The water bottle that can't be knocked down

One the bottle had been printed I needed to coat it in resin. This is because 3d printing creates quite an open structure making it very light, but not quite watertight! I painted each piece in layers upon layers of coloured resin, sanding back and each layer to get a smooth surface. I then traced Taye's bubble writing into a file for the vinyl cutter so I could stick his writing on the bottle. Finally, I attached a screw thread and lid from an existing water bottle to the top coating that in resin too before varnishing the entire thing.

With such a complex and precise shape the best approach would not be by hand but through 3d printing. This would allow me to construct the shape as a whole on the computer before slicing it into the two parts I needed so that I could have both an enclosed bottle and an open dish for the concrete to sit. This approach allowed me to be super accurate and to do things like making sure the top of the bottle fitted the standard neck of water bottle tops so I could add a screw thread in.

My first approach is always to use hand techniques, initially I thought to turn the egg/cone shape from wood using a lathe, then to slice into the two parts I needed, the bottle and the weighted base. Next to vacuum form these shapes to create a plastic shell. However I ran into some problems, the size of the shape would be too large to vacuum form in the accuracy that I needed, furthermore it would be difficult and time consuming to acheive the exact shape on the lathe. Then I had the additional issue of how the two parts may fit together as the vacuum forming does not allow for the ledges and notches I would need for it to hold together.

Initially, I jumped straight into my workshop but quickly realised this idea would require a lot more working out than I first thought! I returned to the drawing board and started to plan things out. Initially, I got some fillable baubles with the same diameter as the base of a water bottle to test the counterweighted technique although realised the next day that the weighted base was too light and the weight of the water was greater meaning the center of mass for the object was not low enough. I took inspiration from the shape of eggs as they also had a changeable centre of mass. I had to both take into account the density of the water being held and the density of the concrete base to make sure the centre of mass sat below the water level even when filled. Once deciding on the shape that would work best for this idea I needed to do some maths to make sure that the cone would hold approximately 500ml of water.