The HERMS design/build process started with sourcing some stainless tube. On the telephone Geordi Stainless said multiple times that they had 6m lengths of 1/2 inch/12mm thin walled (0.9mm) stainless tube in stock, unfortunately when I drove there they had sold it all and only had 1.2mm wall thickness. In addition, full 6m lengths of tube were not so easy to get home in the car:
With some practice, coils were easy enough to bend with the thin-walled stainless tube:
While the completed HERMS did not take long to make and - in itself - was very cheap to build, all the different prototype builds did take quite some time, and effort, and pushed the end-cost up so that it was not that much cheaper than buying a pre-made coil ... and I now have a collection of reject-stainless tube:
Continued ... HERMS.