Bondo, and the like

[6spd68]

All over our forum, and everywhere else; people seem to really knock body fill.  It seems to be a constant topic whenever we scrutinize another's Charger.  I'm just wondering why?  Let's be real for a minute, what percentage of our restored cars DON'T have at least a little fill?  Unless we're going to go with lead fill, or replace the whole damn piece; what other options would one have to smooth out that little ding, or fill that tiny hole after you've blasted the piece clean?

I dunno, maybe I'm just too new school?  Don't get me wrong, I wouldn't buy a car that was rotted through and had 40% Bondo fill.  On that same token though; I wouldn't have a problem with patches here and there on my car.  If the person doing said body work was able to make my car look flawless after the paint was on; what does it matter? (Cue the 'perfume on a pig' reference  ) 

I also understand the difference between restoring a car to show quality, and restoring to driver quality.  So many of us on here have our cars to drive.  Sure we take them to shows, but are we there to win $, or just to have a good time?

Not looking to get flamed on,  , just looking for honest opinions.

[TUFCAT]

I love the smell of it. 

[HANDM]

When I see entire cars skim coated in the green stuff on these dime a dozen "restoration" shows, it makes me wonder how much filler is underneath.......

[green69rt]

I get the impression that the problem is not with the filler itself (other than brand preferences) but with the workmanship or the use of it in certain cases.  Filler, primer surfacer, glaze, etc are all tools that a lot of us have used.  Problem is when we see a car that has 1/2" of filler over a big hole or dent.  It should have been fixed to the point that the filler is just needed to get the last 1/16" - 1/8" of good surface.  On this site, I've seen so thick filler used that it's amazing, it's a lazy mans way out.   The filler should not be used to hide problems, just make that last little touch up to make the car look good.  Also when filler gets really thick, I would be worried on how it behaves over time...cracking, blowouts.

[Dino]

Filler is there to skim and smooth the surface that would otherwise take hours and hours to smooth out by metal work alone.  That's just not doable for any body shop trying to make a living because you wouldn't want to pay for it.  The problem with filler is that it is used to replace metal work, and that's where it goes wrong.  There is a maximum thickness for a given filler to use and that rule gets broken more often than not.  There is also a very long wait period to let it dry properly although I'm sure the products have become a lot better since I used it.  In collision you sand the filler as soon as possible, usually after infrared drying of 5 minutes.  Look at that spot in a few weeks or months and you'll be able to see imperfections.  Properly done you let it air dry for a week, but again who can afford that?

I like to get the metal at least to where I need no or little filler, but I do like to use spray filler where I can.  It gives you enough material to block sand the panels with a fairly coarse grit and leaves on enough to smooth it for the next stage.

The cars you see that are super straight without any filler whatsoever are usually showcases as the man hours to do this are staggering. 

Filling an actual dent in the middle of the panel should always be a big no no though.  There's so many tools to pop out dents from the front or behind that there's really no excuse to do this.  Those who do don't know how to use a hammer or are just plain lazy.  Skim coating an imperfection is perfectly fine as long as you know the limitations of the product.

It all comes down to cost in the end.  Take one of those wavy 2nd gen rear quarters people complain about for instance.  Do you take the time to work the metal until it's straight or do you sand and fill until it's straight?  When done right nobody will ever see the difference so it becomes a matter of time frame, how long does each take?  I've had customers who said they did not want a drop of filler on their car and I obliged, but they did pay for it and not a little either.

[hemi-hampton]

The only problem I see with Bondo or Body filler is when somebody buys a rustbucket, fills the rust holes with a old sock or metal tape or duraglass & then proceed to fill rust holes with bondo. After a few months these rust holes start to bubble & fall apart. BUT, Just a few months earlier some poor sucker just paid big bucks for this heap because he liked the pretty shinny paint & seller told him it was a solid rustfree car with no bondo, Sound familiar? HPLAG & all those others    LEON.

[Dino]

Old sock.   

Sadly there's a lot of truth to that, the stuff we find under the shiny paint right?   

I can count the times I saw rotten out frame rails reshaped with fiberglass filler and caulk.   

I once saw a fairly rare Italian sports car that a customer brought in to have the driver's side quarter replaced.  I looked at it and it was flawless so I asked why he wanted it changed.  He opened the trunk and showed me the chicken wire poking through the inside.  There was about 5 inches of filler in there with the chicken wire, newspapers, and what looked to be ground up wine corks.  If someone is that good in making the outside look perfect, why not do it right the first time?   

[ws23rt]

Filler is there to skim and smooth the surface that would otherwise take hours and hours to smooth out by metal work alone.  That's just not doable for any body shop trying to make a living because you wouldn't want to pay for it.  The problem with filler is that it is used to replace metal work, and that's where it goes wrong.  There is a maximum thickness for a given filler to use and that rule gets broken more often than not.  There is also a very long wait period to let it dry properly although I'm sure the products have become a lot better since I used it.  In collision you sand the filler as soon as possible, usually after infrared drying of 5 minutes.  Look at that spot in a few weeks or months and you'll be able to see imperfections.  Properly done you let it air dry for a week, but again who can afford that?

I like to get the metal at least to where I need no or little filler, but I do like to use spray filler where I can.  It gives you enough material to block sand the panels with a fairly coarse grit and leaves on enough to smooth it for the next stage.

The cars you see that are super straight without any filler whatsoever are usually showcases as the man hours to do this are staggering.  



Filling an actual dent in the middle of the panel should always be a big no no though.  There's so many tools to pop out dents from the front or behind that there's really no excuse to do this.  Those who do don't know how to use a hammer or are just plain lazy.  Skim coating an imperfection is perfectly fine as long as you know the limitations of the product.

It all comes down to cost in the end.  Take one of those wavy 2nd gen rear quarters people complain about for instance.  Do you take the time to work the metal until it's straight or do you sand and fill until it's straight?  When done right nobody will ever see the difference so it becomes a matter of time frame, how long does each take?  I've had customers who said they did not want a drop of filler on their car and I obliged, but they did pay for it and not a little either.




Dino you have answered this question about bondo nicely.  

My addition to this is that the word/name bondo is a brand name.  I feel for the company that lives with the stigma of what we are talking about. (bad repairs).
Is it not true that when someone says their is bondo in the car it brings a negative?
Some of us will remember the term lead sled. It took more talent to use lead and manufactures used it as well.

Add--- While prepping my c500 for paint I spent a lot of time filing (factory)lead from the roof to blend the curve to the back glass. Est. a half pound of lead.

[Baldwinvette77]

I think its just because of how alot of people use it, IVE SEEN PEOPLE FILL FRAME RUST WITH IT!!!!!

But honestly i could not be bothered if its just small pin holes or molding holes or welds or stuff like that

[TUFCAT]

If it wasn't for the dust, the factory would have used bondo.

[Kern Dog]

I used to use Bondo but found out that there are better body filler products out there to use. Sorta funny: I once saw a promotional leaflet with a can of Bondo. You could get a red BONDO jacket for a low price if you included several receipts for proof of purchase.  
Yeah.. Like I'd want anyone to know that I used SO MUCH Bondo that I got a jacket to prove it!

[don duick]

I can tolerate bondo only if I applied it. My paint job is now 10 years old. I applied 4 kilos of bondo and about 2 kilos was wasted and sanded off. So far so good no cracks or bubbles. 

[Stevearino]

It's all a matter of degree. Body filler gets a bad rap because of the chicken wire and newspaper crowd. It's a tool and a damn good one. Just like any tool it needs to be used in the proper manner or you get a bad result. 

[nvrbdn]

It's all a matter of degree. Body filler gets a bad rap because of the chicken wire and newspaper crowd. It's a tool and a damn good one. Just like any tool it needs to be used in the proper manner or you get a bad result. 

[Mike DC]

  
It's like makeup on a woman.  Or photoshop in print media.  Or computer effects in movies.  

Used in moderation, it's great.  But the potential for abuse is tremendous.  And the slightest bit more than just right is far worse than not enough.  And when it's used just right, you may not know it's there at all.  So it gets a bad rap.



Bondo poses a temptation to abuse it because you CANNOT use it to bridge openings.  Rust holes, etc.  You can pile the stuff on pretty thick in some cases.  The truth is plenty of people have gotten away with 1/4" thick or more, but you'll get flamed for admitting to using that much.  But the stuff ONLY works if it is backed by an UNBROKEN layer of steel underneath.  

Rust holes behind the bondo --> ambient moisture gets to the bondo --> the bondo expands & cracks --> the steel continues to see moisture --> more rusting.

   

[Aero426]

A quote from K & K team body man Robert Gee; a master of his trade:    "Ain't nothin' I can't make with sheet metal, pop rivets and bondo".

[c00nhunterjoe]

My car is full of bondo and I dont try to hide it. 

[1974dodgecharger]

my whole is made of 99% bondo...no sheet metal needed to build these cars.

[Kern Dog]

"my hole is made of 99% bondo"

   

[fy469rtse]

I didnt need to use it , It buffed right out 
filler has to be used , i saved my qtrs , they were creased, from a rear end tap some where in this cars previous life, badley repaired then , i replaced bottoms only , slight layer there to cover welded area, if i had to metal finish that , i would be still there doing it 
new floors rear cross member tail panel trunk floor , slight skim to even panel out , would never been able to get them straight enough,

[Stevearino]

A quote from K & K team body man Robert Gee; a master of his trade:    "Ain't nothin' I can't make with sheet metal, pop rivets and bondo".

People in the sport used to marvel at the great looking speedway cars Robert Gee used to build. What most people don't know is that after they would build the car roughly out of sheet metal he would mix a gallon of bondo at a time right on the roof of the car and then proceed to cover the entire car sometimes up to 1 to 2 inches thick in places. He would then proceed to sculpt the car. Those cars were slick but the bodies weighed a ton.

[Mike DC]

People in the sport used to marvel at the great looking speedway cars Robert Gee used to build. What most people don't know is that after they would build the car roughly out of sheet metal he would mix a gallon of bondo at a time right on the roof of the car and then proceed to cover the entire car sometimes up to 1 to 2 inches thick in places. He would then proceed to sculpt the car. Those cars were slick but the bodies weighed a ton.

I've heard a lot of comments like that about early racecars.  Doesn't that end up being excessive, though?  I mean, it takes time & effort even to sculpt bondo.  And repairing any kind of damage would have been a NIGHTMARE.  Those cars got banged all the time.  You'd think the repairability & weight issues would have limited the pileup. 

[Indygenerallee]

I mean, it takes time & effort even to sculpt bondo.

not really, you would be shocked how fast some 36 grit on a air board file eats it up...... Don't ask me how I know 

[Stevearino]

People in the sport used to marvel at the great looking speedway cars Robert Gee used to build. What most people don't know is that after they would build the car roughly out of sheet metal he would mix a gallon of bondo at a time right on the roof of the car and then proceed to cover the entire car sometimes up to 1 to 2 inches thick in places. He would then proceed to sculpt the car. Those cars were slick but the bodies weighed a ton.

I've heard a lot of comments like that about early racecars.  Doesn't that end up being excessive, though?  I mean, it takes time & effort even to sculpt bondo.  And repairing any kind of damage would have been a NIGHTMARE.  Those cars got banged all the time.  You'd think the repairability & weight issues would have limited the pileup. 

You know Mike. It took a long time for the use of English Wheels and refined metal shaping techniques took hold in the sport . Bondo was the only way to get there most of the time. Especially in the old days when you had to beat the side of the car out between race tracks. Also speedway cars became a specialty in the 80's and onward so you would build cars like the one I described for Daytona and Talladega only. Drag reduction was and still is king at those tracks and nothing slicks a car back better than bondo. As far as the weight goes most of the G forces are through the floor of the car as opposed to lateral at those tracks because of the severe banking so weight is not as much of an issue. It can in fact be a slight advantage because once the car is up to speed there is a certain amount of momentum that a heavy car generates which can factor in to passing.  Back when Dale Jarrett was running for Robert Yates one of the best speedway cars they had did not have any added lead in the rails because it was already so heavy.

[Mike DC]

   
I've wondered - how much ballast did they need to add to a typical 70s NASCAR to bring it up to the rule?  What did those things weigh before ballasting?  I recall they used aluminum-head 426 Hemi motors.