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Steel as a homebuilt material ?

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Speedboat100

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I have been checking out the options for along lasting efficient wind turbine and in the wake of Elon Musk found out that 0.02 mm steel sheet is 30% lighter than a 3 mm plywood would have been....as a blade/wing covering.

Could it be used in a homebuilt ?

Has it already been used ?
 

Riggerrob

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Steel tubing is routinely used in homebuilt welded fuselages.
Sheet stainless steel is much rarer in airplane construction. Back during the 1930s, both Budd and Fleetwings built a few airplanes from sheet stainless steel, shot-welded.
Budd was primarily in the business of building railroad cars and developed several new construction methods. One invention was shot-welding ... sort of like spot welding, but timing was critical to avoid changing the temperature of stainless steel. Most tof the related patents are about super-precise electrical timers.
The first Budd airplane was a copy of a fabric-covered, Italian, light, flying-boat. It sat - un covered - outside a Philadelphia museum for 40 or more years. Budd's second stainless steel airplane was the Conestoga military transport. Conestoga introduced many innovations like stainless steel, tricycle landing gear and a rear cargo ramp. Budd Conestoga competed directly with Douglas DC-1, but with only 40 built, Budd never had the time to perfect the design to compete with Douglas' DC-3.

That paper-thin Chinese steel looks good for honeycomb structures. MInd you, glued honeycomb requires sterile, precisely-controlled factory conditions and tooling. A few kit planes (e.g. Jim Bede) include aluminum honeycomb sandwich panels, but those panels were factory fabricated with homebuilders only gluing one panel to another with fancy adhesives, aluminum strips and a few rivets. Pop-rivets were primarily to clamp sheets together until glue dried.

Perhaps the next innovation involves corrugated stainless steel sheets shot-welded together with a flat skin welded on the outside (see Shorts Skyvan).
 

wsimpso1

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I do not know of any. Probably pretty good reasons why not.

Any material can be used. Does the product benefit from it. Depending upon the airplane, we may only have steel tubes in the stick and rudder mechanisms or the fuselage and tail feathers may be primarily steel tube with fabric covering.

Using it as an airfoil skin seems to be trouble. There are several criteria: Skins deform with the spar set until you reach critical loads for buckling/crippling. Really thin steel, like aluminum and composite skins must either buckle in a safe manner (no permanent deformation) or not buckle; They must also carry airloads to the to the underlying structure without yielding; then they have to attach to the underlying structure.

If all of these will work, terrific. Then all you have to do is be able to get it built, test it, assemble it, and fly it. I would post a guard at an airshow. Somebody ( air show morons) will touch it, then press on it. Or try to use it as a writing desk. Or set a squalling toddler on it.

The big issue with many materials is we are frequently limited to some minimum gage for the outside surfaces of the airplane - you just can not succeed in building, flying, and showing the airplane unless that skins are some minimum thickness. If all it had to do was fly, it could be much lighter. But it has to be substantial enough for the rest of the scenarios it will see. Bending stiffness dominates this issue, which goes with E and t cubed. For same yield strength, steel can not really be less than 70% the thickness of aluminum, yet it is almost 3 times the density, so it will clearly be heavy at any minimum gage.

Billski
 

Dan Thomas

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I have been checking out the options for along lasting efficient wind turbine and in the wake of Elon Musk found out that 0.02 mm steel sheet is 30% lighter than a 3 mm plywood would have been....as a blade/wing covering.

Could it be used in a homebuilt ?

Has it already been used ?
3mm is 1/8" thick plywood, and I don't think many homebuilts would have skins that thick. 1.5mm is more common, so there goes the weight savings.

Depending on the stainless grade, the tensile strength might not be there either. For instance, type 304 has an ultimate tensile strength of 51,500 psi, yield strength of 20,500 psi and 40% elongation in 2”. (From 304|316 Stainless Steel Sheet) That's pretty low, and pretty soft stuff. I long ago did some testing of 1.5mm Baltic birch ply and came up with a tensile as high as 25,400 psi. with almost no difference between yield and ultimate. A 1" wide strip of 1.5mm birch took 1500 pounds of pull before it broke; a 1" wide strip of .02mm 304 stainless would take 16 pounds before it started stretching and would break at 40 pounds. It would likely just rip loose from rivets, like paper.

Stainless 316 has a tensile strength 80,000psi and elongation is 50%. A 1" wide strip of .02mm of that would break at 63 pounds, after stretching 50%. Sounds more like Spandex to me.

Wood is hard to beat for strength vs. weight. Its chief drawback is decay. Aluminum is a far better compromise.
 

cheapracer

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Many Russian fighter jets were/are made from stainless, 400 series, which is a bit like Chrome Moly.

I still hold it in my mind that there is a possibility for a 40 to 50% perforated metal with a fabric covering.
 

Speedboat100

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Standing ovation for the replies !

Well what if you make it 0.04 mm thick...then you don't have to paint it...like you have to paint plywood....and it remains the same weight ?

Any difference ?
 

Dan Thomas

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Standing ovation for the replies !

Well what if you make it 0.04 mm thick...then you don't have to paint it...like you have to paint plywood....and it remains the same weight ?

Any difference ?
Doubling the thickness doubles a very low strength. Don't see the point. 0.04mm is 1/635 of an inch, or .00157". A sheet of printer paper is around .003"", or twice as thick. Does that put it into perspective? It's essentially stainless tinfoil.
 

Speedboat100

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Well seems like these options have been checked before......there is little if no substitute for aluminium ?
 

Mad MAC

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Depending on the stainless grade, the tensile strength might not be there either. For instance, type 304 has an ultimate tensile strength of 51,500 psi, yield strength of 20,500 psi and 40% elongation in 2”. (From 304|316 Stainless Steel Sheet) That's pretty low, and pretty soft stuff. I long ago did some testing of 1.5mm Baltic birch ply and came up with a tensile as high as 25,400 psi. with almost no difference between yield and ultimate. A 1" wide strip of 1.5mm birch took 1500 pounds of pull before it broke; a 1" wide strip of .02mm 304 stainless would take 16 pounds before it started stretching and would break at 40 pounds. It would likely just rip loose from rivets, like paper.
With stainless its all about the degree of cold working, the above figures are not for full hard, full hard 301 & 304 are about 175 ksi.

Having ran the numbers for a 301 full hard, 0.015" thick dumbbell spar verse the standard extruded cub spar, it comes out about 7% lighter but also carries a 27% reduction in stiffness. So if you are designing a wing that doesn't require great bending stiffness, such as a biplane wing it could be worth looking at (which is funnny as they went out of fastion the same time as biplanes largely).

Note:
the above thickness used is a commercially available grade.
the calculation assumed crippling critical, also there isn't a lot of crippling methods for SS compared to Aluminum.
I used a Cub spar because it was the closest drawing of a spar to what I was considering.
Yes making it in full hard would be an issue.
 

Speedboat100

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Titanium...how does that compare with steel in price ?

Musk says steel is 50 x cheaper than carbon.
 

wktaylor

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Geeez guyz… units are everything... I work with the French AF... and in#-to-SI unit translations are important.

0.02mm = 0.0008-inch = very thin foil
0.20mm = 0.008-inch = thick foil
FOIL ONLY comes in annealed [SHT] and has no buckling resistance

By the way... 3xx series CRES sheet can be acquired in various Hardness/tensile strengths... from MMPDS [replaced MIL-HDBK-5]
H= function of strain hardening

304(typ) // FTu-KSI // FTy-KSI // %-elong@FTu/break
A[SHT] // 73 // 30 // 40 dead-soft
1/4H // 124 // 69 // 25 easy to cut
1/2H // 141 // 93 // 18 easy to cut with effort
3/4H // 157 // 118 // 12 tough to cut without power-tools
H [full] // 174 // 137 // 9 VERY tough to cut, even with power-tools
 
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