air in laminate

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#1

I too have trouble from time to time with air in my laminated parts.

I am making some parts using clear gel coat sprayed into the mold. I let it gel for 2 hours, then i lay down a completely dry layer of carbon fiber. I work that layer down with my hands and a cheap plastic grocery bag, so i don’t snag the weave. I get all the bridging out most times.

Next i brush in plenty of vinyl ester resin, then i use plastic squeegies to move the resin over and into the first layer of cf cloth. Next i lay down the second layer of carbon fiber and wet it out with resin after it is placed onto the mold. This second layer i just brush down lots of resin. I don’t let it pool in areas… i remove the excess pooled resin by hand. If i need a third layer of cf then i do the same as i did with the second layer.

Now i lay down nylon peel ply, then 10 oz breather cloth, 1 layer. Then i vacuum bag the whole thing. As the air escapes i work the bag and laminate into all the corners and recesses, making sure the vacuum bag pleats are located where needed.

I let the vacuum run for 4 to 12 hours depending on how soon i can turn it off. The resin only needs 4 hours under vacuum to cure past the gel state.

When i demold the laminate i notice air trapped in between the tows of carbon fiber and some air bubbles between the clear gel coat and the cf.

I do not use a vacuum “suction cup” thru the bag and on top of the laminate. Instead i insert the vacuum line into the bag and wrap the end of the line with breather… plenty of breather so no air is kept from moving. I line the underside of my envelope vacuum bag with breather so air can move thru the bag. I also use that layer of breather over the top of the mold and it touches the other breather for air transfer/movement.

What am i doing wrong?

#2

this is why people do infusion over regular vacuum/wet layup.

#3

I could never get good results vacuum bagging if I tried to saturate the cloth inside the mold. The only times I was able to get good results was by saturating all my cloth on a separate table using a squeegie and then putting the already wet cloth into the mold.

In the end, even for my small scale hobby use, the method is too slow and messy so I just switched to infusion. I’ve been avoiding infusion because of everything I read about how you can easily ruin a part etc but I actually think it’s easier and less stressful than trying to rush laminating a part so I can have enough time to bag it before the resin starts to kick.

#4

I would say, just because you are laying down dry fiber, and soaking the top later. The air bubbles get trapped in the fiber/gel interfaces. Need to wet the fiber out well, then slap it on, and then rub it down. That way, you have the resin soaked through, with someplace for the air to go, before you “force the air into the gelcoat” kinnda deal. Hope that makes sense.

#5

Similar to what Riff method, I pour resin on the mold first and then lay a layer of dry fiber on top. Then I press down to wet it and repeat the process. This method forces the resin up through the fibers rather than trying to make the resin push out air.

#6

Yes thats basicaly what I do, brush a thin layer of resin onto the mould surface then apply each cloth wetting out each before adding the next layer. then bag it up. I almost never do anything CF with a gelcoat and it almost always comes out plenty good enough. :slight_smile:

#7

+100000 this is a good way, try it.

#8

Sounds good, I will wet the mold with resin first. I’ll post my results after.

#9

so simple, yet i have never thought of that. cheers :slight_smile: