I'm doing something wrong...but what?

General Composites Discussions Composites Talk
#1

before i start let me state this:

i aint got a vacuum gauge. …and i know its wrong . and probably the cause of all my troubles.

but let me start from the top.

im making a small item , a headlight “eyelid” for a car, in 2x2 twill carbon ,with either epoxy or vinylester. first shot , was vinylester. 1 layer of clear gelcoat in the mould, and carbon with vinylester after that. peelply, resinflow (green mesh) and vacuum bagged. turned out ok, except a couple of bubbles near the rim.

2nd try, real failure. same thing as before, but with epoxy. for some reason, i got lots of bubbles all around.

3rd try, infusion with vinylester (my epoxy was too thick for infusion. lots of bubbles all around again, and im thinking maybe i shouldnt use too much resinflow around the edges in case it doesnt follow the contours of the mould there…

another thing… we use a small refrigerator pump, and the workshop is not in my house, so we can’t leave it on…im guessing some small leak caused the mould to get air and come up…

here are some photos

the bubbles between gelcoat and vinylester:

here you can see the bubbles (of the 3rd try)

#2

too big a disaster

even the peelply is not stuck on everything…

the fabric seems “crushed”

#3

are you doing infusion or weylayup/vacuum? because you state this “1 layer of clear gelcoat in the mould, and carbon with vinylester after that. peelply, resinflow (green mesh) and vacuum bagged. turned out ok, except a couple of bubbles near the rim.”… It sounds like you did a wetlayup then used a infusion mesh… but if your doing infusion and your turning your vacuum off before resin gels up, it is possible your getting air in it then, or you may need to degas your resin, or you may have bridging going on. many possibilities

some of your problems I think are bridging… use a rubeer squeegie to push in the corners while baging. dont go full pressure until you know your bag/material isnt bridging

#4

i just got some stretchlon 200 in today…its very thin and boy does this stuff stretch, i only do hand wet layups so it should work perfectly for me, also bought a brand spankin new robinair 5cfm pump for $190 on craigslist…didnt have a single drop of oil and had the paperwork with it…awesome deal for me :stuck_out_tongue_winking_eye: spent $25 for the part to make the vacuum line and all the fittings

#5

hojo thanks for your reply.

the first 2 were wet layups with vacuum. i added the green mesh so that trapped air would find an easy way out, and towards the pump. i,m thinking in my next infusion to keep the green mesh only in straight parts and away from edges, where it might cause bridging

still, i think a small leak and me turning the pump off (cause i had to go home :o )might have been the main cause of all this…

#6

The pics where the peelply wasn’t in contact means MAJOR bridging, or there wasn’t a vacuum at all!
I would suggest using perforated release ply, and then breather cloth if you are doing wet lay-up. Infusion medium is not going to work as well for what you want it to do.

One must maintain vacuum until the resin gels/cures, otherwise you are stuck with air going back in, plain and simple. Also, make sure there are NO bag leaks in the first place, because you can let air into the vacuum, making it leave bubbles.

#7

Get a vacuum gauge

Without it, you’re just wasting time.

#8

thanks for your replies guys. we had to shut the pump off and leave, it was late at night, and we’re afraid to let it run all night cause its a refrigerator pump and normally those are cooled off the system of the fridge. we’re gonna buy a wall plug with a timer so we’ll put it to shut off after about 2 hrs… and of course put a vacuum gauge to make sure we’re pulling enough.

i’m not using breather, as i couldnt find any right now, so i got 1 layer of peel ply, and resinflow (green mesh) i’m gonna keep a strip of resinflow in the middle of my part , where its straight, in order to keep it away from the edges, thus making the bag conform easier to the curves around there. cheers for all your help. :slight_smile:

#9

For breather material, try some fabric stores for thick fleece or flannel cloth.

But test panel any new material first…