Two warm-airfans underneath. I need to bake the mould to ensure dimensional stability because I didn’t have the resin or room warm enough when I laid it up. This tooling resin is funny stuff and needs the ambient and resin temp to be at 20C or more to trigger the exotherm.
So, time to tidy the garage and prep a tip-run.
4 layers of 450gsm, and whatever tooling resin Nord produce. I’ve almost finished now, but calculate I need about 3kg more resin than I have, so have stopped. It was a bummer because I had enough time to get totally done. Better order another 25kg
It has a much lower styrene content than laminating resin as well, which is nice. I catalysed it at 1% and that was enough. For mixing 1kg the brush was just starting to drag as the pot was finishing.
I expected a harsher exotherm though. But puzzled at that. I will post cure the mould though.
Not a lot to see really. 4 layers of 450 down. Rollered in with a bristle roller, and a heater in there on low to be sure the exotherm kicks in at these temps and 1% catalyst.
This is the first time I’ve used mould making resin and it’s odd stuff. Very gloopy. It also dissolves the binder brilliantly.
right then. time to turn this huge amount of gelcoat into a mould. First stage is to get down the first thin coupling coat.
First spraying of the gel-coat below, and PVA above. I will let this lot dry off and then spray the second coat tonight. The second coat will be white, so u can be sure I have good coverage. Mound making tomorrow.
When trying to overspray the PVA with a very dilute solution, we find it fish-eyes and no amount of brush-work puts it right.
Peel it off, wash it off, and start again
I could have gone for leaving the matte finish from the original PVA I laid down but then that would have negated all the benefits of using the really nice shiny plastic. Only option is to clean it all off and start again. If I was to go with a matte finish, it would mean lots of time spent polishing parts rather than letting the part material do the work for me.
So, here’s the tub, with a dust cover over the top. Great, thinks I – all is now ready for spraying. To be sure it’s ready, I have vacuumed it and cleaned it with a micro-pore cloth and panel-wipe.
Now, I’ve started spraying the PVA. There’s still lots to do though – I want a nice thick heavy coat on. It’s a shiny finish PVA, but it’s not coming up as shiny as the original back on the poly board.
So, my potential problem is that I have left it a little tacky when I put the dust cover back on. It will, or it won’t stick. It is release film so I stand a chance. worst case is I get a sponge brush from East Coast Fibreglass, and they reckon you can get a good finish from that.
Needless to say, I can resurrect some of the finish imperfections here in the final part. The final part will have an outer layer of clear gel-coat which will take a bit of flatting and polishing if I need it to.
Here’s a brief video I’ve done showing the tub pattern part as it stands now. All the shapes are right and the flanges are on. I wanted to show the flanges, as well as how I support them.
So, I was taking a wander around East-Coast Fibreglass because I needed more 100gsm chopped strand map to act as the first layer when laying up to prevent print-through in a mould. I came across something called Finishline Polyester Veil. What you’d normally do is put a layer of 100gsm chopped strand mat down first, and let that go off. Then put your heavy 450 down afterwards.
This stuff, being a felt doesn’t need a binder (to hold the chopped strands together) which means (apparently) it has a better chemical grip on the gel-coat. Then, once it’s set, you can put the final 4 layers of 450gsm down. Hopefully this will give me a great finish and is really cheap. I have had print-through before, so I know not to let this happen.
Then I discovered that Marbocoat do a release agent called Fastcote, which you wipe on and it leaves a shiny release surface. I called them today and it is good for epoxy. Fantastic. Everything that contributes to a nice surface finish is welcome.
I will test it first before I use it, I think.
I’ve welded the brackets to hold the underfloor bracing on and tacked them onto the chassis. They only need two tacks. I don’t want them to be any stronger than something that can be taken off with a chisel.
