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Old Jan 26, 2013, 02:48 PM
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external tank materials help

Ok i got another question for the experts

I appears as the plane im building will need an external tank, the space where it will fit is tight, so once its in there.. its in there for good.

What is the best material to make a tank with? weight being an issue so it must be as light as possible.
Brass?
Tin?
Steel?
SS steel?

Obviously stainless would be best but heavy... ive built small brass and copper boilers for my steam engine before.. so soldering up a tank would be a breeze, what im concerned with is corrosion, ive read and heard different things about brass and tin...

How will they hold up over time to glow fuel?

Ive thought about using a visine bottle for a tank.. but it does not fit in the space...

Provided is a crude ms paint sketch of what i have in mind...

Tips, suggestions, all greatly appreciated
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Old Jan 26, 2013, 05:53 PM
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Time/age isn't really an issue.
If you fly it it will eventually be a writeoff.
If you don't fly it, it doesn't matter.. does it?
Stuff a balloon in there and replace it after a dozen flights.. simple and effective :-)
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Old Jan 27, 2013, 01:54 AM
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My oldest plane is about 30 years, so you do want to consider the life-time of the tank...

Both Brass and tin works. The corrosion is not a very big problem, as it is very slow, just empty the tank at the end of the day. If there is fuel left in the tank and you don't use it for 5-6 years then you'll get some green mush from brass, but with regular usage and not leaving any fuel in the tank it is fine. I've made mine more pointy at bottom, where the pick up is, to make sure that all off the fuel will get out.

You can also make tanks out of plastic containers, like film canisters. The silicon fuel lines will seal well if you have a snug fit in the plastic.
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Old Jan 27, 2013, 02:43 AM
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Quote:
Originally Posted by surfer_kris View Post
My oldest plane is about 30 years, so you do want to consider the life-time of the tank...

Both Brass and tin works. The corrosion is not a very big problem, as it is very slow, just empty the tank at the end of the day. If there is fuel left in the tank and you don't use it for 5-6 years then you'll get some green mush from brass, but with regular usage and not leaving any fuel in the tank it is fine. I've made mine more pointy at bottom, where the pick up is, to make sure that all off the fuel will get out.

You can also make tanks out of plastic containers, like film canisters. The silicon fuel lines will seal well if you have a snug fit in the plastic.
Thanks

I was going to make the tank curve down to the pick up tube, it's just a rough paint sketch....

Im well aware, of the film canister and balloon tanks, they are too big, this will be smaller than a 1/3 oz tank, for a cox 010. in a small 24 ws scale plane, the tank goes behind the firewall, with the vent and filler tubes near the windshield.

For weight reasons i thought about using, 005 brass for the tank.. too thin? will it corrode through fast?, got some 010 brass also... but heavier..
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Old Jan 27, 2013, 05:11 AM
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My oldest tank is made form .25 mm (.010 inch) brass and has lasted for +30 years, but I haven't tried anything thinner than that. Half the thickness is probably fine too, but the tubing and solder should to be taken into account too, and you might not gain that much (in weight) in the ready product. On the other hand it doesn't to hurt to experiment a little, it is a hobby after all.
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Old Jan 27, 2013, 03:51 PM
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Thanks. i read somewhere that certain solder (lead free silver bearing?) reacts with the nitro and will corrode... i got a few different types, so will experiment.
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Old Jan 29, 2013, 02:24 PM
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a finger from a nitrile rubber glove makes a long lasting balloon tank in just about any size you want.
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Old Feb 18, 2013, 11:30 PM
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Have been playing around making tanks, it seems the corners wont seal, no matter what i do, i built a custom aluminum tank, that was a perfect fit, but kept getting pin hole leaks at the corners, all corners overlap, and every thing is tight, after 6 hours of trying to get it airtight, i gave up and lost my temper.

I may try it again i have a few ideas.. but.. Im now thinking of heat molding my own plastic tank using a 2 piece male/female mold..., i decided to stay away from brass and tin, as they do corrode.

Too much work for a tiny tank.


Zagnut... the front of the fuse will be sheeted, once the tank is in there, its never coming out, so a balloon is unacceptable. There will be no access to the area.
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Old Feb 19, 2013, 10:49 AM
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Tin and brass have been standard tank materials since the dawn of time. I wouldn't worry too much about corrosion. Check out this thread where Al Rabe (world class control line builder and flyer) shows how he builds his tanks.
http://www.clstunt.com/htdocs/dc/dcb...opic_id=314440

If you can mold one out of plastic more easily, then by all means do that,

Jim
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Old Feb 19, 2013, 01:14 PM
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Thanks for the link.

Molding one would not be easier, but will last forever, im surprised nobody makes aluminum tanks, lighter than brass and tin, not too hard to build, using aluminum brazing rods.
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Old Feb 20, 2013, 09:59 PM
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Well i gave up and went with brass im running out of time for this project. If it corrodes so be it.

Very easy to do in brass, i used 005, aluminum pickup/vent/filler tubes and my soldering iron, first attempt came out airtight, fits great in its space, slightly 3 times the capacity of the stock cox 010 tank.

There is a dip in the tank where the pickup tube is located, as previously discussed.

Thanks to everyone for your help
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Old Feb 21, 2013, 12:37 AM
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Here is a tank that I made some 30 years ago, it is still fine in terms of sealing;
(it is lying donw in the image but was postitioned vertically in the plane, pickup tube is at the pointy bit)
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Old Feb 21, 2013, 01:03 AM
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Quote:
Originally Posted by surfer_kris View Post
Here is a tank that I made some 30 years ago, it is still fine in terms of sealing;
(it is lying donw in the image but was postitioned vertically in the plane, pickup tube is at the pointy bit)
You used 010 brass for that one correct?

I made a few aluminum tanks. but could never get them air tight, soldering and brazing, it just doesnt flow as good as ol fashioned plumbing solder.

Glad to hear your tank has held up for so many years.

I dont have much time left for this project, so i thought screw it, just get it done, the experts know better

Thanks for your help, i much appreciate it.

Heliman420
AKA mx862 on CEF
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Old Mar 01, 2013, 12:15 AM
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Methinks you may have problems with fuel feed due to the fuel sloshing around in that wide tank.
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Old Mar 01, 2013, 10:49 PM
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Thats what im afraid off, i tested the tank and tilted my test stand back and forth side to side, engine ran fine, the tank had a gradual dip in the bottom, with the pick up tube in the center of it, hard to see on the pics.

This is for a cessna, i wont be doing any "maneuvers" with it...

Will find out soon enough... i have doubts it will even get of the ground
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