I welded some quarter repair panels in my 40 coupe. I've skimmed over the area with filler, and I'm sanding it, but is there a trick to getting a nice double curvature surface? I'm doing my best by feel and eye, and I think I know where the remaining low spots are, but I'm no expert. So are there any secret tips? Thanks Mart.
Kinda hard to just tell someone via text - especially without seeing the surface. I use a combination of folded 40 then 80 grit (sticky back airfile paper folded to stick to itself) for the smaller areas, different blocks & sponge pads depending on the curvature of the surface for larger work. Sand using 45 degree strokes criss-crossing back & forth. ~ Paul aka "Tha Driver" Giggle Cream - it makes dessert *funny*!
Hey Mart, First make sure you have enought plastic filler on the surface to cover the low spots. "IF" you've done a good job of shapin' the panel with the cheese grater/surform tool you've gone a long way towards savin' yourself alot of sanding work. First start by sanding ,cross hatch wise, across the panel, left to right in , say 12''X12" sections, much like typing on a page. Once you have made it to the bottom of the panel, and having achieved a good general shape, start again at your top left and sand top to bottom, over the previous cross hatched pattern. As you work the repair, always use your hand to compare the areas you have worked, against those yet covered. Cut your self templets from the other side of the vehicle, made of card board, if you are havin' a tough time gettin the shape. Good Luck-
I added more since I originally posted, after I thought about some issues: You may not know my credentials, but I worked in the autobody repair industry for more years than I'd like to think, doing both "production work" and work on my own cars...the "right" way. Believe it or not, I use the red Scotch-brite pads cut to rectangles in the length of self-stick 8" D.A. paper (usually 80 grit). Center the scotch brite on the disc of paper, stick it to it, then fold the sides up and over top of it. It will conform to compound contours with persuasion from your hand, and keep you from leaving finger marks; i.e compared to using paper on your naked hand to get into the contours. I am **** about body panels waving back at me...and I like black cars, so I guess you could glean from this that it works...(for me at least) Also, I like to hit the fresh filler with a "mist" coat of a flat lacquer paint, and sand till it was gone. Hold the spray can of flat black about 14" away from your fresh filler, and hit the trigger as you move in one direction across it. Spatter and "pop" are okay, by no means do you want to have a uniform coat...only a spattering. After you begin sanding, dark areas represent low spots, and more sanding...hope this makes sense. I should add...sand in criss-cross strokes.
To add to what was said above. try to use a shorter more flexible block to sand with or else you tend to flatten out the curve in the panel. I have a few of the hard foam ones in different shapes. And sanding back and forth in one direction also tends to flatten. I agree, you should always shoot a guide coat on filler. it lets you know exactly where your at and if you need more body work.
also applying the filler can be a possible source of your problem......Instead of applying the filler in one direction with a straightedged applicator as if you were flattening a low spot on a flat surface,You should use a wider flexible applicator that is larger than the area to be skimmed. spread it horizontally first -Then vertically forming a more compound curved application of filler, to start with......that way you are not "starting out"sanding on an already "too flat"-surface.....
Along with sanding crosshatch strokes and changing sanding direction almost constantly, use a flexible sanding board. You can make one like the one pictured out of a piece of 1/8" thick Perspex sheet cut to whatever dimensions you like. 3M makes the sandpaper in gum backed rolls 2 3/4" wide so that's a good width for one, We have them all sizes from 18" long to 1"x 1/2" for doing tiny areas, like around wiper arms and door jambs. The one in the picture is 1 3/4" x 7". The "handle" is a piece of semi hard foam or rubber epoxied onto the back of the acrylic sheet. I think wife made this one when she worked for Calty, Toyota's design center in Irvine, CA. The final test is to guide coat your primer to find low spots, but that's later in the game. Most bodymen rely on the touch of a flat hand run over the surface to feel high and low spots. works best for some in the dark even! If you don't want fisheye problems inthe paint, be sure and wear gloves while touching though.
What choprods said. Use the biggest spreader you can for the area you're working with. I used to like to use a wide spreader...apply MORE filler than you think is neccesary, and sand the rest off. It becomes hard to level a surface after repeated applications of filler. Try to get it done in one p*** if you can. Like everything else, measure twice, cut once... If you think it will take one s****ful of filler, mix up and apply 2, then sand off the rest. If, after sanding, you find pinholes, you can use either another "light" skimcoat to fill them in, or a "finishing putty" for a perfectly smooth finish. Do NOT rely on a heavy-build primer to fill in pinholes/imperfections. After painting/priming, the heat from the sun can pop them back out.
Im ashamed to come out of the closet here......I have and use a 10" drywall knife.......talk a****st yourselves...... from the visual sense- a good way to check your work other than the guide coat advice posted above is this: look at your work in the shop at night -with a flaslight or a trouble light layed on the floor...you can then observe the work in question in a manner not achievable, in the light of day..... even the most impercievable flaw will be revealed by the shadows of this light.....
Also, to add to this...once you finally prime & wetsand your worked areas, wipe them down with a LIBERAL coat of a wax & grease remover so it's soaked; (you should do this anyways)...then, using a light source such as a trouble light or droplight, shine down and sight down (close to the panel) to spot any waves/imperfections. The wax and grease remover acts as your "shiny" paint coat, and you'll be able to see what the finished panel (in gloss) will look like. If you're going for a flat finish, this may be unneccesary unless you're ****-retentive like me. If you see waves, lowspots, or imperfections, now is the time to fix them before you go any farther.
If you have sheet rolls of 80 & 180, like you tear off and stick on blocks, get nice flat stir sticks (or even if you've got a table saw cut some nice ones) stick the paper on the stir stick long ways and fold it over, you'll have about 1/4 overlap on the one side, stick those together. You can hold this with your 8 fingertips or one hand by the heel of your thumb/palm and your middle finger out straight, and it will conform to almost any curvature, and the tension for holding it down really makes it cut. Since your fingertips are on it you can really feel when it's getting level. Of course you're blocking your guide coat of black , don't prime it, it's a waste of time & primer and you spend all your effort blocking off primer and taking a bunch of plastic off with it & not watching the high and low spots show up through your super light fogged on guide coat , your guide coat should just barely tint your filler (like SEM trim black, or SEM even makes actual Guide Coat, just don't use enamel or Rustoleum or anything gummy, whatever you guidecoat with is coming off anyway, just make sure it sands off dry and doesn't ball up & ruin your sandpaper which will dig grooves in you're work)....so now you've got a good visual happening along with the fine fingertip feel of it leveling off. I block with stir sticks all the time and produced many show winning / "best paint" black cars. Just make sure the sticks are flat & not curled or cupped. This even works for convex, etc..just grind the ends up so they aren't digging in. It works excellent for long straight / skinny / shallow & multiple body lines also since you can use the skinny edge. And they last a long time, after they get worn down they're good for other situations also, edges, in between panels where you can't reach, etc....stir sticks are your friend
I'd just like to chime in, and say the above methods have worked great for me in the past... a long spreader, a long board. Apply the putty in long strokes at about a 45 degree angle from horizonal, I usually pull it up, it seems easier to control that way. I've had great success at sanding at 45 degree angles, prime and block the area, then wet it and watch the reflections. Can't go wrong, but it all comes down to how many times you're willing to go over the panel.
I have used many of the things mentioned here. I keep several different sanding blocks and longboards as well as homade stuff like the Scotchbrite pad with DA paper. Every car has different curves and no one method works the best. I have found one constant, my cheap white plastic longboard.............it has more flex than my stiffer yellow 3M composite ones. Works great on gentle curves.
Wow! Thanks Guys, lots of excellent advice here. Because I do not paint stuff very often I rely on you guys that do this stuff more regular to guide me. I am patient enough to keep at it until I'm satisfied. I think I should have tried more guide mist coats earlier on. I can now see a couple of flat areas that need building up. I'm getting there-slowly! Viva La Hamb! Mart.
What I meant was that you aren't going for complete coverage...you only want to fog it on. If you cover it over completely as if you were trying to paint it, you'll 1) waste paint & 2) gunk up your paper faster. You only need a mist of the paint on the fresh filler to provide enough of a color change to provide a visual reference of low spots when sanding. On spray can should last on doing a whole car...
The Jalopy Journal
