View Full Version : I **** with Fiberglass (Proof Inside)

07-20-2004, 10:51 PM
So I slapped down two layers of fiberglass and popped the mold out of my car. Though I could pretty much determine this as I was making it, I was then able to behold incontrovertible proof that the enclosure was absolute ****. I don’t really have the time, patience, or resources to make another one (and I don’t really think that it would be much better than the first), so I’d appreciate some help in making this thing useable.

Also, I don’t know how you people manage to pull off all the painter’s tape… much of mine refuses to come up. Very Attractive.

Glamour shot:

As you may be able to see from the above picture, the side lying on the ground is rather bumpy. That is not good, I’m sure. True, some of the bumps were formed when I tried to squeeze the last bit of use from the resin as it was beginning to take on a gelatinous consistency; some of those chunks just fell and were glassed over. But many are air pockets of some sort. Very bad.


Also, there are several awkward angles in this mold. My favorite is about 70 degrees, so that when I tried to glass from the horizontal plane up the incline, the material would tend to fall down. Any additional resin seemed only to add more weight and make the problem worse. Extended tampering in the area only stuck the mat to the brush bristles, so that when I pulled the brush away, the entire piece of mat would come with it, and I’d have to reapply. Great fun, I assure you. Anyway, below is a picture of strands of mat that have refused to stick on both pieces of a given angle and subsequently fallen, curled over, and hardened.


On a side note, this is only two layers, and I’ve already gone through an entire gallon of resin.

So… is there any way to salvage this thing to be able to withstand some variety of 15” sub (D2, H2, Oz ME, whatever I eventually choose)?

07-20-2004, 10:56 PM
welcome to the world of fiberglass, you can probably still use it by just adding more layers until it is strong enough

07-20-2004, 11:04 PM
Lay a piece of fleece over it..Start from the center soaking it with resin making sure its adhering to the mold. Work your way out from the middle making sure to keep the creases out of the fleece.
I had to do this after like 8 layers of mat wouldnt stop flexing. The fleece will soak up a good deal of resin and get super stiff.

07-21-2004, 12:31 AM
First off it is salvagable.

Next time for the tape problem, use Vaseline on it as a release agent. But the tape is OK there.

Sand down the area with all the bubbles and "chunks of hardened jelly". Don't try to get them all out, just get the waxxy surface off, then add some resin, when it is almost dry, get some fleece as mentioned before and soak it both sides and spread it out over the whole thing. To do this, it will have to be previously measured out and cut and ready to dip into the waiting container of mixed resin.
Then it should be stiff enough to use, or real close.

And if you used a gallon of resin for that peice, you definately used to much. Only mix a little at a time to get the best use out of it.

slick rick
07-21-2004, 12:35 AM
how much would it cost rougly to make a fiberglass enclosure for 2 12's in a spare tire well?

07-21-2004, 07:35 AM
Yep you used to much resin so far. But your not that bad off. Tape on the underside won't be seen once your done. Sand the beeyatch. And next time use a roller to work out the air bubbles to save yourself some sanding time . :)

07-21-2004, 08:22 AM
thats what i was thinking, since this is the underside, if u can get some fleeve to stengthen it up......looks really DONT Matter/

07-21-2004, 09:03 AM
I was under the impression that fleece has less strength than mat. Also, I’ve read that fleece should only be used to make a shape, not add thickness or structural integrity, and that it is prone to shattering. What exactly would be the purpose of adding the fleece?

What kind of roller would you recommend using? I’ve read that the foam rollers disintegrate pretty quickly when contacted with resin. Do they make ones specifically geared towards fiberglassing?

I’ll certainly sand the bumps and the air bubbles that I’m able to. However, not all can be sanded. Below is a picture of some that are inside the mold, but not bumps; instead, they’re smooth and level with the outer layer. I’d assume that the only way to fill them in (since they’re not really sandable) would be to drill a small hole and use it to inject resin/hardener into the bubbles, or something similar… ?


Regarding the issue of rigidity, there’s still a lot of flex in the fiberglass. Granted, I’ve only laid 2 layers of mat down, but it still bothers me. To correct this, I’ve seen a few people put down a strip of MDF along the straight edges (like this (http://momentum.soundillusions.net/July04/images/fglass7.jpg)) to increase the box’s strength. Would this be a beneficial thing for me to do?

Also, when I’m applying the mat, some more advanced fiberglassers have set down two layers of dry mat before adding any resin, thereby speeding up their application time. Would this be wise for me to try, at my stage, or are there certain difficulties this method entails?

07-21-2004, 10:36 AM
I would just do the fleece then lots of layers of mat, almost like using your piece as a mold.

07-21-2004, 11:55 AM
True, mat is stronger than fleece. I believe the reason they suggested fleece was for cosmetic purposes. I personally would sand out , and or fill the air bubbles. Then put a couple more layers of mat.

Yep they make plastic and metal rollers specificaly for glassin'. Worth thier weight in gold IMHO .

I prefer to glass in some strands of poly rope instead of the mdf strips. Stiffens really well, and it's alot easier to work around corners and curves.

I do several layers at a time, however I "wet" each layer individualy to keep from having soft spots where the resin didn't soak through. :)

07-21-2004, 12:28 PM
by doing the fleece itll give you a new fresh "clean"working surface to mat over and work with

07-21-2004, 01:20 PM
But you don't really need it if you sand all the first layer. Fleece is just going to cover the imperfections, not correct them. The bubbles will still be there, and will still be the weak points. Better to correct the problem than cover them. :)

07-21-2004, 01:25 PM
just sand it down and make it smooth?

07-21-2004, 01:47 PM
I would sand it smooth before I put something over top of the air pockets. Air pockets will cause problems later:)

07-21-2004, 01:57 PM
I’ll be sanding rather than fleecing, then. It won’t solve everything, but hopefully it will be enough for now…

Could you give a bit more detail on the “poly rope” you mentioned? I’ve heard of people doing this; some say that the rope, if added between layers, will cause bubbling. Anyway, it’s generally referred to simply as “rope” … but what kind? Nylon rope? Hay rope? Would string/twine or yarn serve the same purpose?

I just got back from Home Depot, and I had looked for some sort of plastic or metal roller. All I could find was a cheap paint roller with a thin layer of foam and a thick plastic core underneath. I’ll rip off the foam and see how well it works…

07-21-2004, 02:06 PM
Good choice brother man, don't half a$$ it now. ;)

As long as the roller is solid (no holes or anything ) you will be good to go.

The rope is pretty easy. I would do it before you put down anymore layers of mat. Just make sure you get poly rope. Cut it in lengths that will fit inside your enclosure and not interfere with mounting your baffle. Then soak them in resin and lay them out inside your enclosure pressing firm to make sure of good adhesion. Then put a couple more layers of mat on top of the rope making sure to press out the air bubbles around the rope. :)

07-21-2004, 02:10 PM
Do they make the rollers so that they won't stick to the resin? Or do you have to soak the **** thing after every use?

07-21-2004, 02:16 PM
It tends to stick to everything that you don't want it too doesn't it :D . I use some dry mold release on them before hand. The kind that goes on wet and dries. It helps alot. Still have to clean them up some, but it's alot easier :)

07-21-2004, 02:21 PM
How thick would you recommend that rope be? And where would be the best place to buy some in reasonable lengths? A craft store? Hardware?

07-21-2004, 02:34 PM
1/4 " or 1/2" works great. And you can find it at any hardware store, or wally world. :)

07-21-2004, 02:38 PM
Well, here’s what I have lying around. The one on the right I think looks somewhat similar to the poly rope I see in pictures. It’s very old and rough on the hands… I don’t really know much more about it. The one on the left is cotton clothesline from Walmart. I also might have some nylon ski rope, but that would be up in the attic somewhere, and I don’t want to look for it right now.


So… will any of these work well?

07-21-2004, 02:47 PM
Try a sample and see. Take a little piece of each, mix up a little resin. Then soak the rope and let it dry. 1)Did the resin soak in ? 2)Can you crack the resin off of the rope, and the rope is still soft underneath ? 3) And finally is the rope hard as a rock ?

1. if yes good to go
2. If no good to go
3. if yes good to go


07-21-2004, 03:09 PM
I will try that. Thank you. :)

07-21-2004, 09:46 PM
It tends to stick to everything that you don't want it too doesn't it :D . I use some dry mold release on them before hand. The kind that goes on wet and dries. It helps alot. Still have to clean them up some, but it's alot easier :)

I'm guessing that's almost like a waxy substance?....

Have you tried to soak them in mineral spirits or laquer thinner afterwards?

Where could I get one? Wal-mart in the spatula section?

07-22-2004, 12:10 AM
I am 1 also to use MDF strips on some places. I have also used the rope. Each has it's purpose. But for tight spots that needs a quick stiffening, that you can not get mat into good, or rope in right, I mix up saw dust in resin, let it get close to jelly state and add it in. In the pet dept. of Wal-Mart you can find a bag of floor shavings for hamsters and ****. I use that as it has small and large chunks.

Of course you have a large surface that will take rope and more mat the easiest. All is not lost. You'll get it done.

07-22-2004, 12:14 AM
or go to a cabnet shop. its usually free

07-22-2004, 12:18 AM
or go to a cabnet shop. its usually free

If your talking about the saw dust, thats true. But I get the big bag for about $2 - $3. And it last forever.

07-22-2004, 12:21 AM
i didnt know how much it costs. i figured $5+

07-22-2004, 02:16 AM
pics arent showing up for me :S

07-22-2004, 06:56 AM
I'm guessing that's almost like a waxy substance?....

Have you tried to soak them in mineral spirits or laquer thinner afterwards?

Where could I get one? Wal-mart in the spatula section?

Yep, it goes on like any other spray, and it dries to a slick waxy like surface.

And yep that's how I clean the rollers. Soak them in acetone for a few minutes, thne wipe it off. Clean as a whistle ;)

I get mine from a local boat reapair yard. But you can get them at several places online. I don't believe walmart carries them. :)

07-22-2004, 07:34 AM
It refers to this:


maniackilla, are the pictures still not showing up? They should be working fine...

07-22-2004, 09:40 AM
Yep, mat = the actual stranded fiberglass itself bonded to gather with bonding agents and or woven together, that you apply the resin to. :)

07-22-2004, 11:05 PM
you can use mat or clothe for the actual fiberglass but you can put the resin on fleece and other fabrics

07-23-2004, 09:33 AM
Mat builds a whole lot quicker than cloth, but cloth tends to be easier around corners and such. Is mat neccasary ? Depends on what your doing. :)

07-25-2004, 03:27 PM
I'm new here, but I like what I see of the sight so far.

Don't dispare...that is actually a good start.
#1 when sanding watch for sharp "spikes" of dried glass...they feel good.
#2 initial sanding go with a 50 grit to knock down all the high points
to answer some other questions...Rollers from a marine store look like a row of washers stacked together and are made of plastic or metal. They do wonders for knocking out air bubbles.

Mat adds strength, while cloth adds smoothness. To build up strength in a hurry shift the mat 45' degrees from the first layer. The shift in bias adds the strength, third layer of cloth to smooth it all out. So you would add a layer or two of cloth (say 7oz.) then 2 layers of mat, and follow with a layer or two of cloth. Should be bullet proof if the air pockets are taken care of. Also matt comes in many weights. Start with a lighter weight for tight bends, as the heavy weight is only good for flat spots. To get real trick with tight corners mix up some micro ballons (filling powder) with your resin to a thick paste (THINK peanut butter). Smear a layer (a fillet actually) into the corners and lay the cloth over this fillet. No more tight corner to fight the glass cloth and cause air pockets.