Hanaldo
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Yeh it isn't necessary to know the science in depth to get good results, but I find once you understand these things you can predict problems and take measures to increase your chances of success. All comes with experience though, so you'll get there! The formula I use to determine bag size is: ((Depth x 2) + length + width) x 1.25 So twice the depth plus the length plus the width of the mould, plus an additional 25%. Works every time. You still need to go around and make sure that the bag is pushing the carbon into place everywhere though! Definitely possibly to have plenty of bag and still have bridging.
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ChrisR
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A quick search suggests this is a standard laminating resin and a fast hardener, it will not have a low enough viscosity to flow correctly through the part, you may get better results by heating the resin up a touch to 25/30deg C (search on here for method) but check the data sheet. A "proper" infusion resin will have a viscosity in the low hundreds (100-300 mPa s) at 25deg C I've infused 1m before with success and it only took a few minutes, with 3 plys your infusion should take 5min at the absolute most dcfoster (12/05/2015)
Ok that makes more sense. However what did you mean by bridging? The Epoxy im using is Dura-klear 80LS-19A laminating resin, the Hardener is 80LS-20B Laminating Hardener. Curious, I know you say that by running the spiral line across the long side of the part it will travel the shortest distance, but its still covering the same surface area. shorter but wider, Im assuming the spiral feed line creating more places for the resin to flow from helps the ambient pressure push the resin because its not a long 'hallway' but a short wide one.
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dcfoster
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ChrisR (12/05/2015)
A quick search suggests this is a standard laminating resin and a fast hardener, it will not have a low enough viscosity to flow correctly through the part, you may get better results by heating the resin up a touch to 25/30deg C (search on here for method) but check the data sheet. A "proper" infusion resin will have a viscosity in the low hundreds (100-300 mPa s) at 25deg C I've infused 1m before with success and it only took a few minutes, with 3 plys your infusion should take 5min at the absolute most ChrisR, so I need a different hardener or both epoxy and hardener. That sucks if it's not an epoxy used for vacuum infusion, the folks at Revchem Composites swear by it. I wonder if the west systems epoxy would be better as I need to redo and have the part finished by this weekend for an auto show otherwise my car isn't going
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ChrisR
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just so you know (picked it up from one of your posts), "vac bagging" and "infusion" are two completely different methods, vac bagging you laminate (wet lay) then put into the bag and pull the vacuum - so they may have confused what you want to do with it. Infusion is still quite a new concept in a lot of circles. From what I know, West Epoxy do not do an infusion resin. I use Huntsman LY1564 with 3487 or 3498 (I can't remember at the moment) for infusion, viscosity is 250ish mPa s @ 25deg and is a specific infusion resin with a couple of hour pot life. Even wet lay I use one with a 2-3hr pot life, it just saves f-ing a round knowing you're going to run out of time!
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dcfoster
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Ok, so Vacuum bagging is where I would basically 'soak' the carbon fiber, place it into the mold, then bag it and put vacuum. Infusion is where I put the dry fiber and bagging materials in, pull out all the air, then draw in resin?
...Would explain my confusion, most people I talk to refer to Infusion and 'vacuum bagging' as the same thing...or maybe im just not paying attention (which could very well be).
So if I lets say laid out the fiber, painted on the resin then put it in the mold and added the bag, connect to vacuum, that is what this Dura-Klear Laminating resin is for. My only concern is having enough time to get all the layers wetted up then put in the mold then whatever materials on top and sealed down before it starts to harden. Im gonna go look up 'Vacuum bagging' to see if that is a better choice for me for this week until I have more time to source an 'infusion' type epoxy. Unless the solution that Hanaldo gave me will suffice for now (feeding and drawing from 1 side of the mold to the other and not end to end) The west system epoxy I know will work for the bagging method because with the ultra clear hardener it seemed to have a longer pot life than the epoxy im using now.
Lastly, if I need to fix the mold, can I add some tooling gelcoat to the imperfection, let it cure and then sand it smooth? or will that pull away from the surface thats already there? I know I will need to clean the release wax Ive been using.
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dcfoster
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so yeah...I watched a vacuum bagging video.. forget that noise. Thats more materials I need to buy and theres more to learn, maybe when im not on a time crunch. Im gonna do what Hanaldo said regarding the in/out points on the mold and keep my fingers crossed, maybe my toes and eyes too... just for good measure
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Hanaldo
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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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It doesnt have to be absolutely perfect. I just need these blasted bubbles to go away, as well the shallow spots where there is barely any resin in the carbon. My 1st attempt at this approx a month ago I had to skuff the surface of the part and brush on a thin layer of resin atop the part to give it that gloss. Though I suppose a high gloss clear coat of paint will work as well. These are interior pieces so a flat look might suit me better, not sure till I can get an acceptable finished part and then trim and install.
Oh yeah, how long do you hit the resin with a heat gun to get the bubbles out when you brush resin. A few seconds? just leave it on there forever? or is it until you dont see it bubbling anymore? Or is there really no clear answer
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Hanaldo
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Just go over it quickly, you can see the bubbles pop. You don't want to create any bubbles, that means you're boiling the resin.
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dcfoster
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Hanaldo and ChrisR. Thank you very much for the help. I wont have much chance to try out these new suggestions till Friday. But I will update this thread with my results.
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