So, it’s time I completed the write-up of the carbon-fibre footwell, lest alliteration break out o’er the land.
Following on from the sharp-edged part, I then rounded off all the edges using quadrant beading and prepped it for spraying. The process for cutting back and adding the quadrant beading has been gone into at some length in the composite fuel tank section, so I won’t labour it here again.
Here is the part, flatted back, polished and waxed. I waxed it because the wax serves two purposes: performs as a release agent, and gives a shiny surface, filling in all the tiny micro-scratches that come from polishing.
What I’m learning is that you need to add shine on every part of the process in order to get a reasonable shine out of it without major effort at the end.
Here is the part offered up to the fluted sign-board flange. I’ve tried all sorts of methods to get a good straight cut and have settled on a tile shape transferring thingy, and a steady hand with a fresh Stanley knife blade. I’ve tried cutting along steel rules with the Stanley knife, and have found that I get better results with just simply cutting by hand and eye. You can see the green breaker-tape sealing the flanges to each other; resins can’t stick to the tape, so you get a simple seal and don’t have to worry about release agents. Similarly, you can see the moulding wax filling the gaps between the parts and the sign board.
A word of note here – sign-board is far too flimsy on its own to be a flange material, so it needs to be backed up with some form of stiffer board (I use 6mm ply), glued together with hot-glue. Similarly, the ply needs to be glued to the base and part using triangular gussets. Here you can see the whole thing set back at a distance, and get an appreciation of context.
It puts the gel-coat on its skin or it gets the hose again. What you don’t see is me spraying the whole affair with a couple of coats of PVA release agent first. Again,that’s been covered against the footwell tag.
Three layers of 450g CSM backed up and set in poly-resin. You can see how I’ve taped the thermocouple to the part in the oven to avoid over-heating. The part can easily exotherm to 40,50C and if the oven doesn’t sense that, it can add more heat than is needed and the part will over-heat and be trashed. This is also both halves of the mound made together and going in for the final bake.
I’ve split the moulds and you can see a few things. Firstly, the finish looks matte, and this is due to me also adding a chemical release agent on top of the wax to be super sure it was going to come out. From a seasoned mould, this isn’t a problem, but for a green mould that’s a one-off, belt-and-braces is what you need. The arrowed part is where the mould took some of the body-filler from the part with it, so even with all this extra releasing, I still had a mild sticker.
Here are the two mould-halves re-attached to each other. The flanges have been drilled and cross-bolted (M8, because they were handy). The shiny side has been polished by hand quite quickly with Farcela compound, just to demonstrate the difference between the ‘out of the part’ finish, and the final polish before a part gets pulled.
Here is the whole mould backed in breather cloth. Because I’ve split and then reattached the splits, it won’t be easy to get a vacuum tight seal for a pleated bag, so I’ve got to go for an envelope bag. Breather fabric is just a soft, cheap, disposable cloth designed to absorb resin. The red circle shows a part of a corner I didn’t notice wasn’t properly wrapped and this caused a punctured bag. Click here to see a close-up and to see how easy it is to puncture a bag.
I’ve already made the post about laying up the cloth in this youtube video, and next will be the removal and fitting to the car. Believe, me, it’s f’excellent.