So, based on the sketch I made on the white board (below), I need to calculate just how heavy the tub will be. The main reason I need to calculate this is to be sure the 19kg I’ve taken out by chopping out all that steel and removing the ally panels isn’t then replaced by even more carbon.
I made a trial part, consisting of:
- 4 * 600gsm carbon (2 above the core, 2 below)
- 2 * 200gsm e-glass (1 above the core, one below)
- 1 * 300 gsm aramid (on the bottom, facing the tarmac)
- 1 * 300 gsm carbon (on the top, to look pretty)
- 1 * 10mm thick closed cell foam for the core (in the middle)
The layup is symmetrical around the core, apart from the aramid on the bottom and the facing carbon on the top. I have discounted the weight of clear gel-coat applied to the finished part (assume 1kg at the end).
The part measured approximately 103mm * 204mm, and weighed 130g. This meant a unit weight of 0.006 g/mm2.
From this, I fed the dimensions of the panels above into my CAD package. Given a surface extruded to 1mm depth, it will tell me the mass of the panel, to a bazillion decimal places.
|Part||count||Unit Weight||Total Weight||Running Total|
So, if I go for this, the new tub will weigh 6 kg less than the original steel work.
- 10mm closed cell foam is used uniformly. This won’t be the case – the sides do not need a 10m core – I will probably go for a 3mm core.
- the base, back and top of the tunnel need to be strong in bending load, the sides need to be strong in lateral load. As such, I can use a thinner (or even no core) for the sides. I think I will save 1kg there.