I built a box out of 0.3" (8mm) plywood sheets framed by 3" (75mm) by 2"(50mm) staffs. The box is about 3' (1000mm) each side and 2' (600mm) deep, has a floor but is open at the top. The box should act as a water reservoir, therefore needs to be waterproof (at least on the inside).
In order to waterproof the box I bought sheets of HDPE of 0.04" (1mm) thickness. The sheets are somewhat "semi-rigid", not as flabby as foil, but also not rigid enough to support itself, hence the plywood structure.
I planned to nail the HDPE sheets to the plywood sheets and weld the adjoining edges together. Additionally I wanted to seal the nails in a similar way.
Today I did a few test weldings (I could only get my hands on 0.15" (4mm) welding cord) and was less than satisfied. Probably because of the thickness ratio of cord and sheets the heat distribution was off, the sheets getting too much heat while the cord barely melt.
What other ways are there to waterproof my box (preferably using most of my setup)?
- I know there are easier ways to gather water, I deliberately want to do it this way.
- I welded HDPE sheets before, but always with a thickness of more than 0.3" (8mm).