Hi all,




My name is Craig and live in Cambridgeshire, Been looking at this forum a few weeks now and seems like a great place to learn as im a newbie to composites.

Really enjoying looking at what everyones doing.

Im trying to build a pair of wheel spats which id eventually like to do in carbon. So far ive made a plug out of mdf and foam and taken a 2 piece mould from it which im quite pleased with except I now wish id made the flanges larger. 

Over the easter break ive had my 1st attempt at doing a vacumm bag layup. my layup consisted of 4 layers of 200g woven glass cloth, pelply then breather cloth then bag. For a 1st go im quite pleased as the part came out of the mould easily but to my un trained eye, it looks like my parts are starved of resin. Also the bag connector has left an imprint in the surface.

Time for the questions,

Am I pulling too much vacumm?, is my bag connector in the wrong place or is this also due to too much vacumm?. From what ive read I guess I might need to invest in a regulator?. I left my pump running over night which I was a little dubious about, is this correct?.

Am I right in thinking that it if try using infusion instead then the pump is turned off after infusion is complete.

Im sorry for all the questions on my first post!!.

Any help and advice is greatly appreciated.

Cheers

Craig    

Thanks for your reply ajb100, Little confused about vacumm pressures, I was under the impression it was possible to bleed too much resin out of the stack ??. Assuming I manage a perfectly seal bag, how do I judge when to turn off the vac pump? On my first couple of trys ive left the pump on overnight and ended up with resin in my catch pot. I know its difficult to judge from my poor photos but does my laminate look dry to you?

Again Thank you for your help.




Craig

When I vac bag I tend to work the resin in really well and get as many bubbles out as possible on the first couple of layers and make it really resin rich then just normal resin quantity for most of the others, then an almost dry layer as the final one, then peel ply, bread wrap then breather that way when the vacuum pulls it doesn't starve the mould surface layer. You're not going to pull huge amounts of resin out of the stack so don't worry about that too much (unless you work on 40% fibre 60% resin or higher and the carbon is swimming!!)

What you have to think about when vac bagging is if you have a perfectly sealed bag then you should use the pump to bleed out the resin then once you are happy with that (but remember a bit will still bleed out into the breather fabric), clamp the pipe then you will get the compression from the vacuum from the air pressure on the bag. keep the bag sealed until the resin has cured