Making Custom Tanks

I asked this question in another thread but it sort of got lost I guess....was a long thread and the question was at the bottom. I noticed that a lot of the fellows are always discussing where to buy a special sized tank for this plane or that. And I was wondering why you all don't just make a tank to fit your particular problem aircraft? I have been making tanks for years, and trust me, I ain't no metal bending wizard! It started years ago for a profile plane I designed that needed a special tank that no one made....so I took an old uniflow tank apart and made one using it as a basic template. I just rough carved a peice of pine to the shape I needed and wrapped the appropriate tin around it (bought at my local LHS) It was not pretty, not even by my low standards, but it worked! My tanks still ain't too pretty but they do work and they do fit the special needs that I often design myself into. Give it a try fellow modelors, you will be surprised how easy it is.....oh yeah....did I mention cheap!? A good tip is to go to your local auto repair/painting place and ask for a couple of old paint thinner tins....they probably have a couple hundred of them laying around....and use them to build the tanks with....its perfect. And did I mention cheap?

My guess about why so many modellers don't build custom tanks is that a majority have similar problems to mine when attempting to solder the tanks together. I get the solder anywhere other than where I really want it. It is the same for me with a gun, iron, or torch. Just all thumbs with those tools!

.
Kiwi

Depending on the can you use, you may have to sand or wire buff the entire surface because some cans have a thin layer of plastic on the inner surface. This is especially true if using food containers.

You have to learn to solder!

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"Whenever you find that you are on the side of the majority, it is time to reform." -Mark Twain

Does soldiering count? I can do that.

I can sweat copper household plumbing with the best of them. I can't solder flat washers for wheel/pushrod retainers for the life of me.

>Does soldiering count? I can do that.
>
>I can sweat copper household plumbing with the best of them.
> I can't solder flat washers for wheel/pushrod retainers for
>the life of me.

OK, solder tips. When you are doing household plumbing, you are probably using a torch and you also use a good flux. Torches are not recommended for model airplane wheels and pushrod retainers, and not even for tanks. A soldering gun is amply sufficient. The hotter the better, however. The key is to get both surfaces hot so the solder wicks into the joint. If you have done household plumbing with a soldering torch, you are amply aware of that.

So, a few hints:
1) Clean the surface(s) good.
2) Use a good 60-40 (tin-lead) solder. OK, so tin is on the "bad" list these days, but for our purposes I don't think anyone is going to die of lead poising. (I haven't heard of too many mothers come running in crying, "Johnny just ate the solder off the wheels of your airplane.")
3) Use a soldering paste or flux if you are having troubles. I can usually solder the little washers without, and tanks as well just using radio (rosin core) solder, but adding a little flux isn't a bad idea.)
4) Shield what isn't being soldered from the heat. With tanks, there is nothing here that we need to worry about. Just heat up one area where you wish to start soldering and when it gets hot enough for the solder to run, apply the solder and move down the joint. With wheels or pushrods, but a piece of 400 sandpaper (facing the washer) between the wheel (or horn or belcrank) and the washer. This will not only help shield it from the heat, but will provide proper spacing and allow you to spin it a bit before tearing it off which then cleans the back side of the washer.)
5) Heat the area (wire and washer, tank stock) to be soldered, not the solder itself. This is probably the biggest "goof" that people make. They don't get the area hot enough and the solder doesn't stick.
6) If all else fails, send it to Brett Buck. (Maybe you had better check with him first. But he does a good job on these things.)

On the heat thing, there is a paste you can get at a plumbing supply called "Heat Fence" that you can apply to any area that you are concerned about getting too hot while soldering. If soldering wheels, for instance, you can put it on the back washer that is already soldered and it will prevent this joint from coming loose even if you get the front joint red hot (no, you shouldn't use a torch.) It was made for plumbing repairs where you don't want the adjacent joints to get unstuck. One tube of that stuff is a life-time supply for a whole club. Good stuff.

LAST EDITED ON Jul-24-03 AT 02:01 PM (CDT)
 
Soldering seems to be a difficult process for alot of guys. I have taught soldering for companies I've worked for and have a few tips.

1. Cleanliness; clean the areas to be joined and a good portion around them. After you have them bright and clean, clean them. Not being funny, solder will not work in the presents of oxidation of the parent metal OR the plating that might be on it. CLEAN IT BRIGHT!

2. Fluxes; there are many, but the most easily obtained and applied is common Plumbers Paste. Contrary to common belief, this paste works well on all solderable metals, including steel. It is also the easiest to clean up with a little lacquer or dope thinner. It not only keeps the metal clean when being heated, it aids in heat transfer. I use it in all of my soldering except electronics. A thin coat on the tank parts will improve the flowability of the solder tremendously. Apply AFTER CLEANING!!

3. Fits; solder is not a great gap filler though it will do some, make sure your parts fit well with a minimum of gaps.

4. The tools; I use a gun for most of my soldering including tanks. The common Weller gun has a tip that is held into the heating elements via 2 hollow jam nuts. I have found almost exclusively that people trying to use these have trouble with heating the tip. This is because the thermal cycling of use both loosens the nuts and oxidizes the tip were its supposed to make contact. Before starting to solder, loosen and snug these nuts a couple times, you'll be amazed at the difference in heating speed and transfer. This holds true for the smaller irons with removeable tips too, loosen and snug to get a good joint that will transfer heat well.

The tips (soldering end) are also a point were much difficulty arises. The most common shape with gun tips is a chisel point, some irons use this as well as a pyramid shaped tip. During the use of the gun or iron, the tip errods and will become pitted. Its odd that its normally the flats that errod while the edges tend to remain intact. Always inspect the tip before you start, if you see ANY pitting or evidence of concavity, file the tip until the surface shows only copper, apply a film of paste, heat and "tin" the tip. The solder should readily cover the surfaces, if not one of two things has occured. Either the surface wasn't clean enough, or you waited too long to apply the solder and it overheated. A good practice it to test the heat while heating by brushing the solder over the tip, when the temp is right, the solder will melt.

A damp rag or spounge are handy for wiping away burn flux and debris from the tip occasionally.

5. Soldering; now that the parts and tools are ready there is a third problem alot of folks experience, getting the solder on the parts. The first thing to do is make sure your tool is hot enough. In the case of the gun, test it as above to make sure its heated enough, DO NOT place it against the work while it heats, this will both slow down the process and cause "cold" joints. With the heat right, touch the tip to the work and the solder to the WORK, not the tool, at the tip, touching the tip is OK, but you won't know if the work is hot enough to be soldered unless you put the solder on it. When I solder I normally lead the tip with the solder along a seam with it just bearly touching the tip, you want the work to melt the solder or the joint will be bad. When soldering tubes, apply the tip to both the tank and tube simultaneously and then the solder to the join. If you cleaned and fluxed it properly and the tool is in good condition and heated properly, the solder will flow around the tube readily and "sweat" the tube into the tank. When soldering things like washers to LG axles, apply heat to the end of the wire and the solder to the wire between the tip and washer. As soon as the melt occurs, lead the molten solder down to the joint and it will flow right in.

Another thought, when soldering washers to wire, make a cardboard dam that fits snuggly to the wire. Put this on followed by the washer then solder. This will do a couple things for you, first it hold a clearance between the washer and the part the wire is being retained in, usually a wheel. Second it will slow the heat flow down the wire, third, it will help keep flux out of the wheel or bushing of the part you are retaining.

Hope this helps,

Ron B.
F4Fguy

Randy:
I was going to jump in here,but you've said it all,and better than I could have.Kudos,and Amen!

I just made my third tank this year. It is for my Demeco Continental. I take an old two by four, rip it on my table saw. Then mesure out the slightly undersize form, saw it out including the two 45 degree angles. I use the steel plate that K&S puts out and their copper tubing. Put the form in a vise and bend the first side around it. The ramaining sides will bend right to the form. Allow some over lap. The fancy indented laps like on commercial tanks aren't necessary. The ends will be the hardest parts to get just right. I always seen to make three, of which two work. Use a punch to make the holes for the tubes. This gives more soldering area for the tubing.The plumbers soldering paste is what I use, but my solder is resin core. Do as the other guys say on how to solder. After two tanks, you will be an expert. Trust me it's easy. You just have to try it. A little fore thought and it's no big deal. I'll bet the guys saying, "I can't do it", probably make beautiful planes. Well, ???

LAST EDITED ON Jul-24-03 AT 12:19 PM (CDT)
 
Great advice here! Thanks. One further question, however. After your creation is all soldered up, checked for leaks, etc., what do you use to clean the inside of the tank in order to remove residual/burned flux, etc.?
Thanks for your help.

Peter,

It depends on the flux. I use paste so lacquer or dope thinner work well. With tinners fluid and other liquid fluxes water is the cleanser to use, another reason I like paste.

Correction, clean the tank BEFORE you test it, that way any flux of resin trapped in holes will be removed. I normally run a sink full of hot water, plug all the tubes and let it soak a few minutes, then I remove a plug and pressurize the tank with a fuel bulb holding it under the water.

Alcohol will disolve most rosin based solder fluxes.

>Alcohol will disolve most rosin based solder fluxes.

Acetone seems to do a better job.

Also, check for rattles. You don't want any little globs of solder running around inside the tank waiting for that last loop of the clover to jump into your pick up tube and stop things up.

Ty reminded me when he spoke of making a mold.....don't do as I did on my first tank....solder the tank on the mold (thinking it would be easier). I left one end off figuring I could draw out the mold....no way! Like it was glued in, had to unsolder the other end and push it out! Seriousely though....I have made tanks to wrap around leading edges, fit on the motor mounts with extra fuel storage down between them. Just about any configuration can be used. Even rounding the top to fit snug under the top cowling for extra fuel, think of the possibilities. The only thing I had ever soldered before was some copper pipe...so if I can do it, anyone can. Give it a try folks, you won't be sorry you did.

I check for leaks by putting the tank in the freezer, then capping it off while cold, and then holding it under hot water in the sink. You'll get more pressure that way than you will with a syringe or squeeze bulb. Someone has pointed out that you should also suck on the tank to see if there is any leak that is closed of by inside pressure. Last two tanks I modified had no leaks. I'm getting better.

I remember Bill Calkins talking about the humongous tanks that are needed for Carrier. Something like 12 oz. on what is actually a pretty small airplane. So the tanks all have to be custom made, and have to fit in all sorts of nooks and crannies in the front of the fuselage.

Is there some product that could be used (besides Solder) to hold the tank peices together? Just curious.

>Is there some product that could be used (besides Solder) to
>hold the tank peices together? Just curious.

Well, you could probably JB Weld, but, why? Solder is going to be stronger, faster, easier to undo if you have to go back in. It just takes a little patience and learning. But, then, so does building that there airplane that the tank goes into.

Oh noooooo....you mean once I build the airplane I have to build an entire airplane to fit around it?