Brushing resin on inside of box

[shizzzon 461]

So, i am going to need to coat the entire inside of my upcoming project in resin.. I have a few questions...

1- Any type of resin and hardener i should use specifically for this or any at Lowes for fiberglassing fine?

2- How many coats or how thick should i make it? 16 cubes GROSS 7kw of power with All-thread bracing.

3- Is it ok if i coat the entire inside with resin, then after it cures, drill out all the holes i need to run my allthread? OR should i already run all-thread and have it braced before coating with resin?

[rmzsuzuki89 61]

I just use the stuff at Home Depot. As to how many coats, I just use one, but pour it on pretty thick and give it plenty of time to dry. And I resin before drilling any holes, as long as you go slow if coming from the outside you should be fine.

[Adrian_D 520]

Why do you need to coat the inside of the box ? mdf is a very smooth surface from the get-go.

[Bdunn23 0]

it makes your box more solid and lets the air move more smoothly and helps to not let any air be released through the wood as does making your corners in the box with all 45 degree angles

[Adrian_D 520]

Resin by itself offers no strength...

[1200 bandit 2]

I just use the stuff at Home Depot. As to how many coats, I just use one, but pour it on pretty thick and give it plenty of time to dry. And I resin before drilling any holes, as long as you go slow if coming from the outside you should be fine.

I'm with you I do the samething.Use a plastic spatula an go slow.

[///M5 2,833]

Resin by itself offers no strength...

and in fact takes away strength

[AlanHall 6]

How does it take away strength?

[///M5 2,833]

It makes the mdf more brittle. Scientifically I am not sure the reason, but in practice it is very easy to confirm. Perhaps re-asking the question in reverse will be enlightening to you as well. How could it possibly add strength?

[efxtruck 0]

If you want the reisen to be at its strongest you don't want to add to much hardener. You want it to be a nice shade of green.

One of my Mom's friends worked as a body person in the army. And she gave me lots of tip.

To the best way to make your resin strong TAKE YOUR TIME.

[williambrea 0]

I did the inside of my box, I bought HD bondo resin w/ hardner and basically made a batch and dumped it into the box and spread it around so it was layering the bottom....

And preferibly do this when your box is not completely sealed, the smell will never go away...

pics of mah job

I put some fiberglass on the corners but it looks like poo... This was my first time doing fiberglass or anyting so you should be okay, just follow instructions on teh box

[AlanHall 6]

It makes the mdf more brittle. Scientifically I am not sure the reason, but in practice it is very easy to confirm. Perhaps re-asking the question in reverse will be enlightening to you as well. How could it possibly add strength?

So you have had mdf just crack apart from being brittle? If you take a carboard box and soak it in resin would it be stronger? i guess terry is a complete idiot and its brittle enclosure is going to blast apart >> http://audioforum.termpro.com/topic/8/27273.html

Edited May 22, 2009 by AlanHall

[Jay-C76 333]

I've never had resin make mdf more brittle.....

I know this for a fact, after actually using this for years

the resin soaks into the mdf and actually makes it tougher.

The f/g fibers will actually make it tough as metal.

Hardened poly resin is rock hard pretty tough itself..

I can snap a 6" wide strip of mdf with ease,

after resin is applied to the surfaces

it's a lot harder to snap....

It also helps around the sub cut out to keep

you from blowing out the holes for screwing the subs in.

Run the all thread before you coat anything,

then apply the resin to the all thread as well.

it will help to minimize any vibrations as well

as seal up the hole from the all thread...

[Thorshammer 1]

I mix 3oz or so at a time and use 6 drops extra of hardener. I always work in smalll batches. From my experience I's drill the holes first for you threaded rod and have them in place before resining. Even goin slow resin chips and cracks when you screw through it and drill through it.

Few Pics of last box

[///M5 2,833]

It makes the mdf more brittle. Scientifically I am not sure the reason, but in practice it is very easy to confirm. Perhaps re-asking the question in reverse will be enlightening to you as well. How could it possibly add strength?

So you have had mdf just crack apart from being brittle? If you take a carboard box and soak it in resin would it be stronger? i guess terry is a complete idiot and its brittle enclosure is going to blast apart >> http://audioforum.termpro.com/topic/8/27273.html

WTF, that has nothing to do with anything.

I didn't say it would make it super weak, just not stronger. I see you avoid my question over why you think it is stronger though but are quick to judge otherwise. If you put mdf on a material tester and test its breaking strength both with and without resin, the piece with resin will break with less force.

[AlanHall 6]

It makes the mdf more brittle. Scientifically I am not sure the reason, but in practice it is very easy to confirm. Perhaps re-asking the question in reverse will be enlightening to you as well. How could it possibly add strength?

So you have had mdf just crack apart from being brittle? If you take a carboard box and soak it in resin would it be stronger? i guess terry is a complete idiot and its brittle enclosure is going to blast apart >> http://audioforum.termpro.com/topic/8/27273.html

WTF, that has nothing to do with anything.

I didn't say it would make it super weak, just not stronger. I see you avoid my question over why you think it is stronger though but are quick to judge otherwise. If you put mdf on a material tester and test its breaking strength both with and without resin, the piece with resin will break with less force.

you said it makes it brittle. In my 29yrs ive learned that something brittle is weak and cracks easy. maybe im wrong about that as well. i think its stronger because it dries hard as hell. its very simple. and wtf ever a "material tester" is ,im guessing you have one of these? and can show use your tests? i will ONLY agree that resin alone is not a strong as resin with fibers or glass mating. but mdf soaks the stuff up and its harder when its done. this is nearly as good as your argument that walls arent loud.. Edited May 22, 2009 by AlanHall

[ABXX49 20]

Customers often ask, "What's the difference between a force tester and a material tester?" Here is a simple analogy that will help. Think of a ruler as a force tester and a micrometer as a material tester. A force tester will work fine for basic force measurement applications where you are mainly interested in peak loads and extension. A force tester will use a force gauge as the load measurement device. A material tester will use precision loadcells and an internal or external extensometer for elongation measurement. Material testers are much more precise and generally offer more performance. Testing under constant loads or when using thermal chambers require a material tester. A material tester should be calibrated on site and calibrated whenever the tester is moved or relocated.

[AlanHall 6]

From Wikipedia, the free encyclopedia

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"Brittle" redirects here. For other uses, see Brittle (disambiguation).

Brittle fracture in glass.A material is brittle if it is liable to fracture when subjected to stress. That is, it has little tendency to deform (or strain) before fracture. This fracture absorbs relatively little energy, even in materials of high strength, and usually makes a snapping sound.

When used in materials science, it is generally applied to materials that fail in tension rather than shear, or when there is little or no evidence of plastic deformation before failure.

When a material has reached the limit of its strength, it usually has the option of either deformation or fracture. A naturally malleable metal can be made stronger by impeding the mechanisms of plastic deformation (reducing grain size, dispersion strengthening, work hardening, etc.), but if this is taken to an extreme, fracture becomes the more likely outcome, and the material can become brittle. Improving material toughness is therefore a balancing

who give a shit if its more brittle? its HARDER thats why its "brittle". to push a piece of MDF to the point of its new found "brittleness" breaking Would be far beyond anything this guys or anyone elses system will do..

[seanbw 1]

if the overall goal is more rigidity why not use a stronger material to begin with? i don't see the point of buying mdf and then wasting time adding resin to make it stiffer, when it appears to me the end result would to make the mdf more prone to fracturing. i'm guessing with resin you get a harder surface that is structurally weaker than the original sheet of mdf, i'm not saying it's going to shatter dramatically like glass but it's possible you could get hairline fractures that would grow like cracks on a windshield.

[///M5 2,833]

It makes the mdf more brittle. Scientifically I am not sure the reason, but in practice it is very easy to confirm. Perhaps re-asking the question in reverse will be enlightening to you as well. How could it possibly add strength?

So you have had mdf just crack apart from being brittle? If you take a carboard box and soak it in resin would it be stronger? i guess terry is a complete idiot and its brittle enclosure is going to blast apart >> http://audioforum.termpro.com/topic/8/27273.html

WTF, that has nothing to do with anything.

I didn't say it would make it super weak, just not stronger. I see you avoid my question over why you think it is stronger though but are quick to judge otherwise. If you put mdf on a material tester and test its breaking strength both with and without resin, the piece with resin will break with less force.

you said it makes it brittle. In my 29yrs ive learned that something brittle is weak and cracks easy. maybe im wrong about that as well. i think its stronger because it dries hard as hell. its very simple. and wtf ever a "material tester" is ,im guessing you have one of these? and can show use your tests? i will ONLY agree that resin alone is not a strong as resin with fibers or glass mating. but mdf soaks the stuff up and its harder when its done. this is nearly as good as your argument that walls arent loud..

Generically speaking when you increase hardness you also increase how brittle something is. Steel for example, when you add more carbon it becomes harder but also more brittle.

Material tester = load frame or a device that cyclically will apply a load to a material to test it. Pretty much everybody who makes any sort of material for anything uses them. In my last job, I not only sold, supported, calibrated, but used them for testing a variety of things. Really common, really simple device.

[Thorshammer 1]

if the overall goal is more rigidity why not use a stronger material to begin with? i don't see the point of buying mdf and then wasting time adding resin to make it stiffer, when it appears to me the end result would to make the mdf more prone to fracturing. i'm guessing with resin you get a harder surface that is structurally weaker than the original sheet of mdf, i'm not saying it's going to shatter dramatically like glass but it's possible you could get hairline fractures that would grow like cracks on a windshield.

Of all the boxes I've seen glassed ( and I've seen a few ) I've never seen one crack or break because of resin and I'm not talking about 1200 watt systems. LOL

[///M5 2,833]

if the overall goal is more rigidity why not use a stronger material to begin with? i don't see the point of buying mdf and then wasting time adding resin to make it stiffer, when it appears to me the end result would to make the mdf more prone to fracturing. i'm guessing with resin you get a harder surface that is structurally weaker than the original sheet of mdf, i'm not saying it's going to shatter dramatically like glass but it's possible you could get hairline fractures that would grow like cracks on a windshield.

Of all the boxes I've seen glassed ( and I've seen a few ) I've never seen one crack or break because of resin and I'm not talking about 1200 watt systems. LOL

And then they wouldn't have cracked or broke without the resin either.

I never said that when you resin MDF that the box will break automatically, just that resin does not add strength but reduces it.

[seanbw 1]

if the overall goal is more rigidity why not use a stronger material to begin with? i don't see the point of buying mdf and then wasting time adding resin to make it stiffer, when it appears to me the end result would to make the mdf more prone to fracturing. i'm guessing with resin you get a harder surface that is structurally weaker than the original sheet of mdf, i'm not saying it's going to shatter dramatically like glass but it's possible you could get hairline fractures that would grow like cracks on a windshield.

Of all the boxes I've seen glassed ( and I've seen a few ) I've never seen one crack or break because of resin and I'm not talking about 1200 watt systems. LOL

And then they wouldn't have cracked or broke without the resin either.

I never said that when you resin MDF that the box will break automatically, just that resin does not add strength but reduces it.

that's i guess the question i'm getting at. aren't there better ways to increase the rigidity of mdf, or stiffer materials that can be used in place of mdf?

[AlanHall 6]

like i said.. then you can show us your reports from your material tester?? and you have yet to explain why it reduces it? answer me this. if the mdf become brittle. it means it became harder, but more easy to break in a stressfull situation. correct? i will aggree.. now do you honestly think that in car audio we will bend the mdf enough to fail because of this brittleness? i dont think so.. ever... so the initial hardness that the resin gives the mdf. makes it HARDER...

[AlanHall 6]

if the overall goal is more rigidity why not use a stronger material to begin with? i don't see the point of buying mdf and then wasting time adding resin to make it stiffer, when it appears to me the end result would to make the mdf more prone to fracturing. i'm guessing with resin you get a harder surface that is structurally weaker than the original sheet of mdf, i'm not saying it's going to shatter dramatically like glass but it's possible you could get hairline fractures that would grow like cracks on a windshield.

Of all the boxes I've seen glassed ( and I've seen a few ) I've never seen one crack or break because of resin and I'm not talking about 1200 watt systems. LOL

And then they wouldn't have cracked or broke without the resin either.

I never said that when you resin MDF that the box will break automatically, just that resin does not add strength but reduces it.

that's i guess the question i'm getting at. aren't there better ways to increase the rigidity of mdf, or stiffer materials that can be used in place of mdf?

sure.. but i dont see anyone wanting to invest the time into steel and concrete for daily drivers. the closest thing we have tested thatt showed gains was birch around .7 box for box swap. but im not sure people like maybe 43 a sheet for that and im sure M5 will tell us how much burch sucks as well..