Access for fuel tank repair

[dav8or 20]

I have to open up my left wing to remove and see if I can get the fuel tank repaired. Does anyone have suggestions for the best way to open this up so it will be easy to recover the area. My wings have aluminum sheet for the forward top portion of the wing covering part of the tank.

Thanks,

Dan

[1avidflyer 1983]

The aluminum should not be going over the fuel tank if it was built according to the plans.  Did you think about trying a tank sealant like KBS coatings or Carswell's tank sealant?  JImChuk

[chopndrag 226]

I'm with Jimchuck on this one . Is it seeping or a waterfall of fuel leaking ? If it's just seeping get a good tank sealant and slosh it around. Way cheaper and less time consuming then removing the tank .

[dav8or 20]

Almost a waterfall coming out of the trailing edge. I removed the wing this morning. All of the wing except the first rib bay has aluminum skin leading edge. It appears to be a maybe a thin plywood over the leading edge of the tank bay. Next time I am out there I will start trying to open it up. Maybe releasing the fabric glue at the first rib with MEK?

[1avidflyer 1983]

If you are going to cut into the fuel tank, I think you will have to put new fabric over the tank area.  A patch that size really needs to go from a structural member to a structural member.  Rib to rib sideways, and front spar to trailing edge front to back.  I don't think you will be able to peal the fabric back and then reglue it into place and end up with it being tight.  Also, it's tight now, so when you peal it loose, it will most likely be to small to glue back into place.  My 2 cents worth and worth every penny it cost you!  :-)  JImChuk

[chopndrag 226]

You'll definitely have to replace the fabric. If it's painted you couldn't re iron it either you would just melt the paint . Again Jimchuck and his 2 cents are right about what you have to do . Hopefully it doesn't end up being a nightmare.

[EDMO 1078]

Cut the fabric about 2" from rib on tank side, so you can bend that part over the ribcap and glue it to the rib.  Don't unglue that rib.  Later, MEK / sanding the fabric on top of the rib will let you overlap new fabric to cover tank.  Tank fabric can be removed from root rib.   EDMO

Edited 3 Jun 2017 by EDMO

[dav8or 20]

I know I can't re-use the fabric all the way across. I was a little unsure about how to attach it to the rib and want plenty of extra material before I start cutting it down. There is also a 2" wide tape run over the top down every rib. I am not sure why. I am hoping I can re-use the section of plywood or whatever it is over the forward part of the wing so I will retain the stripes that were painted. I will peel back enough to see what it will take to remove the tank so I can take it to a shop to see if repair is possible. If it can't be fixed I will probably just seal up that wing and live without that 5.5 gallons.

[chopndrag 226]

I have a set of 9 gallon fiberglass wing tanks for sale . Never been used or drilled . 

[EDMO 1078]

Before I would remove the tank, I would remove the wing, plug the outlets, and use Caswell to see if it will stop the leak.   EDMO

Edited 4 Jun 2017 by EDMO

[dav8or 20]

I will use my borescope camera to see if I can find the leaking area from the inside of the tank. I can already see just looking into the tank that the weld quality was poor when it was built. I am hoping it is just a seam and it can be repaired by a good welder. I can't imagine trying to maneuver the wing around trying to coat the inside of the tank. I know it has to be a seam along the bottom and near the rear because the tank emptied completely. It is raining here today so I cannot work on it.

[Geoffrey Thorpe 31]

I cut out the fabric over the tanks on my not Avid/Fox - as mentioned by others, cut inside the ribs. New fabric overlapped at the spar / trailing edge / ribs. You probably want to peel up the tape over the ribs (not hard, just pick a corner loose with a knife) and put the seam under new tape. I did some videos on the process when I did it - see link in my .sig  Polyfiber repair parts 1-3.  Real snoozers.

In the video I sprayed the poly everything, but I've done broom jobs on similar repairs and they come out, well, not great, but OK.

Edited 4 Jun 2017 by Geoffrey Thorpe

[EDMO 1078]

I will use my borescope camera to see if I can find the leaking area from the inside of the tank. I can already see just looking into the tank that the weld quality was poor when it was built. I am hoping it is just a seam and it can be repaired by a good welder. I can't imagine trying to maneuver the wing around trying to coat the inside of the tank. I know it has to be a seam along the bottom and near the rear because the tank emptied completely. It is raining here today so I cannot work on it.

I think this is the reason they quit using aluminum tanks - You might be better off to replace it with fiberglass tank.   EDMO

[chopndrag 226]

Shameless plug I got 2 tanks for sale 

I will use my borescope camera to see if I can find the leaking area from the inside of the tank. I can already see just looking into the tank that the weld quality was poor when it was built. I am hoping it is just a seam and it can be repaired by a good welder. I can't imagine trying to maneuver the wing around trying to coat the inside of the tank. I know it has to be a seam along the bottom and near the rear because the tank emptied completely. It is raining here today so I cannot work on it.

I think this is the reason they quit using aluminum tanks - You might be better off to replace it with fiberglass tank.   EDMO

[dav8or 20]

Hopefully, I will be able to get down to the airport in the morning and get the tank out to see what the actual damage is. That tank has been in for over 300 hours before having an issue. I liked being able to leave that one full of fuel all the time without worrying about the fiberglass resin issues. There is a very good aircraft welder near me. I will see what they would charge for the repair if it is feasible.

I still need to get my wing open but I suspect those fiberglass tanks might not fit my speed wing. Right now I am thinking that if my aluminum tank is not repairable I will probably leave it out and simply recover that part of the wing. How many people fly for more than 2 hours at a time in an Avid anyway? I have only flown slightly longer than that once. I was definitely ready to stretch my legs after that.

[Bandit 286]

I dropped the poly tanks inside my crap fiberglass ones. Only 10.4 gallons now. Gives me about 1 1/2 hours of Flight. That's about all I can take at one time anyway.

[1avidflyer 1983]

Not telling you what to do, but if it can't be repaired and you are going to do without, I would wonder if I would touch it at all.  Or, if I went through the work of tearing the wing apart, I would get a 13 gallon fiberglass tank to put in there and get rid of the header tank if I didn't want to carry that much fuel around.  I did seal a couple of aluminum tanks in a B model Avid once with KBS coatings..  They did hold for a while, but eventually began to leak again.   JImChuk

PS  got to thinking, this is an Avid right?  In that case, it would be 14 gallon tank.....I think someone had some for sale a while back.

Edited 6 Jun 2017 by 1avidflyer

[dav8or 20]

I have to remove the tank to determine if it can be repaired. If it is determined that it cannot be repaired then it wouldn't make sense to me to go through the effort to reinstall it. Installing the larger fiberglass tank seems like it would be quite an undertaking.

I have a 16 gallon tank in the right wing and a 2.5 gallon aluminum header tank behind the seat. That is around 3 hours of flight time for me with about 30 minutes reserve.

[1avidflyer 1983]

Sorry, I misunderstood. I thought your were referring to the header tank as being the tank in front of the instrument panel.  Didn't realize you had a tank in the other wing.  When you mentioned it was an aluminum tank, I figured it was an early Avid being that it had an aluminum tank.  Also, I didn't mean to reinstall a bad tank, just replace it with a larger fiberglass one.  I guess that's what happens when I assume.  Jim Chuk

[dav8or 20]

No worries. I had forgotten that the earlier Avids had the panel tank. Now I understand somebody wanting to get rid of that one for a wing tank. According to the log books the original builder had aluminum tanks in both wings and replaced the right one in the first year or so with the large fiberglass tank. Heading down now to get it opened up.

[dav8or 20]

Now I wish I hadn't started. The front part of the tank is covered with what looks like foam that must have been sanded to the airfoil shape then sheet aluminum over that covered with fabric. I stopped when I saw the foam. Not sure what I am going to do now. Time to rethink this. Forgot to take my borescope camera with me so I did not get an inside look yet. I will take it down this afternoon.

[1avidflyer 1983]

Am I seeing a fiberglass tank behind the aluminum area, or is that the bottom wing fabric?  JImChuk

[Dusty 126]

The tank is on the wrong side and wouldn't be able to fill right up?but great for transporting

[Geoffrey Thorpe 31]

 The front part of the tank is covered with what looks like foam that must have been sanded to the airfoil shape then sheet aluminum over that covered with

If you run aluminum from rib to rib it will curve nicely and I would think that there would be no need for foam.

[dav8or 20]

The fabric is cut just behind and at the same angle as the tank. The tank is aluminum and painted yellow. It is under the cap strip on the inboard end of the wing and silicon-ed in around the edges. Looks like the foam was used to fill the cap strip gap maybe.

I looked at the seams inside this afternoon and the welding was really inconsistent. A lot of places where they did not get good penetration. I attached one picture of an area that is suspect. It is actually the front inside corner. If that is the leak then it was running down the inside of the fabric from there to the trailing edge.