Hi guys, I'm currently in the middle of making a Suzuki GSX-R 1000 bike kit from prepreg.
I laid a side unit up yesterday and when I went into the oven to prod the carbon about after the initial hour to squeeze the resin into the mould I found that the bag had popped.
So i basically re-bagged the part as quick as i could.

All was fine with the second bag and I cured it for the correct time.
I took the part out the mould this morning to find dryness on parts of the part and there was a slight part that got stuck to the mould.
Is there anyway to avoid these dry spots should something need rebagged during cook time or is it just a case of the part will be useless due to the loss of compression?

Thanks.

Hi Compo,

Interesting questions!

I've got to say that going inside the oven to 'squeze' the resin into the mould is definately not standard practice. Maybe you've got reasons (that I'm not aware of) but generally you laminate your pre-preg into the mould, make sure it down really well into all the corners of the mould, bag it up, really work the bag and ensure it's pressed down really well into the corners, pull full vac, close the bag off and perform a drop-test (i.e. come back an hour later and see if the bag has lost any vacuum) and then put it in the oven.

Because you've not got any extra pressure in the oven (i.e. it's not an autoclave) so burst bags, when you're working with just vacuum pressure, are unlikely to occur one you've loaded the parts into the oven. I know it's happened in your case, and it does happen every once in a while, but it's probably been caused by the bag catching on the oven doors or the rack inside. The other cause is the bagging tape softening in the oven (which usually makes the situation better but can occasionally cause a leak).

If you get a burst bag after the part has been in the oven for over an hour then your chances of being able to salvage a decent part out of it are pretty slim. There's no way that you'll have time to re-bag it (and it not be ruined) but finding what's causing the leak and patching it up (with lots of gum tape normally) is more likely. Whether the parts some out right you'll really have to wait until they're cured to find out. We've been there ourselves so we know the feeling but often you would just have to put it down to experience.

All the best, Matt

Matt Statham
Easy Composites / Carbon Mods - Technical Sales