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MG Midget and Sprite Technical - Is there a trick to body filler?

Hey folks,

I am looking for a bit of advice (as ever) on applying and sanding body filler. I am trying to fill the joins in my rear wings after I did a lower half panel replacement, the problem is it is seemingly taking forever and however many layers of filler I apply and however much sanding I do it's still not coming good.

It is obviously a bit more of an art form than just wielding a spanner, like a good plasterer or carpenter. But the more time I waste getting horribly dusty the more I wonder if I am missing some fundamental trick or technique!

I have a long, stiff sanding block and this does help.

I have started to wonder this evening if I am just trying to force the issue too much. i.e. being in the mindset of "filler is bad" so sanding far too much to remove excess and going too far and ending up with a naff surface finish.

Or does it just take everyone ages!?!

Thoughts and tips greatly appreciated. Thanks in advance guys.

Malc.
M Le Chevalier

It takes a while to get a feel for it. You might want try a body file or different grades of paper (40, 60 ,80 or a 100). Traditionally cellulose 'stopper' was applied on top of primed filler and then flatted down with something like 220 wet and dry (wet) to get a ready for spray paint finish.
Daniel Stapleton

Humidity will play havoc with the dry time

Use the correct ratio of hardener to putty, when applying, I like a multi build up of thin coats plus sanding between instead of 1-2 thick coat, I also like power sanders (air or electric)...I really like all metal bondo instead of the reg pink bondo and make sure the bondo is being applied to clean bright metal, ...not.over primer, or paint, or rust

Use rubber spreaders, when mixing...dont stir the bondo, fold the putty into the hardener, use glass or plexy glass to mix the bondo... cardboard is okay, it just tends to steal chem from the bondo and makes a mess...where the glass / plexy can be scraped to clean perfection, and it wont steal chem from the bondo

Prop
Prop and the Blackhole Midget

Malc,
are you using a guide coat when sanding? It certainly helps identify the high and low spots, and to pick out where an extra skim of filler may be needed. Quickest is to spray a very light dusting coat from a rattle can in a contrasting colour.
Guy Weller

Yep Malc, there is a trick.

Don't bother. Just give it a protective coat of primer, and drive it. As per my finished product. LOL.

But if you really must press on, lay a straight edge over where you're filling, it helps to see where you need the filler. And do as yer uncle Guy says. A coat of paint really helps to see the high and low spots.

And personally, I don't try too hard to get the "spread" perfect. I leave that to the sander.

Lawrence Slater

Did you start by trying to cover the entire area, or just the lowest part first? I find it best to do the lowest area, then flatten, then fill again feathering out further, then flatten again and repeat additional times as needed. I usually get it in two or three passes.
Trevor Jessie

X2 Trevor

Thank you

Prop
Prop and the Blackhole Midget

Was there lead in these seams originally??
My car had lead joins on the panels at the back
Rod
R W Bowers

Thanks for the tips everyone, I will try a few things out and see if I make any better progress.

Fingers crossed.

Also, Rod, not a factory seam, it is a half wing repair panel, so a horizontal seam the length of the wings about 2 - 3 inches above the wheel arches.

Cheers,
Malcolm
M Le Chevalier

One reason why a decent paint job costs Malc....1000 quid for the labour, another 2000 for knowing how to do it.....and another 1000 for the Aberdeen rip off factor....Seriously though, I have been where you are a few times and for the reasons you mention, I would seriously consider giving it to someone who does it for a living. You could save a bit by doing alot of prep work, and of course, everything is negotiable. Seems a shame to risk it when you have spend so much time and effort on it.
Mark O

It is a good skill to learn. I should mention that I flatten the bulk of the filler starting with 40 grit on a flat board when the filler is still warm. If it loads up the paper, then I wait a few minutes. If you wait several hours, then sanding is much more difficult. Of course the final sanding will use something like 220 grit that is easily filled with a high build primer.
Trevor Jessie

It is indeed a good skill to learn, but speaking for myself, practice makes perfect. If I had plenty of time on my hands, a few spare body panels, a good gun and compressor, somewhere indoors to work in, plenty of expensive materials and filler, I could possibly get something half decent within 6 months or so. I would also have a heap of redundant, expensive equipment and no comeback if the job was less than satisfactory - which, unless you are particularly adept, it will be. I guess though a bit of filling work is acceptable as regards DIY, but a good experienced paint guy can do a perfect job in his sleep. May as well give the whole thing over to him.
Mark O

I think it is one of those things that has a steep but short learning curves. Once it clicks, you'll find that it is not as hard and tedious as you first thought. But then again, I was doing autobody work when I was 12 years old.
Trevor Jessie

Actually id do both.....

Do the panal repair the basic bondo work and get it to a point kf looking decent, then turn it over to the pro to do the detail final work....thats the area I struggle,

This way you save money on the tear out, the install, and the basic work, then the pro has to just do the tidious perfection detail work and the paint matching

Best of both worlds....thats what I did with my car, and worked out okay.

Prop
Prop and the Blackhole Midget

Hey Malc,

Yes that's the one area I especially stink at! I don't know why I keep trying it over and over.

The guide coat will help you spot the highs and lows but like you I always put some on and eventually sand it all back off.

Hope you do better than me!
Steven Devine

Let's go back one step. Are you sure you do not have any high metal that needs to be reduced?
Trevor Jessie

This thread was discussed between 01/09/2014 and 02/09/2014

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