Discussion in 'Project Logs' started by InsolentGnome, 27 Nov 2018.
that's a lot of work and patience, but great technique , can't wait to see the result
Thanks! That's why it's dragging out, patience isn't my thing!
And now the fun stuff, making the mold. I'm starting off with a few layers of gelcoat.
Gelcoat is a polyester resin, like the resins for fiberglass, used for the outer coat. It's durable, finishes up nice, and works great with fiberglass resins since it has a lot of the same properties, like not curing in air, allowing follow up applications of gelcoat or fiberglass to bond chemically with the previous layer. If you've got a fiberglass reinforced tub in your house, gelcoat is most likely what your seeing, backed by layers of fiberglass. In fact, a lot of tubs are made very similarly to how I'm going to make this mold, by applying a thin layer of gelcoat on a mold and then backing that up with fiberglass.
And here's what I'm using, plain white gelcoat but I'm gonna dye it blue. Normally you'd use a tooling gelcoat for a mold, which is harder and more resistant to damage, but I'm not planning on making 100 shells a day so regular gelcoat should work and that's what I have on hand. The dyeing it blue is to help with casting the shell. If I'm casting with gelcoat, I can see thin spots in my coat, but more than likely I'll be using CF or a similar composite and the blue will let me see spots where I might have a gap.
I'm going for two layers of gelcoat, about half a pint for each should give me coverage.
After brushing it on. You could spray it, but it's not necessary since the finished side depends on the plug and not what the exposed surface looks like.
I gave each coat about a half hour to an hour to set up before the next coat. After the gelcoat was down, it was time for the fiberglass backing. This is the resin I'm using, polyester layering resin. It doesn't include a wax so that the outer skin of a coat doesn't set up and the next layer can bond with it.
For the first layer, I'm using chopped strand fiberglass. It doesn't have the woven look because this is just strands of fiberglass laid in a sheet and held together with a binder that the polyester resin dissolves.
And laying up the first layer.
Next layer I did woven fiberglass because I had a roll laying around that wasn't being used up.
And a last layer with more chopped strand. There's no real reason to have mixed the layers or what order they are in. Chopped strand takes up a lot of resin and adds bulk and strength quickly whereas woven cloth is thinner and uses less resin. Since I'm looking for bulk and strength, the chopped strand is more what I want. Woven cloth for the whole mold would work fine as well, it would just take a lot more cloth.
And with everything all cured up, things got a little meh...
I pulled my divider off and realized that I had a lot of void spots and just an all around bad finish. I blame this on not getting all the wax off the divider and the gelcoat being able to pull off while curing. Also, my registration glue dots, not the best.
But it's what I've got so lets start by cleaning up the edge.
It just so happens that my new job and company is fiberglass and gelcoat repair so this shouldn't be a problem. I started the fix by grinding out all the rough spots.
Then after some sanding to make sure the patches had something to bite onto, I layered in some gelcoat, leaving some dips for my registration.
And then sanded it out.
It's not perfect but I figure any imperfections are just extra registration. And it could be a problem that my patches are only mechanically bonded to the mold instead of chemically bonded, but that should only be a problem while making the second half of the mold, and I've got an idea about that.
And last time I said something about a sponsor...check out this beast.
I want to thank GeForce Garage for sponsoring a RTX 2080Ti for the build and for being great to work with all around. They're always helping me out if they can and getting me in on cool projects. This will definitely go a long ways towards making this the fastest thing at a LAN.
Thanks for following along, more to come soon!
Fun with toothpaste. I figured the delay was more about winter.
The cold weather has slowed down a lot of my fiberglass work. Hard to get this stuff to cure in a 30 degree warehouse. My basement isn't as bad but still requires a space heater to get the cure into the 30 minute to 1 hour range.
Continuing with the mold making, after getting my edge sorted out, it was more wax in case I rubbed through a spot somewhere and since the flange had never been waxed.
To be honest, I tried to pull the first side off so it would be easier to fix and that was a non-starter, so I wanted to make sure this side was at least easier to pull off. Not only did I use the mold release wax, but I put on a coat of PVA wax as well. This will dry to a thin film and washes up with water. Should make everything come apart easy.
And then it was the same as last time, couple layers of gelcoat followed by fiberglass.
Once I had that all laid up, before popping anything apart, I drilled my holes for the bolts to hold the mold together.
I'm kinda guessing on the bolts so I went overkill. Just a few 5/16" bolts.
Then it was time to see how all this came out. The second side, the one with the PVA came off pretty easy with a little wedge application between the flanges. It's almost perfect, though it does have a few imperfections I'll have to fix.
The first side...well...
It didn't seem to want to let go. Obviously the PVA was a very good idea on the other side. The gelcoat managed to grab on and pop some of the filler and epoxy off with it. It took 3/4 of a box of paint stir sticks to wedge in to get it to finally let go.
So lesson learned, just waxing isn't enough especially if the plug isn't polished to a mirror finish. Luckily a lot of the filler comes off with a razor blade. It's stuck, but it's not STUCK.
So after a lot of razor blade on mold action and some sanding, I got the side cleaned up.
It's got a 120 grit sanding on it, which will have to get a lot finer, but first I need to fix any imperfections. So bring on the dremel to grind out any voids and then I'll patch it back with some gelcoat and sand it nice and slick.
Once again, thanks to GeForce Garage for sponsoring this madness!
Thanks for following along and I'll see you next time!
I'm a learnin' stuff. I like that.
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