Showing the basic steps I took, this mk I tank is an important learning step for me. I have actually used this tank, once was enough to find all the problems with this design.

Vimeo Video:

Video journal of the "missile launcher" (since it likes to launch the inner tube like a missile if you dont tape the end cap on when using it).

This shows construction of the first 16mm ~100ft I built (ended up being 86.5ft in this one).

There are problems with this design I didn't know about or think of until I went to use it.

This design takes a long time to construct, is very difficult to load.

I would also recommend if using the heliacal-spiral type like this desig of mine, to have the spiral track cut into a tube (perhaps a wooden solid cylinder?) about 0.5cm+ deep so the film can be crank-wound on.

Currently, at the moment I recommend a 2D spiral type on a base board that gets placed into a bath, a spiral may seem hard to make, but you can do it with vertical rods (nails, dowel, otherwise, etc) rather than two tracks at bottom and top like a 35mm/120 roll hand processing tank for still film.

If your film needs to touch against something (such as the rod 2D spiral type or rack processor, or this tank in the video) wind it on so the emulsion side is not touching anything, then it is perfectly fine.

I'll make a new tank and show a video, as well as mixing up useable formula for processing ECN-2 at some point.

I'll be scaling up my final design when I find the perfect design after building enough 100ft tanks for 400ft and 1000ft and 35mm as well.