Archive for category Fuel Tanks
The Right Tank Is Leak Free! (12/31/10)
Posted by Ethan Jacoby in Construction, Fuel Tanks, Wings on December 31, 2010
1.5 Hours -
I couldn’t think of a better way to end my construction log postings of 2010 than to report that my right fuel tank is now leak free!
I wanted to get the tank on the wing for tomorrows skin riveting session, so I tested it a day or two earlier than I had planned. After attaching the leak test kit components to the tank, I started to pump some air into the tank. Almost immediately, the balloon inflated. Before, the tank had so many leaks that the balloon wouldn’t even inflate. Needless to say, the balloon getting bigger was a welcome sight!
After pumping some air into the tank, the balloon inflated almost immediately.
Next, I sprayed the tank with soapy water and carefully checked for the telltale bubbles of a leak. I found none!
After inspecting the tank several times for leaks, I rinsed off the soap and dried the tank. It’s finally time to set the tank on the right wing. As with the left tank, I nudged the tank into position and then used some of the screws to get the tank lined up perfectly. Once aligned, I loosely installed all of the bolts, followed by the rest of the screws. Finally, I went back and torqued the bolts and tightened the screws.
Both wings now have completed, leak-free, fuel tanks!
On to some skin riveting.
Right Fuel Tank Re-Sealed (12/29/10)
Posted by Ethan Jacoby in Construction, Fuel Tanks, Main Structure, Wings on December 29, 2010
1.5 Hours -
To start this work session, I removed the remaining blue vinyl from the inside of the right top outboard wing skin. Once all of the vinyl was removed, I clecoed the skin to the right wing. This was mainly done to get it out of the way.
The four top skins are now ready to be riveted to the wings. A number of people have riveted these skins solo, but after spending a few minutes trying to figure out how to do it, I decided it was time to call in reinforcements. So, hopefully my Dad will be able to come help soon…otherwise, my girlfriend is going to get a crash course in how to shoot rivets!
Next, I decided to inspect the right fuel tank one more time, and, if everything checked out, seal it up. Using an inspection mirror and flashlight, I carefully checked the baffle/skin seam in each bay of the tank. The sealant fillet looked great the entire length of the tank, so I mixed-up a batch of sealant and started sealing the access covers on the baffle. I applied a thin layer of sealant around each access hole and then clecoed on a cover. Once all of the covers were sealed and clecoed, I started riveting them on with AD-42-H closed-end pop-rivets. As with the z-brackets, each rivet was twirled in sealant before being installed. I’ll give the sealant a week to set before leak testing the tank…again.
The right tank has been re-sealed...hopefully all of the leaks have been taken care of.
More Fuel Tank Work and Right Wing Prep (12/26/2010)
Posted by Ethan Jacoby in Construction, Fuel Tanks, Main Structure, Wings on December 26, 2010
3.0 Hours -
I only expected to spend about an hour on the plane today, but that quickly turned into three. Unfortunately, if I would have quit earlier, I would have prevented a big dimpling mistake.
First, I checked the new baffle/skin sealant bead that I had applied in the right fuel tank over the last couple of days. I used a flashlight and an inspection mirror to visually check the continuity of the sealant. I found a couple of areas that were questionable, so I went ahead and applied more sealant on those areas. I’ll check the tank one more time before sealing the covers on, and I’m also considering testing the tank with some water before closing it. Basically, I would lay the tank on its side, add enough water to cover the baffle/skin join, and then wait a couple of days to see if any water leaks out. I would then flip the tank and repeat this to check the other side. This may be overkill, but it would be nice to know the seam is fixed before closing the tank up again. However, I may also just close the tank and take my chances.
Next, I returned to the remaining deburring and dimpling tasks on the right wing structure. The entire top side of the wing still needed to be deburred and dimpled, which took some time, but I managed to get through rather quickly. With this done, both wings skeletons have been completely deburred, dimpled, countersunk, etc.
Finally, I decided to start doing the final prep on the right top inboard skin. I removed strips of the blue plastic with a soldering iron and then deburred all of the holes. Next, I worked on tapering the forward area where the inboard and outboard skins overlap. To taper the skin, I once again marked off a triangular area and then ground it down with a 2″ Scotchbrite wheel mounted in a die grinder. Once the taper was finished, I continued with the Scotchbrite/die grinder combo and deburred the edges of the skin. Then, I started to dimple any holes in the skin that could be reached with my pneumatic squeezer. I was almost finished, when I decided it was time to join the “extra hole” club. While making dimples on the inboard most rivet row, my finger slipped on the squeezer trigger causing the squeezer to quickly squeeze two dimples. The first was in the correct rivet hole, but the second created a second hole right next to the correct one. Once again, I’m not the first person to do this and there are a lot of ways to fix it. Fortunately, this mistake will be covered by a fairing and nobody but me will know it is there!
My finger slipped on the trigger of my squeezer while I was dimpling this skin. At least the fix is easy and it will be covered by a fairing.
While searching for methods on how to fix my dimpling error, I decided to try making a picture medley of my construction log photos. I had tried this before, but I didn’t have enough pictures at that point to make the final product look descent. Credit where credit is due…I got this idea from Brad Oliver’s build site and the software is free and easy to find by doing a search for “photo medley.” The final picture may end up as my new header photo on this site.
Click this image to enlarge it and you will see that it is composed of pictures from my construction log.
Right Fuel Tank Repair Continued Part 3 (12/25/10)
Posted by Ethan Jacoby in Construction, Fuel Tanks, Wings on December 25, 2010
0.5 Hours -
Before heading to my girlfriend’s parents for Christmas dinner, I mixed up another large batch of sealant and applied it to the top baffle/skin joint. As before, once the sealant was on, I sat the tank upright while the sealant sets.
Next, I’ll give the tank a close inspection. If everything looks ok, I’ll seal it up…again.
Merry Christmas!
Right Fuel Tank Repair Continued Part 2 (12/24/10)
Posted by Ethan Jacoby in Construction, Fuel Tanks, Wings on December 24, 2010
2.1 Hours -
A few of my baffle access covers still needed to be deburred, so I started off the day by doing that.
In order to center the access covers over the holes in the baffle, I used a cardboard template, in the shape of a ring, to draw 4.5” circles centered over each hole. Using the circles as a guide, I could easily align each cover for drilling the rivet holes. I started by drilling all of the holes to #40. Once all of the holes were drilled, and I knew that edge distance was sufficient, I enlarged the holes to the proper size for my closed end pop-rivets.
I used my cardboard template to center and draw a circle around each hole in the baffle. Then, I could line up my cover with the drawn circle and use the cover to drill the baffle.
The outboard most bay is a tighter fit, so I'm using a 4" cover and only 6 rivets.
Next, I started prepping the tank for re-sealing by deburring all of the new holes and scuffing the mating surfaces with a Scotchbrite pad. I then cleaned the interior of the tank as well as I could by vacuuming it with a shop-vac. Before sealing the access covers on the tank, I may try to wash the interior of the tank with some water or fuel to make sure there are no aluminum shavings left inside.
Finally, I cleaned the tank with MEK and mixed up a batch of sealant. I made a fairly big batch (110 grams) because I have a lot of sealant left and I want to be extra generous applying it as I try to seal any leaks. I applied the sealant to the bottom baffle/skin joint using a tongue depressor inserted through the baffle access holes.
Ready to start re-sealing the baffle, I paused, while mixing a batch of sealant, to take this picture.
Even with an inspection mirror and light, It was difficult to see what I was doing, so a lot of the sealant application was done by feel. After finishing the bottom join, I sat the tank upright, hoping that gravity might help move the sealant into any gaps. I’ll seal the top joint tomorrow and close the tank after a few days and a very close inspection of the new sealant.
Right Fuel Tank Repair Continued (12/23/10)
Posted by Ethan Jacoby in Construction, Fuel Tanks, Wings on December 23, 2010
1.0 Hours -
The 4 inch test cover I cut simply didn’t leave much room for error in drilling the rivet holes. Because of this, I decided to try 4.5 inch covers instead. Unfortunately, 4.5 inch hole saws are expensive, so I decided to cut the circles out by hand on the bandsaw.
I made a template out of cardboard and then used that to trace five circles on some scrap aluminum. Using the bandsaw to cut them out, they turned out better than I expected. In other words, they were relatively round!
After all of the covers were cut, I used my cardboard template to drill rivet holes in one of the covers. After the first one was drilled, I used it as a drilling guide for the remaining pieces.
I made a cardboard template as a guide for drilling holes in one of the covers. The first cover then served as a drill guide for the others.
I’ll have to use one 4 inch cover on the outboard bay. Because of the orientation of the z-brackets in this location, there’s not enough room for a 4.5 inch cover. Since the spacing of the rivet holes is very tight on this size cover, I opted to just drill the holes by eye instead of making a template.
Finally, I started to deburr some of the covers. Sometime this weekend, I should be able to match drill the baffle to the covers and apply new sealant inside the tank.
Started Right Fuel Tank Repair (12/21/10)
Posted by Ethan Jacoby in Construction, Fuel Tanks, Wings on December 21, 2010
1.3 Hours -
Well, I’m finally starting the big repair task on my leaking right fuel tank. The first step, drilling 3” holes in the baffle was, by far, the most difficult thing I’ve had to do on the plane so far. The task of drilling the holes wasn’t difficult, but mustering the courage to drill a bunch of holes in my fuel tank, which I’ve worked incredibly hard on, was challenging!
I drilled centering holes on the baffle over each bay of the tank. These holes were simply to help me get the hole saw started. Then, I chucked a 3” hole saw in my electric drill and cautiously drilled the first hole. With a lot of noise and flying aluminum shavings, the saw cut through the baffle and left a nice circle. Before drilling the rest of the holes, I checked to make sure the hole would be big enough for me to reach in and apply new sealant to the baffle/skin seam. Seeing that there would be plenty of room for this, I drilled the rest of the holes.
A lot of aluminum shavings were created when drilling the holes in the baffle. I'll carefully clean the tank before sealing it up.
My plan was to not cut a hole in the baffle over the inboard bay, but to just remove the the access cover on the inboard rib. Well, I removed the screws easily, but I had a lot of trouble with the cover itself. I tried to get something under the cover to pry it up, and I even tried to heat the area to loosen the sealant…no luck. The tank sealant is very strong once cured, and, while I’m sure I could have removed the cover with some more persistence, I decided that it would be easier to cut another hole in the baffle than to continue to work on removing the access cover and risk ruining the cover, the inboard rib, or the fuel sender. Besides, cutting the baffle holes turned out to be relatively easy.
Next, I deburred the baffle holes using a small Scotchbrite wheel in my die grinder. After a couple of passes, I had smooth, perfectly round holes.
All of the baffle holes cut and deburred.
Finally, I used a 4” hole saw to cut a cover blank for the 3” holes in the baffle. I used this blank to make a few templates that should help me with centering and mounting the baffle access hole covers. However, it looks like 4” covers may be too small edge-distance wise, so I may have to get a 4.5 inch hole saw or cut some circles by hand.
I made a few templates to help with covering the new access holes in the baffle. From left to right: one of the 3" cut-outs from the fuel tank baffle, a 4" cover made for the baffle, a ring made from cardboard that will be used to help center the 4" cover over the 3" hole, a paper template that will be used to drill holes in the covers.
The Left Wing Has a Complete Leading Edge (12/16/10)
Posted by Ethan Jacoby in Construction, Fuel Tanks, Leading Edges, Wings on December 16, 2010
0.7 Hours -
After work today, I had a little time to work on the plane. I managed to finish fastening the left fuel tank to the wing. To my surprise, all of the z-bracket bolts went in easily! Once I loosely installed all of the bolts, I went back through and tightened them to the proper torque. Then, I finished installing all of the skin to spar and skin to joint strip screws.
The tank went on the left wing surprisingly easy...everything lined-up well.
All of this went fairly quickly because I got smart and purchased a small, Black and Decker cordless screw driver. This looks like a miniature drill, but I don’t have to worry about over-torqueing fasteners because it applies less than 60 inch pounds of torque at its highest setting. At $30, it may be one of the best purchases I’ve made!
Once all of the screws and bolts were tightened, I gave the tank a quick inspection. The leading edge/tank joint is about as good as I could have hoped for. There are no gaps on the top side and only a single, small gap on the bottom near the spar. The gap on the bottom is so small that I will probably leave it as is.
The top leading edge/tank seam is perfect!
The bottom leading edge/tank seam has one, slight gap. However, the camera makes it look bigger than it is and I will probably leave it.
Before moving on to something else, I wanted to seal up all of the openings on the left tank. The only openings still open were the fuel drain, fuel pick-up line, and vent line. To seal up the drain, I installed the drain valve. For the fuel and vent lines, I just pulled some balloons over the AN fittings on the outside of the tank. These should keep bugs out, but still allow the tank to “breath” as air pressure changes.
I wanted to close up all the holes in the tanks in order to keep insects, etc., out. I installed the tank drain valve and a couple of balloons on the three remaining openings.
With the left wing ready for top skins, I’m getting to the point where I can’t put off repairing the right fuel tank much longer. My plan is to cut access holes in the baffle…one hole for each bay of the tank. After the holes are cut, I’ll be able to reach into the tank and apply a new bead of sealant along the baffle/skin joint. In preparation for this, I marked the center of each bay on the baffle. These marks will be the center of the 3” access ports I’m planning to drill.
I can't delay my right tank fix much longer. I've marked the baffle for drilling access ports.
Left Tank On Wing (12/14/10)
Posted by Ethan Jacoby in Construction, Fuel Tanks, Main Structure, Spars, Wings on December 14, 2010
2.7 Hours -
The left tank couldn’t go on the wing until I finished prepping the spar, and I still had some countersinking and priming to do on the top side of the spar. To get to this area of the spar, I had to remove the top, inboard skin (the only skin I still had clecoed to the wing) and the wing walk doubler. I removed these two pieces from both wings and finished countersinking the fuel tank area of both spars. After finishing countersinking, I primed the area and moved on to another task while the primer dried. Fortunately, this is the last countersinking I have to do on the spars.
While the primer on the spars dried, I started working on the wing walk doublers. These only had to be deburred, dimpled and primed. Most of the dimples could be done with my squeezer, but some of the holes in the two middle rows had to be dimpled with the c-frame. Because the top sides of the doublers are completely covered by the wing skin, I decided to prime the entire surface, front and back, of the doublers rather than just priming the rivet lines. These can now be set aside until it is time to rivet the top skins.
The wing walk doublers are ready for primer after being deburred, dimpled and scuffed.
The wing walk doublers post primer
Next, I set a few rib to spar rivets that are not used to attach the skins and get covered when the tank is in place. The plans are unclear about how to handle these rivets. In fact, I couldn’t even find them on the drawings. It looks like other builder’s are mixed as to whether or not to even set rivets in these locations, but I decided setting rivets here couldn’t hurt, and, since they could all be squeezed, it wasn’t a difficult or time consuming task.
The left tank on the wing!
Finally, it was time to install the tank on the left wing. After setting the tank on the spar and sliding it into place over the leading edge joint strip, I loosely installed all of the screws. By doing this, I was able to slightly nudge the tank into proper position and line up the bolt holes. Then, I loosely installed 6 of the z-bracket bolts. So far, everything has lined up perfectly. Once I loosely install the rest of the bolts, I’ll go back through and tighten everything down. Right now, it looks like by leading edge/tank gap will be acceptable without having to install any shims.
After setting the tank in place, I loosely installed some of the bolts.
I also loosely installed all of the tank attach screws. It looks like the joint between the leading edge and tank will be nice and tight.
Leading Edge Riveting/Left Fuel Tank Test (12/12/10)
Posted by Ethan Jacoby in Construction, Fuel Tanks, Leading Edges, Main Structure, Spars, Wings on December 12, 2010
3.5 Hours -
The first task on my to do list today was to rivet the leading edges to the spars. I’m not deviating from the plans very often, but this is one case where I did. The plans call for solid rivets to connect the leading edge ribs to the main wing spar. Even with a riveting partner, I think this would have been very difficult. Instead, I opted to substitute pop-rivets, a tactic many other builders have used here. My rivets of choice are MSP-43s and MSP-44s. Based on their rated strength, they should be more than adequate.
The space for installing the leading edge rib/main spar rivets is very tight for all but one of the ribs. I had to use my modified rivet puller (with one side ground down), along with an angled rivet spacer that I described in an earlier fuel tank post. The spacer allows me to put a slight bend in the shank of the pop-rivet, giving me more space for the rivet puller, while still allowing me to apply even force across the entire rivet head. Using this method, my arms were still exhausted by the end of the session!
It's a tight fit for these leading edge to spar pop rivets. Solid rivets would have been a serious pain in the ass.
Once all of the leading edge to spar rivets were set in both wings, I set-up my squeezer and started squeezing the leading edge skin to spar rivets on the left wing. After these rivets were set, I was tired of riveting, and decided to leave the skin to spar rivets in the right wing for another day.
The left leading edge is permanently riveted to the spar.
Next, I installed the stall warner access cover plate in the left leading edge. There’s no real reason this needed to be done right now, except that I just wanted to get some parts off my work bench. The cover plate is installed with ten #6 screws. I was a little surprised at the size of the gap that is present between the cover plate and the rest of the leading edge skin. Generally, everything in the kit has been very close tolerance to far. Fortunately, this will be on the bottom of the wing where no one will see it.
The stall access cover has a bit of a gap all the way around. At least it is on the bottom of the wing and won't be seen.
The last thing I did today was to perform a leak test on the left tank. This is the first time I tested this tank, so I had to move all the test equipment over from the right tank. When I started to pump air into the tank with a bicycle pump, I became a bit worried when the balloon didn’t start to inflate. However, all of the sudden, when I started feeling around the balloon for leaks, it rapidly began to inflate!
I don’t think waiting for a couple days to see if the balloon stays inflated is a good leak test (plus I know there are leaks where the balloon is attached to some tubing), so I went ahead and sprayed the tank down with some soapy water. After a close inspection of all the rivets, I’m happy to report there are NO LEAKS in the left tank! Too bad I still have some leaks in the right tank to fix…
When testing the left tank, the balloon inflated and a soapy water spray-down showed no leaks!
-
You are currently browsing the archives for the Fuel Tanks category.
Interesting Stuff
Help Me Buy Some Rivets
