Fiberglass vs. mdf

[Falcons 5,000+ posts]

Sorry for cluttering the message boards today but I'm getting a bunch of ideas together. Is fiberglass lighter than mdf? And how thick should one make for an enclosure using fiberglass? Thanks in advance for all the help guys.

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[goingdef 10+ year member]

yea fiberglass is much lighter then mdf but nowhere near as denseand I would say a minimum of 3/4" and a ton of bracing worked in to the glass on the inside.

 

[butterMilk 10+ year member]

It really depends. How powerful is the sub? How good at laying down fibreglass are you(no air bubbles)? Fibreglass doesn't like large flat areas, it is strongest when there is lots of curves. So if the box has large flat areas, you will want to make them out of MDF anyway. For a strong enclosure I would aim for 1/4".

 

[butterMilk 10+ year member]

yea fiberglass is much lighter then mdf but nowhere near as denseand I would say a minimum of 3/4" and a ton of bracing worked in to the glass on the inside.

3/4" ?? are you aiming for bullet proof?

 

[Falcons 5,000+ posts]

I've never glassed before. But it will be a fun project for me to try. I have a pretty good idea all laid out in my mind.

 

[butterMilk 10+ year member]

Is it getting cold out there? Or do you have a heated garage to work in? Cuz fibreglass sux to work with in colder temperatures. Takes longer to dry and what not.

 

[Falcons 5,000+ posts]

Is it getting cold out there? Or do you have a heated garage to work in? Cuz fibreglass sux to work with in colder temperatures. Takes longer to dry and what not.

It's between 50-60 depending on the day. Plus I'm in no hurry. I have nothing but time //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[goingdef 10+ year member]

3/4" ?? are you aiming for bullet proof?

not bullet proof but flex proof at least, I haven't ever made a glass enclosure but I've had quite a few sailboats and was thinking back to the large flat areas of the hull.

 

[Falcons 5,000+ posts]

What's a good type of fiberglass resin and mat to use? After talking to you guys about thickness even if I make a 3/4" box there will be enough room.

 

[goingdef 10+ year member]

What's a good type of fiberglass resin and mat to use? After talking to you guys about thickness even if I make a 3/4" box there will be enough room.

On that one I sure someone here is much more qualified to give you that recommendation I always just bought the best kits my marina had to offer and used a fine woven glass for smooth surfaces and chopped glass for inside corner areas that needed to be solid (keep in mind I'm talking about a boat though not a box !)

 

[butterMilk 10+ year member]

You do not have to make it 3/4" thick, trust me. Once you start laying the glass you will realize its not necessary and would take forever.

We are not building sail boats here.

How big will the box be? I have a 12jlw7 in a fibreglass box I built. Its about 1/4'', and its hella strong. And yes put some internal bracing, I used a good quality 5/8'' wooden dowel. 5 pieces placed where I thought would need more strength. Oh and a 1/2'' mdf bottom, with a 1.5'' front baffle. Zero flex.

 

[Falcons 5,000+ posts]

It's gonna be roughly 1.5 cubic feet sealed after sub displacements.

 

[goingdef 10+ year member]

You do not have to make it 3/4" thick, trust me. Once you start laying the glass you will realize its not necessary and would take forever.
We are not building sail boats here.

How big will the box be? I have a 12jlw7 in a fibreglass box I built. Its about 1/4'', and its hella strong. And yes put some internal bracing, I used a good quality 5/8'' wooden dowel. 5 pieces placed where I thought would need more strength. Oh and a 1/2'' mdf bottom, with a 1.5'' front baffle. Zero flex.

Like I said I have no exp I take your word on it! But now I'm thinking it could be a really good material if you say you can get away with as little as 1/4" overall thickness but how much bracing is needed for that to stop flexing a dowel for about ever square ft of flat area?

 

[Kangaroux 5,000+ posts]

1/4 - 3/8" worth of fiberglass is enough to stand on. Like said before fiberglass is strongest where there are curves which is convenient because the reason you're using fiberglass in the first place is cause they're curves

 

[Falcons 5,000+ posts]

I'm gonna love this. With the compartments that I don't even use in my trunk I'm literally going to lose 3 inches of my trunk and that's it. Beats a 3/4" mdf box taking up half the trunk. I can't wait to put this plan forward