On Thu, 18 Mar 2004 13:07:22 +0000, Corky Scott wrote:

The last thing I'd mention is that because 4130 is stronger and stiffer,
you can probably use tubing that is lighter than mild steel to construct
your fuselage and still have a strong fuselage. In airplanes, saving
weight is almost a formal religion. The more weight you save, the more
weight you can carry, or the better the performance or both.

Corky Scott

4130 is certainly stronger than mild steel, but the modulus of elasticity
of all steel is about 29-30 ksi, with very, very small variations
depending on alloy. So for a given tube diameter and wall thickness, the
mild steel tube and the 4130 tube will have the same stiffness. If you
increase the diameter of the mild steel tube to make up for it having a
lower strength than the 4130, then the mild steel tube will be stiffer
than the 4130 tube.

The following links show modulus of elasticity of 29 ksi for mild steel,
and 29.7 ksi for 4130 steel, or a 2.5% difference. Not really significant.

http://www.matweb.com/search/Specifi...bassnum=M1030F

http://www.matweb.com/search/Specifi...bassnum=M4130A
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