Londons Autobody

Bondo Basics – Apply and Sand

Bondo Basics – Apply and Sand (part 2)

This is a follow up to:  Bondo Basics – The Art Of Body Filler

When applying and sanding bondo your gonna want to be fully assured you know what you’re doing. This will save you time and materials in the long run. Don’t bother starting with the bondo until you have made sure your damage is pulled, patched, ground down, blown off, wiped clean and ready.

To Begin you have to make sure your area you are applying the body filler to is completely roughed up. Grind the area thoroughly with 36 grit sand paper or at a minimum of 80 grit. Take your air gun if you have one and blow off all the dust and grit from grinding. There are steps people like to avoid, I’m guilty too, but you learn some shortcuts pay and some don’t. Here’s one commonly overlooked. Wipe it down. Take the wax and grease remover and treat it as though you were painting it. The bondo has to stick completely or it will chip and flake, in other words it won’t feather for you and it will tick you off and waste time and materials. If your damage is repaired right you shouldn’t have to apply more than two or three coats to have a finished repair.

Alright, to the tools needed. Generally you want a 5 – 9 inch sanding block. The sandpaper you need will be the common 36, 80, 120 works well sometimes, 180 then 320 for feathering before primers etc. A DA Sander is used by some, but the same sandpaper applies, choose the same grits.

The methods: Depending on the size of the damaged area, mix only enough to fill the damage completely. Be sure to apply enough – this takes a little to get used to. One important note is that you will not spread the bondo perfectly, it shrinks in an you will end up with a low spot. Apply enough body filler so it’s built up a 1/8 or so. Not more than that, you will be sanding your butt off, this gets old Take your 36 grit or 80 grit, depending on the amount  of area you will be sanding. If you think you can lightly sand and feather in one or two coats, then stay away from the 36 grit unless you know when to stop. It puts some pretty deep scratches in the bondo and the area around the bondo where you will be sanding over. Use 80 grit to avoid excessive scratches. For most larger dents you will want 36 grit and your larger or largest file board.

With the panel prepared and the bondo spread,  let it harden. If you have a mess you can carve on it with a knife to get some of the stragglers you slopped on it off. If you wipe on body filler when it is not set up it will surely stick and you’ll have to sand them off. Let it harden and pick it off later.

For large dents that you know will need at least 3 coats of body filler it’s best to have a rasp or body file hand plane. It works somewhat like a cheese grater. Let the bondo set up real good, feel the bondo and it should be a little warm but not cold….if it’s cold it will be too hard for the rasp if it hardens.  Take the plane and begin filing in one direction. This is very rough but effective way to cut your panel. This takes a little getting used but it will save you quite a bit of time, sandpaper and your lungs from tons of dust. Use it on the first coat only, the rough coat. You will be turning right around and spreading another coat of bondo over it, after you blow it off real well of course . This is used to help get the filler straight. The low spots will not be filed. Note: To help Identify the low spots… spray the filler with a cheap flat black paint, the cheapest fastest drying kind you can find. DO NOT USE ENAMEL SPRAY PAINT, you don’t have all day to let it dry. Find a cheap lacquer paint, Walmart brand works good at .94 cents a can. Simply dust it, don’t put a full coat of paint on, just enough to add contrast to the body filler to identify where you have sanded. This will greatly assist you identifying what and where you are  sanding. High spots are gonna sand first of course. Keep attacking them as you sand until  all the guide coat paint around them is off. If you have sanded the filler and panel is free of the spray paint you applied, chances are you are real close to a finished repair. But there are other things to look for and consider.

Take your inline sander or manual long board of choice or hand sander and begin sanding in a criss-cross (X) pattern. This is extremely important if you do not want waves. Sand at a 45 degree angle in all directions to each other. This helps cut the filler evenly. If you sand in a straight line…. you get a straight line. This is not rocket science and there are no tricks. You have to watch what you are doing. Don’t go nuts sanding, do it methodically. Sand And Feel, Sand And Feel. Pay attention to body lines. They will have to be included in your sand and fill process. For straight lines use tape and sand up to it, reverse and sand down to it. Use tape when applying bondo to get a straight line. Apply the body filler over the edge of the tape and remove the tape before it hardens. If the filler hardens you’ll be sanding the tape too, so pay attention.

Apply bondo as many time as it takes to fill the low spots. If you have high spots you’ll know it. If the metal is showing and the bondo isn’t sanded… you have high spots. These will not go away. There are two ways to deal with this, only one is the right way. You can fill the whole panel up with body filler and sand and sand, or you can take your pick hammer and carefully tap them down. Tap them down!!! Don’t be afraid to use the hammer, you will need it until you are finished and satisfied. Don’t cheat, if it’s high… tap it down lightly…tap, tap, tap.  All the bare metal showing is high so tap the bare metal and beyond an inch or so. Stop sanding if you see this, they won’t go away and you’ll be getting further from straight. You’ll have to tap them all down and apply more body filler.

When you know your getting it close switch to the light grits. Use 80 grit paper and feather all the edges of the bondo and the paint together. It may feel a little rough and that is normal. You are filling the dent, the primer you use next will take care of the small scratches.

Another note: When mixing the bondo try to avoid flipping it over like taffy. Roll it over and spread mix it. You don’t want to let air get trapped in there. You will end up with pinholes eventually. Pinholes are just that. Small little pits in the bondo. These can be filled later with a glazing putty, but try to avoid excess air when mixing.

After the 80 grit sandpaper begin to taper down on the sand paper. Use 180 to feather any scratches in the paint near the filler. Finish with 320 to assure you won’t have sand scratch swelling later on down the road. The smoother you get the panel from here on out the nicer the repair will be as a finished project.

Wipe it down, look for pinholes, fill them with glazing putty if you have them. If not get that primer ready and spray on 3 good coats. Dust your primer with the black spray can and begin sanding again. I’ll write about the primers next.

Good Luck with your project. You’ll learn from experience, you can’t screw it up if you know these basics to bondo. It’s easier to do than explain

For further reading on Body Fillers  go here:   Bondo Basics – The Art Of Body Filler (part 1)

Tags: autobody techniques, body filler, Bondo, corvette repair, fiberglass repair, heavy weight gold filler, pinholes, sanding techniques

Fiberglass Basics – Easier Than You Think!

Fiberglass Basics – Easier Than You Think!

Does the word fiberglass intimidate you. When you think of fiberglass maybe your thinking you need a whole new set of skills. If you have ever used, or should I say mixed bondo, you are half the way there.

Working with fiberglass can be very effective and very simple. The key to a solid fiberglass repair is to plan ahead of time. Make sure you have the proper equipment. You will need:

• Fiberglass mesh, or preferably a fiberglass kit. It includes enough material to fix a rather large area
• Get yourself a decent pair of rubber gloves
• Depending on the size of the repair you’ll need a piece of cardboard, for mixing the resin/hardener
• Another peice of cardboard and some duct tape, (read below)
• A good industrial or at least a sharp scissors
• A old small paint brush, or some cheap acid brushes for applying the resin

When preparing to repair fiberglass, and you have your supplies as far as fiberglass necessities, of course you’ll want to analyze the damage very good. This gets overlooked very easily. When fiberglass is damaged in an accident it usually cracks, even if they are hair line cracks. They may not seem like much, but when it comes time to paint and certainly over time they will show up. You cannot build a bridge over cracked fiberglass with primers nor does bondo (body filler) hold forever. You will need to grind down all the damaged areas!

To Start wipe the area off where you are now going to grind. You’ll want to grind the area and all the little cracks down, at least a 1/16 of an inch. If you can grind further go ahead. If you can get behind the damage like say on a hood of a semi, then you can grind the inside as well. This is the proper way to do it, but I have had great success either way.

Take a tape measure and measure the area you have ground. If it’s ten inches then you  will need 30 inches of fiberglass matting. When repairing fiberglass it is essential to lay down 3 layers of mesh intertwined together to get the proper strength to hold the repair together, forever. You do not want vibrations or minor bumps to crack your repair again. Of course you cut it wide enough to fill the hole. Most fiberglass repairs will need some sort of backing plate behind the huge hole. This is where the other peice of cardboard comes in. Cut the piece an inch or so larger than the damaged area all the way around. Now the duct tape. Tape it in there real good for now. You are gonna have to find a way to get behind it. Use what works. I have had it where I can’t get behind So I tenderly have had to nurse it from the front side, holding it tight in place until it is set up, wear your gloves, you’ll be in good shape..

Now for the mixing of the fiberglass with the resin. Resin is the bonding agent, mixed with the hardener so it sets up. It is somewhat like mixing body fillers. It basically uses the same hardener,  same principle in mixing. There are a few different ways to do the next few steps:

• Pour out enough resin to be sure to coat all the pieces of mesh completely. You’ll normally need a 1/2 cup or more for most repairs. Don’t be skimpy here, you want to have enough to coat the glass. If you pour it in a container try to keep an idea how much is in there. Apply a few inches of hardener in the container and get mixing. If it’s hot you have about 10 minutes to to work so again have your fiberglass mesh ready to go. Take your mixture of resin over to the vehicle you are working on and brush liberally around the damaged are with the resin, put it as thick as will hold, but try not to let it go running onto the floor or the tires
• Another more messy technique I’ve seen is to pour out the resin on the cardboard and mix it there. Take your mesh and dredge it in it till it is coated… like chicken.  Caution though, this is very messy, I shake my head when I see this, but it will coat the mesh and probably the work bench and you really well.  Use the first method and paint it on.
• Take the cut mesh and press it around the outside where you put the resin, you want it to soak in there together.  Apply one piece of mesh at a time, this will allow you to soak each piece real good for a strong fix. If you have your cardboard backer it’s probably gonna be a permanent part of the repair. If you want it off you have to work at it carefully before the resin is set, but avoid allowing the fiber glass to fall in the hole, so let it set up a little and work quickly. Once you have the first piece on apply resin over the entire mesh, do these steps with all 3 pieces. Don’t worry if the fiberglass matting seems to be falling apart, it’s a good thing. The more intertwined the pieces are the stronger the repair.
• Let the repair set till it is hard as a rock. You want to grind on it or use a sander with 36 grit sandpaper to begin to flatten and form it out. DO NOT sand through the fiberglass around the edges of the repair, that’s why we ground it down another 1/16″. It should hold and be able to sit there without any problems, you’ll be grinding and finishing off with a couple coats of bondo.
• With the repair set up and ground down it may not hurt to test the strength of the repair. It should not give in, you should be able to push on it and see the rest of the panel moving in and out with you. If not repeat the fiberglass steps again, add a few more pieces and bond it to the strongest areas.
• If you feel the repair is strong enough, blow it off good and begin with the bondo. If you haven’t read Bondo Basics – The Art Of Bondo,  now would be a good time, you’ll want to read that before you begin with fiberglass.

Those are the basics for you, you can repair almost anything with fiberglass. Done properly you’ll patch boats, be able to put a front end on a Corvette, fix or replace a headlight bucket on your beloved Semi, I’ve even fixed bumper covers with it, to hell with the bumper repair kits!

Tags: body filler, Bondo, bumper repair with fiberglass, corvette repair, fiberglass mesh, fiberglass repair, hardener, mixing resin and hardener, repair bumpers, resin, sanding techniques, semi repair

Bondo Basics – The Art Of Body Filler

By: London Vande Zande

Where would the world be today without the luxury of  Bondo. Ever since I can remember, well 20 years or so, it has been all the hype.  You have yourself a nice looking muscle car or any car for that matter and the first thing everyone wants to know, even if they don’t say it is “ how much bondo, looks really nice, hmm how much bondo, bondo bucket?”  Well I’m here to say that bondo is an absolute necessity if you are going to have a nice looking, straight paneled ride.

Let’s get one thing straight about the use of body fillers (bondo). It is not, and I repeat not for cars that have rust. It is not for cars that have holes in them. That is what you have a welder and patch panels for. If you think bondo will hold or last over a hole of any size you’ll be assuredly let down.  All those hopes and dreams of having that ugly hole patched will certainly come back and haunt you. If not today, which is sometimes all the longer it takes,  give it a year. Moisture will have a field day pushing out the plastic filler and leave you again worse off with a  rusty, bubbling, bondo’d up sick  looking disgusting scabby eye sore! - geez  London  ”take that bondo”

Bondo, or plastic filler, body filler, call it what you want is great stuff, but it is made to smooth out panels. It’s a filler in the sense that it fills waves and imperfections in metal. It doesn’t take the place of it. It is a cheap and easy replacement for  the use of lead. If you have holes you really need  metal to patch them, and truthfully it’s much quicker to simply cut a piece of metal and tack it in there. It will last if done right for years, especially if you keep it dry and clean. If you live where I do near the great lakes “keep it out of the salt”.

All body fillers are basically the same. Some claim to be better than others, but seeing as we’re not patching holes anymore with it, I go for the one that sands the easiest.  These are known as the light weight body fillers. They usually sand quite easy, and they won’t clog up the sand paper nearly as bad as the heavy weight (gold) fillers.  I personally stay away from the ‘bondo‘ brand, don’t know why really, maybe it’s the nightmarish name from my past, but that’s neither here nor there, I go with the Evercoat brand.  I have had great success over the years and  see no need to change.  They haven’t been able to improve too much on it over the past 15 years.  I have experimented with most brands and weights over the years and one thing they have in common is how to mix it. The single most greatest factor in mixing bondo is the temperature where you’re using it. If it is 60 degrees in the shop it will take 15-20 minutes or longer to set up, if it’s 80-85 degrees where you are, you have just enough time to mix it fast and run to get it spread.  Mixing  is the standard 1 inch ribbon of hardener / golf ball size filler. If it’s hot, cut back a tad. If it’s cold, DON’ T add more for it won’t help.  That can and usually will create pinholes and gummy bondo that will not sand well. You are forced to let it harden on it’s own or put some heat on it. Heat the panel first a little if you can, it will help at least to get it to start setting up. Have patience, if you get on it right away it may let go, or flake off the panel and you’ll be starting over. Let it bond to the panel thoroughly. Take your nail or a pocket knife and scratch on it. I usually nurse it awhile till it sets up just enough where I can carve any mess I made out of it spreading it , off. It saves time when it comes to sanding. Take a look at the “Video’s” page for a hands on view.

They make a plethora of tools to work with bondo, most of them will be trial and error for you, you’ll find a system that works for you and have all the confidence you’ll ever need in working with body fillers. I’ll have to save the sanding techniques for a upcoming article, they need explanations, for they all are good for some things and not so well for others.  Stay in touch!

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Tags: body filler, Bondo, bondo bucket, heavy weight gold filler, light weight filler, mixing bondo, pinholes, plastic filler, rust, rust holes, sanding techniques