bondo to smooth mdf surface?

I'm building a sub enclosure out of MDF and I want to smooth out the surfaces (edges included).  Can I apply bondo to the MDF to accomplish this.  My thinking is that the bondo can be sanded down and it would cover any seams, nail/screw holes, can be sanded down and paint would come out smooth on it. 

I'm just concerned whether or not the bondo would adhere to the box or would I have to worry about it cracking.

Your input is greatly appreciated.

Mike

Just sand the mdf first then use very little bondo then paint....

Youd be surprised what happens to MDF when you sand it......

Yeah...I know the flat surface of MDF sands down well, however...the cut edges don't do so well.  Plus...I don't want the seams to show when it's painted either.  My plan is to paint the box a high gloss black to match the exterior of the car.  I just didn't know if the bondo would be a good option to work with.

I also didn't know that I could just put resin on the box either.  I will definitely do that to make sure it's sealed really good before adding the bondo.  Hopefully...I'll have pics of it completed in the next couple weeks.

Thanks for the input fellas!!!

resin wont be strong and will be brittle.... if your gonna do that put down a thin coat of duralast or somthing.... just ruff the mdf up a bit to get a strong grip

Sorry had batteries on the brain.. its duraglass

Its a fiberglass filler that has strands in it... this way it hardens. some people then sand it a bit and add just a bit of filler to smooth it out. and then do the final sand. but for you,you may just need the duraglass.

Yea...

Doing just resin is brittle like I said before... And doing just bondo can crack.. I know theres not much stress but you want somthing strong and seal the seems good id go with duraglass

And duraglass is pre-mixed or do I have to mix it? 

Can you think of any other coatings I may use for what I'm trying to do???

Yeah...I'm sure it's MDF.  The suface of it is indeed smooth, but that's not the problem.  My problem is the cut edges of the MDF...maybe the problem is that I've used just primer in the past.  From what you're saying...sealer/primer would make the cut edges appear better, right?

What would be a good product to apply to the outside of the box if I want hide the seams from where all the boards meet???

Thanks!

if the edges are rough, then I would consider adjusting the height of the blade and the type of blade you are using. I found that with most blades, setting the blade to just 1-1.5 tooth above the top of the board will help minimize the tearing of the board as it is being cut.

Second, consider changing the blade of the saw too. If it is tearing the edges, then it's too rough or you are pushing too hard on the wood as it is cutting. Let the blade do the work, not the pressure. If you are not applying pressure on the wood and letting the blade do the work, then consider getting a blade for soft woods. That will take care of the problem to begin with.

As for what you have now and want to make it look better, yes and no. You will need to use a high-build primer/sealer. Depending on how bad the edges are, several light coats will be needed. Don't use a heavy coat because that will weaken it.

For the seams, I like to use one of several products. My personal favorite for blending seams is good old carpenter's glue. It will pull the seams closer and fill in the gaps. From there, I would use a flush trim bit on a router/trim router to make it as smooth as possible. Use a couple of coats of high-build primer/sealer and sand that down to make the seams disappear.

Ganbatte ne!

The edges aren't getting torn up due to the blade, I was just talking about how the cut edges aren't as smooth as the face of the MDF.  However, using a build up primer/sealer makes sense...that's exactly what I'll do.  I've already sanded all the edges so that they are smoothly blended into the surface...now I just want to work on making the seams disappear for when I paint it.

Thanks for the suggestions, I'll let you know how it turns out!!!

Mike

Oh, my mistake. I didn't quite understand what you were talking about exactly. Due to the construction of the MDF, you'll never get a perfectly smooth cut face. All that can be done to perfectly plane it is to seal it and go from there.

Please post pictures. Ganbatte ne!

Keiika

My bad for not making it clear...it's all good.  I'm using that Kilz2 primer and it seems to be doing the job.  I put it on heavy with a brush, so I'll sand it down with a fine grain paper to get rid of the brush strokes, prime it again with a roller and then hit it with the paint.  Once the edges have saturated enough, it'll smooth out with the sanding and then it'll take the glossy paint the way I want it.

Thanks for the input though.  I should have pictures soon as I get my friggin sub from Pioneer!!!  (of course they're draggin their feet on this as it's a replacment sub).

Mike

No problem. LOL sorry about your sub problem, but it seems to be pretty common there... What I find that frequently works is to call them repeatedly. Keep up the inquiries and they tend to respond faster.

Ganbatte ne!

Keiika