With the close up shots of the joints I thought I might explain how these Zinn frames were brazed and the less than perfectly smooth joints.
They were hand brazed in one pass and left "as brazed". What you see is straight from the torch, no built up fillets and, importantly, no filing. The minimal heat input allowed the tubing to retain optimum tensile strength and eliminated the risk of damage from purely cosmetic filing. This allowed us to use thinner, lighter tubes with confidence.
At the time Reynolds didn't recommend fillet brazing 753 but they were "officially happy" with our technique.
Andy