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Steve Pearson wrote: ...
Sport 167 and Sport American Tue, Dec 15 2015, 7:28:38 am
I tried since the early 80s to get US produced 7075 tubing but we have never used 7075 tubing from any domestic source, nor has there been any interruption in our supply since we started using it almost 30 years ago. The 6 sizes of tubing 42/44/50/53/60/62mm x 0.9mm in the Sport 167 were produced to my specifications and they are the same sizes commonly adopted by most manufacturers today. The Sport American used the same 6061 tubing sizes as the HP and some earlier models which saved money but resulted in an 8 lb weight penalty. In the air, the Sport American performed well and handled almost as well as the Sport 167. You can find the manuals at https://www.willswing.com/support/manuals/ and a list of HGMA certified gliders that we have produced at https://www.willswing.com/hgma-certifie ... g-gliders/
Hi Steve,
What tempers for the 7075 have you been using?
Steve, with respect to the differences described on PAGEHERE,
what proceses of formation are in place on your tubing choices?
Thanks,
Joe
Answer from Steve:
Steve Pearson wrote:It's drawn-seamless 7075-T6. It starts with a 500 kg billet and up with a .035 inch wall without ever having a discontinuous wall structure. Extruded tubing, like our airfoil shapes, is formed with a simple bridge die. The yield strength of 7075-T6 is often close to 80k psi -- truly extraordinary material. It's funny that we were subjected to years of fear-mongering from other manufacturers, telling customers that their gliders would soon disintegrate from corrosion. Nevertheless we were very cautious and for many years we swabbed the inside of all the tubing with a corrosion protection compound.
So, in Steve's answer I read that he uses two types:
1. Drawn-seamless for the round tubing choices at temper T6 for the 7075 alloy.
2. Extruded tubing for airfoil shapes.
I wonder what the challenge has been about obtaining U.S. domestic supply of the choices Steve makes. I wonder if the challenge has been overcome.
Steve clarifiying wrote:7075 thin wall tubing cannot be produced by extrusion. The airfoil shapes and other extruded profiles are generally 6061-T6 or 6063-T6. For slender columns in compression, 6061-T6 is equivalent to 7075-T6 since all alloys of aluminum have about the same stiffness. The 6061-T6 airframe tubing is generally seamless-drawn since this process produces higher quality tubing. American producers have no interest in producing thin wall 7075 tubing because it's so process intensive.
Some study starts:
Clarify: "drawn" "extruded" "seamed" | "seamless" | tempers | uses | challenges | trade-offs | specifications | comparisons | working it | inspection | supply | costs | tests | incidents | alloy specification | corrosion protection compounds |
The Differences Between Drawn & Extruded Aluminum
http://www.twmetals.com/7075-drawn-aluminum-tubing.html
http://www.kaiseraluminum.com/customers/products/extrusions/tube/
http://www.sapagroup.com/en/na/profiles/drawn-aluminum-tubing/
