Wing Tank replacement - ALMOST-

[rdooley79 28]

Hey Guys,

 

I almost have my old wing tank removed. Only problem is that the tank has no gap between the tank and the front spar. The rear spar had a lot of room and I was able to use some safety wire to work through the silicone and it's separated but the front spar is so close to the fiberglass with no gap that I can't fit even some .020 safety wire to cut the silicone. I definitely don't want to pry on the tank because I don't want to damage the spar. It's very tight and I can't use a screwdriver or a paint scraper, only a razor blade is able to slide between the fiberglass tank and the spar but there is no mechanical leverage to persuade the tank in to coming loose. I don't want to go at it with a dremmel because if I nick the spar, it's done, replace the spar and rebuild the wing. As much as I want a nice shiny set of freshly covered wings. My bank account doesn't.....

It seems that the only solvent is Xylene (Strip-Rite @ HomeDepot) that will soften the Silicone. 

 

Has anyone had a tightly fitting wing tank? What did you do to get it out?

 

TLDR; silicone adhesive and a tightly fitting wing tank won't budge. How do you remove a tank without damaging the spar?

 

Thanks Guys,

R

 

[allonsye 85]

Are you trying to save the tank and reuse?  The tank could be repaired should it be necessary to cut into it to free it from the spar.  Pictures of the scene of the crime would be enormously helpful.  I'd seal that thing as well while it is out.  Caswell plating is supposed to be very very good.

paul

Edited 1 Feb 2016 by allonsye

[tcj 150]

I used some of that super strong ultra thin fishing line to cut the silicone.  I think it was Spiderwire.  10 or 20 pound is about .005 in. thick.  It won't hurt the spar.

[Bandit 286]

If you are replacing the tanks just cut it apart.

[rdooley79 28]

Fishing line may be possible. I'll grab a spool of that and see if it works, can't hurt. 

 

What solvent would you try? MEK and Acetone are neither effective at breaking down the silicone. Xylene is the only thing that seems to soften the silicone but that's just what some people on the internet are saying, so who knows what that's worth. 

 

Cutting the tank is the obvious answer but is too risky being so close to the spar. Not going there. The last thing that I want it to nick the spar. Just too critical to even get close to with a cutting device. I can't pry on much, again the spar is the only thing there to leverage against. If I damage the spar the whole wing is wrecked. 

 

Fortunately I have a good A&P helping with this project but he's stumped as well. Just way too risky for all the obvious solutions. the caveman approach is not the way to go here. As Matt Damon said, "I'm going to science the $#!t out of this." 

 

What solvent will break down Silicone?

I'll get some close up pics soon.

 

Edited 1 Feb 2016 by rdooley79

[Av8r3400 1179]

Silicone isn't that strong. If you have the rear loose, you should be able to lift the back of the tank and separate the front.  If it's that tight, there will be very little silicone in there. 

[rdooley79 28]

I tried lifting the tank up but it is very secure. whoever put this tank in definitely did not want it moving or coming out. The problem is that the spar seems to be twisting with the force of the tank. The tank is long enough to be a large lever. 

I'm just wary of doing anything that may even be close to damaging the spar. 

Fishing line is recommended and a good to try next. no risk of damage either.

 

[EDMO 1078]

Larry,  What about cutting the top or bottom of the tank enough so you could get some heat on the front inside of the tank to loosen the silicone and try pulling the tank off gently?  Air out the tank good first so get rid of any gas fumes.

EDMO 

Edited 1 Feb 2016 by EDMO

[Av8r3400 1179]

Silicone would need to be heated past the melting point of the aluminum to release, and chopping up the tank will just make a mess...

The fishing line idea sounds most effective.  Like I said on TeamKitfox, I'd be very leery of using a solvent to soften the silicone for fear of damaging the rib to spar adhesive.

Edited 1 Feb 2016 by Av8r3400

[Kahle76 22]

You might try the flat rib lacing cord. 

[TJay 1041]

Maybe push a putty knife in there then a screw driver between the tank and the putty knife. That way your prying on the Putty knife instead of the spar

[allonsye 85]

Here Here for the string as a cutting tool idea.  I've done so with PVC.  I imagine it'll work on nearly any material short of steel.  Keep us appraised.

https://search.yahoo.com/yhs/search?p=cutting+pvc+with+string&ei=UTF-8&hspart=mozilla&hsimp=yhs-001

 

[rdooley79 28]

We got the tank out! Ended up cutting a lot of it out and then working it back and forth until the silicone started to give way. 

I don't have a picture of the tank out. but here it is before and after cutting the fabric.

Next is to install the new tank and then start the covering process. 

 

I've talked to guys in the past that said they didn't spray their poly-brush/spray on. they just brushed/rolled everything.

Reading my PolyFiber manual it wants to use a HVLP sprayer and a ton of respirator equipment and a paint booth. While that may be possible, it will increase the cost and time of this project exponentially. I don't want to spend a $1000 on painting that little section of the wing. Plus it would look sooooo good that the rest of the plane would be bad by comparison. I need to match the dull C+ grade paint job on the plane now. Not apply an A+ paint job on the patch for the tank. At that rate it would be better to strip the plane and shoot the entire thing in a booth. Plus the only booth I have access to is at an automotive paint shop that is super high quality and very expensive to set up. This plane does not warrant a very expensive paint job. 

So can I roll or brush on the paint? The rest of the paint job is fairly flat and dull. There are quite a few blemishes in the paint elsewhere and honestly it's not a "pretty" paint job but it is intact and hard wearing. I really just want to make it good enough to blend in with the rest of the C+ quality paint job. I need a C+ grade paint repair.

 

Any thoughts? How can I paint this bird with the poly system but not be another $1000 in the hole?

Thanks!

[1avidflyer 1983]

I painted both of my covering jobs with a cheap Harbor Freight spray gun and I think they came out fine.  One reason for the paint booth is to keep the overspray from getting on other things as well as keeping the painting area clean.  If your not worried about that, have at it where you can.  Outside isn't very good though if you can avoid it.  Being your just doing the one wing, can't you hang some plastic from the ceiling big enough to keep the wing inside?  With just having to spray the tank area, I wouldn't worry to much about fresh air, use a resperator, shoot it and get out of there till it's ready for the next coat.  You do have to brush in the first coat of poly brush,  but I don't think it will work very good to do the rest of the coats that way.  This stuff is almost as thin as water when you use it.  YMMV  Jim Chuk

[rdooley79 28]

yea, problem is it's in a buddys hanger and he won't spray in there......My hanger is drafty with no heat. His is insulated with heat. It's consistantly below freezing here in CO so I am stuck with paying to use his space. He is fairly adamant about taking it to an automotive spray booth for any spraying..... That just means a lot of money to me. I hate to be put in this situation, bleeding money.

 

 

[Geoffrey Thorpe 31]

I did a broom job when I took my right tank out. It's ain't as pretty as it would be if it were sprayed, but it works. Sprayed when I did the left side in a small area with plastic hanging around in my garage. I wouldn't do it in a hangar with the potential for overspray on other aircraft.

Video of the sprayed side https://youtu.be/0nZhtbG4VHE?list=PL3ea3YrO-K5hlHDwFTh4KCwlKzn8BrDQE

Edited 6 Feb 2016 by Geoffrey Thorpe

[1avidflyer 1983]

Maybe you will get some warm weather and you can do it in your hangar.  Otherwise, you could do the brush in poly brush now, and wait till it warms up for the rest of the work.  Would have to make sure it gets cleaned real good when you put the next coatings on, any grease or oil will cause the later coats to fisheye.  Jim Chuk

PS  just looking at your pictures again, and wondered, are you doing all this work with the wing still on?  It would of course be a whole lot easier with it off.  My replys were thinking the wing was separate from the plane.  Maybe you could check with various body shops in your area.  Maybe they would be willing to let you use their booth after hours.  Jim Chuk

Edited 6 Feb 2016 by 1avidflyer

[Geoffrey Thorpe 31]

Oh -one more thing - the side I did with a brush was during the winter in an unheated hangar.

[rdooley79 28]

The wing is now off the plane with the strut removed as well. 

Has anyone used the single shot mix your own spray cans?   http://www.preval.com/

I have some of these from a past project. Might be a good way to not need a HPLV system with breathers and all of that stuff that's (in my opinion) overkill for a small paint session like this.

 

Do you have any brush vs. spray pic's? I'd like to see how it turned out.

 

Geoff, 

I'm watching your video series on youtube now. I've been looking for exactly this thing on youtube but as you said in your video, there isn't much. We should have your video series as a sticky link for people to watch. Great to see you go through the process. 

Great Videos!

 

 

 

Edited 6 Feb 2016 by rdooley79

[Geoffrey Thorpe 31]

I don't have pictures of the two sides handy -they wouldn't show much from a distance. But when the light is right you can see where the white is a bit thin with a bit of the silver showing through in the brush strokes. Probably an extra coat brushed crosswise would have fixed that. Right now the airplane looks a bit like a patchwork with the different repairs of different vintages... :-)

And, I'm glad you like the videos. Thank you for the comment.

Edited 6 Feb 2016 by Geoffrey Thorpe

[rdooley79 28]

Update

Much further along.

It's going back together and fabric has begun to be glued and stretched. Poly-system, glue, pinking, silver, paint. A good friend that has covered MANY airplanes is guiding me and making sure it all goes together correctly. We're using this as a teaching opportunity so I can do these repairs myself and also to keep the cost down. Fabric is a new thing for me but I'm very mechanically inclined and just need practice and guidance.

Yesterday we accomplished a lot. Things are drying now. Hope to make more progress tomorrow.

Tank is siliconed in place with the special silicone KF sent with the replacement tank.

New standoffs between the ribs and the tank had to be made as the spacing is slightly different than the old tank.

New brass fittings set with JB weld. Also new spacing with the bottom cap strip was needed to ensure a nice flat bottom of the airfoil.

One unfortunate discovery was when removing the flapperon brackets that the backing plates, old glue wasn't sticking any longer and needed to be re-glued in place to ensure the rivets capture the backing plates for a strong mechanical attachment after re-covering the section.

Below you can see the pictures, worth a 100000 words.

[TJay 1041]

Just out of curiosity why did you JB weld in the fittings, I have never heard of anyone doing that. Is this a new trick?

[EDMO 1078]

Just out of curiosity why did you JB weld in the fittings, I have never heard of anyone doing that. Is this a new trick?

TJay,   I have worked with JB Weld before, and it gets hard.   I don't think that it will be as good for removing/replacing fittings as the _Permatex?_____ Aviation #3 non-hardening stuff that Akflyer told me to buy.  EDMO

Edited 14 Feb 2016 by EDMO

[rdooley79 28]

More progress!!!! 

I've learned a lot about working with fabric. We used special chafe tape on all corners, ultralight putty to feather any gaps or cracks especially on the leading edge, sanded everything down and then a light wipe down with lacquer thinner just to be sure no oils were left. We then used glue under and on top of the fabric, working the glue in with my finger and removing as much excess as possible (tricky at first but got the hang of it, way less goobers at the end). Made doileys for the gas cap and drain plug fittings. cut out the drain holes in the trailing edge as well as punch the flapperon bracket holes. My buddy worked the iron and got a nice shrink to the fabric, much better than the old loose fabric. He also was able to work the glue and some of the small wrinkles down with his smaller iron (hobbico RC airplane monokote iron) and got everything looking very good. Next we got lunch, hungry! Once we got back the pink went on both sides and I saw drips on the back side, so I know I got good penetration. Today another coat of pink was put on and we plan on a third before going to the silver. 

Below are the pics in order of build up.

 

We decided to use JB weld for a number of reasons. It's impervious to fuel, sets VERY hard, does not crack, 1/4 brass barb fittings or the vent and fuel level won't ever need to be removed, the 3/4 bung to 5/8 npt bung is permanently fitted but I can remove the 90` main fuel fitting if needed but I can't see any reason to remove them. Not like brass is ever going to degrade. Also the previous owner had used JB weld and I was impressed with how strong it was especially considering how thin the wall is on the fiberglass tank. Any thread in the fiberglass is more of a mechanical "suggestion" rather than a strong thread that can sustain any amount of torque, easily stripped. 

[EDMO 1078]

I hope you can post the CPS football strut tank post again in "Avid and Kitfox Parts Suppliers" - It didn't stay posted on here long enough for guys to see it.

Good progress on tank replacement and covering.

EDMO

Edited 17 Feb 2016 by EDMO