because I hate this stuff, and once you mix it up you're committed to a few hours worth of messy work with essentially no interruptions.

Fuel Tanks - Proseal bottle #1

Happy Easter! Before some evening family plans, we decided to start the proseal adventure! Since we're familiar with it and it seems to work quite well, we're sticking with using the same stuff we used on the empennage, "Chem-Seal" #CS3204 from Aircraft Spruce. It comes in a 3.5oz bottle, and I've got 4 on hand... we'll see how far this amount goes (I'm assuming we'll need more at some point).

We started off with the station looking like this:

Beginning the proseal adventure!

Unfortunately, we don't have any pics of the process itself because, well, we were wearing gloves covered in the most terrible chemical substance known to man. It's not terrible because it's particularly harmful, it's terrible because it's like they designed this stuff to stick to *everything* but yet come off of *nothing*. And it's so goopy. I swear, due to entropy someday the whole earth will be covered in proseal. Sarah still loves it though-- it reminds her of cake icing. She even ran to the kitchen to use an icing scribe to manage this stuff... actually it was a great idea and helped a lot. I'll just need to remind her we need to get a new scribe now and not re-use this one on food. :-)

Anyway, we're now one bottle of proseal down, which got us through all of the R tank stiffeners and about 2/3 of the L tank stiffeners, as well as both fuel cap flanges and the R tank sump flange. We're "wet riveting" which means we're setting the rivets right away instead of waiting for the sealant to partially cure. It's messier this way, but I think it will be easier to have a clean-looking finished product. We were able to exhaust the whole 3.5oz bottle before it hardened, so that was good news too! Here's our completed work:

R tank stiffeners prosealed and riveted

R fuel cap flange

This next week may be tough to find a block of time to do another batch, but we'll see how things go. It's coming together though!