4130 On PA-18 Rudder

[Aeronut]

I‘ve read some back and forth about subbing 4130 for 1025 parts as well as the FAA AC talking about subbing materials on vintage planes. The only area I‘m still muddy on is bended parts like the -2 part from the PA-18 rudder drawing. Has anyone subbed 4130 for the called out 1025? If so have you had any problems with bending 4130 or also 4130 bending from aerodynamic forces while flying? If I‘m correct the higher carbon content makes 4130 more ductile but perhaps I‘m mixed up.

 

[Steve Pierce]

I have used 4130 on every tubing repair I have made over the last 20 plus years from landing gear, fuselages, control surfaces etc. Never an issue. I do have a roller that I roll the control surface trailing edges on.

 

[Aeronut]

Thanks, Steve! I assume you didn‘t change the dimensions such as wall thickness and diameter?

 

[Steve Pierce]

Always the same diameter, sometimes have to go up in wall thickness if I couldn't get .028" and substituted .035".

 

[dgapilot]

I think most of us use 4130 simply because it is generally easier to find in the sizes needed for aircraft repair. 4130 is a little harder to form and will work harden more when bending it. If you have a source for the original material in the sizes you need, great. More often than not it would be a special order, and with tubing, that would be a mill run of about 1000 feet. Don’t think you want that when the repair only calls for a couple feet.


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[Aeronut]

I appreciate the feedback and thank you!