What's wrong with bondo?

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Well I might be starting a war here, but...my driver side floor pan is
a rusty mess, and I can watch the road go by under my feet as I drive. I could
put new metal in there - but it would be much cheaper, simpler, and
faster to just lay some fiberglass. The floor pan is not structural, so I don't really
need metal there; I just need something to keep the water out, and
to keep my feet from going through.

Anything wrong with that? Why does everyone hate bondo?

Phrog
1972 FJ40
 
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With the repeated beating and water your feet will give the floorboards, bondo is not a good idea-period. If cheap is your goal than just cut out the rust, POR-15 it, and rivit on some sheetmetal and paint it black.
Bondo will promote rust by trapping it between it and the metal.

TK
 
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With the repeated beating and water your feet will give the floorboards, bondo is not a good idea-period. If cheap is your goal than just cut out the rust, POR-15 it, and rivit on some sheetmetal and paint it black.
Bondo will promote rust by trapping it between it and the metal.

TK
yes:beer: bondo is only used to smooth over, such as real small dents, and things of that nature, not to fill.
 
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With the repeated beating and water your feet will give the floorboards, bondo is not a good idea-period. If cheap is your goal than just cut out the rust, POR-15 it, and rivit on some sheetmetal and paint it black.
Bondo will promote rust by trapping it between it and the metal.

TK

I have to agree. Just rivet in more metal if you don't have to means to weld in a new floor board. Bondo will eventually crack and fall out.
 
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Fibreglass is not "Bondo"

Just for clarification, although Bondo may make fibreglass kits, fibreglass and "Bondo", in the traditional sense are not the same.

I agree with many of the other comments, Bondo should only be used for smoothing out body imperfections (i.e .final dings that cannot be removed by metalwork). However, some people use it as a lazy man's body repair kit and don't care how thick it is applied. The real way to go to replace Bondo is to use the old fashioned method of lead work (use for imperfections not to fill holes and certainly not to replace floor pans).

I fibreglassed my driver side floor pan just to pass the safety inspection here in Alberta. I think I did a relatively good job and it served its purpose. However 2 years later, I now have to replace the work as the fibreglass patch (whole floor) separated from the inner door sill, the B-pillar separated from the B-pillar floor cross member such that the entire driver side B-pillar was only held to the vehicle by the roof mounts, the rear quarter panel (also mostly iron oxide) and the latched closed door!

If a job's worth doing, do it right. Get a replacement panel (first), cut out the cancerous floor pan, weld in the new one, paint, protect and you'll be happy with the result and you'll have increased the value of the truck by ate least the panel you put in. :)

If you just want to drive, any of the aforementioned repair methods will work.
 
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if not properly applied and the cancer not stopped in its track, it will only progress until you cut out the rust, use a proper coating and put something in its place. both bondo and fiberglass patches expand and contract at a different rate than the steel in the rest of the floor. If you take this in mind, you will see the patch will eventually work itself loose and possibly give you a bigger hole when it fails. If you are in a wet climate, water will eventually work itself between the repair and the body and this will also expand and contract different than both the body and the patch. Water will also expand when it freezes, possibly forcing the patch from the body. If you plan on keeping your rig, do it right. if you can't afford to properly, cut out the rust, apply a coating to stop it and put a temporary alum or steel patch over it until you can do it properly.
 
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Bondo (the filler) is bad. It is porus and sucks water in next to the good metal and causes it to rust. Bondo (the fiberglass) is great for certain applications. Like hiding that license plate you just pop riveted onto your floor pan.
 
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Well it's unanimous. I don't have the time/$ to get new metal any time
soon - but, based on everyone's comments, I won't bother with fiberglass.
It all goes well, I'll be able to put in new metal before I do the full
Fred Flintstone (feet on the ground as I drive).

Phrog
 
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Well it's unanimous. I don't have the time/$ to get new metal any time
soon - but, based on everyone's comments, I won't bother with fiberglass.
It all goes well, I'll be able to put in new metal before I do the full
Fred Flintstone (feet on the ground as I drive).

Phrog

if you don't have a welder; you can trim the rust a little, put some rust inhibitor on the raw edges, cut out an overlapping patch with some hand shears and rivet in the "patch". put some seam sealer on the edge of the riveted patch.

cheapo riveter about 10 bucks

hand shear about 15 bucks
 
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This is the only way I would do a floor repair short of the tedious edge fit metal with complete weld all the way around.

If you overlap, make sure its minimal.

if you don't have a welder; you can trim the rust a little, put some rust inhibitor on the raw edges, cut out an overlapping patch with some hand shears and rivet in the "patch". put some seam sealer on the edge of the riveted patch.

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