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Steel aircraft spar

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cheeka

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Hey guys,

I am trying to find out if there have been aircrafts that used steel spars & so far it looks like the "Thrush" line of cropdusters are the only ones. Are there others out there? Any pictures of the spars? Is the construction similar to an aluminum wing (laminated angles and rectangular bars)? Why don't we see more of these? Aren't steel spars perfect for an aerobatic aircraft?
 

BJC

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Most aerobatic aircraft use either carbon fiber or wood spars. A few older designs use aluminum.

I don’t know of any that use steel.


BJC
 

TFF

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The Stinson Reliant is steel tubing. Steel is heavy enough that once you balance strength, complexity, and weight, it is not as good as aluminum.
 

Mad MAC

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I think some of the english pre WWII aircraft used roll formed steel spar caps. But for most GA sized aircraft the loads simply are not sufficient to warrant the sizes that give good stability in compression.
 

BBerson

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The Dyke Delta has a steel tube truss spar. Makes folding hinges easy to weld on.
The C-172 has about a 3 foot piece of steel angle in the upper cap at the strut, as I recall.
 

mcrae0104

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Why don't we see more of these?
Minimum gauge: it's tough to get shapes thin enough and small enough, especially for light planes.*

*Edit: assuming you are talking about a built-up beam as described in the OP. A truss spar might be a different animal.
 

Mad MAC

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The worst feature of the spitfire spar is that it is really easy to crush if one isn't really careful, having seen a brand new spar in a completed wing crushed when someone tried to bolt on the fake cannon.
 

Riggerrob

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The Beech 18 has a steel tube center section spanning from engine to engine.
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Yes, but Beech 18 steel spars suffered cracks.
Many of those cracks started with side-loading as WW2 student pilots learned the finer points of cross-wind landings. Beech 18 was not the easiest airplane to land!
By 1945, USAAF started noticing cracked wing spars in its AT-11 bomber trainers. Apparently AT-11s landed more often than other Beech 18 variants. The USAAF developed a steel strap to reinforce the wing Center section.
By the 1960s, the FAA made spar reinforcements mandatory. The high cost of reinforcements forced many Beech 18s into retirement. One disadvantage of reinforcing straps is they require drilling dozens of screw-holes in the original spar. Fifty years later, some of those holes have admitted enough water to rust out the original spars.
 

DaveD

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For metal parts in compression stability is more important than strength... they will fail due to buckling not compressive failure of the material itself. For buckling, shape and cross sectional area are the critical properties, even for heavily loaded components like spars, the thicker cross sections required for stability tends to push the design towards Aluminium.

Even if you compare on a purely material "strength to weight ratio" (specific strength) basis 6061-T6 will outperform most steels (taking a very crude example - Steel is 2.9 times more dense than Aluminium but only twice as strong)
 

wsimpso1

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Meyers 200 center section is a steel tube truss. It is hanging the retractable main gear, the outer wing panels, the flap and retract actuators, and a bunch of other stuff.

Billski
 

Pops

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If I remember correctly, the Piper Aztex has a steel tube truss wing spar in the fuselage center section and a steel tube cage around the cockpit.

The Russian Yak-3 also had a steel truss tube spar in the fuselage.
 

pictsidhe

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I believe that all the German built Hortens used wood spars in the wings, with a steel tube fuselage. Not sure if that counts as a spar, though?
 

TFF

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All steel tube spar center really does is make a no material change or attachment until outside the fuselage. It's more about manufacturing. I think full spars is reall more accurate for the discussion.
 

cheeka

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Thanks a ton for the replies, the Stinson is pretty unique with its welded steel tube wing structure. What about fighter jets? What are the Migs made out of?
 
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