Steel in aircraft construction, 1935-45?

[tomo pauk]

Not everyone was swimming in the light alloys in that time, people were trying to make aircraft from steel tubing, wood and canvas (in different %-age, of course). My question - how much - as percentage of weight - steel can be used in making of 1st line combat aircraft of the specified era before the weight penalty kicks in?

FWIW, the suggested steel wing for the Ta 152C:

 

[Howard Gibson]

Not everyone was swimming in the light alloys in that time, people were trying to make aircraft from steel tubing, wood and canvas (in different %-age, of course). My question - how much - as percentage of weight - steel can be used in making of 1st line combat aircraft of the specified era before the weight penalty kicks in?

FWIW, the suggested steel wing for the Ta 152C:

View attachment 853085

The Martin Baker MB5's frame was steel tube. The aircraft was a state of the art superprop.

Steel has three times the elastic modulus and three times the density of aluminum. Steel alloys suitable for aircraft space frames are stronger than available aluminum alloys. If your structure is a truss with members loaded only in tension and compression, the two materials will have the same rigidity. A truss member loaded in compression, and any monocoque structure of a given weight, will fail in buckling, which puts the smaller, thinner steel sections at a disadvantage . Steel is more weldable than aluminum, especially if it has to be high strength, although a lot of truss frames were screwed together. For any cantilever structure of a given weight, aluminium will be stiffer and stronger.

A steel tube structure probably will be covered by fabric, which will balloon out at extreme speeds.

Given that aluminium monocoque was state of the art during World War II, we have to ask why we would do anything else.

The original Hawker Hurricanes were perceived as monoplane Furys, and designed with Hawker's traditional steel tube fuselage. The original wings were a composite steel and aluminium structure covered in fabric, but this was quickly replaced by aluminium monocoque. Hawker was reluctant to start using new fabrication technologies. A lot more Hurricanes were ready for the Battle of Britain than Spitfires, so maybe they made a good call.

The original Junkers monoplanes of World War I were made from steel sheet. They switched to aluminium pretty quickly.

Lots of other WWII monoplanes stuck with traditional structures. The Moraine Saulnier 406 fuselage was a truss structure of steel, aluminium and elektron, all covered by fabric. The wings contained some parts in stainless steel, and they were covered in Plymax, described as a composite of plywood, covered on both sides by thin metal, aluminium in the case of the M.S.406. My references don't say what kind of plywood. You can still buy panel sections of balsa with metal coverings on either side. The Russians were building all-aluminium aircraft prior to the war, but their single-engined fighters were mostly plywood, with the Yaks using steel tube frames. Again, they probably were not willing to re-tool factories and retrain workers. The steel-tube fuselage Yak3s were superprops at low altitude. The limitations on these aircraft were engines rather than steel structure. The Russians switched to aluminium monocoque after the war.

The Japanese experimented with wooden structures. All their front-line combat aircraft in production and combat, were aluminium monocoque. Aluminium must have been dear to them, but they managed. I am not aware of steel structure.

The Germans were recycling crashed allied bombers, so they were not running out of aluminium. Perhaps the Ta152H's high aspect ratio wings required higher strength material. Judging from the technical descriptions I am reading, their wings had quite a fancy structure. Making long, skinny wings fully aerobatic must have been interesting.

 

[EwenS]

The Armstrong Whitworth Albemarle used a steel tube frame covered with wood. 602 built in WW2

Armstrong Whitworth Albemarle - Wikipedia

en.wikipedia.org

 

[Shortround6]

Steel was often used for high stress areas like landing gear attachments, spar reinforcement, wing to fuselage attachments.
The weight for strength ratio could favor steel.
Steel was not good in large areas that did not require great strength.
Both materials had different alloys that had different properties so sometimes a shortage of a particular alloying element might make a difference.
There may not have been one answer. Using Steel did not work for the US in transports but transports are not built to high load factors so a heavy structure cuts into the payload. A fighter with a high load factor and skinny wing might want to use Steel. Strength of a wing is not only the materials but the thickness and cord dimensions.

 

[Howard Gibson]

There may not have been one answer. Using Steel did not work for the US in transports but transports are not built to high load factors so a heavy structure cuts into the payload. A fighter with a high load factor and skinny wing might want to use Steel. Strength of a wing is not only the materials but the thickness and cord dimensions.

I am sure the Focke Wulf Ta152H's wing configuration was based on aerodynamic requirements. The structural designers just had to cope.

It is easier to make a thick wing rigid and strong. Early monoplanes had thick wings. This Junkers G38 is a bit extreme, but lots of British aircraft had thick wings too.

 

[MikeMeech]

Hi
For those that are interested in the materials of the period here are some details, first from 'Metal Aircraft Construction' by M Langley (Third Edition, Revised and Enlarged 1937), discussion on 'Steel':

From 'Materials of Aircraft Construction' by F T Hill (Fourth and Revised Edition 1940), some data tables of material specifications in use, for comparison:

All based on the knowledge of materials at the time. Hopefully of interest to some.

Mike

 

[SaparotRob]

I can't wait to drop Eutectiferous in conversation!

 

[bf109xxl]

My question - how much - as percentage of weight - steel can be used in making of 1st line combat aircraft of the specified era before the weight penalty kicks in?

It depends on your definition of "1st line combat aircraft".
40%

 

[cammerjeff]

Maybe not combat aircraft, but I would Compare the performance of the Douglas DC-5, and the Budd Conestoga. It the closest apples to apples comparison I can think of. They are similar in size, and engine power and configuration. Granted the Budd was larger overall, but also had more Power available. It may give an Idea about how the steel construction effects payload, speed, and range.

Douglas DC-5 - Wikipedia

en.wikipedia.org

Budd RB Conestoga - Wikipedia

en.wikipedia.org

 

[cammerjeff]

Or for singled engined A/C how about comparing the North American BT-9 or Vultee BT-13 with the Fleetwing BT-1? Again not combat A/C but similar types, and configuration, and engines.

North American BT-9 - Wikipedia

en.wikipedia.org

Vultee BT-13 Valiant - Wikipedia

en.wikipedia.org

Fleetwings BT-12 Sophomore - Wikipedia

en.wikipedia.org

 

[bf109xxl]

The production of the airframe for Yak fighters consumed ~115 kg of steel and ~233 m of steel tubes, a meter of which weighs approximately 1.35-1.5 kg. I don't know exactly what the final weight of steel in the structure was, but I guess it exceeded 350 kg.

 

[tomo pauk]

Maybe not combat aircraft, but I would Compare the performance of the Douglas DC-5, and the Budd Conestoga. It the closest apples to apples comparison I can think of. They are similar in size, and engine power and configuration. Granted the Budd was larger overall, but also had more Power available. It may give an Idea about how the steel construction effects payload, speed, and range.

Douglas DC-5 - Wikipedia

en.wikipedia.org

Budd RB Conestoga - Wikipedia

en.wikipedia.org

Seems like a capable transport to me, the Conestoga. Compared with the Bristol Bombay, with 11.5k lb of difference between the empty and loaded weight for the former and 7.4k lb for the later.
SAC sheet: Conestoga

Luftwaffe transport command might've just sat down and weep, with their Ju-52s
On a related note, Arado was trying to pitch the 'simplified transport aircraft' types to the Luftwaffe, that would've been using just ~5% of light alloys (a 2-engined type) and ~6% (a 4-engined type) - a major change vs. the Ar-432 that used 27% of light alloys. Steel was to comprise ~25% of the weight (I reckon that is for the structural members - doh), while wood was to be at 50-60%.
Another aircraft to feature steel as the very important building material was the B&V P.211.02 jet fighter, where the steel elements were used as the base of the aircraft structure.

 

[MikeMeech]

Seems like a capable transport to me, the Conestoga. Compared with the Bristol Bombay, with 11.5k lb of difference between the empty and loaded weight for the former and 7.4k lb for the later.
SAC sheet: Conestoga

Hi
A bit of a strange comparison, the Bristol Bombay, first flight 23 June 1935, and Budd Conestoga, 31 October 1943? If you want to stick to a Bristol product a closer design to the Conestoga would be the Bristol 170, first flight 2 December 1945. For the Mk.I & II the difference between Empty and all-up weight, 23,500/36,500 lb, is 13,000 lb.

Mike

 

[MikeMeech]

Hi
Aircraft designers and manufacturers had thought about and even built 'metal' aircraft from the early days of aviation. The merits of using 'steel' and/or 'aluminium' alloys had also been thought about. Here is Sydney Camm's view on the subject from his 'Aeroplane Construction - A Handbook on the various Methods and Details of Construction Employed in the Building of Aeroplanes' published in 1919 but written during WW1:

Mike

 

[tomo pauk]

Hi
A bit of a strange comparison, the Bristol Bombay, first flight 23 June 1935, and Budd Conestoga, 31 October 1943? If you want to stick to a Bristol product a closer design to the Conestoga would be the Bristol 170, first flight 2 December 1945. For the Mk.I & II the difference between Empty and all-up weight, 23,500/36,500 lb, is 13,000 lb.

Mike

Conestoga gained 60% of the difference between empty and gross weight vs. the Bombay, for 20% more power.
The 170 gained over the Conestoga 15% of the difference in the empty and gross weight, for 65% of more power.

BTW - seems like the Harrow was a better bet than the Bombay, achieving 9.7k lb, despite having a bit worse engines than the Bombay.

 

[MIflyer]

TAAAAADAAAAAA! I give you:

The Budd RB-1 Conestoga, made out of spotwelded Stainless Steel! Designed in WW2 to overcome a feared shortage of Aluminum. The USN ordered 200; the USAAF ordered 600, designated C-93.

 

[bf109xxl]

TAAAAADAAAAAA! I give you:

The Budd RB-1 Conestoga

My question - how much - as percentage of weight - steel can be used in making of 1st line combat aircraft of the specified era before the weight penalty kicks in?

 

[MIflyer]

As for a weight penalty, the Atlas ICBM was one of the most efficient vehicles ever built in terms of mass fraction and it was made out of stainless steel. The SpaceX Starship is made out of stainless steel as well.

 

[Crimea_River]

Hawker Hurricane fuselage backbone was steel tubing

 

[tomo pauk]

Suggested steel cowling for the late marque 190Ds:



Perhaps more plausible since it was not a structural member?