Why is it so i important to get rid of the air bubbles in fiberglass enclosures?

 

One reason is that the area around a bubble can easily be cracked or shattered, thus there will be an obvious weak point. Second is how air voids affect the sound of a box. A resonation can occur, and really screw up the sound quality of the speaker. This is the same reason plywood is not used, too many voids.

 

Would it affect the sound if I left a few small air bubbles?

 

Probably. But maybe not enough for your ears to tell. I mean, you would have to buildone box with the bubbles and one without. Connect them both and see if you hear a difference. Most may not be able to tell. But some could. And some could vibrate the box enough with the sub to cause the box with the bubbles to crack apart.

 

Im trying to get all the bubbles out of my second layer now but there are so many.

 

how are you laying down your fiberglass?..the best way would be to cut strips and lay them down after they've been brushed with resin. That would be the best and strongest way, although a little time consuming, but just add multiple layers and you'll be fine.

 

what ive been doin is gluing the pieces down and then resining them, but maybe on my next layer i will put resin on them first and then lay them down.

 

One problem of polyester resin is that it cures so quickly. But this is also why it is so popular. I have, and have seen the use of a piece of glass. Stretch the strips across the glass, coat with resin, then put the strips where they need to be. When the resin begins to cure chill out for a few minutes. Then come back and scrape the glass clean with a strait razor. Then you are ready for the next layer. Another technique is to put a thin layer of resin down, then the fabric, then coat with resin being sure to saturate the fabric. A squeegee or bristle roller may be used to force air bubbles out of the fabric.

Try the info links/tutorials at www.fiberlay.com and www.fibreglast.com

Also, the glue a decent theory, but not a good way to find success with glass. If the spray adhesives would not affect the cure and bond strenth of the resin they would work good. But I don't want to be the one to test this.

 

One of the new things Ive seen guys like steve brown and fishman use is fiberglass mixed with body filler. I don't know if this will realy help the bubble issue for you or not. Why do you think your getting so many large ones? Are you doing it in a cold damp area? Keeping heat on it? Not applying it smoothly across all areas?

 

I use either glass or ceramic microspheres to lower the viscosity of my resin for better fabric saturation. Another easy to find material that works as well or better is graphite. Graphite will make resin flow almost like water. And gives a hard black finnish.

 

thanks for all the suggestions I'll use them when i get all the bubbles out of my second layer and start on my third. One reason I think I am getting so many bubbles is the resin dries quickly and begins to stick to the brush when I brush it on the cloth.

 

I think the catalyst is MEKP. Don't use as many drops, and the reaction will be slower. You could also do the glassing in a cooler room. But move the glass to a warmer room to allow to fully cure for at least 24 hours.

 

DaMax... check your mixture of resin and hardener. If it is setting so fast, that you can't even get it spread out, you may need to cut back on the hardener amount just a tad. This might allow it to stay wet a little longer, thus giving you more time to spread it on the cloth. Might take it a little longer to dry in between layers, but you save that time anyways by not having all the bubbles. That's one of the things that make fiberglass so tricky, every little thing matters, temperature, humidity, sunlight, wind, etc...

The way I did it was, I put a coat of resin, then put down the peices of cloth, then put resin on top of the cloth. This way the surface is wet under the cloth, then on the top too. You have to soak the cloth thru and thru, and try to work out from the center of the peice of cloth to push out bubbles.

Hope this helps....DMAN

 

Ill try that when I start on my next layer. Would it be best to add an extra layer since I have removed more than half of my second layer because of the air bubbles?

 

Consider that layer a learning experience. But really, it's the overall thickness, the fabric, and the resin that determine the strength. Not the number of layers. Really, hte only layers that matter are the outer layers on each side. So the top and bottom layers are most important, then the total thickness and the resin.

 

Thinking logically, YES would be the correct answer here. Means you are taking off some of the layer for the bubbles, if you add another layer, it will be 1.--thicker,,,,2.--stronger,,,,and 3.--thicker and stronger. That's a good thing!! Go ahead and put a good layer on top, fully soaked, as few bubbles as you can manage, and make sure it's solid,,,you should be OK......Good Luck!!,,,,DMAN

 

thanks