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body prep advice please

1K views 14 replies 3 participants last post by  rrmccabe 
#1 ·
I've run into some low spots on a hood and don't know what to do. The attached photos show how the hood is apparently low everywhere there is an underhood brace. I can't get to those to beat them out, so is this going to mean too much bondo? I'm ignorant about this stuff, so all advice welcome.
 

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#2 ·
Did your hood get that way while sanding it with a DA? To me it looks like you're applying to much pressure while sanding? What is the make and model of that project, I don't recognize it. Without being there and feeling the hood up I think I'd reprime it, apply two to three coats of urethane or better yet polyester primer and block it out by hand with 120 or 180 on a long board. Use light long strokes with a guidecoat to judge your highs and lows. Working a hood needs to be done by hand with light pressure otherwise the metal just flops up and down around the hood bracing. If the hood is badly warped I'd look for another one or try to work the metal up. Sometimes if you have a low spot directly above a brace it can be corrected by cutting a few of the glue spots loose with piano wire then the skin will raise naturally then reglue the cut leaving the skin at it's proper level. Hope this made sense. Bob
 
#3 ·
I am with Bob on that one. Looks like you are pressing hard to strip and the backing supports are giving you more support in that area.

Not a big deal but when you block it you will want to make sure you dont press too hard.

When you get to fill primer shoot some guidecoat on it and give it a gentle (let the sandpaper do the work) block with something like 220. Should show you if its low or not.

Rich
 
#4 ·
Thanks baddbob.

Yes, I sanded with the 6" DA you see there, 80 grit. I intended to take it down to bare metal even though I think that's all factory paint on it. After I get it down to bare metal I'm going to spray epoxy and then do bondo.

No pressure; I just moved it around as evenly as possible. These pictures were taken as all that dead red disappeared. The only dip you can really feel is that egg-shaped one at the front edge in the 2nd photo. The only place I rocked the sander up on edge was going over the cowl vents. I had to hand sand in the sharp angles where those ridges run down each side of the hood. The 3rd photo shows a couple of places where it was apparently chipped all the way through the 3 layers.

BTW, why would it have 3 layers anyway? Would it have come from the factory with 4 -- the gray and white primers, red color coat and a clear coat?

This is my wife's '88 VW Fox. It's the sacrificial lamb that's going to teach me how to paint.
 
#5 ·
rrmccabe said:
I am with Bob on that one. Looks like you are pressing hard to strip and the backing supports are giving you more support in that area.

Not a big deal but when you block it you will want to make sure you dont press too hard.

When you get to fill primer shoot some guidecoat on it and give it a gentle (let the sandpaper do the work) block with something like 220. Should show you if its low or not.

Rich
I wish you two could really put your eyes and hands on this instead of just my photos. There's no substitute for the real thing, I know, and I appreciate you taking the time and effort.

I didn't press on it at all (took forever to get to this point even though each layer is very thin). Anyway, if it was from pressing too hard, wouldn't the braces be the high spots and it would be bare there first? This thing has a really dead paint on it. There is no shine at all to the red and the white under that actually has more shine to it. The engine was once overheated to the point that it quit. Could that have warped the metal or is this the way it came from the factory? No high or low spots were obvious before I started sanding it.
 
#6 ·
The dark grey primer looks like factory Ecoat to me but the lighter primer makes me think this might have been a replacement panel. Did you buy the car new? look at the hood mounting bolts where they attach to the hinge, if they've been turned it may be a replacement hood. Be carefull with that DA, make sure your paper is sharp and turn the air pressure down so you don't create heat. Go nice and easy on a hood. Bob
 
#7 ·
I can see the bracing is an X shape in the center area of the hood by the high spots that are cut through in your photos. These small imported cars have really lightweight hoods and flex quite a bit. Once you get her primed and blocked you'll see where you are in reguards to straightness.
 
#8 ·
The whole car has those same 3 layers. I'm the 2nd owner of the car and at first thought somebody sprayed a base coat over a white car and never finished the job. I bought it for $500 on an impulse when my son's Caprice and my Volvo were both going nuts from electrical problems. My wife fell in love with it and now I have to "make it shiny". That's all she's interested in, but I want to use it to learn how to do epoxy/basecoat/clearcoat so I don't mess up my project later.

Is "ECoat" some kind of primer/filler? The gray is duller than the white coat.

Should I go ahead and sand it to metal and spray epoxy?
 
#9 ·
The Ecoat is a primer that is applied at the factory when the parts are dipped. I'm not sue if VW was using this back then but probably. Yeah, I'd sand it to bare metal and apply epoxy, usually taking it down to the ecoating would be enough but I see some small rust spots in one of your close up shots that look like they were under the primer. If you don't strip it completely you might miss some of these. If the whole car has the same primers then it must be all factory applied. Your going to have a job that'll outlast the car when it's done.
 
#11 ·
Grouch,

As you said its hard to tell in photos. But I would bet you lunch (you have to come here) that they will all block out fine. The small egg shape is obviouslly a ding and will need a little bondo or straightening if you prefer. I would bondo it myself.

So get your fill primer on it. Put a contrasting guide coat and using pretty course paper like 220 or maybe even 180 on a long rigid block give it a good blocking using little pressure letting the sandpaper do all the work.

Probably take a couple coats. Once your guidecoat is looking good you can drop to finer paper to get it smooth.


Rich

PS: I like your name. Thought you were my Dad for a second ! haha
 
#12 ·
rrmccabe said:
Grouch,

As you said its hard to tell in photos. But I would bet you lunch (you have to come here) that they will all block out fine. The small egg shape is obviouslly a ding and will need a little bondo or straightening if you prefer. I would bondo it myself.
I hope you're right about them blocking out. That will also be a fairly new experience for me. The last time I primered a car I had no advice and put about 2 gallons on a Caprice (the ground, grass and trees got a lot of it). That egg shape is not very deep but can be felt with the fingertips. I'll fill it, like you say, after the epoxy.

rrmccabe said:
So get your fill primer on it. Put a contrasting guide coat and using pretty course paper like 220 or maybe even 180 on a long rigid block give it a good blocking using little pressure letting the sandpaper do all the work.

Probably take a couple coats. Once your guidecoat is looking good you can drop to finer paper to get it smooth.
Should that guide coat be the 2k urethane primer or is it an additional coat of something between the epoxy and the urethane?

rrmccabe said:
PS: I like your name. Thought you were my Dad for a second ! haha
Hey, I'm not *that* far over 50! I admit to earning the nickname, though.
 
#13 ·
As soon as you get your 2K on the car use guidecoat. You can use cheap sandable spray can primer or use 3M dry guidecoat in a can.

It will just show you stuff you cant see with the naked eye. So if you are spraying gray primer, then get some black primer in a can and mist the entire car. Block the car till the guidecoat is gone, or you start to hit metal or your epoxy below.

If you have really low spots you can evaluate at that point if you need bondo or metal work in that area. You are trying to accomplish two things. Leveling and smoothing. You have to level first. This requires fairly coarse paper to level something. Long strokes in a diagonal pattern. Dont worry about scratches as they will come out later. Once "leveled" you can move on to smoothing. If you try to jump to fine sandpaper too quick it will ride the waves and make it smooth but it wont be straight.

This is something I fought for years and finally realized I need to quit worrying about scratches on the first step and just get it straight.

There is time later for getting the scratches out. The guidecoat process will teach you a lot. Will show you the flaws as well as how the edge of a block can cut into a radius.

Rich
 
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