Getting started

[kovmat]

Just started on my first panel. It seems to be going Ok but just wanted a sanity check. This panel has 2 coats of filler. I still have a few low spots. As you can see it has some curve to it and it is loaded with lots of small dings. I am using the small 3M block with the nails in it.
t134_3453.jpg

t134_3454.jpg

My questions are:

1) Should I be using a longer sanding block and should it be a flexible block?

2) If I discover a high spot, can I just tap that down or will it cause a problem since I have already put filler around it?

3) some of the high areas expose the bare metal after sanding, I assume that is not a problem as long as they are not sticking up.

4) How perfect does it have to be before I go to the next step (High build primer)? I have not used a guide coat yet, right now just going by feel. I plan to use a guide coat to check it before I spray the high build primer.

Any other comments would be appreciated.

Thanks,
Matt

[showcar]

Since you already mudded it and it's a deck panel you should use a pic and tuck the metal under(creases metal). Do it slowly and take a block and keep checking it so it's just under. You can do that by watching the scratches develop. I'd also use a bigger block and topcoat that whole panel. It should be all filler with stuff barely poking out if at all. But first block it out in one direction and look carefully at ALL the areas that are raised to find the fresh scratches(highs). Bang those all down and skim. If you wanna raise something you might be able to pull some up to with a studgun as long as it's not too close to filler I'd hit it with 80 than guide it to check. Then I'd knock it down til it's pretty much flat. Then guide lightly with 180.

It almost has to be perfect and undetectable to the touch. If you're worried I'd just do the best I can and get some slicksand. That'll help.

[Len]

1) Should I be using a longer sanding block and should it be a flexible block?

Yes, a 16" (or larger) block for the large areas works well.

2) If I discover a high spot, can I just tap that down or will it cause a problem since I have already put filler around it?

If you're going to tap the metal down slightly use a lot of light taps. In most cases hitting it too hard creates more problems than it solves.

3) some of the high areas expose the bare metal after sanding, I assume that is not a problem as long as they are not sticking up.

That's right, you'll probably have a lot of spots where metal is showing.

4) How perfect does it have to be before I go to the next step (High build primer)? I have not used a guide coat yet, right now just going by feel. I plan to use a guide coat to check it before I spray the high build primer.

That would be a perfect job for spraying Slick Sand (sprayable filler) over the entire panel then guide coating and block sanding with something like 120 or 180 on a long block.

Slick Sand Link

Sanding Block Link

Sandpaper Link

Guide Coat Link

[kovmat]

Thanks for the replies. Is the slick sand a substitute for high build primer or do I spray my high build primer over that? And if so, should I block sand both layers?

Thanks,
Matt

[Phil V]

Just started on my first panel. It seems to be going Ok but just wanted a sanity check. This panel has 2 coats of filler. I still have a few low spots. As you can see it has some curve to it and it is loaded with lots of small dings. I am using the small 3M block with the nails in it.
t134_3453.jpg

t134_3454.jpg

My questions are:

1) Should I be using a longer sanding block and should it be a flexible block?

2) If I discover a high spot, can I just tap that down or will it cause a problem since I have already put filler around it?

3) some of the high areas expose the bare metal after sanding, I assume that is not a problem as long as they are not sticking up.

4) How perfect does it have to be before I go to the next step (High build primer)? I have not used a guide coat yet, right now just going by feel. I plan to use a guide coat to check it before I spray the high build primer.

Any other comments would be appreciated.

Thanks,
Matt

Matt, it appears to me that you have a natural ability for doing this type of work (and I mean that as a compliment).

!. sanding block - yes you should be using a longboard hand sander or air file long sander (16" long). I and most other pro's use the air file sander with 36 grit to hog the mud down then 80 grit to fine tune it. Finally most of us finish off the area with anywhere from 80 grit to 180 grit on a hand long board just prior to primer. A couple different companies make a hard plastic hand longboard sander that would work well in your application (handy but not necessary).

2. tapping down high spots. -- Tapping down high spots is not only acceptible it is necessary in most cases. Its not necessary to use a dolly on the backside of the metal. Depending on the high spot I might use the pick end of my bodyhammer or I might use the flat face of the other end of the hammer (just depends on the high spot and there is no right or wrong way to do it. which ever works best for you at the time). A lot of the time a spot is low is because there is a high spot like a "brow" thats not allowing the metal to be flat. Tap that high spot/brow down you get rid of the "oil can" effect and the panel with be firm and flat.

3. High spots and bare metal - the reason for block sanding is to expose the high spots and the low spots. So in the process of block sanding the high spots will be exposed first. The part that takes practice is figuring out when to stop sanding. part of the secret is in getting rid of most of the high spots before you apply your first coat of bondo.

4. how close does it have to be ? - The closer you get the bondo to being flat the less sanding of the primer you'll have for later. Again thats an issue best answered with practice. Keep in mind that high fill primers main function is in eliminating small imperfections, so the bondo work does not have to be perfectly flat, just close.


Len mentioned Slick Sand which is a polyester primer (in other words "spray bondo"). it works good for block sanding serious imperfections. It is used over bondo and bare metal for serious block sanding. It does bascially the same thing as regular 2K high fill urethane primer its just the polyester primer usually has more film build. Its not necessay to use "spray bondo" but in some cases it can speed up the operation. Boils down to a judgement call for the guy doing the work.

[showcar]

I like to ad that if you have a good compressor that can push an air file go with that. It's always better to perfect your bodywork thru bondo instead of primer. It takes more time to block out imperfections with primer than filler due to the grits. However, if you plan on repriming than it's better to have the primer deal with it due to the lower grit you'd be using to block. I've never primed twice but it's just common sense to view it like that. I base my decisions on learning and knowing what covers what.

[kovmat]

Phil,

Thanks for the compliment, my grandfather used to always say that he was a block and tackle man, block headed enough to tackle anything. That must be where I get it from.

The guy that was doing some of the sheet metal work for me stopped by this evening to look at what I was doing and he pretty much mirrored what you guys told me here. It is always good when the experts agree.

He suggested starting with the hammer and dolly, I spent about an hour on it and already it is a whole lot better. Fortunately, I only put the filler on half the panel and that side was not as bad. I think after doing the hammer work it is going to go a whole lot easier

I did buy a longer block today and my neighbor has a air file that he will let me borrow. I have a pretty large compressor so I don't think I will have any issues running it.

Thanks again for all the input.
Matt