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AWOL
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+xDefo wet the cloth out. Another possibility is to spray a clear gel coat into the mould first, its viscosity will allow it to stay where you put it and then you'll be able to stand a chance of applying your resin on the back of it and maintain a fully wetted surface. I'm in the middle of such adventures myself for those occasions where prepreg or infusion arent on the cards. Thanks for the advice CaveDweller, It's definitely a learning curve - but the passion is strong so I'll run a few test pieces over the next few weeks, then hopefully drop a nice infused piece on here soon-ish
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CaveDweller
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Defo wet the cloth out. Another possibility is to spray a clear gel coat into the mould first, its viscosity will allow it to stay where you put it and then you'll be able to stand a chance of applying your resin on the back of it and maintain a fully wetted surface.
I'm in the middle of such adventures myself for those occasions where prepreg or infusion arent on the cards.
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CaveDweller
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Hi, indeed just like a polished car bonnet in the rain by releasing your mould by the very nature of what that release is achieving is going to stop resin being able to wet out the surface and it will pool into globules! An old faded dull car bonnet will wet out in the rain no problem. Its a very annoying side effect that's for sure.
This is the big challenge with what you're trying to do. You need to stop throwing money at large components and make a small test piece to get the process sorted. You need a method of consolidation one way or another, the fabric will never in a million years conform the that lovely shape just held down by good luck alone. Get your bagging gear out and do some tests. It won't be easy to wet lay this part and have a good surface coupled with minimal weave distortion.
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AWOL
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+xWe've had mid-30 degree ambients in Perth lately, so it wouldn't be impossible to PVA that mould inside 30 minutes. If the PVA was touch dry when you moved ahead then it wouldn't be a problem. Realistically, that issue would present itself in a different way, it wouldn't cause seperation issues. But on the topic of PVA, are you spraying or brushing it? I can't remember if you mentioned in your first post. The results will be infinitely better if you are spraying it, so if you don't have spray equipment I would recommend grabbing a Preval sprayer from Supercheap and applying it that way. To me, it sounds like the PVA isn't a complete film on the surface and you are mostly applying the epoxy to the waxed mould surface? In which case, a low viscosity resin is going to seperate and pool very easily. I would suggest using a thicker laminating epoxy, and you could try wetting out your carbon on a sheet of plastic before you apply it to the mould. Use a squeegee to squeeze out excess resin, and then just take your time making sure it all conforms to the mould surface. You will likely still get a few voids because this isn't an easy shape to do without vacuum, but it isn't hard so hard to fix compared to what you have now. We have just brushed on the PVA, although we recently picked up a Preval sprayer so will definitely be using it on our next attempt I like the idea of pre-wetting out the carbon on some plastic first, we may try that also Although I am now keen to attempt a few vac bagging projects (quite a bit smaller) and may revisit this again once we can master vacuum - because as you mentioned, it is quite hard to get it to hold on all the shape
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Hanaldo
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We've had mid-30 degree ambients in Perth lately, so it wouldn't be impossible to PVA that mould inside 30 minutes. If the PVA was touch dry when you moved ahead then it wouldn't be a problem. Realistically, that issue would present itself in a different way, it wouldn't cause seperation issues. But on the topic of PVA, are you spraying or brushing it? I can't remember if you mentioned in your first post. The results will be infinitely better if you are spraying it, so if you don't have spray equipment I would recommend grabbing a Preval sprayer from Supercheap and applying it that way.
To me, it sounds like the PVA isn't a complete film on the surface and you are mostly applying the epoxy to the waxed mould surface? In which case, a low viscosity resin is going to seperate and pool very easily. I would suggest using a thicker laminating epoxy, and you could try wetting out your carbon on a sheet of plastic before you apply it to the mould. Use a squeegee to squeeze out excess resin, and then just take your time making sure it all conforms to the mould surface. You will likely still get a few voids because this isn't an easy shape to do without vacuum, but it isn't hard so hard to fix compared to what you have now.
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AWOL
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+xare you letting your pva dry completely? To fully dry pva over a mold of that size in 30 minutes, you have to have a lot of airflow going. If it is pooling up in corners/creases, it could be releasing water into your layup when the resin heats it up later It is possible that I was a little hasty with letting the PVA dry I appreciate all the input so far, and will apply this information when next making the next 'test' carbon part
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M.R.
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are you letting your pva dry completely? To fully dry pva over a mold of that size in 30 minutes, you have to have a lot of airflow going. If it is pooling up in corners/creases, it could be releasing water into your layup when the resin heats it up later
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AWOL
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+xHi! I used to do hand wet-lays with West Systems 105 and they never turned out well without vacuum, especially on moulds with a lot of contours like yours, 105 is simply too runny for that! (too low viscosity) All surfaces that are not almost horizontal will have the resin running off them and pooling in the low areas, even when laying up one layer at a time and. I do not think you will ever get a good result without vacuum bagging it. where the resin runs off, there will be voids in the fibre, when cured these will not really let new resin bond to them. You could try to use som way of mechanically compressing the layup in the mould, I've used plastic bags of hot water to do this, since they will conform to the mouls shape, and speed up the cure to boot :-) Hi Dravis, Thanks for the reply .. That helps greatly I did wonder if it was a viscosity problem, but not having enough experience under me it is hard to compare I do have vac bagging gear but have just been putting it off trying to perfect the disciplines one step at a time - but I guess its time to step up and improve the results - even if there's some trial and error involved I do like the out-of-box thinking re: the hot water bags
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Dravis
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Hi!
I used to do hand wet-lays with West Systems 105 and they never turned out well without vacuum, especially on moulds with a lot of contours like yours, 105 is simply too runny for that! (too low viscosity)
All surfaces that are not almost horizontal will have the resin running off them and pooling in the low areas, even when laying up one layer at a time and. I do not think you will ever get a good result without vacuum bagging it. where the resin runs off, there will be voids in the fibre, when cured these will not really let new resin bond to them.
You could try to use som way of mechanically compressing the layup in the mould, I've used plastic bags of hot water to do this, since they will conform to the mouls shape, and speed up the cure to boot :-)
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Matthieu Libeert
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+x+xhmm strange! I would recommend you to try the same technique you are using on a glass plate! that way you can do every step and try to analyze now and then through te glass wat is happening on the surface. That way you will already be able to see if the carbonfiber is wetting out enough and if the resin is working ok to go through the fibers till mould surface That's a great idea - I'll try that for sure (on a smaller scale haha) Thanks again for the advice .. stay tuned No problem, hopes everything turns out ok for you!
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website: www.mat2composites.com  
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