I am doing a little experiment with my speakers that I am attempting to do an automotive finish on. If you have followed this post:
http://www.diyaudio.com/forums/multi-way/247049-sad-realization-mdf-not-flat.html
you will know what I am working with. Basically MDF cabinets glued together. My understanding is that if not addressed, the seams of the cabinet will show through the paint eventually. The experiment that I am doing involves drywall tape and auto body filler. Basically I am taping the seams the same way that a drywall installer would tape the seams in drywall. The process is to put down a thin coat of auto body filler along the seam, press in a strip of drywall tape, run a taping knife along the tape to force out any extra auto body filler from underneath the tape. After it sets up I go over the entire surface with the auto body filler and then sand everything flat. I used some Bondo brand filler because it was the only thing that I could find locally. After sanding, my arm feels like it is going to fall off. I was reading that Evercoat is easier to sand, TVRGEEK actually suggested it on that last thread. Which Evercoat body filler is the easiest to sand, or does anyone have any suggestions of other brands that are easy to sand (easier than Bondo brand)?
http://www.diyaudio.com/forums/multi-way/247049-sad-realization-mdf-not-flat.html
you will know what I am working with. Basically MDF cabinets glued together. My understanding is that if not addressed, the seams of the cabinet will show through the paint eventually. The experiment that I am doing involves drywall tape and auto body filler. Basically I am taping the seams the same way that a drywall installer would tape the seams in drywall. The process is to put down a thin coat of auto body filler along the seam, press in a strip of drywall tape, run a taping knife along the tape to force out any extra auto body filler from underneath the tape. After it sets up I go over the entire surface with the auto body filler and then sand everything flat. I used some Bondo brand filler because it was the only thing that I could find locally. After sanding, my arm feels like it is going to fall off. I was reading that Evercoat is easier to sand, TVRGEEK actually suggested it on that last thread. Which Evercoat body filler is the easiest to sand, or does anyone have any suggestions of other brands that are easy to sand (easier than Bondo brand)?
To me bondo seems to sand OK. The outer skin seems to clog the paper, but once through that it sands fine.
Have you tried a very rigid glue? Unibond 800 is excellent.
Vacuum Pressing Systems -- Veneer Glue
Smear a bit of the glue on the "endgrain" of the MDF when you glue up the seam and see what that gives you. Might be easier then coating and blocking out the entire cabinet.
Evan
Have you tried a very rigid glue? Unibond 800 is excellent.
Vacuum Pressing Systems -- Veneer Glue
Smear a bit of the glue on the "endgrain" of the MDF when you glue up the seam and see what that gives you. Might be easier then coating and blocking out the entire cabinet.
Evan
HI
First find one that's suited to wood products ,another way is to epoxy prime first then use a spray polyester .The epoxy seals the timber/MDF and give the poly better adhesion .
The filler I've been using with great results is the 3M Platinum Plus easy to sand and no pin holes .
Automotive Aftermarkets Home:3M? Platinum? Plus Body Filler
After filling don't forget to HiFill to level the surface and sand off. If not using HiFill prime then putty sand flat then prime again .
There are also a professional range of paint products for timber/wood products . A most of automotive products aren't suited for timbers or guaranteed by the manufacturers if used over wood products .
Cheers
Mal
First find one that's suited to wood products ,another way is to epoxy prime first then use a spray polyester .The epoxy seals the timber/MDF and give the poly better adhesion .
The filler I've been using with great results is the 3M Platinum Plus easy to sand and no pin holes .
Automotive Aftermarkets Home:3M? Platinum? Plus Body Filler
After filling don't forget to HiFill to level the surface and sand off. If not using HiFill prime then putty sand flat then prime again .
There are also a professional range of paint products for timber/wood products . A most of automotive products aren't suited for timbers or guaranteed by the manufacturers if used over wood products .
Cheers
Mal
Last edited:
You can also seal the cabinet first with a primer then use the 3M filler over the top .
Make sure both sides of the cabinets are sealed.
Cheers
Make sure both sides of the cabinets are sealed.
Cheers
As a audiophile who's also a car nut, I'd recommend a good high-build primer suitable for MDF. You can find products (and probably expert suggestions) at an established auto body supply store in your area. I've used DuPont 3240S with good success on a number of products. Afterwards you can block sand (I go with 400, 800, 1200 grit) and seal, for a mirror-like finish.
Bondo is probably not worth the effort--goes on too thick, adheres poorly to wood, and (because it goes on thick....) leaves you with a TON a sanding to do.
You also might want to check with a good woodworking shop in your area; they use all sorts of fillers to finish their products (although I bet they are not trying to build quality furniture out of MDF).
Next time, consider a good grade of plywood..... or you might want to try to "face" your current project with a veneer of quality wood, you might get a great looking end result.
Bondo is probably not worth the effort--goes on too thick, adheres poorly to wood, and (because it goes on thick....) leaves you with a TON a sanding to do.
You also might want to check with a good woodworking shop in your area; they use all sorts of fillers to finish their products (although I bet they are not trying to build quality furniture out of MDF).
Next time, consider a good grade of plywood..... or you might want to try to "face" your current project with a veneer of quality wood, you might get a great looking end result.
Bondo followed up with there glazing spot puddy can bring nice results. I never tried 3M fillers but vouch for 3M sfuff I use it at home and work they make a stand up product. Don't try and save a buck get the good paper it pays in the end.
Thats an interesting idea, the drywall tape. You can also get mesh fibre glass tape. This little read might be helpful.
What's the Difference: Paper and Fiberglass Mesh Drywall Tape - Fine Homebuilding Article
The same rules should apply other than your using automotive filler and not drywall compound.
Thats an interesting idea, the drywall tape. You can also get mesh fibre glass tape. This little read might be helpful.
What's the Difference: Paper and Fiberglass Mesh Drywall Tape - Fine Homebuilding Article
The same rules should apply other than your using automotive filler and not drywall compound.
I guess I will give the glazing spot putty a try. I want to get it all prepped and then beg the auto body shop down the street to put an automotive finish on it. Not sure if they will do it but we will see. I should have asked them first what they would coat the mdf with. I tend to get ahead of myself quite frequently.
I used Evercoat Spot-Lite 100445 on my last project. Compared to Bondo or Featherlite it sands like a dream. Still need to use a high build primer though.
Interesting that no one has mentioned the Fact that MDF is quite poor in knock around durability, ie: real life wear and tear uses.
The edges Shell ...easily. Just like Glass does.
Regardless of finish
The edges Shell ...easily. Just like Glass does.
Regardless of finish
To get around it use round overs or facet the edge's .Knocking a corner can be a real pain in the butt.
Like fitting car doors during a resto job .
Cheers
Go to the Evercoat web and read about their various products. Easy to sand is not always the most important question. Any filler with not quite enough hardner will be hard to sand as it will not be as hard. Standard body filler is for up to a 16th inch fill. That is far more than you need on a speaker box ( I hope!) They make skim coat smoother fillers.
Spot putty is ONLY for filling in pinholes and that one little scratch you did not find. It is very soft. It is not a surface filler.
Spot putty is ONLY for filling in pinholes and that one little scratch you did not find. It is very soft. It is not a surface filler.
The other problem with spot putty is it can sink over time . There are glaze fillers for filling scratches and pin holes .
2 pak HiFill's are the way to go .
Cheers
Stay FAR FAR away from that spot putty. It does not have catalyst and will never really cure.
When I worked at a body shop, we would use body filler, some glaze if small imperfections, then a couple good layers of a polyester catalyzed primer (spray body filler), and then a 2k primer before any paint was sprayed.
Anyone who has ever done any fiberglass work or body work would never ever use an air dry spot putty.
The easiest body filler to sand that I've used is Rage Gold Extreme, then Rage Gold, Rage, and then Z-Grip. I always bought Z-Grip from my own personal filler needs. There was a filler by U-Pol called Dolphin that is supposed to be the cat's meow too.
When I worked at a body shop, we would use body filler, some glaze if small imperfections, then a couple good layers of a polyester catalyzed primer (spray body filler), and then a 2k primer before any paint was sprayed.
Anyone who has ever done any fiberglass work or body work would never ever use an air dry spot putty.
The easiest body filler to sand that I've used is Rage Gold Extreme, then Rage Gold, Rage, and then Z-Grip. I always bought Z-Grip from my own personal filler needs. There was a filler by U-Pol called Dolphin that is supposed to be the cat's meow too.
Has anyone tried Epoxy resin mixed up with Microballons and the right amount of hardener? I know from building and repairing boats that that combination is brilliant for filling gaps. It toughens up wood till it's almost like a metal and will never come apart. The wood breaks before it does, even hard wood! You mix in the microballons until you get the paste to the consistency you want to work with but if anyone tries this, for gods sake get the correct solvent for epoxy resin or an accident becomes permanent.
- Status
- Not open for further replies.