P-51 fuselage fuel tank

[ThomasP]

Does anyone know what form of construction was used for the 85 USgal fuel tank - ie aluminum tank with SS outer shell, or maybe total non-metal except for fittings, etc?

 

[MiTasol]

Hi,

I feel that the handling described in the Eglin test report 4-43-23-1 is much more complicated than the illustrations and text in Horkey's information that you posted.

Eng

Language is always changing/evolving so there is also the possibility that terminology/definitions have changed over the years as the phenomena became better understood. Add to that even things that an individual fully understands and writes about in what they consider obvious language does not mean that another person will comprehend, let alone fully understand, what the that person has written - especially some 80 years later. Add to that prior to ww2 and television what a word or phrase meant is New York was often different in LA, let alone London or Sydney because of linguistic isolation.

 

[MiTasol]

Does anyone know what form of construction was used for the 85 USgal fuel tank - ie aluminum tank with SS outer shell, or maybe total non-metal except for fittings, etc?

All the WW2 metal tanks I have seen are either alloy frame with mild steel casing riveted and then soldered to become leak proof (Ki-43) or 100% what appears to be auto body steel with the steel "frame" spot welded to the top half shell then the bottom half shell seam spot welded to the upper shell.

I know some P-39 tanks and the A6M tanks were 100% alloy except for the attachment hardware.

USAAF TO 01-3-46 identifies the steel as Terneplate which is not a material I had ever heard of. The dictionary description is terneplate, steel sheet with a coating of terne metal, an alloy of lead and tin applied by dipping the steel in molten metal. The alloy has a dull appearance resulting from the high lead content. The composition of terne metal ranges from 50–50 mixtures of lead and tin to as low as 12 percent tin and 88 percent lead. The tin serves to wet the steel, making possible the union of lead and iron, which would otherwise not alloy. Terneplate is made by a process similar to galvanizing or tinplating—i.e., by dipping the sheets into a series of heated baths, the first of a zinc chloride flux, followed by the molten terne metal, and finally one of palm oil. Terneplate has the strength and formability of steel and the noncorrosive surface and solderability of terne metal. While it is still used for roofing, gutters and downspouts, and casket linings and in the manufacture of gasoline tanks for automobiles, oil cans, and containers for paints, solvents, resins, and so on, it has largely been replaced by other, more durable steel products that are easier to manufacture.

Remember the prime requirement once the USAAF decided that drops were needed was the use of non critical materials and this was a common material of the day.

 

[MiTasol]

I should have added that other tanks are listed in TO 01-3-46 as terneplate low carbon steel, fibre, low carbon steel sheet, "plywood or aluminum".

There have been mentions in older documents of paper tanks which I think probably means paper reinforced bakelite - the same stuff the Spitfire instrument panel is made from.

Fibre probably means fibre reinforced bakelite.

Both are better known as versions of Micarta.

 

[Engineman]

Does anyone know what form of construction was used for the 85 USgal fuel tank - ie aluminum tank with SS outer shell, or maybe total non-metal except for fittings, etc?

In Bill's great book, P-51B MUSTANG, he writes that the prototype 85gal internal fuselage tank was metal. The production tanks are described as self-sealing Firestone constructed tanks.
Generally, self-sealing fuel tanks have a layer of soft rubber covering that swells and helps stop leaks from a bullet size hole. A better description of the specific "Firestone" construction
might be available somewhere?

Eng

 

[drgondog]

IIRC - the Firestone (and Goodyear) self sealing tanks are flexible - had to be to install as kits per FSB-73-90. The production tanks were laminated for strength. That said I do not recall whether the baffle was of the same material as the tank itself.

The prototype was welded steel, non-sealing, with very similar outside dimensions, but 90gal capacity..

 

[drgondog]

Well, I think Bill is commenting on changes that added weight that moved the C of G rearwards and compromised handling, which then caused the extra modification of the controls, which made the control forces heavier, which makes the general handling characteristics less pleasing.

Eng

On these examples, no to CG effect, Yes to 'compromised handling'. The modifications restricted the ease of roll and rudder authority. They were driven by challenges experienced due to yaw issues encountered (i.e. throttle changes, high speed rudder input during sideslip or terminal dive trying to reduce drift/Hunt to right with left rudder input) which occasionally led to failure of horizontal or vertical stabilizer and subsequent empennage attach failures.

The DF improved vortex flows over the empennage which increased differential loads (vertical and side) over the empennage. The reverse rudder boost lessened rudder input from pilot at higher speeds, lessening the compound effect of vortex with rudder control surface input.