I also worked on the left bottom skins. I completed deburring and dimpling the outboard skin. I deburred and smoothed the edges of the inboard skin, and started dimpling it.
This time, BEFORE doing the dimpling I used the roller tool to put a slight bend where the outboard skin overlaps the inboard and where the skins attach to the main spar flange. Also before dimpling, I used a sander and ScothBrite to make the scarf joint.
Finally got to spend some quality time with the project today. Hooked up a bicycle pump to the fuel pick-up fitting and put a balloon on the vent line fitting. Squirt bottle full of soapy water in hand, I set out to find the leaks. The only place I have leaks is on the baffle. It turns out that only 3 corners of the baffle are leaking. The two top corners are the worst. There the leaks are in the corner and back along the baffle for a few inches. I drilled out the rivets in those locations and will attempt to squeeze ProSeal down in there with maybe a skinny syringe. I’ll also hit the corners with more ProSeal and seal along the outside of the entire baffle. I’m confident I can take care of these leaks without any problem.
You can see the nasty bubbles in the last shot:
Leo was so disgusted, he had to look away.
Smoothed the edges of the left bottom outboard skin.
Bad news. I set up the left fuel tank for leak testing. It is leaking in the corners where the baffle, skin, and end rib meet. I put a big glob of ProSeal there when I was putting on the baffle, but I guess it wasn’t enough. The good news is that it’s easy to get more goop in those locations.
There also seems to be leaks along the baffle edge near the ends. However, these might be a by-product of the corner leaks. I’m going to buy a kiddy pool tomorrow, fill it up with water, and submerge the tank while pressurizing it. That should indicate quickly where the leaks are. I want to fix them all in one session.
Bummer, but not the end of the world.
Here’s the fuel lube and caps I used to do the test. (After the fact I found out that Van’s sells a nice test kit that includes one cap and a nice fitting for attaching a bike pump to the drain flange.)
Deburred the outside of the left outboard bottom skin.
Since we didn’t get to sealing up the tank yesterday, I thought we weren’t going to get it done this weekend. But Julie was kind enough to help me, even on Mother’s Day. This kindness may have come at a big price. We test drove convertibles afterward. I think she’s hooked.
Sealed up the left tank. I had a lot of miscellaneous stuff to do before dropping in the baffle. There were a few places that I wanted a little more ProSeal, particularly around the end rib. I also had to seal and rivet in the anti-rotation bracket for the fuel pick-up. With that done, I followed the directions exactly for sealant placement for the baffle. The bead of ProSeal needs to be right next to the line of rivet holes for the baffle. I might have put it a tad bit too far forward. We’ll see. [The second image is a little fuzzy, but you can see the bead is some distance from the rivet line. Don’t do this. Put it right next to the rivet holes.]
Julie helped place rivets, and I squeezed them in place and moved clecos around. Then we tackled the brackets with pop rivets. I have to say that pop rivets are easy, but not exactly fun. I had some alignment issues on the brackets and had to chase most of the holes with a #30 drill in order to get the rivets to fit. Not sure what happened there. I dabbed a little sealant on all of the blind rivet heads. From there, I sealed the access panel in place and ran out of sealant. I had just enough to dab on the threads for the socket cap screws. I was going to dab sealant on all of the baffle rivet heads, but I didn’t have any sealant left. I’m not sure it’s really necessary anyway. The baffle should be sealed inside of the rivet line. I think I’ll leak test it and then dab on sealant if necessary.
Even though you don’t think it could take long, this was nearly a 4 hour session with an hour of prep work yesterday.
One trick I discovered is in the use of clecos. The instructions say to cleco every hole. If you do that, you’ll be cleaning literally a hundred clecos. I put clecos in about every 10th hole around the baffle, and then used 6 or so clecos in every hole just ahead of where I was about to rivet. I just moved the same clecos around. That way I only had about two dozen to clean.
I also set the tank forward end up to cure. That should help the sealant creep down into the skin/baffle seam. That stuff really does move around a fair amount while it’s curing.
Whew! What a relief to (hopefully) have that one tank done. I’ll leak test in a few days.
Did all of the cleaning prep-work with MEK for the final session on the left tank. Made sure the inside was cleaned out, cleaned all of the mating surfaces, set out all of the rivets and soaked them in MEK, and prepared all of the tools needed.
Finally worked up the nerve to cut out the hole in the left wing skin for the pitot mount. I used a unibit in the corners and connected the holes with a cutoff wheel in the Dremel. I just filed and sanded from there.
Julie helped me rivet a few of the -4 rivets holding on the leading edge. I had to grind down the offset rivet set a bit.
With a 2X gun and an offset rivet set, it took a lot of pressure to set these rivets. I cranked it up to 90psi, and it still took a while to set them. On the 5th rivet, the set slipped off the head a little. I think the duct tape had just worn out on the set. She got frustrated, so we stopped there. I drilled out the rivet without any drama.
More prep for the final ProSeal session on the left tank. Taped off areas that I don’t want sealed. Pulled out all the rivet that I will need. Torqued the vent line fitting to 50 in-lbs using a crow foot wrench. Used a multimeter to make sure the center pin of the coax connector had good continuity with both plates, and no continuity with the tank itself. Likewise, I made sure the outside of the coax was well connected to the tank and not the plates. Made sure one more time that everything will fit correctly.
Touched up the dimples in the rear spar with the deburring tool, per the instructions. I put a slight bend on the edges of the leading edge and top skins that either overlap or abutt another skin. I used the hand seamer for that. It would have been easier to use the roller, but that only works if you haven’t dimpled the skin yet.
I sanded the forward corners of the top skins where they overlap to create the “scarf” joint. A few people seem to overdue this, so I went slowly with some coarse emory cloth. I finished it off with a Scotch-brite pad. After clecoing the skins on, I might do just a bit more sanding.
I went over the instructions for the Gretz pitot mount one more time to make sure there isn’t anything else I need to do before riveting on the top skins. Nope.
It seems like I’ve clecoed the skins on and taken them off a million times, but it’s best to make sure everything is set before making them permanent. Just a few more minor things to do before riveting.
Oh yeah. Almost forgot. I ordered a heated AOA pitot from Dynon today.