muddyboots wrote:
As shocked at BW's posting such an interesting thread, I must also say that it would be really neat to build your own Airacobra in your barn using nothing but wood patterns. I know next to nothing baout metal working, so this has been a really bried but interesting inro to it...Could somebody maybe use this as a intro to aircraft metal working? What are the metals you use for sheet metal, and framing, and stringers, and such? what do all those numbers mean?
You have asked a question that requires a lot of detail but in short the numbers 2024-T3 refer to the material type (aluminum) and condition of heat treat. T-3 is "softer" then T-4 and 7075-T6 is "harder" then T-3 or T-4. Different areas of an aircraft require the different material and is dependant on what the engineer calls out in the drawing. Generally the harder the material the more stress it can take. 7075-T6 could be used in a wing spar web and the attaching angles, and the spar cap might be made of 4130 chrome Molly steel. Think "I" beam in shape. On commercial airplanes the skin is usually T3 or T4, but in high heat areas it might be stainless steel, titanium or inconel. On Boeing airplanes floor beams are T4 the skins are T3 and the frames are T6. I have made frames for an F-104 using the hammer forming method. I started with the original frame traced it onto maple then compensated for bend radius, and material thickness. The aluminum was 7075-T6 as the final condition but I had to use 7075-T0 and that means the material was very soft (T0) for forming. After I beat the S H ! T out of it I sent it out to be heat treated to the final condition of T6. I have also made frames and structural pieces for a BF-109 using original drawings, back then they used a lot of duraluminum and had to convert it into modern standards since duraluminum is not practical. Basically the equivalent material was T4. Confused? Me too?!?
If engineers had to build aircraft they would be designed differently
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