hand lay-up- epoxy-air bubbles-advice?

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#1

As the title states, I am experiencing air bubbles - mostly on sides and inside corners. My second effort with epoxy was much improved, as I took great care in continuing to tap those areas throughout the layup process. Is this primarily an issue of technique? And, if so, plaease make some suggestions. Or, would product selection help me eliminate these pesky air bubbles?

First photo shows my mold which I have used many times for gelcoat with polyester resin layups.
Second photo attempts to show a corner air bubble about 1/16" to 3/32" deep.
Third photo is of a very shallow void where the first layer of material has pulled slightly away from the mold surface.

#2

Your fiber is bridging. As a matter of fact, how much weight of fibers are you using, and how much epoxy? Your parts seem pretty soaked.

#3

I brushed-on a coat of epoxy allowed to sit until it began to set a bit.

Then veil, followed by 2 oz. cloth, 4 oz. cloth, 3 of 6 oz. cloth and on the walls, 2 more 6 oz.

In total (resin and hardener), almost 2 ounces of resin was used in this 3" X 6" part.

#4

Use gelcoat, btw what do you mean herman by “fiber is bridging” ?

#5

Maybe the angle is bad, but do you have northside of a cm gap before your first layer? Bridging, as in the fiber is cutting the corner too fast (probably during curing in this case).

Perhaps you should look into vacuum infusion Mikey. It’s quite cheap to start, just cut that months beer money :wink:

I’m guessing your previous composites in the mold were opaque and you couldn’t see any issues.

#6

Is there a gelcoat I can use with epoxy resin?

These air bubbles and voids are on the surface of the part, not embedded below the surface. Since they are primarily in the corners, bridging is likely what I’m experiencing in those areas and I suppose better layup technique would solve it. Any suggestions for that?

#7

I used high density filler (20%) and epoxy dye on my surface/gel coat on my mold and that worked well.

#8

So you thickened (filler) the first coat with the filler? Did you allow this coat to begin to set before continuing? How did the introduction of dye help you?

#9

Yes just in the first layer, I let it tack before moving onto the next coat. Just to where your fingering is transferred but none sticks to your finger. The dye just gave me a contrast so that when I was laying up in my mold the surface is visible.

#10

Okay. I tried another one this week. I allowed the first coat of epoxy resin to set up somewhat before beginning with the application of cloth. Coupled with the conscientious brushwork in the corners I was able to produce the best results yet. Today I’ll try again. Looks like patience and focus on technique are pretty important on this piece. Thanks, Mike

#11

May-be i am not truely getting the just of everything ,and are you using Poly bond , after the fact ( on top of the part / or jell ? ) and from the looks of things …in your pics .are you using CSM in your layup , with Epoxy .

#12

I do not know what Poly bond is…? I am only using epoxy resin and cloth (2 oz., 4 oz. and 6 oz.). Like I stated in my last post, it seems as if technique has cured most of my air bubble issues, but any suggestions are welcome.