Epoxy repelling on mould

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Epoxy repelling on mould

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M.R.	M M.R. posted 6 Years Ago HOT Post Details
M Group: Forum Members Posts: 3, Visits: 19	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 Edited 6 Years Ago by M.R.
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AWOL	A AWOL posted 6 Years Ago Post Details
A Group: Forum Members Posts: 9, Visits: 72	+x M.R. - 3/8/2018 7:25:23 AM 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 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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Hanaldo	Hanaldo posted 6 Years Ago HOT Post Details
Group: Forum Members Posts: 2.5K, Visits: 28K	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	A AWOL posted 6 Years Ago HOT Post Details
A Group: Forum Members Posts: 9, Visits: 72	+x Hanaldo - 3/8/2018 11:06:07 PM 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. 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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CaveDweller	CaveDweller posted 6 Years Ago HOT Post Details
Group: Forum Members Posts: 10, Visits: 279	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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CaveDweller	CaveDweller posted 6 Years Ago HOT Post Details
Group: Forum Members Posts: 10, Visits: 279	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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AWOL	A AWOL posted 6 Years Ago Post Details
A Group: Forum Members Posts: 9, Visits: 72	+x CaveDweller - 3/12/2018 2:20:58 PM 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. 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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