You guys have any tips on metal tank fabrication?  What type of soldering tool works best? techniques? solder?

Thanks,
Scott

HI Scott,

Personally, I use a Weller, or Craftsman, 100/140 Watt gun for the soldering, but many will say that an "iron" will work best.  I am too impatient for the iron, they take too long to heat up! LOL!!  Either way, after about 50  years of soldering, both are good for the job.  Getting every thing clean is very important, plus using a good flux and I use rosin core most of the time.  Stay Brite "Silver Solder" (not true silver solder) works pretty good, too.  It melts at a slightly lower temp.  Making good bends and fits between the parts is very important.  Solder will not really work good to fill gaps.  I punch the holes for the tubing with a scratch awl since it leaves a bit of material flanged around the hole to help create a better joint.  And you already know that copper tubing is better than brass for the tank plumbing.  

I have a pine "buck" carved to 2" wide and 1" deep like the traditional Veco tanks to form the tank body from.  A pair of Vise Grip "sheet metal pliers" is good for the job of bending the tin.  A pair of sheet metal tongs will work if you have them along with good sheet metal shears.  Regular soldering techniques apply, just sweat solder the joints.

Edit: Tim typed faster than I did! LOL!!

Big Bear

From what direction do you punch the holes for tubes, to put the flange on inside or outside of tank ?
Or does it make a difference ?

Also easier. Over on Stuka Stunt, Al Rabe has a pictoral on building his planes.   In one of them he shows how he makes his tanks to fit his airplane designs.  It may take a while to find it, but it is there.  And like building planes, it takes practice to get it right.  I am still trying to get it right.

Here's my tank, so far.  It is made of DuPont lacquer can stock.


Note the block to the left.  The tank is 1 1/2 inches thick since the Legacy has a short nose and a regular tank is too long to fit.

Looks just fine, Scott!  Give it a good washing out and a pressure test under water.  it should be good to go.

Big Bear

Tim,

Yea, I rinse tanks with a very diluted mix of soap and hot water. Then I rinse with lacquer thinner.

Somewhere out in cyberspace there's a web site by a Dutch guy who makes his own combat engines, and makes fuel tanks out of balsa wood laminated with aluminum foil.  The aluminum foil provides fuel proof-ness, the balsa provides structure.  Everything is glued up with epoxy.

I can't find his website though.  The most amazing thing wasn't the fact that he makes his own engines (that's impressive), or that he makes fuel tanks out of balsa (amazing, impressive, and even sensible when you think about it), but that his girlfriend helps him assemble engines.  Now that's impressive (and she's a keeper).

Back to one of your original questions: it looks like you are using Stay-Brite, which is the solder of choice.

I use a heavy duty Weller solder gun. It's, I think, 300W. Works pretty well, but I also have a backup soldering iron if needed. The old big stick type.

This 80 watt Weller was recommended on either SSW or SH forums.

I got some stainless flatstock (not rolled) from McMaster-Carr that looks like the cat's PJ's, but haven't tried it yet. You need to use Stay-Brite low temp silver solder, and I couldn't find any around here. Not at the LHS, McLendon's, or Fry's. I did not try Radio Shack, but doubt if they'd carry it. Finally scored some at Tower Hobby. When I get a tank made, I'll let ya know how the "stanley steel" works out. Charlie Martin made his F1C tanks out of stainless shimstock of some sort, and used Stay-Brite. Looked very neat. 

The Stay-Brite flux is highly corrosive, so I may use a substitute. I'm also pondering a neutralizer that would be more stout than baking soda. Maybe lye? Other ideas would be very welcome, no lye! (pun intended).  Steve 

What's the life expectancy of a carbon fuel tank? Or a balsa one/

Most likely until it starts leaking Randy,,

I use the .022 silver bearing solder from Radio Shack. It is rosin core, and I think 2% silver. I use it for everything including tanks, and it makes beautiful joints that seem to be plenty strong. I used it on the cabane struts on my 78" biplane 25 years ago, and they are still good.

   I have made *a lot* of tanks over the recent years. As most people have mentioned, soldering is usually the downfall. The materials are not nearly as important as the technique. Even regular old 40-60 electronics solder is plenty durable enough, and unless you are using old rusty tin cans, rosin core is fine and you don't need any sort of harsh flux. Some of the milder plumbing flux can help in tough cases with some surface corrosion or loss of tin plating. I would personally make new clean parts than struggle with acid flux but it does work.

   Having the biggest, baddest soldering gun you can get certainly helps, and there is no reason to use anything like a heavy wand iron, in fact, that will probably make it harder to do. You want the hottest tip you can get but you don't need or want a lot of capacity behind it because you want only local heating. But I have seen excellent jobs done by guys with 25-watt pencil irons. You don't want to use a torch directly (although Floyd's butane-heated iron indirectly heats and works fine). A standard propane torch will evaporate the tin from the surface in seconds.

     The most important thing of all is to make sure that every bit of solder flows, and is hot enough to flow like water at some point. 40/60 will get a vaguely blue surface tone when it is hot enough and fully liquified. Done correctly it only takes a tiny amount of solder, and you can work it around over a pretty remarkable distance if it's hot enough and the seams are tight. By far the biggest problem is the tendency to glob on solder barely at the melting point without having it wet both side of the joint. There should be negligible thickness to it and only small fillets at 90 degree joints (like where the tubes go in). I have seen some instances where tubes had what looked like a volcano, I kid you not, a 3/4" diameter cone built up around the base of it, that despite using about an ounce of solder, still leaked. Solder has to flow *like water*, if it will stand on its own in a clump, it's not hot enough.

    The converse also happens - if you get it too hot, like with a torch, you will evaporate all the tin and then you will get beads of solder. Same thing will happen if the surface is not clean, or not compatible. If that happens, then you are essentially compelled to use an acid flux. Start with the mild stuff and if that doesn't work, then work you way up . The flux that comes with the little Sta-Brite kits is about the strongest you can get and it will easily solder to stainless steel and chrome, but it will also corrode anything it touches severely. I have done some repair jobs where I ate away half the tip of my 350 watt Weller gun in about 10 minutes with Sta-Brite flux. But it did clean it up to get good flow. As near as I can tell, you can't really entirely remove it so its its just a matter of time before whatever it is corrodes. I usually prefer to make a new tank part than use Sta-Brite flux.

 After soldering the only other really key is cleaning it out.  Most of the design features are just another argument waiting to happen but it's also not that important.

      I will be making some tanks soon so maybe I will document the process.


    Brett

    

I couldn't find my Stay-Brite flux recently, so I used Nokorode Tinner's Fluid, which worked a treat.  Nokorode Tinner's Fluid may be extinct, but the label says it's HCl and zinc chloride. 

I thought they'd get soggy after awhile.  They do if you use the wrong resin.  Dave Fitzgerald had many flights on his, which convinced me to try it.  It's the bees' knees if your plane is nose-heavy.

    In both WWI & WWII and early on in the Korean War, there were Paper & Wood Disposable Gas Tanks for fighter planes and some of the smaller light bombers.    

One final thought.  Never use brass!  I once made a tank from brass shim stock because I didn't have any tin plate.  It repeatedly cracked at the corners!

  My dad made all of his tanks from shim stock. They all cracked eventually. I have made a few 1/2A tanks with it and they stayed together but I sure wouldn't count on it.

   I also made one from aluminum (welded with the eutectic welding rod they were selling at the 96 NATs) but that was *in no way* worth the effort.

   Brett

   I also made one from aluminum (welded with the eutectic welding rod they were selling at the 96 NATs) but that was *in no way* worth the effort.

   Brett
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 Brett,

 What was the main problem? I've thought about trying to make an aluminium tank, just for curiosity. I have great experience of brazing with Castolin Eutectic #190 and see no reason why it would not work.

 Lauri

 Aha, I understand. But that's only a tool problem. The castolin stuff that I have is about 1/16" dia. And it's quite malleable so perhaps I can pull it even thinner.
 The biggest problem with aluminium is to keep the temperature up and even. Also, the melting temperature of aluminium is not far from the melting point of the braze. Aluminium shows very little warning signs before melting (no glow), for this reason you must use correct flux that indicates the correct temperature. But yeah, I believe you that it's not easy.
 Another possibility is to assemble the tank together with solder & flux and then put the whole thing into oven. And to wait what happens. I've done it with simple thin-walled parts. L

My butane-powered portable soldering gun is made by W.L. LENK.  I bought it to take to the Tucson VSC after trouble the previous year at Tucson.  In the spark ignition event, two flyers had broken wiring in their planes ()I was one of them).  We jury-rigged back into operation, but a portable soldering iron would have been ideal.

Floyd