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i`m with out a doubt a novice body man. i have been practicing body work on a spare door for my 50 ford.my problem is that i took all the paint off the door,spead body filler,sanded, and repeated till my arm fell off and primed with spray can filler primer.the panel is smooth but i can still see where i put my filler. should i sand the primer and re prime? should i mix some sealer primer and shoot? what should i do? i`m trying to figure it out before i move onto the real deal.
Ah, the joy of bondo!!! You need to use a long "sanding block" about 2 1/4" x 17" long. and start with 60 grit paper. When you sand, take long strokes, that start on the "unbondo'd" surface of the door, and continue all the way across your 'bondo patch" and onto the unbond'd part of your door again. Hold the sanding block at an angle to the direction of your stroke. Give it 25 strokes, then change the angle of the board to the opposite of what you were holding and then take 25 more strokes. Then change the direction of your strokes by 90 degrees, so that you are sanding "crossways" to what you were doing before, and repeat the above. Then switch to 120 grit paper and repeat. Then switch to 180 grit and repeat above. You are attempting to 'feather edge" the patch of bondo so that there is no transition that you can feel with your fingers between the bondo patch and the surrounding steel. If you can not feel the transition, then you should not be able to see it after a coat of primer.
Depending on the primer and filler you can somtimes see the filler as it is a different porisity. You can use high build primer or several coats of primer sanding litely between coats. If you do as Brian said you'll get it flat it just takes time.
Another thing to be aware of, is that if you repair a damaged portion of the door, then all of the repaired area, including the weld, (if it is a welded patch), must be below the contour of the surrounding metal. This is best accomplished with a dolly and a flat faces hammer. If any of the repaired area sticks up above the surrounding surface, then you will need to apply filler to a much larger area in order to 'blend" it into the surrounding contour without an obvious "bump". In a perfect world, the repaired area should set about 1/16" to 1/8" below the surrounding metal, before any filler is applied. If you get it really close, but it is still visible after a few coats of primer have been applied, then you can try a very light coat of 2-part "blending putty", which is a very liquid form of body filler that can be lightly trowelled with a good spatula around the interface between the repaired area and the undamaged area. This stuff sets up quickly and is much easier to sand than the normal body filler. It feather edges extremely well, to 'blend" the repair into the surrounding bodywork. This stuff has a bad name in the industry, because before the advent of 2-part formulaes, it would continue to shrink for about 6 months after it was applied, and the bodywork would show up 3 months after the fact under the finished paint. Now that the stuff is available in a 2 part formulae, it cures completely due to a chemical reaction, not evaporation, so shrinkage is not as big an issue. I use a product called "Evercoat" by the makers "Rage" body fillers, and am very pleased with it.----Expert bodymen use very little of this stuff. Occasional bodymen like myself, use a lot of it. It really helps an "occasional" bodyman achieve expert looking repairs.---Brian
Part of the secret to a good repair is knowing when to stop sanding. Many novice bodymen think it is absolutely necessary to sand away every possible trace of bondo, except for in the immediate area where the repair was made. If you do that, you will actually leave a "crater" in the overall surface, which is immediately visible as soon as it is primed. When sanding a repaired area. You do NOT want to see a clear line of demarcation between the bondo'd area and the surrounding metal. that either indicates that the filler is sticking up above the metal, or has been sanded down untill it is below the surface of the metal. Rather, what you want to see, is a 'fade" from the metal to the bondo'd area, that you can not detect when lightly running your fingers over the surface, from steel to bondo.-----------Also, and I can not stress this enough---do not use a short sanding block and sand only in the area where the bondo was applied. Use a long sanding board as I mentioned in my earlier post, and take long sweeping strokes, so that the board "floats" on the surface of the undamaged metal---this will help to prevent "cratering" your repair below the metal surface.
I hate bodywork worse than snakes!!! I am good at it, because I have been building hotrods for over 40 years, and have never been able to afford to have my bodywork done by "professionals".---and I would rather not drive a hotrod than drive one with lumpy, bumpy, bodywork. I can achieve professional results---it just takes me 5 times as long to do it, and 10 times as much time as a pro shop would. I taught myself to paint, and I am a fairly good painter---same reason---I couldn't afford to have someone else do it. But I still hate bodywork worse than snakes!!!!
thanks alot to brian and cffisher. i think because i`m useing a small sanding block its killing me. and i did sand away the transition between bondo and metal.all i have left is where the repaired part is. i shaved the door handle, welded in the metal plates. that part looks good it is blened nice with the edge of the door. it`s the other side, their was a dent that i couldent knock out so i filled it and i kept sanding off the traces of bondo. which i would have needed to blend into the metal.
also some one told me that i should use tiger hair after i weld any panel. they said said it would prevent the bondo from flexing. how true is this.
http://www.autobody101.com/
This site is free and contains a wealth of info for the first time body man ,it makes for some good reading and gives you a pretty good idea of terminology and process.
To be completly honest I haven't used tigerhair in a very long time it just dosen't finish right. If you need that much bondo you should do a little more hamer&dolly or pulling. I've seen bondo on cars over 1" thivk thats just lazy and can fall out. If your going to do the job try as hard as you can to do it right. Keep the filler as thin as you can, and use a long board
I only use tiger hair when the welded areas are down where slush and water off the road can splash onto the back of the panel. Ordinary bondo will act like a "wick" and if the panel is not 100 percent welded, the bondo will pull water thru any perforations on the welded seam, and then it will create more rust and eventually lose its grip to the metal and pop out. The tiger hair is far more waterproof, so on any weld seams that are down in the splash zone, I use tiger hair for the first application of filler. Tiger hair is much stronger than ordinary body filler also, so if its a high crown area or outside corner, tiger hair is less apt to break out.
These guys already gave you some good advice, so I will be repeating a bit but also have some to add. Use the longest block you can comfortably use in the area you are working. It will be easiest to get things straight on a decent sized area with a course grit, i use 36 grit if regular filler, not a finishing type. worry about switching to a finer grit and taking out scratches after you have your plastic filler nice and straight by either going over with 80 and 180 or putting a nice neat and tight skim coat over the whole area and sanding again with a finer grit. When you are working with filler, you want to fill aways past your actual low area (Its best to get it worked out primer with hammer and dolly work as well as knock down any high areas). Sand in an x pattern completely from one end to the other end of you filler spot or as far as you can until it feathers out on the edges. Use your hand and feel what things are feeling like. Once its feathered out well if you don't have high areas that need more sanding, stop, and if you still have low areas, you need another layer of filler. I like to start working the filler when its still a little soft and sandings easier even if it loads the paper a little. But if it is tearing out instead of feathering, you should let it sit longer before you continue sanding.
The spray can filler not real good. Will be a lacquer primer, which shrinks a lot. Can shrink and have sand scratches show up later or leave rings around filler areas. Its best to let it sit for a least a couple days before final sanding for paint and allow it to shrink. Years ago its all their was to work with, but today epoxy and urethane primers are much better. Epoxy is the only primer that is not somewhat pourous and has very good adhesion to metal and will provide good corrosion protection over sanded and clean metal. They normally don't sand real nicely or have a lot of fill, so many will apply epoxy primer first , do filler work over the epoxy, re epoxy when filler is all blocked straight to seal and cover spots through to metal, and apply a high build urethane primer for it fill for blocksanding and scratches, and its sandability. That lacquer primer will provide little in the way of protection over bare metal, and also isn't best for adhesion to it. 2k primers are superior but it is very important to protect yourself when spraying to avoid getting in lungs and nervous system and have good ventilation. And also you need spray equiptment as they can't be put in a can and stored on a shelf, as they have a relatively short pot life when mixed.