[GarryGraves]

Over the past few months, I've tried about 6 times to build myself some fiberglass enclosures to sit on both sides of the cubbies in the hatch. Needless to say I failed each time, and the serious lack of information on the subject coupled with frustration has led me to almost give up all hope of ever getting the huge box out of my hatch while keeping my bass. So what I need from y'all is one of three things:

1. A dumbed down walk trough to working with fiberglass
2. Somebody to build the molds themselves for me
3. Approval to use the existing plastic panel as the base of the mold itself

Any info or help would be greatly appreciated, this is the home stretch to finishing my interior once and for all.

 

[Greg S]

Garry, have a look in this photobucket album of mine.
Hatch Enclosure Photos by gstoddard | Photobucket

It is a pictorial documentation that covers when I built a sub enclosure into the rear hatch door. Different spot but similar process.

Do not use the plastic as part of the enclosure. Fiberglass does not bond to plastic worth a **** and it is not strong enough to hold up to the pressures a sub enclosure produces. You can use it as a mold to build the base off of, like I did using tape in the hatch door.

What problems are you having specifically. I've done this for years(10+) so I've got a little knowledge on it.

 

[GarryGraves]

The molds I'm making are not hard enough. 4 were no better than laminated tape and the other 2 either bent out of shape or plain out cracked too much by time I got it out the car. Am I supposed to be using fiberglass mat? Because I'm only using the resin. How many coats do I put on before I pull the mold out?

 

[zinger]

Yes, you MUST use fiberglass mat. I haven't done any fiberglass either, but I plan to (attempt to) build an enclosure for the side of my cargo area.

Here are several online tutorials that I've been studying. Of course each is basically showing the same process, but some things are shown/explained better in different tutorials.

Step By Step Fiberglass

Building a Fiberglass Speaker Box

Building my own custom sub enclosure for cubby-holes - Scionlife.com

Fiberglass subwoofer box - a tutorial

 

[Greg S]

As said above, you have to use mat. The resin is just to bond the mat fiber to each other. Resin by itself will just crack and shatter as you have discovered. The tutorials that zinger posted are good ones to read. One thing to keep in mind when making the base mold is that it needs to be able to come out. You don't want sections that will get stuck as you are trying to pull it out of the car. If needed block those sections off so that the mold will release easily.

 

[GarryGraves]

Alright now I finally getting the info I've been needing. 1 final question though, how do I apply the mat? Do I apply the wet resin onto the masking tape and throw the mat on it, then resin mat resin mat til it's thick enough?

 

[Greg S]

Alright now I finally getting the info I've been needing. 1 final question though, how do I apply the mat? Do I apply the wet resin onto the masking tape and throw the mat on it, then resin mat resin mat til it's thick enough?

Exactly! For any large flat areas just use 3/4" MDF, it's quicker and stronger than fiberglass and you can bond the fiberglass to it easily.

Keep in mind is you want as little resin as possible, just enough to wet out the mat. The strength in fiber glassing is all in the mat, the more resin you have the weaker and more brittle it becomes. Also if it is hot when you do it, mix small batches of resin and use less catalyst than recommended so that the resin doesn't harden up too quickly on you. I generally use 8 oz. of resin at a time.

 

[zinger]

Follow question for you Greg (since you seem to know what you're talking about):

I am trying to figure out the best way to fasten an enclosure to the car. I've seen a few places recommend industrial strength velcro. I'm worried that may not be strong enough. I don't want it to become a deadly projectile in an accident. I know the factory (Bazooka) sub installation calls for cutting a hole in the plastic to gain access to a nut welded to the inside of the quarter panel. Do you think it would work to put a piece of mdf on the back where the nut is and glass it in, then drill a hole in the mdf to bolt it down? I'm guessing I should use a rubber washer on the bolt head to seal it since I want a sealed enclosure.

 

[Greg S]

Follow question for you Greg (since you seem to know what you're talking about):

I am trying to figure out the best way to fasten an enclosure to the car. I've seen a few places recommend industrial strength velcro. I'm worried that may not be strong enough. I don't want it to become a deadly projectile in an accident. I know the factory (Bazooka) sub installation calls for cutting a hole in the plastic to gain access to a nut welded to the inside of the quarter panel. Do you think it would work to put a piece of mdf on the back where the nut is and glass it in, then drill a hole in the mdf to bolt it down? I'm guessing I should use a rubber washer on the bolt head to seal it since I want a sealed enclosure.

That should work fine. I'm a big fan of bolting enclosures to the car, you'd be amazed at what can come flying loose in an accident. I'm not clear on where you are wanting to glass the mdf to though. That would be my only concern as fiberglass doesn't bold to metal or plastic well at all. And definitely yes on the rubber washer.

 

[zinger]

I'm not clear on where you are wanting to glass the mdf to though.

When I find exactly where the nut is I have to cut/drill a hole in the plastic panel for the bolt to go through. Then I put the tape and/or foil in the cubby. After I put on the first layer or two of mat I'll put a piece of mdf (maybe 4"x4") over the bolt access hole, then as I add more layers of mat I will go up and over the edges of the mdf so it is incorporated into the enclosure. I'm hoping that will be strong enough to hold the enclosure in place after I run the bolt through the mdf and into the nut on the quarter panel.

The only other places I can see to possibly bolt it down would be to extend the fiberglass to where the 2 D-rings are (like 2 small fiberglass wings). I could unbolt the D-rings and refasten them over/through the fiberglass. I don't think that would be as strong though.

Thanks for all of your advice :grin:

 

[Greg S]

OK, that makes sense now. Yes, what you are thinking of doing will work great and give you a solid mount to the car.

 

[GarryGraves]

Alright guys so I gave it another go and tried the right side cubby again. 4 layers of resin/mat/resin/mat seems to have given me quite a sturdy box. I pulled the mold out and gave it a decent stress test and it seems pretty stable. I started on the left side cubby and it's still drying as I type so hopefully that one comes out just as good. Tomorrow I'll be trimming the enclosures and ordering the mounting rings. Now I just have to decide which direction I want to mount them, so far straight up seems to make the most sense. Also Greg, I have no idea just how strong fiberglass is by feel, so my confidence with these enclosures holding up at full volume is getting me a bit worried, can I drill out a small hole on each one and do like a fake vent/port to relieve pressure or should I just have confidence 4 layers will be sturdy enough? It's sturdier than the plastic cubby is though, I can tell you that much.

 

[Greg S]

Rule of thumb is that when built the enclosure should not flex when pushed hard with your thumb.

Generally if it is 1/4" thick it should be strong enough. I would say 4 layers is not thick enough, but it depends on what weight mat you are using. I generally use 1.5 oz. mat and build up at least 6 layers, if not 8-10. Also remember that fiberglass is stronger in curved area than it is in flat areas.

Do not drill a hole as this will change the characteristics of the enclosure and also you will get whistling as air is forced through the small hole.

 

[zinger]

Alright guys so I gave it another go and tried the right side cubby again. 4 layers of resin/mat/resin/mat seems to have given me quite a sturdy box. I pulled the mold out and gave it a decent stress test and it seems pretty stable. I started on the left side cubby and it's still drying as I type so hopefully that one comes out just as good. Tomorrow I'll be trimming the enclosures and ordering the mounting rings. Now I just have to decide which direction I want to mount them, so far straight up seems to make the most sense. Also Greg, I have no idea just how strong fiberglass is by feel, so my confidence with these enclosures holding up at full volume is getting me a bit worried, can I drill out a small hole on each one and do like a fake vent/port to relieve pressure or should I just have confidence 4 layers will be sturdy enough? It's sturdier than the plastic cubby is though, I can tell you that much.

So I'm going to add here, even though I may not know 100% what I'm talking about lol. Hopefully someone will correct me if I'm wrong.

Regarding the hole to relieve pressure: I believe the pressure inside a sealed enclosure is what makes the woofer response more accurate, which is one of the advantages of a sealed enclosure. That's why I mentioned putting a rubber washer around the mounting bolt and why you need to seal around the wiring cup as well as between the sub and the mounting ring.

As for making it ported, ported enclosures need to be larger and the hole is a very specific size. Ported enclosures with a hole also have a tube inserted in them that is a very specific length. The size of the hole and length of the tube will emphasize a specific frequency depending upon their respective size, so you can't just put in a random hole and expect it to sound good.

 

[Slorocket]

^^^ Right on the money zinger. Sealed means sealed. Ported tube sizes will vary in diameter and length to adjust frequency to the box size and sub design. Yeh, it is that specific...

 

[GarryGraves]

I didn't know it boiled down to all that. I'm a fan of ported boxes, I've actually had 3 over the years and are certainly my preferred style. I'm able to do the math but just too lazy, I'll just keep it sealed and do the 6 layers probably. Should be fine. Hopefully.

 

[GarryGraves]

Alright so update: over the past few days I've managed to add 2 more layers of resin and mat each, then mounted the speaker ring in the right side enclosure and covered it with fleece and 2 coats of resin. I wanna do 3 more coats of resin on top of that and add in the mat inside around the ring and the sticks to reinforce those as well. Tomorrow I'll be doing a testfit and a dry run with it to make sure its going to be stable, then its just a matter of making it look nice and securing it well enough. I can't quite thank you guys enough for all the help you all have been, especially Greg, you're my hero bro hahaha!

 

[Greg S]

Alright so update: over the past few days I've managed to add 2 more layers of resin and mat each, then mounted the speaker ring in the right side enclosure and covered it with fleece and 2 coats of resin. I wanna do 3 more coats of resin on top of that and add in the mat inside around the ring and the sticks to reinforce those as well. Tomorrow I'll be doing a testfit and a dry run with it to make sure its going to be stable, then its just a matter of making it look nice and securing it well enough. I can't quite thank you guys enough for all the help you all have been, especially Greg, you're my hero bro hahaha!

Just make sure you actually mat and resin the whole structure, especially the fleece. Fleece and resin is not strong enough to withstand the forces of a subwoofer. The fleece is just for shape it still has to be glassed just like the base for the same strength levels. Once the fleece is completely soaked and sturdy you can go ahead and remove the sticks completely, they were only there to get the ring positioned, you don't need them in there any more.

 

[autobotguy]

Just make sure you actually mat and resin the whole structure, especially the fleece. Fleece and resin is not strong enough to withstand the forces of a subwoofer. The fleece is just for shape it still has to be glassed just like the base for the same strength levels. Once the fleece is completely soaked and sturdy you can go ahead and remove the sticks completely, they were only there to get the ring positioned, you don't need them in there any more.

Why not just mat and resin the ring scaffolding into place? A little extra framework is well worth it.

 

[GarryGraves]

Wow, you save the day again Greg! I was just going to do pure resin on top of the fleece and throw it in there to test. I'll do few thick coats of resin/mat to finish it up then.