sub box/resin?

rideit · Criminal Joined: 14 Aug 2006 Posts: 50

how do you apply resin on a sub box made from mdf,
what are the step's?
what kind of resin, only resin or resin and mat? inside and out side of box?

scott_fx · Criminal Joined: 07 Dec 2008 Posts: 96 City: Los Angeles

when i build boxes i usually use resin on the inside for a super air tight seal. i just mix up the resin, poor it in and move it around. it's eaisest if you do this in a few applications to get the most even coat possible. that is purely to help with the sounds. if you're talking about sealing the outside to make it water proof/resistant. i'd scuff up the wood with 60 grit, use tack cloth to clean up the dust and then apply it with a brush. When i build my box i think i'll just seal it with a primer and paint then carpet it.

rideit · Criminal Joined: 14 Aug 2006 Posts: 50

I just want to waterproof it, I used rinho liner last year but it doesn't look like it's holding up that good.... just the stuff you can get in a gallon can..
Do you think the resin will hold to the rinho liner?

scott_fx · Criminal Joined: 07 Dec 2008 Posts: 96 City: Los Angeles

i wouldn't think it would. the resin is actually pretty brittle when used alone. if the rhino liner has any flexibility to it and you smack the box accidentally... the resin will probably crack and start to chip away.

8122pbrainard · Outlaw Joined: 10 Feb 2009 Posts: 111 City: Northfield

CPES first (clear penitrating epoxy sealer)http://www.jamestowndistributors.com/userportal/search.do?freeText=cpes&page=GRID&history= then paint, glass or Rino.

rideit · Criminal Joined: 14 Aug 2006 Posts: 50

maybe I can get the rhino liner off, then start over with just the resin, What type of resin should I look for, is there diff type's or is resin resin?
thank's for the info!!!!

8122pbrainard · Outlaw Joined: 10 Feb 2009 Posts: 111 City: Northfield

MDF is really a poor choice for making anything around moisture (a boat!) unless it's completely sealed. I know many do make things like speaker boxes out of it and unless others have sealed them, I wouldn't be surprised if they too don't have a problem. Even MDF sealed, exterior ply is a better choice.

Yes, there are different resins. The two basic choices are polyester and epoxy. Polyester is hygroscopic plus very brittle (as mentioned) without glass fibers. Stay away from it. Epoxy resins aren't hygroscopic, stronger, more flexable and have far superior adhesion.

If you can get the Rino liner off, you will find puffed up, mushy and falling apart areas where water has gotten in. If real bad, you may need to start over on the boxes! Whatever you do, the CPES is the key to sealing. Then, you can go with whatever finish you want. The CPES has a very low viscosity like water so it really soaks in deep. Multiple coats are needed until the wood won't take anymore. You basically end up with a piece of plastic!!

The glue you use for the box is important too. Elmers Ultra (gorrila glue but cheaper) is a water proof polyurethane. Then there's Franklin Tite Bond III that is a waterproof "white" glue.

WakeMikey · Addict Joined: 29 Mar 2008 Posts: 640 City: Fridley

Bookmarked!

jrbishop4 · Newbie Joined: 29 May 2007 Posts: 43 City: Peoria

Call your local lumber yard and ask them for MDO it is a outdoor version of MDF. We used it to make signs for our ski club and after 5 years outside it still looks good as new. It will cost a little more but if it means you don't have to build a new box every year it may be worth it.

Wakeboarder3780 · Posted: Feb 26, 2009 6:23 pm Post subject:

I've done my fair share of sub box / speaker enclosures. What you want to do to me sounds like a combination of things.

As far as sub boxes go in general, MDF is a perfectly fine application and to make it air tight inside all you need to do is lay down a bead of silicone caulk around every edge inside.

As far as boat applications go, I agree MDF isn't the best choice (or any wood for that matter). Enter the custom fiberglass box. I'm currently making one right now for my 2000 blazer.

I think what you currently have right now is a huge mess. You have a wooden box with some liner material on it and most likely some junky areas of wood as well. IMO, what you should do now is first of sand / grind the outter box down until you have nothing except good quality, non rotten wood. If you were a good man and went with 3/4 inch thick wood when you first built it, you should have plenty of material to take down to achieve this. Belt sander would be your tool of choice.

Finally you have something you can start over with. I would buy a few packages of glass mat (the woven kind for strength, not the cloth). Along with this buy a canister of fiberglass resin (and hardener if it doesn't come with it). I usually buy all of the above at fleet farm, but I'm not sure if they have one in your area.

Finally, grab a couple tupperware containers (they will be ruined afterwards so use like a cottage cheese container or something disposable) and mix up some fiberglass resin / hardener. Make sure you have some cheap paint brushes that you plan on using once and throwing away each time. I would apply 6 different times, one for each side of the box.

What I would do is lay down tinfoil on your works surface (release agent) and cut out a 2-3 pieces of mat the size of a side of your box. Lay the first piece down on the tinfoil and start "painting" resin over it. After it is fully saturated, place the second piece down directy on top of it. Repeat with third layer. You now have a thickish layer of fiberglass. Now take your box and apply resin straight onto the wood and get it nice and tacky. Then turn your box so the side you just applied resin to is facing down and set it right on top of the sheet you just made.

A day later when it's all set and hardened, sand off the edges back down to where the wood actually is (square them up). You can use the ruined paint brush from the day before as your current days mixing stick.

DISCLAIMER** You MUST wear a real respirator for fiberglass sanding / grinding or you will PERMANENTLY damage your lungs. Don't screw around with the little dust masks, glass particles never leave your lung tissue and will build scar tissue). There is NO substitute to a full respirator, this is a must have.

Anyways, repeat for all sides and then sand the surface of the fiberglass nice and smooth (use body filler to fill pockets if necessary). Once you have it all smooth either carpet or paint to your style of choice. Once you're done I would go inside and silicone caulk the edges to make sure it's air tight. If you are super anal, put silicone caulk on the cracks inside the box to ensure air tight enclosure. Let me know if you have any other fiberglassing questions, I've done my fair share.

Here are some pics from the beginning of my current project:
http://picasaweb.google.com/schampers.russ/SubBox#

Things that make the job easier:
Respirator (everything is easier when you are alive)
Belt Sander
Orbital Sander for smoothing surfaces (could get away hand sanding)
Latex gloves while fiberglassing to keep fingers non sticky

rideit · Criminal Joined: 14 Aug 2006 Posts: 50

wakeboarder3780,
thank's for the write up, I did use 3/4 mdf so I should be good,, I think I'll try what you said!!!

8122pbrainard · Outlaw Joined: 10 Feb 2009 Posts: 111 City: Northfield

rideit · Criminal Joined: 14 Aug 2006 Posts: 50

8122 I'm going to use cpes and then do the fiberglass with the mat matterial!!!

Hollywood · Posted: Feb 27, 2009 1:15 pm Post subject:

I think building a new box would be much easier at this point.

Wakeboarder3780 · Posted: Feb 27, 2009 1:44 pm Post subject:

Hollywood is actually probably right. The only thing this will save you is the cost of wood and the time re-cutting the wood. Up to you.

rideit · Criminal Joined: 14 Aug 2006 Posts: 50

If I start over should I use the outdoor MDO? or MDF w/CPES and the resin?

8122pbrainard · Outlaw Joined: 10 Feb 2009 Posts: 111 City: Northfield

ridit,
I would CPES even the signboard (MDO) just to be safe and also it acts as a primer for the coating of your choice. Since the MDO may be harder to find plus more expensive, I'd go with the MDF.

rideit · Criminal Joined: 14 Aug 2006 Posts: 50

kool, thank's for the help