Working with Body filler

[Conaway2]

Help ! I’m using body filler on rear coupe quarter panels after welding in patch panels that needed some modifications to fit. After applying filler and sanding and feathering edges multiple times, I’ve primed the whole panel and checked the straightness by holding a light close to the panel and looking across it….

The panel looks lumpy….I’ve used an orbital sander to smooth the filler.

I am not skilled at body work at all - how do pros get a curved panel smooth and flat with no lumps ????

Many thanks !
Jim

[wrndln]

I was told some time ago by a very good body person to use a piece of ABS 1/8" thick cut to the size of a paint stirring stick. You wrap the plastic ABS "stick" with 80 grit or whatever. You can bend the plastic "stick" a lot to conform the curve of the panel as you sand in a cross X pattern. I was having problems with some small dents in the top of my 28 special coupes quarterpanels. Once I got some ABS and cut it to the right size, it was amazing how well it worked. I have used this method many times since I found how to do it back 10 or 12 years ago with great success.

Hope this helps.
Rusty Nelson

[chrs1961815]

This is what they make big sanding blocks for.
https://www.tptools.com/Professional....html?b=d*8198

[Big hammer]

I’am not a pro but it’s time to put the DA away and build up your arm muscles by using sanding blocks. Sanding in an X pattern! use a guide coat to show high and low’s! Practice Practice and again Practice

[ronn]

what everyone else says and also, put less rather then more filler from the onset.

this is no different then using spackling compound on drywall. less is more and practice practice practice.

[Duke]

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Yes, no DA, flexible long sanding block, work in a cross pattern. Less is more with filler, use a wide flexible spreader to apply.

[nkaminar]

Use a long flexible sanding block. The paper has sticky back on it so it adheres to the block. Visit your local auto paint supplier. lightly spray an alternate color, just a dusting, on the surface and you can see where the high spots and low spots are when you use the sanding block.

[JoeCB]

Yes , what was said.... and good ole' wood paint stirring sticks still work good

Joe B

[Oldbluoval]

Answers here are spot on.

Don’t forget PPE respiration. That dust, and most body materials, are not good for ones health. Read data sheets.

[CA Victoria]

The block/stick must be flexible.
As mentioned: Using a guide coat technique works well to resolve hi-lo spots. Try using a black or white lacquer (dries quickly).
Wiping the area with a rag wet with medium reducer will help to highlight imperfections hard to see with the eye.

[chrs1961815]

I wouldn't use lacquer paint as a guide coat to see as you will not be using it as your topcoat. Bad idea mixing that together and not worth the headache. Find a guide product made just for that purpose that is compatible with your paint system or do what I do and just spray a coat of primer that has gloss and use the gloss to see imperfections.

[Synchro909]

Lacquer paint under a two component paint is a no no. You would be asking for trouble unless you put an isolator coat between them.

[Conaway2]

Thanks for all the comments - I understand what I;m doing wrong now. I can find only flat large sanding blocks online. Do I need to make my own flexible sanding block, or are they commercially available ?

Thanks - Jim

[bruceincam]

Look around here ----- bunches of sanding blocks:

https://www.eastwood.com/search/?q=sanding+blocks

[Mulletwagon]

Worked for a master body man years ago. His sanding block of choice was a 2 X 4 !!

[Oldbluoval]

There are great tutorials on YouTube

[ModelA29]

You can't have any foam or padding behind the sandpaper. If you do it will allow the sandpaper to follow the current shape into the low spots not just take off the high spots.

[ModelA29]

Originally Posted by chrs1961815

I wouldn't use lacquer paint as a guide coat to see as you will not be using it as your topcoat. Bad idea mixing that together and not worth the headache.

All your guide coat should end up on the floor so it won't matter and lacquer dries fast.

[bruceincam]

Originally Posted by Mulletwagon

Worked for a master body man years ago. His sanding block of choice was a 2 X 4 !!

That works too --- I have a section of "rough cut" 2x4 that works really well in my hands. I can't really explain "the why". It just works.

[Conaway2]

Originally Posted by ModelA29

You can't have any foam or padding behind the sandpaper. If you do it will allow the sandpaper to follow the current shape into the low spots not just take off the high spots.

Thanks - this sounds like good advice and makes sense.

Jim

[Conaway2]

Originally Posted by Mulletwagon

Worked for a master body man years ago. His sanding block of choice was a 2 X 4 !!

How do you use a flat block on a curved surface like a rear quarter panel ?

Thanks - Jim

[Mulletwagon]

Originally Posted by Conaway2

How do you use a flat block on a curved surface like a rear quarter panel ?

Thanks - Jim

Experience and skill. An in-line air sander is basically a powered 2 X 4. On a curved surface like a quarter panel, the technique is to start at the extremities of the bondo patch and work towards the crown. After the plastic was formed using 36 grit the scratches were smoothed with 80 grit. The area was then sprayed with primer and then coverd with red putty using a squeegie. A rubber sanding block was used to wet sand the putty with 100 grit to fill the minor imperfections. After a final primer coat and sanding with 320 grit the area was color sprayed. Anyone with basic mechanical skills could learn autobody work with a little practice. A good skill to develop if planning to do restorations.