This post is basically a lessons learned post. Thankfully the first thing I did meant all the other lessons learned have ultimately only caused harm to my wallet and my schedule.
After failing to get a seal on my mould, and in discussions with Warren, the best way forward with this tunnel is to take a fibre-glass part from it which won’t need a vacuum. It can just be laid in. This means I can crack out a quick part, ensure excellent surface finish, and then make a mould from that using a full mould making system.
The first thing to do is apply release agent to the mould, and I went for spraying in PVA (to make it all blue).
PVA Spraying Lessons Learned
- advice – not a lesson because i didn’t make this mistake – use a clean airline, not one that goes through an inline oiler.
- make sure you attach your airline fully to your spray gun, else it may fire free, hit the deck and spray dust and crap onto your mould
- you want a light mist each pass – anything heavier and you may get runs
- when you’re spraying near the bottom, you may blow crap from the floor onto the part
- because the mould is very smooth and well finished, you don’t need to spray loads of PVA in to go blue, you can do it with a wipe of the cloth. meh – that was plenty of time wasted, but at least I now know how to put it down in such a way that i can take a part off concrete.
- Spraying a mould this size to get that much blue meant I used nearly a litre of PVA.
Laying in fibreglass lessons learned
- for three layers of 450gsm chopped strand mat, your remaining last litre of resin isn’t enough. Not nearly, nearly enough.
- trying to put the glass in in 6 big pieces just means it all falls down
- don’t try to fit the glass to the mould and flange – let it hang way down each side – that way the weight of the glass stops it falling into the mould.
- OR, cut yourself lots and lots of 6″ strips of glass and lay them in – it’s not a competition to get the smoothest inside of a part – that comes later with the proper infusion part.
- it’s handy having a skip outside to throw away the glass that has only some resin on.
Starting again
- it was sensible to cut my losses when I did
- I’m really relieved that I used PVA release agent – it’s water soluable
- I will pull what I can out of the mould, wash the release agent out (from where I manked it up with grit from the garage floor)
- Blast it with the power hose and start again
- I’ll wipe in the PVA this time
- I now have a 25 litre drum of resin and the right amount of catalyst – no chance this will happen to me again.
