Metal fuel tank materials?

[MIflyer]

The C-131/T-29 was designed with "wet" wings rather than fuel cells. The airplane seemed like a good choice for a gunship, being plentiful, currently supported, newer, and much more powerful than the C-47. But they discovered that the gunfire vibration caused leaks in the wet wings and so the AC-47 became the gunship rather than the AC-131.

 

[MiTasol]

I watched a friend of mine putting a new bladder in a Bonanza wing.

I looked at the size of the bladder and the size of the holes and said, "You have GOT to be kidding me!" It looked like you were trying to stuff a football into a test tube. But it went in.

And the Bonanza bladders are only a few mm thick though admittedly the access for the P-39 tanks is great. For the hose clamps access is a totally different story though.

 

[Shortround6]

And the Bonanza bladders are only a few mm thick though admittedly the access for the P-39 tanks is great.

Bonanza bladders aren't meant to seal up bullet holes from high power rifles....
Unless you are flying somewhere really strange

 

[MiTasol]

agreed but the OP was discussing ww2 vintage fuel tanks as their question was Were the shells of most ww2 era internal fuel tanks made of carbon steel? so that is the context I replied to.

 

[MIflyer]

The Ercoupes built right after the end of the war used "ternplate" which was steel covered with solder to make them easier to seal. They then went to Stainless Steel and then finally standardized on aluminum for the later models.

The P-38 drop tanks made in WWII were made from steel. There is a article I posted elsewhere here that described their manufacture.

 

[MiTasol]

agreed but the OP was discussing ww2 vintage fuel tanks

The Ercoupes built right after the end of the war used "ternplate" which was steel covered with solder to make them easier to seal. They then went to Stainless Steel and then finally standardized on aluminum for the later models.

The P-38 drop tanks made in WWII were made from steel. There is a article I posted elsewhere here that described their manufacture.

Most drop tanks were steel or composite as there was no sense in wasting strategic materials on something that was probably going to be "donated to the enemy"

 

[sotaro]

To give an idea of volumn loss, take a sheetmetal box (of any size) and line it (sides, bottom, etc.) with 3/8" (10mm) plywood.
10mm is a minimum, the sealing material could be as thick as 1/2" (13mm) depending on the time, material and nation.

You'll find that the internal volumn of your box decreases quickly. You'll also find that the empty weight of your box has suddenly increased in weight considerably, too.

A cube is the optimal rectilinear shape for minimal surface to volume area. 20" x 20" x 20" equals 8,000 cubic inches. If the self sealing wall thickness is 1/2" for ease of calculation, the interior volume is 6,859 cubic inches, or 86% of the external volume. All those little tanks would get heavy and small.

 

[MiTasol]

Looking at the P-39 blueprints the hole the #4 tank fits in is 14.25 inches wide and the tank is less than 24" long and probably under 10" high at the deepest point. For more information to Library Drawings: 14-139-174 | AirCorps Library

Because these were subcontracted there is not much other info on the drawing but if you work on that tank being 12" x 24" by 9.5" you will have close to the true volume. Likewise using a 1/2 wall thickness will give an approximate internal volume of 11x23x8.5 so you can see that the lining significantly reduces the internal volume. On the P-40 tank in my earlier post the wall thickness is typically around 3/4 inch but that is a much larger tank so the % of volume lost is far less.

 

[RichardSuhkoi]

To give an idea of volumn loss, take a sheetmetal box (of any size) and line it (sides, bottom, etc.) with 3/8" (10mm) plywood.
10mm is a minimum, the sealing material could be as thick as 1/2" (13mm) depending on the time, material and nation.

You'll find that the internal volumn of your box decreases quickly. You'll also find that the empty weight of your box has suddenly increased in weight considerably, too.

But much better than burning to death

 

[RichardSuhkoi]

Many of those bladders were made by Ball Band in Mishawaka Indiana, They also made Red Ball Jets! Ball Band eventually became Uni Royal, naugahyde!!

Around 1998 I bought old inventory of a parts business and had maybe 8 bladders dated I think 1950? I think they were Goodyear. They had no cracks and I have them away and they were used as water toys. An old mechanic told me to install them there was a way to roll them coated with talcum then a sort of blower was placed and you inflated and deflated until they popped into place without a crease. Any crease would cause failure.

 

[GrauGeist]

But much better than burning to death

Self sealing tanks helped protect against rifle caliber projectiles and small fragments of AA shrapnel, not cannon rounds or large AA shrapnel (or approximate bursts).

 

[MiTasol]

Around 1998 I bought old inventory of a parts business and had maybe 8 bladders dated I think 1950? I think they were Goodyear. They had no cracks and I have them away and they were used as water toys. An old mechanic told me to install them there was a way to roll them coated with talcum then a sort of blower was placed and you inflated and deflated until they popped into place without a crease. Any crease would cause failure.

That applies to the non-"bulletproof" bladders which are made from thin material but the "bulletproof" ones are rigid and ones I took out of a P-40 in the late sixties did not even flex when a large person stood on them. Well baked in the wing in the sun for years. I do not know how flexible they were new but I would suspect not very.

 

[Greg Boeser]

The Germans made what was one of the first non-metallic bag-tanks, for the Bf109F. I.e a flexible skin of synthetic rubber and fabric housed in a metal frame to keep the shape.

Sadly for them, they found out after a while that their version of 100 octane fuel reacted to the synthetic rubber (Perduren and Perbunan) and the fuel then lost its detonation resistance,
destroying the engine. It was incredibly difficult to investigate as the reaction took from 2 to 4 weeks, so aicrcaft "just filled" showed no symptoms at all, and aircraft taken on only very short trips showed moderate symptoms as the fuel in the tank was always "slightly" degraded. It was always a problem to a certain degree as the engines were always near the knock limit, and rarely were the fuel tanks totally dry, as then you dont even make it home, so degraded residue built up.

This was also a problem with self-sealing tanks installed in early F4Fs. The inner liner would break down, clogging fuel lines and resulted in crashes. It took a while to figure out what the problem was, because most planes were not recoverable.

 

[yosimitesam]

The self sealing tanks ("bladders") often had to be "suspended", somewhat, with special connectors. This was to prevent hydraulic shock from the gasoline at the bladder walls from damaging critical parts of the plane, when impacted by a .50 cal (12.7mm) round, for example.

 

[Greg Boeser]

Martin designed the Mareng fuel cell, which was a non-rigid bladder, consisting of 1/8" vulcanized rubber outer shell, 1/8" crude rubber sealing layer, 1/8" neoprene inner layer, with a .035" neoprene fuel resistant lining, that was coated with zinc chromate. These were hung inside the wings by fasteners, and could be quickly removed for repair or replacement.

 

[GrauGeist]

Sadly, quite a few combat photos showing stricken B-24's fuel bladders blown out of the wing by flak and cannon-fire.

 

[YakMan]

The fuel tanks in our Yak C-11 and Yak-52 are rivetted aluminium for lightness. They are pressure tested when first manufactured to test the joints for leaks but only to one or two pounds per square inch. After that the tanks never see any pressure at all being permanently vented to atmosphere. The Yak-11 and C-11 are direct descendants of the WW2 Yak-3 fighter, the wing in particular is 100% Yak-3.

 

[MiTasol]

On DC-3s and a lot of other aircraft with alloy tanks they are pressure tested at regular intervals to detect cracking.

In my experience the alloy tanks in the DHC-2 Beaver are very prone to cracking as they age. I saw multiple cracked tanks in Beavers as early as 1970.

 

[MIflyer]

I saw a YAk-11 for sale at an auction held at Kermit Weeks place. A friend of mine said, "Buy that, and put an Allison on it instead of that radial and you've got a pretty good copy of a Yak-3."

 

[cvairwerks]

Both my Stinson and Fairchild use welded aluminum tanks. I've helped redo a BT-13 center section. The original sealing method was zinc chromate paste. Messy to deal with, but sometimes more forgiving than polysulfide sealants.