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Author Topic: Flushing flux from a tank  (Read 3774 times)

Offline Mark Mc

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Flushing flux from a tank
« on: March 16, 2018, 01:39:11 AM »
I just made up a tank using K&S tin plate and 60/40 solder.  I cleaned up the outside, but what is the best way to flush out the residual flux from the inside?

Mark

Offline Brett Buck

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Re: Flushing flux from a tank
« Reply #1 on: March 16, 2018, 09:40:53 AM »
I just made up a tank using K&S tin plate and 60/40 solder.  I cleaned up the outside, but what is the best way to flush out the residual flux from the inside?

     Soap and water followed by lacquer thinner. It's easier to clean up if you leave the back of the tank off, clean it up, then attach the back. Then you only have to clean the flux from the rear cover. When done, fill it about half-full with fuel, and let it sit for about a day, shaking it up periodically. I also beat the corners against the bench lightly, just in case, to knock anything loose. If you hear anything, take off the back and remove it.

     Even with all that, usually, something comes out in the first few flights, so I use a Crap Trap filter until at least the first tubing change.


     Brett

Offline Mark Mc

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Re: Flushing flux from a tank
« Reply #2 on: March 16, 2018, 10:07:03 AM »
Thanks, Brett.  I should have thought ahead and did what you say to clean it up before closing out the end.  But I was on a roll, happy with how easy the solder was wicking in the joints, so I just zipped through it and pressure tested it.

Mark

Offline Tim Wescott

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Re: Flushing flux from a tank
« Reply #3 on: March 16, 2018, 01:33:23 PM »
Thanks, Brett.  I should have thought ahead and did what you say to clean it up before closing out the end.  But I was on a roll, happy with how easy the solder was wicking in the joints, so I just zipped through it and pressure tested it.

He said it's better, not necessary.  I don't do the step of cleaning before I pop on the back cover -- I just put it together, and clean it up more or less the way Brett recommends.  I do keep the filter on, always, though.
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Offline Dan McEntee

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Re: Flushing flux from a tank
« Reply #4 on: March 16, 2018, 07:40:35 PM »
  If you have good fitting seems, then only apply flux to the outside of the joint and don't over do it. If it's a good, tight fit and clean, you don't need much flux. You won't have to flush out what you don't put on!  White vinegar is another good "fluid" to flush tanks out with.It helps neutralize the acid in the flux, even though it is an acid in itself. it will eat rust but not bother the tin on an older tank also.
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Offline Lauri Malila

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Re: Flushing flux from a tank
« Reply #5 on: March 17, 2018, 02:25:32 PM »
You like taking risks, Engineman?

Offline Howard Rush

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Re: Flushing flux from a tank
« Reply #6 on: March 17, 2018, 05:27:59 PM »
How much flux could a flux flusher flush if a flux flusher could flush flux?
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Offline Brett Buck

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Re: Flushing flux from a tank
« Reply #7 on: March 17, 2018, 05:37:37 PM »
I stays stuck in there. Just leave it in, it might slowly dissolve over time ...

   It certainly does not. It flakes and is not significantly soluble in fuel, in fact, you usually find flakes of hardened flux in th4e filter. Which is the reason to run a good filter like a Crap Trap to avoid any problems.

     Of course, this is the reason to both use clean technique and to use proper flushing with a real solvent like lacquer thinner or Flux Remover.

     Brett

Offline Russell Shaffer

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Re: Flushing flux from a tank
« Reply #8 on: March 17, 2018, 06:51:51 PM »
If you use a syringe with lacquer thinner be sure to use a cheap one.  It won't survive the experience.  A tiny funnel is good.
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Offline wwwarbird

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Re: Flushing flux from a tank
« Reply #9 on: March 17, 2018, 09:54:45 PM »
How much flux could a flux flusher flush if a flux flusher could flush flux?

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Offline Air Ministry .

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Re: Flushing flux from a tank
« Reply #10 on: March 18, 2018, 11:12:02 PM »
Boil the swine in water with a table spoon of baking soda , shake flush a few times & burn the fingers ! .

Ive found new tanks take a few runs to ' settle  in ' setting wise  , untill theyve had fuel thru ,
to coat the insides ??
So Flushing a few times with old leftover dregs fuel seems to solve that issue .

I do that or C R C / WD 40 after the Boiling .

Offline Larry Renger

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Re: Flushing flux from a tank
« Reply #11 on: March 22, 2018, 02:34:18 PM »
I wonder if crock pot treatment with antifreeze would do it?
Think S.M.A.L.L. y'all and, it's all good, CL, FF and RC!

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Offline Brett Buck

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Re: Flushing flux from a tank
« Reply #12 on: March 22, 2018, 08:39:49 PM »
I wonder if crock pot treatment with antifreeze would do it?

     Just pour in a few ounces of lacquer thinner and shake it for while, let it sit nose down and nose up for about 10 minutes, and suck it back out. This is a solved problem.

     Brett

Offline Lane Puckett

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Re: Flushing flux from a tank
« Reply #13 on: May 01, 2018, 09:22:56 PM »
has anyone done any testing with the newer water soluble flux? 

Also if you hit McMaster Carr there are a number of newer flux's available
water soluble
fast-flushing flux
nokorode flux

Then there are a whole bunch of no-clean solders that the electronics industry are using to avoid the very corrosion issue I try to avoid.  In addition to avoiding the flux floating around in the fuel line.

Offline Dan McEntee

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Re: Flushing flux from a tank
« Reply #14 on: May 02, 2018, 05:44:07 PM »
has anyone done any testing with the newer water soluble flux? 

Also if you hit McMaster Carr there are a number of newer flux's available
water soluble
fast-flushing flux
nokorode flux

Then there are a whole bunch of no-clean solders that the electronics industry are using to avoid the very corrosion issue I try to avoid.  In addition to avoiding the flux floating around in the fuel line.

   All of that stuff may work very well, but even using the  old fashioned stuff, with careful construction and application, you don't really need to get an flux inside the tank. Remember, you are applying solder from the outside. Apply your flux after you have joined the components. Before you put the last end cap on, clean out the tanks as best you can and have a good visual in you mind of how clean it is. If that last end cap is nice and tight fitting, you will need VERY little flu to get a nice solder joint. I have seen commercially made tanks that have large amounts of rust in them. I think the form the main body of the tank, dip the ends in a flux tube, slap the and caps on and solder away. They can't take the time to flush each tank to be profitable so the flux remains. A lot may have to do with the attention to detail and skill of the guy building the tank. But if YOU are the one building YOUR tanks, you will know what is going on in the inside and have some confidence in it.
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Offline Dave Hull

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Re: Flushing flux from a tank
« Reply #15 on: June 23, 2018, 10:09:24 PM »
Definitely use the lacquer thinner. But no reason to ruin a syringe filling the tank. I am happy using a wide mouth glass jar (I like dill spears....) and put a couple inches of thinner in it. Put the tank in, nose first. Rotate around until you see it spewing air bubbles and you can be sure that the thinner is going in one of the other tubes. Standard vents are easy, and so far, I have not had a uniflow tank that wouldn't fill up via the same treatment. When I say "fill up," I don't mean that literally. If you can get an ounce into the tank and keep sloshing it around, that seems to be effective. When I drain the tank, I like to run it onto a paper towel and back into the jar. That does two things: I can see what kind of crud and how much of it I was getting, at least anything that won't dissolve; and, it keeps the crud out of the jar so it is ready to use the next time. I label the top "Lacquer Thinner for Cleaning Tanks" so I don't get it mixed up with anything else.

I like to put an oil/kerosene mix into the tank after it is cleaned out, then slosh and drain, and then cap it. Then it is good even if the first flight does not happen right away. Since I build slooooow, I never know how long it might be before the tank gets wet.

I have nearly always used at least some castor in the fuel--until recently. Those two planes used plastic tanks, so no worries. But I recently changed the tank in one of them to see if I could get a better engine run. It seems like I should be putting some "storage oil" into that tank from now on. What are the rest of you guys doing?

I have always wanted to build a tank from stainless with the hope that the "thin tin coating going away leading to rust issues" could be dispensed with. Maybe one of these days....

Dave "McSlow"

Offline Ken Culbertson

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Re: Flushing flux from a tank
« Reply #16 on: July 09, 2018, 07:48:06 AM »
   It certainly does not. It flakes and is not significantly soluble in fuel, in fact, you usually find flakes of hardened flux in th4e filter. Which is the reason to run a good filter like a Crap Trap to avoid any problems.

     Of course, this is the reason to both use clean technique and to use proper flushing with a real solvent like lacquer thinner or Flux Remover.

     Brett
I had flux flakes ruin my day at a local contest last month.  "New" tank from a commercial source we all use.  Started coming out after about 10 flights.  When I popped the end cap there was enough junk in there to start a junk yard.  My bad for not running a filter (no room, not even for one of the skinny ones) and I had flushed the tank when I got it.  Brett is right, they don't soften, they just linger around the intake and wait till you are level inverted.  I don't know how they know but they do.  Fuel "cans" can also contribute.  Filter everything then do what I did, chicken out and use a plastic clunk tank.

Ken
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Offline Brett Buck

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Re: Flushing flux from a tank
« Reply #17 on: July 09, 2018, 11:29:18 AM »
I had flux flakes ruin my day at a local contest last month.  "New" tank from a commercial source we all use.  Started coming out after about 10 flights.  When I popped the end cap there was enough junk in there to start a junk yard.  My bad for not running a filter (no room, not even for one of the skinny ones) and I had flushed the tank when I got it.

    Right. Fuel doesn't touch it, it sticks like varnish on the head of the a Fox 35, until the vibration and flexing shakes it loose.
 
    Part of the problem with commercial tanks is that either fits well, or you make do somehow (like, the tubing comes out at a bad spot and you just work around it). They have to put the tubes somewhere, and the canonical location for the pickup tube is right at the front just like a Veco T21 series. This is the worst possible place in most cases, either it aims right at or hits the back of the cylinder head on profiles, or it winds up right over the engine mounting screws on inverted or upright mounts and leaves about 1" of space for flexible tubing.

    The solution is to modify it, so the pickup comes out of the side of the wedge. Then you can get enough length in the rubber tubing to put in a filter. Despite what anyone says, it makes no different at all where the tubing exits the tank. It *does* matter where it goes afterwards.

   Most commercial tanks are not cleaned out very well, so filling them with thinner and shaking them up a few times is pretty much mandatory.
   



Quote
...they don't soften, they just linger around the intake and wait till you are level inverted.  I don't know how they know but they do.  Fuel "cans" can also contribute.  Filter everything then do what I did, chicken out and use a plastic clunk tank.

     I much prefer fuel in cans, but you can't use the same old can for years, just refilling it, or you will get rust eventually. I like cans over plastic bottles, because they keep light off the fuel, they aren't as prone to damage-induced leaking, and pack in the car well. But you have to keep using new ones, just toss the empties. I also have 4 separate filters in the fuel can pickup line, although I have yet to find more than the tiniest specks of anything stuck in them. The silicone supply tubing gets sticky and falls apart before the filters need cleaning (about 15 years...), at least with Powermaster, SIG, and other quality fuels I have used.

    Brett

Offline Fredvon4

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Re: Flushing flux from a tank
« Reply #18 on: July 09, 2018, 01:19:02 PM »
I always cringe at the field seeing clear plastic fuel jugs with no towel covering them...but the guys seem to do alright week in and week out using up the gallon

Me, I prefer metal cans and buy them every year of so at a local Sherwinn Williams or on line when the price is right. I keep quarts, Half Gallons and gallons

http://www.thecarycompany.com/containers/metal

My last batch of Nitro and Methanol from Torco was in opaque White thicker Gallon Jugs... First gallons were in typical thin clear jugs

My sport flying has gravitated to more and more Plastic clunk. Here I can control the fuel supply and not have to open a tin tank.  Some Brodak Tanks were suspect and caused too much grief...all the GRW tanks from RSM I am using have never been opened..Each is on a profile stunt plane and work as intended
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Offline Ken Culbertson

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Re: Flushing flux from a tank
« Reply #19 on: July 09, 2018, 01:54:41 PM »
    Right. Fuel doesn't touch it, it sticks like varnish on the head of the a Fox 35, until the vibration and flexing shakes it loose.
 
    Part of the problem with commercial tanks is that either fits well, or you make do somehow (like, the tubing comes out at a bad spot and you just work around it). They have to put the tubes somewhere, and the canonical location for the pickup tube is right at the front just like a Veco T21 series. This is the worst possible place in most cases, either it aims right at or hits the back of the cylinder head on profiles, or it winds up right over the engine mounting screws on inverted or upright mounts and leaves about 1" of space for flexible tubing.

    The solution is to modify it, so the pickup comes out of the side of the wedge. Then you can get enough length in the rubber tubing to put in a filter. Despite what anyone says, it makes no different at all where the tubing exits the tank. It *does* matter where it goes afterwards.

   Most commercial tanks are not cleaned out very well, so filling them with thinner and shaking them up a few times is pretty much mandatory.
   



     I much prefer fuel in cans, but you can't use the same old can for years, just refilling it, or you will get rust eventually. I like cans over plastic bottles, because they keep light off the fuel, they aren't as prone to damage-induced leaking, and pack in the car well. But you have to keep using new ones, just toss the empties. I also have 4 separate filters in the fuel can pickup line, although I have yet to find more than the tiniest specks of anything stuck in them. The silicone supply tubing gets sticky and falls apart before the filters need cleaning (about 15 years...), at least with Powermaster, SIG, and other quality fuels I have used.

    Brett
I prefer cans too but all we can get here in cans is Powermaster.  I have a bad can of 5% and one of our group has 2 that ended up being the purple stuff.  We suspect that they are buying up old inventories so we are a bit Powermaster shy.  Since Mike's was forced out of business you can probably get more CL related hobby stuff in Lybia than you can in Dallas.  I have been using Wildcat 10% that an RC shop caries but I keep the bottles under cover.  I am running it in both my OS35s and 46LA.  Somehow I don't think caster is right for both but there is enough here for me to research that one.  Thanks for the feedback.

Ken
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Offline Chris Belcher

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Re: Flushing flux from a tank
« Reply #20 on: July 09, 2018, 04:00:41 PM »
I contacted VP fuels about the purple stuff. I thought this was handled years ago but their response was "Air 10 and 15 are dyed". I explained the issue, am waiting to hear back. This purple dye did lightly stain my white Legacy on just the first two flights. Not trying to hijack the flux thread here, but has anyone else seen the dreaded purple AIR 10 or 15?

Offline Ken Culbertson

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Re: Flushing flux from a tank
« Reply #21 on: July 09, 2018, 04:27:02 PM »
I contacted VP fuels about the purple stuff. I thought this was handled years ago but their response was "Air 10 and 15 are dyed". I explained the issue, am waiting to hear back. This purple dye did lightly stain my white Legacy on just the first two flights. Not trying to hijack the flux thread here, but has anyone else seen the dreaded purple AIR 10 or 15?
No but I have seen your purple legacy.  I have half a can of AIR 5% at home but I don't think it is purple.

Ken

Just got home - it is GMA 5/22 and it is not purple.
« Last Edit: July 09, 2018, 07:47:14 PM by Ken Culbertson »
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Offline Dan McEntee

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Re: Flushing flux from a tank
« Reply #22 on: July 09, 2018, 05:40:06 PM »
   From what I have seen of commercially made metal tanks, I am of the opinion that they form the main body of the tank, then dip the ends in flux then pop on the ends for final soldering. That is how, I think, that all that crap gets in the brand new tank. Depending on what they are using for "flux", it may be corrosive enough to eat away the tin and start rusting the steel immediately. Add in any shelf time and you have a mess inside. On tanks I have made, where things like amounts of flux used and where it is applied is controlled, I have never had a problem with the inside going funky. Some store bought tanks that I have had and have seen have had an unbelievable amount of crud in them. I use both metal and plastic, depending on what the airplane is, and what I have on hand. Sometimes the shape of the plastic tanks just won't work, and some times they can work to your favor also. You just gotta figger it out.
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