Bondo on top of epoxy???

[doug hodder]

I called the guys at West Systems today and spoke to the technical staff...My question was about using bondo over epoxy. Now I know these guys are selling their product, but I am going to have a fair amount of fairing to get the roof where I want it prior to painting. I was looking for a quicker/less expensive method rather than the fairing compound. Their answer was that the bondo tends to want to shrink over time and will pop from the epoxy. I've used bondo in the past on top of epoxy, but that was on a tear with an aluminum skin, so if it shrunk and popped, I never saw it. Wood will tend to move more than a lot of other substrates that bondo would typically be applied over. Does anyone out there have experience using bondo over epoxy on wood, with an auto finish and what was your results over time...Thanks in advance...Doug

[Lesbest]

If tour filling for fairing wht don't you mix up some more epoxy and use sawdust,micro balloons, or corn starch for the thickener, and sand away? I know it tends to be harder than the bondo, thus more sanding but if you mix enough filler it sands easier. The corn starch works real well and isn't too bad to sand. Good luck. Les

[Gaston]

Hi Doug
the Purple tear is covered with body filler'
the front has no foam( polyester eats foam) so I faired the panel some before I glassed it then after the glassing was done I applied about 5 gal. of filler to the result (whole trailer) and blocked it to smooth the shape.
Primed it with urethane primer filler and painted it
It shows some weave show thru, and some shrinkage from the joints in the underlying foam BUT so far no shrinkage I can blame on the body filler, and no apparent "ringing" around the edges of the filler. I think all the stuff i'm seeing is from the epoxy and glass
Only time will tell what exposure to weather and time will do to it but so far its OK

[Lesbest]

Sorry didn't answer any of your questions! Yes I have seen the results of those combinations. 1963 Chris Craft Connie--Rotten wood, dug out the punky part,slopped on some west epoky till it was running everywhere, cleaned up ajacent planks of runs and drips, filled cavities with bondo-sanded-painted with interlux and 3-4 years later was the best looking part on the hull. Didn't pop out and they fished on Lake Erie with it every week. 18-20 miles out etc. so it got a real workout. I'd give it a try. NOW Good Luck, Les

[rasp]

i'd stick with thickened epoxy and would use 2 to 1 not the west system stuff.
check here http://www.fgci.com/ they are the least expensive on the market. i have used their 2 to 1 stuff to build two kayaks and they are still together after 5 years.

my thoughts on west system is that it is all that is advertised, but too expensive, and at 5 to 1 it is a health risk. as i know several folks that developed health problems after using it. that is why i stick with a 2 to 1 expoxy.

[steve wolverton]

Now wait a second...

[doug hodder]

thanks everyone...and Gaston...I surely can't argue with your results. I just couldn't remember what was done where on your tear, wood foam etc.... And for those of you that haven't seen his project...2 words in-credible!! I think I'll do a combination...for the "heavy" lifts, I'll use the epoxy and thickener...and then bondo to just skim coat the smaller problems, more like a spot putty use...

Rasp...I agree...West is not a cheap system, but I've had good results with it, 2 scratch built boats, 3 tears so I know it and what I can get away with while using it. I usually wait till West Marine or whoever carries it has resin on sale, or at least a deal + I get coupons at least from West Marine, so can get it considerably cheaper...however, I think I'll check into the materials you are recommending...thanks...Doug

[apratt]

Doug, in the auto industries a lot of cars had aluminum hoods and when they had dents or dings the recomened procedure was to use bondo. You know that a car hood get a lot of heat from the motor and that aluminum will expand and contract a lot. I would not worry about having bondo over expoxy. I never had any failure reported to me.

[doug hodder]

Steve....are you suggesting what I think you are???? doug

Les...I've had good luck using sawdust out of the cup on the sander as it's a lot finer and blends into the resin a lot better than the dust out of the extraction system on the saw...but never tried Corn Starch...Doug

[Arne]

I got some really deep gouges in the front corner of my tear.... i.e., it hit something.... I used bondo to patch it about 5 months ago, and nary a crack has developed...

I ground out the broken pieces of wood, put the bondo in with a 6" putty spackle knife... worked out fine. I found out better to not diddle with it... put it in, let it harden... add a bit more if needed as a second coat.

[rasp]

Now wait a second...

get the ZZ all the time, but don't even play a guitar

[Juneaudave]

I sure can't match the expertise of all these guys, so this is a "for what it's worth."

Bondo is not my favorite filler over the long haul for thicker applications. I believe it works well on a solid substrate, particularly for a skim coat. If you have areas that need a lot of depth of filling...I would patch those with epoxy then skim coat with Bondo. Having looked at the quality of your work through the board, my guess is that your probably obsessing and what we are really talking about is pretty minor. Bondo will work just fine.

[doug hodder]

that's pretty much what I decided on Dave...and yes, maybe I'm obsessing on it, I'll be the first to admit that...but I'm not a "Rat Rod" sort of person...if it doesn't look like I want it to...it doesn't go out of the garage. (now that can be trouble) And first and formost, If I sell it, I don't want it coming back in the future with some sort of problem..a paint job is only as good as what is under it....lots easier to do it now, rather than re-doing it later.... doug

[asianflava]

Isn't bondo primarily used for filling grinder scratches prior to paint?

People started using it in thicker and thicker applications, which it wasn't designed for. Which is where it got it's bad rep.

[apratt]

You are only suppose to go up to 1/4 inch with bondo, no thicker. If more than that, then it tend to have problem like crack and fall off.