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Fiberglassing Q&A

13K views 121 replies 36 participants last post by  EpicenterDesigns 
#1 ·
This is a section completely devoted to fiberglassing questions people have or helpful tips and tricks. Anybody who has a question about a fiberglass project or anything post it here and somebody will chime in and we will all try and help you out as much as possible. :)
 
#35 ·
Just look for glazing putty or "Icing". They are polyester type fillers that are very thin and leave virtually no pin holes. You can find it in a small red tube at most automotive stores. As for sand paper get them all. You are going to use them and don't be cheap get quit a few of each cause you will go thru it fast. 36,80,120,220,400,600,800,1500,3k and buffing compound.
 
#39 ·
Well u already have the two that u would use most of. I wouldn't go without some sort of glazing. You could get away with not doing a high build primer, I would just use extra sealer.

There really isn't a right or wrong way to do fiberglass. There are steps in the process that make it easier. I was taught by one of the best in the industry who now is at galpin auto sports. Anyway, I have taken the process he taught me and changed it a little bit. It's really about finding a process that works best for you and repeating it over and over.

Buffing compound is used for if you wet sand it will leave a chalking haze in the clear and it will bring the shine out and bury any perfection.
 
#43 ·
I wanna touch on a few things I have read in this thread.

Fleece is no good IMO. Sure, it is cheap as hell, but it soaks up ALOT of resin. Resin is one of the more expensive items when fiberglassing. So treat it as such.
For stretching material, I use a poly lycra blend that stretches in every direction plus some. I forget the exact name but when I re-up I will get it for ya. It is thicker than a t-shirt. I like it for the stretchiness, it holds shape without sagging like grill cloth and takes very little resin for the base.
People like to cut corners and just resin fleece, do some body work and then wrap or paint it. But I can walk up and push my finger thru it. So it has to vibrate causing cancellation of your speakers and inducing noise to the output (rattling).
Add a few layers of 1.5oz mat. You want to use as little resin as you need. The mat should just become wet and almost transparent. Resin is brittle. Too much resin will make a brittle piece.

If you use a fiberglass roller, which I suggest if your gonna do anything more than once, you can roll the air bubbles out and leave a smoother surface. Lessening the bodywork stages. Especially the need for reenforced filler.

Some people still use milkshake mixes. I use to, I admit it. But in the end it is more work. And more money.
Your mixing your expensive resin in with bodyfiller. Then your gonna have to sand it. It gets extra hard due to the resins added in. So basically your wasting time and money.
Spend money on a quality bodyfiller. It lays down smoother. Has ingredients that eliminate or lessen the chances of air causing pinholes. That means less filler used and less sanding. That's time. Time equals money.
I shape bodyfiller in the green stage with 40grit. I do almost all the sanding in 40grit if it will be a wrapped piece. Some 80 for cosmetic reasons.
If the piece needs to be textured, I sand down to 80grit. If it will be painted, I do the bodywork to 80 and then spray a poly filler on like Slick Sand or Feather Fill G2. I use both and each or terrific. I sand those down with 220. They sand like chalk. Very easily. Then work it down to 400 before a base.

I think I touched on most things. This is just my process, or some of it. But if there are any questions I will try to answer them when I have time.
(I am no expert and this is what works for me)


 
#44 ·
I wanna touch on a few things I have read in this thread.

Fleece is no good IMO. Sure, it is cheap as hell, but it soaks up ALOT of resin. Resin is one of the more expensive items when fiberglassing. So treat it as such.
For stretching material, I use a poly lycra blend that stretches in every direction plus some. I forget the exact name but when I re-up I will get it for ya. It is thicker than a t-shirt. I like it for the stretchiness, it holds shape without sagging like grill cloth and takes very little resin for the base.
People like to cut corners and just resin fleece, do some body work and then wrap or paint it. But I can walk up and push my finger thru it. So it has to vibrate causing cancellation of your speakers and inducing noise to the output (rattling).
Add a few layers of 1.5oz mat. You want to use as little resin as you need. The mat should just become wet and almost transparent. Resin is brittle. Too much resin will make a brittle piece.

If you use a fiberglass roller, which I suggest if your gonna do anything more than once, you can roll the air bubbles out and leave a smoother surface. Lessening the bodywork stages. Especially the need for reenforced filler.

Some people still use milkshake mixes. I use to, I admit it. But in the end it is more work. And more money.
Your mixing your expensive resin in with bodyfiller. Then your gonna have to sand it. It gets extra hard due to the resins added in. So basically your wasting time and money.
Spend money on a quality bodyfiller. It lays down smoother. Has ingredients that eliminate or lessen the chances of air causing pinholes. That means less filler used and less sanding. That's time. Time equals money.
I shape bodyfiller in the green stage with 40grit. I do almost all the sanding in 40grit if it will be a wrapped piece. Some 80 for cosmetic reasons.
If the piece needs to be textured, I sand down to 80grit. If it will be painted, I do the bodywork to 80 and then spray a poly filler on like Slick Sand or Feather Fill G2. I use both and each or terrific. I sand those down with 220. They sand like chalk. Very easily. Then work it down to 400 before a base.

I think I touched on most things. This is just my process, or some of it. But if there are any questions I will try to answer them when I have time.
(I am no expert and this is what works for me)


LOL....come on Jon!!

You are so very right. I tell people all the time that fleece is no good. The whole point of the stretch is simply getting a base for the glass to lay on. Not to mention the waste of resin like you stated.
Also, another big thing is the tape. I prefer to use painters tape as opposed to masking tape. It comes off much easier from the carpet as well as the material when pulling molds. I also like to use a mold release.
Milkshakes are a waste of material and add un wanted weight to the project. Instead use additives like micro balloons or fumed silica. These act just like filler giving the resin some thickness but also adding in strengthening it.

I think Jon made some very good points for those starting out to follow. Which should lead to less work and a better end product!
 
#47 ·
can you lay mat over bondo?

Whats up got a quick question im building a fiberglass box for my wifes scion tc now the question i have is i used ponte instead of fleece to attach to my mold now that i sanded the wrinkles out of where the ponte met the mold some spots are un even and have craters now im wondering i want to bondo the craters so that my mat will lay flat and not have bubbles can i do that ? lay fiberglass mat over bondo? will it stick? thanks for the help before hand
 
#48 ·
Whats up got a quick question im building a fiberglass box for my wifes scion tc now the question i have is i used ponte instead of fleece to attach to my mold now that i sanded the wrinkles out of where the ponte met the mold some spots are un even and have craters now im wondering i want to bondo the craters so that my mat will lay flat and not have bubbles can i do that ? lay fiberglass mat over bondo? will it stick? thanks for the help before hand
Is the ponte part of the sub enclosure or just cosmetic?
If its just cosmetic, there is no need to lay any mat down.

If its part of the enclosure. Lay the mat first. I would cut a bunch of small pieces and do your big voids first. Once u get the entire enclosure matted. I always use dura glass to fill big holes, sand that, and then go onto a lightweight filler
 
#56 ·
I use 1/2" - 3/4"

Keep in mind some doors aren't all that flat and you may need to cut pieces on the door to get the new panel to lay flat. Other things to consider are the relocation of window, door and possibly mirror controls. Figure out how you want to mount the panel to the door before you actually fiberglass anything because you don't want to finish the panel and realize you've got to make it ugly by putting screws/bolts in visible areas. It's a lot to think of if you haven't already done so. I usually try to make do with what I've got as a factory and build on top
 
#53 ·
Yes! FG is strongest when it is shaped. Fiberglass only works when you mix resin and matte. People skimp out and do a layer of just resin and then bondo over it. This is not the proper way of doing it. And will lead to problems down the road.
 
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#55 ·
Agreed^
 
#62 ·
what is a good wall thickness for a sub enclosure?
i am considering modeling an enclosure around the rear of the back seat and will need to make alot of the curved areas out of glass. also could the port be made from fg
 
#63 ·
I would shoot for 3/8" to 1/2" at least. But it really is gonna depend on the shape and how much actual structure you use. Everything can be made from FG if you want. Its just limited by your imagination and fabrication skills. Just don't bite off more then you can chew and you should be fine.
 
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#65 ·
So I built a fiberglass box for.my girls scion tc I have it tucked to the side of the hatch its sealed its a sundown e10 on 800 watts rms its not hitting as hard as I would like it too is there a way to port the fg box to maybe make it punch harder or get more bass ? I know the sub gets down because I had it on a 1.15 cu box at 34 but took it out to save space do you think maybe I have to make the fg box larger to get more punch out if it
 
#66 ·
Put packing peanuts into the fiberglass box till full.
Transfer peanuts to a standard box larger than the speaker box.
Mark the level of the peanuts in box and then do your math to figure out how many cubic feet you have to work with.
Figure out if you have enough space to port the box to what you would like.
If so, port it. If not...... rebuild? Polyfill?
 
#76 ·
enough to fill the entire enclosure loosely, if it's not packed in loosely you run in to the reverse effect. also depends on using polyfill stuffing or batt. i personally use batt and line the walls, the batts I use are about 2 inches thick. i cut the piece I am going to use than spray a little adhesive on the wall it's going on. I usually listen to a few songs before I add any more, if i do add more I just cut the piece and place in box and listen to same songs to see if I like the sound better. you'll have to play around with different amounts to find if it did improve. if you don't have polyfill already, I wouldn't buy any just yet look around the house for old pillows (obviously not feather pillows) first.
 
#72 ·
When doing door pods what type of matting do you use... I used to be able to get kevlar/CF hybrid cloth for free from work but now I can't. Looking on ebay I see 3-4'' rolls of different matt. Stitched, chop, etc...
 
#73 ·
Your mainly going to use chopped matte in most builds. Sometimes woven is used. But mostly chopped. And you go by weight. I typically use 3oz for most projects but have heavier weights if needed. Width really doesny matter as you want to tear it into 4x4 pieces in the in.
 
#78 ·
thanx for the tips, ive done a fair bit of bodywork so working with glass isn't totally foreign to me. the glass is lightweight as apposed to the wood and i would prefer to keep it as light as possible. i know for flat panels glassing in some wood for supports is important. as for biting off more than i can chew.....i tend to jump in head first no matter how deep the water :)
it is through our mistakes we should learn the most....those aren't lumps on my head they're knowledge bumps ....each one a new lesson:)

i appreciate all the help you all offer and say many thanx to everyone.
take care and have fun
 
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