I'm restoring a 1946 Cessna 120 and replaced the main spar for corrosion. I'm ordering new drag wires for the wing. Univair offers stainless drag wires for all of the bays, and has an option for 4130 for bays 3 and 4.
Would you recommend the 4130 or stainless for bay 3 and 4?
Drag Wire 4130 vs SS
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elliottseiler
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Re: Drag Wire 4130 vs SS
Issue with 4130 steel is that its susceptible to rusting while stainless steel on the other hand resists rust and corrosion. Personally I wouldn’t be worried about utilizing stainless drag wires from Univair because that company has FAA/PMA approval to manufacture those parts.
On the other hand although stainless is tough, the 4130 steel drag wires will handle higher strength loads in tension. If I’m not mistaken bays 3 & 4 cover the areas where the front and rear lift struts attach. You would have greater strength with the 4130 drag wires in those areas. I would opt for the the 4130 steel drag wires in bays 3 & 4, and use the stainless rods in the other bays. If you epoxy prime the 4130 steel you would be fine.
On the other hand although stainless is tough, the 4130 steel drag wires will handle higher strength loads in tension. If I’m not mistaken bays 3 & 4 cover the areas where the front and rear lift struts attach. You would have greater strength with the 4130 drag wires in those areas. I would opt for the the 4130 steel drag wires in bays 3 & 4, and use the stainless rods in the other bays. If you epoxy prime the 4130 steel you would be fine.