I'm looking to built a small, portable fixed-gantry router.

The lightest weight ones I have found are around 30kg, with an A4 or A3 sized working area. This is pretty light, but perhaps not quite light enough.

From what I read, most people advise going for the heaviest machine possible, using thick aluminium or steel for construction, so as to avoid vibrations.

Since the machine needs to be portable, it needs to be as light weight as possible, which rules out using very heavy aluminum or steel sections.

I read about people using epoxy-granite, or filling their sections with sand, and wondered if a machine made from welded, connected, hollow sections could have those hollows filled with water, thus doubling or tripling the weight of the machines on-site.

Drain the water for transport, refill at the destination.

Thoughts anyone?