# 4130 Tube Steel Alternatives?

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#### rkirk77

##### Well-Known Member
What alternative steel grades can be used for building a Pietenpol Air Camper fuselage, and how would much would I have to compensate the tube thickness?

#### Dana

##### Super Moderator
Staff member
As with everything in aviation, "it depends". Each component is different. Where the limiting factor is tube compression bucklilng, it wouldn't matter as the tube's strength depends on its elasticity, not ultimate strength. For tension or bearing loads, the alloy's strength does matter and you'd have to allow for the replacement material's reduced strength.

Often, however (and I'm not saying it the case here; I don't know) older prewar designs were designed for lower strength tubing like 1025. Later, 4130 became commonly available and relatively inexpensive so manufacturers switched to that even though its extra strength may not have been necessary. The Pietenpol is an older design that may have been designed for lower grade steel but the plans you're building from may been altered later to use (and require) 4130's greater strength.

Whatever you do, it should be specified as seamless (not welded) tubing.

Dana

#### rkirk77

##### Well-Known Member
The plans call for SAE 1025.

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#### Hot Wings

##### Grumpy Cynic
HBA Supporter
Log Member
The plans call for SAE 1025.
The problem I had years ago when I too was investigating the use of this grade of steel rather than 4130 is that the only way to get a reasonable quantity was to order it through the local steel supplier. They could get it but the cost was 3 times what I could get the same size from Aircraft Spruce - including shipping!

You might have better luck in a large city?

#### rkirk77

##### Well-Known Member
My thought was to use common SAE 1020 tube.

#### Jan Olieslagers

##### Well-Known Member
I've heard rumours of tubing available in carbon fibre. One French homebuilt ultralight bases upon that stuff, and shows an impressive ratio of empty weight vs. MTOW. Some pics at L'Agrion - Imgur

#### Dana

##### Super Moderator
Staff member
The "common SAE 1020" tubing is likely welded DOM, not seamless.

Dana

#### BBerson

##### Light Plane Philosopher
HBA Supporter
My thought was to use common SAE 1020 tube.
See if you can find 1/2" .035" 1020 that is any cheaper than 4130 from Aircraft Spruce and post it here please.

#### BoKu

##### Pundit
HBA Supporter
See if you can find 1/2" .035" 1020 that is any cheaper than 4130 from Aircraft Spruce and post it here please.
Also, note that 4130 prices at Wicks Aircraft are currently a fair bit below ACSs. I saved about 20% on a big steel tubing order a few weeks ago.

But BBerson's point is a good one: The relatively high volume of trade in 4130 probably makes it less expensive than 1020, even though it is stronger.

Thanks, Bob K.

#### cheapracer

##### Well-Known Member
Log Member
1020 is fine, DOM or seamed.

The only difference it will make is if the yield is exceeded if you crash it (where DOM is superior), that's a personal choice you will have to make otherwise the actual strength of the frame isn't changed.

BTW, 4130 is very much an American affair, most race cars and off road racers for example in the rest of the world are built with 1018/1020 DOM and if the impact is enough to exceed it's yield then your chances of walking away were already well surpassed.

#### BBerson

##### Light Plane Philosopher
HBA Supporter
Race car roll cages are typical 1/8" x 1-3/4". Actually, a lower yield can be good in a crash structure.
I doubt race cars use much 1/2" x .035", however. Usually the rules require a specified size and alloy.

4130 is commonly called "alloy" and is "air hardening". That means the post weld strength is very good.
Ordinary 1020 cold rolled carbon steel (not alloy) is soft post weld.
Having said that, I would still use 1025 1/2"x .035" if I could get it. Because in most cases it doesn't matter if the post weld strength is less.

#### cheapracer

##### Well-Known Member
Log Member
Race car roll cages are typical 1/8" x 1-3/4". Actually, a lower yield can be good in a crash structure.
I doubt race cars use much 1/2" x .035", however. Usually the rules require a specified size and alloy.
Nope, go read the rules, SCCA website is the easiest. By the way, you can use 1010 DOM under FIA/SCCA rules as well.

Sports cars such as Donkervoorts and Caterhams are constructed typically from 1" x 0.040 - 0.060" seamed ERW box tube and they take a hell of a lot more pounding than any aircraft.

4130 is commonly called "alloy"
All steels are "alloy" as are most metals.

#### BBerson

##### Light Plane Philosopher
HBA Supporter
Nope, go read the rules, SCCA website is the easiest. By the way, you can use 1010 DOM under FIA/SCCA rules as well.

Sports cars such as Donkervoorts and Caterhams are constructed typically from 1" x 0.040 - 0.060" seamed ERW box tube and they take a hell of a lot more pounding than any aircraft.

All steels are "alloy" as are most metals.
Of course....

I was obviously referring to common industry use of the term. (Meaning expensive alloys)

Again, the needed 1/2"x .035" thick or less cold rolled 1020 is not readily available here. Even .035" is too thick for my aircraft.
I actually need .018" but can't find it.

I found this in the 909 page scca rule book, which confirms my comment about use of the words "alloy" and " mild steel":
TUBING
1. Seamless or DOM mild steel tubing (SAE 1020 or 1025 recom-mended) or alloy steel tubing (SAE 4130) must be used for allroll cage structures. Alloy and mild steel tubing may not bemixed. ERW tubing is not allowed.
2. The following table shows the minimum allowed tubing outerdiameter and wall thickness by vehicle weight:

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#### Turd Ferguson

##### Well-Known Member
HBA Supporter
Also, note that 4130 prices at Wicks Aircraft are currently a fair bit below ACSs. I saved about 20% on a big steel tubing order a few weeks ago.
The Chassis Shop sells 4130- 1/2" x .035" for ~$.50/ft. Compare that price to ACS or Wicks ridiculously marked up price of >$2.00/ft for the same thing. Plus the nearest outlet is a 1hr drive for me. No cutting/crating/shipping charges.

#### BJC

##### Well-Known Member
HBA Supporter
The Chassis Shop sells 4130- 1/2" x .035" for ~$.50/ft. Compare that price to ACS or Wicks ridiculously marked up price of >$2.00/ft for the same thing. Plus the nearest outlet is a 1hr drive for me. No cutting/crating/shipping charges.
This might be a different Chassis Shop, but it is priced per foot :

BJC

#### Turd Ferguson

##### Well-Known Member
HBA Supporter
This might be a different Chassis Shop, but it is priced per foot :

BJC
Never try to multitask -lol. The truck load I bought ~3 yrs ago was ~50% less that the typical "aircraft" suppliers.

#### BBerson

##### Light Plane Philosopher
HBA Supporter
This might be a different Chassis Shop, but it is priced per foot :

BJC
It is priced per INCH.
No 1/2" listed.

#### BJC

##### Well-Known Member
HBA Supporter
It is priced per INCH.
No 1/2" listed.
1/2 X 0.035 is $0.40 per foot. BJC #### BBerson ##### Light Plane Philosopher HBA Supporter 1/2 X 0.035 is$0.40 per foot.

BJC
Per inch on my screen for 4130. They don't list 1/2" tubes in DOM.

#### BJC

##### Well-Known Member
HBA Supporter
Per inch on my screen for 4130. They don't list View attachment 364781/2" tubes in DOM.
You are right - I mis-typed it. That was the purpose of my first reply, with a link (that has gone dead) to a page pricing it per foot.

Thanks for getting it straight.

BJC