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Steve Broad
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Group: Forum Members
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+xSorry Steve, long day yesterday - I thought you meant combined weight of the finished component rather than individual weights of the reinforcement and resin. Carry on! :-) But you made me think for a bit :-)
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Hanaldo
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Group: Forum Members
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Sorry Steve, long day yesterday - I thought you meant combined weight of the finished component rather than individual weights of the reinforcement and resin. Carry on!
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Steve Broad
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Group: Forum Members
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+xA 2:1 fibre:resin ratio and perfect surface finish with wet-lay vac bagging? That would be 66% fibre and 33% resin. Given most OOA pre-pregs are around the 40% resin mark, as is resin infusion, I am somewhat dubious - however if that is the case, I think you have made a mistake by switching to pre-preg! No, 2 to 1, so for every 2gms of fibre there is 1 gm of resin or 100gms of fibre and 50gms of resin, so the percentage of resin to fibre is 50%. I have weighed cloth before and after and my 'best' is a 51% increase in weight.
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Hanaldo
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Group: Forum Members
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A 2:1 fibre:resin ratio and perfect surface finish with wet-lay vac bagging? That would be 66% fibre and 33% resin. Given most OOA pre-pregs are around the 40% resin mark, as is resin infusion, I am somewhat dubious - however if that is the case, I think you have made a mistake by switching to pre-preg!
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Steve Broad
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Group: Forum Members
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+xHi Steve, We haven't actually done a video on Vacuum Bagging assisted wet lay (as opposed to Resin Infusion or PrePreg) which is why you probably haven;t seen mention of it in a tutorial, however, in most circumstances we recommend a maximum vacuum level of 20-25% for this kind of process (hence why the VB Starter Kit is offered with a vacuum regulator); the theory being that with higher vacuum levels, resin is drawn away from the surface of the mould, through the perforated release film and into the breather/soaker. Different forms; laminate thicknesses, materials, etc. will require varying levels of vacuum pressure so there is no hard and fast rule. Yeah, just looked :-) 20-25%? Blimey, hardly worth doing :-) Always used 99.99% as have never been told differently. Don't recall it being mentioned in YouTube videos. Isn't the idea of perforated release film to remove excess resin and the number of holes designed to regulate the amount of resin removed. I have got close to a 2:1 fabric/resin ratio with no evidence of dry areas/pin holes. My car shell is now almost completely carbon and the interior panels, dash, floors and rear wheel tubs are completely carbon. However, I have progressed to Prepreg now so no more wet stuff for me :-)
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Rich (Staff)
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Group: Administrators
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Hi Steve,
We haven't actually done a video on Vacuum Bagging assisted wet lay (as opposed to Resin Infusion or PrePreg) which is why you probably haven;t seen mention of it in a tutorial, however, in most circumstances we recommend a maximum vacuum level of 20-25% for this kind of process (hence why the VB Starter Kit is offered with a vacuum regulator); the theory being that with higher vacuum levels, resin is drawn away from the surface of the mould, through the perforated release film and into the breather/soaker. Different forms; laminate thicknesses, materials, etc. will require varying levels of vacuum pressure so there is no hard and fast rule.
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Steve Broad
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Group: Forum Members
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+xI don't know, why Steve never had problems with dry areas, but the international consensus is, that you don't use full vacuum in a wet lay vacuum bagging process. This would degass your resin inside the fabric, where it is unlikely to escape. And there will be air in your resin, at least because you used a brush. And degassed air inside the resin is what is called "pulled to much resin out" or "dry fabric". My question is: if you are able to achieve a good vacuum, why don't you infuse the part? Imho it is easier, in the end faster and will give a perfect finish. At least much more likely, than a wet layup would. Ignorance is bliss :-) When I started there was no mention of not having a full vacuum. Laid up, bagged and switched on the pump with no way of accurately regulating the vacuum. Watching EC's videos I saw no mention of partial vacuums, rather an emphasis on getting a perfect vacuum. Better vacuum = denser laminate was/is my understanding. Don't understand why you would want a partial vacuum and why it isn't mentioned in EC's videos (if is is I have missed it). I am not a professional but have had no issues with dry areas, maybe I have just been lucky :-)
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oekmont
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Group: Forum Members
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I don't know, why Steve never had problems with dry areas, but the international consensus is, that you don't use full vacuum in a wet lay vacuum bagging process. This would degass your resin inside the fabric, where it is unlikely to escape. And there will be air in your resin, at least because you used a brush. And degassed air inside the resin is what is called "pulled to much resin out" or "dry fabric".
My question is: if you are able to achieve a good vacuum, why don't you infuse the part? Imho it is easier, in the end faster and will give a perfect finish. At least much more likely, than a wet layup would.
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Steve Broad
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Group: Forum Members
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+xThanks Guys. I'll get some new resin and sort out an area for the breather and give it another go. I'm not beaten this easily. I assume we are talking 'normal' vacuum bagging as opposed to infusion? If so, I am not sure why you are using less than full vacuum. I have always used full vacuum with no issues. The better the vacuum the better the final result. How I do it: Use as much resin in weight as you have cloth. IE 300gms of cloth = 300gms of resin/hardener. When you vacuum the the part the peel ply, perforated release film and breather cloth will regulate the final resin content. Use at lease two layers of breather cloth. Slowly add vacuum, stopping at regular intervals to make sure the bag is being pulled fully into all the corners. If not, release the vacuum, pull more bag into that area and try again. Once you are happy with the bag, go to full vacuum and leave it there until the resin has cured. Never had a problem with dry areas
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Crusader
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Thanks Guys. I'll get some new resin and sort out an area for the breather and give it another go. I'm not beaten this easily.
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