Need some Bondo Tips

karstva

karstva

Sr Member
Ok, I need some help with the whole bondo thing, I have used it and do use it with mixed success, not so much on the mixing, but the application. I see pictures of helmets and props that have been bondo'd and sanded, but never pictures of what it looks like right after its been applied. Mine always seems misshapen and lumpy and requires a lot and I mean a lot of sanding to knock it down, and then after that it still doesn't seem even to me. I would really appreciate some tips, pictures of projects anything that would help me hone my bondo skills, I know practice makes perfect but a little push..or in my case shove in the right direction would be appreciated. Thanks guys.

Karst
 
When you apply bondo ,you need to do it in layers. Not one big splash, that way you can sand inbetween layer and see how much more you need to apply.

/Conny
 
Yep thin and a few layers is best. You can use a stiff brush as well to get it flat, also start sanding/shaping well it is still leathery. You can get the bulk off without much trouble if you do it before it sets hard.
 
I forgot to add, If you do it outside when its a bit cold then the time it takes to harden is longer. Its good if you need to work with it longer.

/Conny
 
darthchiro said:
Yep thin and a few layers is best. You can use a stiff brush as well to get it flat, also start sanding/shaping well it is still leathery. You can get the bulk off without much trouble if you do it before it sets hard.
Click to expand...

YES! I agree, it is very important to sand the bondo while it's still "green". Take big, quick strokes with 40 grit sand paper and work your way to 80 and 120 as the bondo gets harder. You then can skim (thin) coat it with another layer of bondo and you can let it get hard and sand it smooth. For best finishing results you can spray on a high building, catalyzed, sandable polyester primer (Duratec) over the prop and sand it ultra smooth.
 
Last edited:
JtotheP said:
YES! I agree, it is very important to sand the bondo while it's still "green". Take big, quick stokes with 40 grit sand paper and work your way to 80 and 120 as the bondo gets harder. You then can skim (thin) coat it with another layer of bondo and you can let it get hard and sand it smooth. For best finishing results you can spray on a high building, catalyzed, sandable polyester primer (Duratec) over the prop and sand it ultra smooth.
Click to expand...


ahhh ok, I see where I have been going wrong, I have tended to apply it in larger wadges, so thin layers, and I can start to sand and shape while its still green. Oh and thanks for the polyester primer name, where can I get some of that? Will an automotive shop carry that or a DIY store like Lowes/Home Depot? Does anyone have any pictures of bondoing before the sanding and after they can post?

Karst
 
Couple of tips -

For big blobs of bondo, you can cut through them with a knife after the Bodo has started to kick (but before it has hardened). When you first mix it, it's the consistency of pudding. Before it gets rock hard, it will gel up a bit and have the consistency of hard butter. At this point, you can start slicing through it with a knife. (Try it too soon, and it will pull away from the surface you spread it on. Try it too late and you may as well beat it with a rock.)

Also, you can smooth out Bondo a bit with some lacquer thinner and a brush. Obviously, if you are spreading the Bondo on a surface that will react to the lacquer thinner, this isn't a good idea. But on hardened fiberglass - no problem.

The idea this to experiment. Mix up a couple of good size batches and play with it as it hardens. Just mix it up into a blob and let it harden right there. Poke it with a stick. Cut it with a knife. Once you get the basics of mixing (the more the hardener, the faster it sets) and how temperature affects it, you'll get a better feel for what you can accomplish with the stuff.

Gene
 
Gene has the right idea; but instead of a knife use a cheese grater so you do not accidentally cut too deep and you can get the bondo into shape easier this way. then use some 40 grit to shape it up then use 80 grit to lessen the harsh 40 grit scratches. on your second wipe (never try one wipe it usually never works out) add a little polyester resin to the bondo so it will wipe on really smooth. Finish it off in 180 grit and prime with a nice high build primer.
block your primer with 180 grit re-prime. Wet Sand with 400 or 600 then paint.

somtimes it takes 2 wipes with bondo before adding the resin; just depends on how much filling you need
 
karstva said:
ahhh ok, I see where I have been going wrong, I have tended to apply it in larger wadges, so thin layers, and I can start to sand and shape while its still green. Oh and thanks for the polyester primer name, where can I get some of that? Will an automotive shop carry that or a DIY store like Lowes/Home Depot? Does anyone have any pictures of bondoing before the sanding and after they can post?

Karst
Click to expand...

Duratec is the expensive brand, but the best. You can get a product called Shop Line JP 205 at an automotive paint supply store or just ask for a product that is a polyester primer/filler. You won't find this at Lowes or Home Depot though. This is a catalyzed primer and it uses the same mekP that FG resin uses. Acetone clean up for your gun.
 
Last edited:
For smooth curves a hacksaw blade works well since you can hold a nice even curve with the blade and use the toothed edge to cut back the high spots.As said above it works very well for roughing out the shape as the body filler hardens.
 
Guys you have no idea how helpful this is. I will definately be using your tips and techniques and thanks for the photo of the work in progress, that bondo texture is exactly how mine ends up looking I want to get it smooth as I can with out the dimples and divots. Thanks again.

Karsten
 
You must log in or register to reply here.

Similar threads

BlindCaptainobv
Murderbot TV show PDA/communucator prop replica, would love some feedback how close i am.
Replies
6
Views
299
BlindCaptainobv
BlindCaptainobv
Antonis13
Need advice for my cardboard sculpture.
Replies
14
Views
609
greenmachines
greenmachines
Anthonypars
Need help finding Yosemite Sam gun box
Replies
1
Views
426
drusselmeyer
drusselmeyer
Kroenen77
Need mirrored silver lense material
Replies
14
Views
579
Kroenen77
Kroenen77
C
Friday The 13th: The New Blood Mask Tips
Replies
0
Views
801
codyhillyer
C
Back
Top