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dcfoster
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Flow media? is that the cloth or the mesh? also you mean cling film like the stuff you use in the kitchen to seal food containers? do i smooth it on the gelcoat or just lay it over. tape?...odd ive been sanding down the gelcoat alittle and that has helped smooth out the surface alot. there are a few spots where I went into the resin underneath. im hoping release agent will work the same or do I need to layer gel coat on that as well? Hanaldo (13/05/2015)
Apologies, should have looked up the resin. You may be able to get away with it. I have infused with regular laminating resin before, but it's usually only on very small parts where surface quality isn't a big deal and I just don't want to waste good infusion resin on it. You may have to accept that it isn't going to be a perfect result though. A couple of things I might suggest changing: double up your flow media. This will waste a lot of resin, but it does help flow speed. Do as Chris suggested with heating up your resin, but be aware that this will shorten your pot life, so it may not be viable. Warm up your mould a bit too. At least make sure everything is at 25 degrees C minimum. You might want to set up a second feed line about half way across the part, in case your resin starts to gel before it finishes. Have a second batch of resin ready to mix up and go before you start so you don't have to mess around with that half way through. Again be aware that this might give you a less than perfect surface finish, but if you're in a pinch... Regarding your tooling gelcoat, that is generally the best way to repair a mould. You will just want to scrape out any chipped or loose gelcoat with a scalpel, and again make sure you clean it well with a solvent, especially if you have already applied release agent to the surface. Acetone may be a bit harsh on the gelcoat, isopropyl alcohol would be better. Furthermore, if you are using polyester or vinyl ester tooling gelcoat, then it won't cure hard unless you add 5% wax-in-styrene, or place a piece of clear packing tape or cling film on top of it then leave it to cure.
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dcfoster
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Here are a few pics of the mold so you can see the dips. Like I said I wet sanded, 320 grit>400 grit>1000 grit and got most of the low spots out, just need to fill now I guess. |
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dcfoster
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ChrisR, Hanaldo? My 2nd to last post I asked about clarification on covering the gelcoat after I reapply it to fix the mould. Also is that for all gelcoats or only certain types? Im fairly certain the gelcoat I am using gets to a tack free state and thats only with 1 side not exposed to air. Though maybe not... I cant remember now.
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Hanaldo
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Sorry mate, thought I had replied. You won't need to cover the spots where you have sanded through the gelcoat, they will release fine. If you are using a polyester or vinyl ester gelcoat then you will need to cover it up or add wax-in-styrene, otherwise it won't cure to a stage where you can sand it without it clogging your paper. Or it might eventually, but it will take ages. If you are using epoxy gelcoat, then you don't need to do anything, you can just mix up a small amount and apply it and let it cure hard.
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dcfoster
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so again, covering it up means that I am completely sealing it from air? do I smooth the plastic wrap onto the gel coat or just lay it over and will it stick to the gel coat once it cures? Im assuming the wax-in-styrene is a product.... can I just fill the imperfections clay/wax and make sure to use mold release on the clay? thanks again
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Hanaldo
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Correct. The styrene based gelcoats are air inhibited so that you can lay up onto the side exposed to air. So you either need to cover it up, or add wax-in-styrene (yes it's a product) so that the wax rises to the top while it's curing and provides a barrier between the gelcoat and the air. When using cling wrap or tape, smooth it down over the top so the gelcoat is covered. Just be aware that this method can result in having to do a fair bit of work sanding flat, as the gelcoat will wrinkle with the film on top. Your mould is in pretty bad shape, so you may be better off simply filling the imperfections with wax or clay. Not really worth putting the time into repairing those imperfections when the rest of the mould isn't perfect. Also, not sure if you did it intentionally or not, but you shouldn't skip wet standing stages. You can't go from 400 grit to 1000 grit, you will never sand out the scratches from the 400 with 1000. You need to go through the stages, so 400>600>800>1000, then if you want it to be glossy you can compound.
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ChrisR
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You certainly do need to step the grits, as Hanaldo says 400-1000 is too big a jump. It depends how many parts you want off it, if it's just 1 or 2 then fill the voids with fillet wax for clay / Plasticine each time, wet lay with vac bag (you have 99.99% if not all the kit already - you may need breather fabric if you haven't got it) make the first layer super resin rich then sand/polish/lacquer the part once you pop it out. If you're going to make 10+ spend the time and polish the mould up, fill the voids with wax/etc make a part then remake the mould taking your time doing it so you don't get any voids
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dcfoster
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Regarding the sanding, yeah I really didnt think about it at the time. The package I purchased had 320/400/1000/1500, odd that there were no 600 or 800. I picked up some from the composite supply company locally so I can fix the sanding work. Question on that, so long as everything is level and such, how long do I sand at each grit? a few passes, a few seconds? all day? (I know that last was an extreme example).
Yeah I know that mould is jacked up, I will either do extensive repairs on it or I will just remake a new one. The resin for the mould I found out whilst using it that it was bad so who knows how long it will stay usable. I will hope I didnt mess up my gelcoat repair, I laid the wrap over it but its not pushed down, and its been 'curing' all night and day. If I pushed it flat against it to 'completely' remove it from air will it cure then or did I screw it up?
lastly, the composite supply company over here doesnt sell fillet wax, they sell a soft body clay. Can I use that to fill the imperfections for the infusion, and if so do I need to put mold release (read carnauba wax) on the clay?
Im just going to infuse and add a second feed line to cover myself in case it doesnt make it the length, I dont have any of the 'vacuum bagging' material needed, I only have 'infusion' material only and the local supplier sells certain things in very large quantities and until I get better at this im not going to buy large amounts.
..edit: is paraffin wax a suitable substitute to filleting wax? I would think no, but figured I would ask. I did a google search and cant seem to find a suitable answer
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VVS
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I'm pretty new to this so limited knowledge, you getting top information from the guys on here, we lucky to have this forum BUT from the little ive learnt
the mould is everything,
if you want perfect parts you need a perfect mould, that mould looks scabby so without years of experience you going get a scabby looking part ive found the more time spent at the start saves time in the end, it seems to double at each stage.
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dcfoster
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Group: Forum Members
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Yeah im figuring that out the hard way. but in this case ive kinda backed myself into a corner and need to make a suitable part asap. if I can get it molded without major bubbles I can fix it, its the major bubbles that are causing me problems. VVS (14/05/2015)
I'm pretty new to this so limited knowledge, you getting top information from the guys on here, we lucky to have this forum BUT from the little ive learnt
the mould is everything,
if you want perfect parts you need a perfect mould, that mould looks scabby so without years of experience you going get a scabby looking part ive found the more time spent at the start saves time in the end, it seems to double at each stage.
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