As I think about having this thread make sense, there is a ton of background info I’ve skipped over, so I will be inserting that periodically. Here is some more background before I upload pics from my phone and babble about Trial 2…
An advantage of resin infusion over hand lamination is that much less resin is used; the compressed fibers take less resin and the process forces you to think about how much to mix so there is less waste. With a higher glass to resin ratio the parts are stronger and weigh less for the same laminate schedule. Unfortunately there is a lot more waste material like bags/films and peelply.
Another advantage of infusion is that there are way less fumes to worry with; there are some fumes from the resin container while mixing and infusing but almost nothing while the resin cures (I run a tube from my vac pump exhaust to the outside where it dissipates). When you peel the bag off after cure there are resin fumes, but not a whole lot.
From what I have read, it seems best to infuse from the lowest to the highest point – that way any air gets pulled out by the vac pumps and the resin does not ‘cut off’ dry areas that are then no longer connected to the vacuum. Gravity helps keep streaks of the resin from racing ahead on vertical stuff but not on horizontal stuff (like decks). With flat surfaces like decks some people infuse from the center outwards and some infuse from the edges in. The infusion plan is probably one of the more important things to consider – it drives set-up and materials as well as if you fail or not. I’ve come to the conclusion that for flat panels and ones with slightly elevated centers (like my decks with cores), it is better to infuse from the outside in since it is also going up. Another reason to infuse from the outside in on flat panels is that the area for the resin front keeps getting smaller as the resin infuses so the infusion does not stall as easily. With a boat hull in a mold they infuse it upward from the keel. If I had a dish shaped part I would infuse from the center. With an upside down hull or a cabin top they infuse it from the edges and then upwards towards the center. For now I’m just going to think about decks. There is a bunch of discussion on this in the boatdesign thread; everyone seems to have an opinion.
Controlling the resin flow pathways so that resin does not race ahead along lines in the fabric or core is important. Once an area is cut off by resin racing ahead and joining another resin area (think like huge ant pincers), the only way to get it to infuse is to puncture the ‘dry’ area with a large hypodermic syringe (I got syringes from Tractor Supply) connected to a T in the vac line with a shutoff valve, pull a vac on the void until resin saturates the area and gets into the syringe, then close the hole with tacky tape while withdrawing the needle. Seems like a giant pain that I want to avoid.
One source of air is bubbles or dissolved air in the resin; ya gotta be careful to not stir in air when the catalyst or hardener gets mixed in. Some guys put the resin in a vacuum chamber for a while before mixing and then let it stand for a couple of minutes after mixing before starting the infusion. Some put it under vac after mixing (before infusion). On my second test panel I got a small bubble – I think it was from mixing even though I thought I was being pretty careful and let the mixed resin stand for a minute or so before infusing. But I probably won’t mess with a vac chamber- thinking I’ll just let it stand a little longer before infusing.
|