By ahender - 9/3/2020 7:31:25 PM
I am close to finally infusing a 12' female canoe mold. It will be an ultralight and consist of one layer s-glass, core, one layer s-glass. I am always looking for tips on resin infusion. The three tips I list are from the below link:
https://explorecomposites.com/2019/11/19/troubleshooting-vacuum-infusion
I would like to get feedback on:
1) Degas the resin before infusing. Is this mandatory?
2) Do not turn off the vacuum pump until the part has gelled. I'm using a borrowed oil-based pump and really doubt it would would run continuously for 24 hours. I assumed that once I determine the bag does not leak, I can clamp off the resin hose and close the vacuum gauge I am using between the pump and mold. Is this a bad idea?
3) The resin bucket has to be below the part being infused. Resin pooling is the given reason. My thought is if I clamp off the resin line prior to the resin flow getting to the edge of the part, there would not be a resin pooling issue. Am I incorrect?
Thank you.
Alan
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By explorecomposites - 9/4/2020 3:50:49 PM
Hi Alan,
I'm the guy who wrote the article you reference - and it's not really a how-to (working on that) but a what to consider if you're having problems!
1 - you don't need to degass unless it solves your problem - in some cases it helps. For a thick mold (guessing 5-8mm of e-glass solid laminate?) you will have a lof flow-front speed and the resin will effectively degass itself.
2 - This one I am pretty confident on. Yes people have good results with small parts and perfect bags - sometimes - but a large mold is not the place to experiment. The only case that this is really fine is with a double-bagged infusion where the inner bag is just for the infusion and the outer bag provides compaction - this is int he crazy-fussy end of things and nobody here probably needs to consider this method.
I have worked with many very experienced infusion experts and none of them ever suggest that turning off the vacuum on a large part is a good idea. The goals should be: very high vacuum for several hours on the dry stack to degass and de-water the stack. Do the job (mold, resin, everything) at an elevated temperature - uncomfortably warm is best. Infuse at a controlled speed - don't worry about it taking a while if you have the pot life for it. Don't just let it rip! Make sure you have a good resin break and / or use MTI hose or Dahlpac to keep resin from clogging your vac manifold. Decrease the vacuum to 75% or so to keep any moisture in the resin from turning to gas. If you have an excellent mold with a good drop test - a really good one - then you should be ok with this. A leaky mold - even a little leak - will ruin you. Leaving the vacuum on prevents small leaks from being catastrophic - and keeps the resin from pooling under then bag if there is no hydraulic "head" on the bag cavity. You've got a couple grand in this mold - might as well leave the vacuum on - it won't hurt if you have decent resin break solution and it can only help! Also, if you're going to post cure in the mold - leave the vacuum on for that whole process.
3 - The height of the bucket thing is a minor consideration but it can cause real problems if you get it wrong. The best prevention is a careful eye on the process and an understanding of the effect of gravity on the resin pressure. If you camp off the resin before the part is 100% full this shouldn't be a big issue.
Watch out for the 2/3 of part rule you mentioned in your last post - its all about the volume of resin needed and if that much resin gets into the part.
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