Bondo work is a PITA!
03-11-2007, 03:04 AM
#1
Burning Brakes
Thread Starter
Bondo work is a PITA!
I'm in the process of trying to patch a hole underneath the passenger side of the car. That gook stuff turns into cotton candy in about 3 minutes and 2 or 3 minutes later it's hard as a rock. I'd put some over the hole and it would fall and hit the cardboard. Figured it couldn't be any different than patching a roof with the screen mesh but the car bondo is 10 times harder. It's almost time for the second doing and if you ever have to use Bondo, only mix up a small amount. Heck, patching a hole in the wall is a 100 times easier.
03-11-2007, 03:49 AM
#3
Safety Car
The more hardner you put into the mix the faster it sets. I used to make large batches but used less hardner to a make it a more pink than red color. It gave me more time to work with it. I would have used fiberglass cloth and resin to repair the hole.
03-11-2007, 05:58 AM
#4
Instructor
For a overhead situation like this, cut out a piece of cardboard to cover the hole (make it slightly bigger) and cover side of the cardboard facing the hole with clear plastic wrapping tape, like the 2" stuff you use to tape up cardboard boxes. The tape stops the bondo from sticking to the cardboard. Next - cut a wooden stick to length so you can jam the stick between the garage floor and cardboard over the the hole, to hold the cardboard in place.
Mix your bondo and place it on plastic tape side of the cardboard, put the cardboard in place and secure with the stick. As some members have already mentioned you can vary the amount (anywhere from a lite pink to a red) of BPO (hardener) that you mix into the bondo. If you are using a small amount of hardener (pink) make sure to especially mix it in well.
The other thing one needs to know is to work the bondo before it gets completely hard. When bondo cures, it goes from a gooey semi liquid putty to a cheese like state and then hardens to its rock hard final cure stage. The trick is to do all the major forming (sanding) when the bondo is at the temporary (5 minutes or less) cheese like state. A tool made by Stanley called a Surform works best for this. Body men call these a "cheese grater" because that's what the blades look like. The Surform blade holders come in several different sizes. A lot of guys work with just using the blades (with out the holder). The blades are available in different lengths and shapes -flat and rounded. Any body shop supply or probably Home Depot has them.
You should remove all the excess bondo while it is in the cheese like stage using the Shurform blade and using heavy (36-40) grit sand paper, loose or on a sanding block. If necessary apply more bondo and work it again until you are satisfied with the repair. Use a very light finish coat to fill the 36 grit scratches and a final sand using 80 grit. It you want to get a finer finish, sand again with lighter sandpapers-150 /220 grit.
I originally wrote this on just to use bondo (body putty) but as others have mentioned it is probably better to use a fiberglass patch. There is a structural "bondo called Dynaglass which is much stronger than regular bondo but for most hole patching, a fiberglass patch is the way to go.
Mix your bondo and place it on plastic tape side of the cardboard, put the cardboard in place and secure with the stick. As some members have already mentioned you can vary the amount (anywhere from a lite pink to a red) of BPO (hardener) that you mix into the bondo. If you are using a small amount of hardener (pink) make sure to especially mix it in well.
The other thing one needs to know is to work the bondo before it gets completely hard. When bondo cures, it goes from a gooey semi liquid putty to a cheese like state and then hardens to its rock hard final cure stage. The trick is to do all the major forming (sanding) when the bondo is at the temporary (5 minutes or less) cheese like state. A tool made by Stanley called a Surform works best for this. Body men call these a "cheese grater" because that's what the blades look like. The Surform blade holders come in several different sizes. A lot of guys work with just using the blades (with out the holder). The blades are available in different lengths and shapes -flat and rounded. Any body shop supply or probably Home Depot has them.
You should remove all the excess bondo while it is in the cheese like stage using the Shurform blade and using heavy (36-40) grit sand paper, loose or on a sanding block. If necessary apply more bondo and work it again until you are satisfied with the repair. Use a very light finish coat to fill the 36 grit scratches and a final sand using 80 grit. It you want to get a finer finish, sand again with lighter sandpapers-150 /220 grit.
I originally wrote this on just to use bondo (body putty) but as others have mentioned it is probably better to use a fiberglass patch. There is a structural "bondo called Dynaglass which is much stronger than regular bondo but for most hole patching, a fiberglass patch is the way to go.
Last edited by Daddy J; 03-11-2007 at 11:51 AM.
03-11-2007, 07:44 AM
#5
Burning Brakes
I'm in the process of trying to patch a hole underneath the passenger side of the car. That gook stuff turns into cotton candy in about 3 minutes and 2 or 3 minutes later it's hard as a rock. I'd put some over the hole and it would fall and hit the cardboard. Figured it couldn't be any different than patching a roof with the screen mesh but the car bondo is 10 times harder. It's almost time for the second doing and if you ever have to use Bondo, only mix up a small amount. Heck, patching a hole in the wall is a 100 times easier.
Roy
03-11-2007, 09:13 AM
#6
Race Director
03-11-2007, 10:05 AM
#8
I am afraid that his bondo patch will fall out. Not right away, but within a month. The "flex" is different. Its a short term fix. Pull the seat & carpet, glass over it now. Good Riding !!!
03-11-2007, 11:19 AM
#9
Safety Car
03-11-2007, 11:43 AM
#10
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03-11-2007, 08:52 PM
#12
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I'm going to move this to Paint/Body for you. Perhaps you can get some additional advice there also. 
03-11-2007, 11:33 PM
#14
Advanced
Slicked,
The proper way to fix that hole in your floor is to take the seat and carpet out an fix it from the top. It should also be done with SMC resin and fiberglass, either mat or cloth. If you try to fix it with regular fiberglass resin, it will not stick.
Grind at least 1"-2" around the hole, clean the bottom of the car around the hole well enough for some tape to stick. Stretch this tight and reinforce it with some cardboard. Now lay the glass from the inside.
Hope this helps.
Dan
The proper way to fix that hole in your floor is to take the seat and carpet out an fix it from the top. It should also be done with SMC resin and fiberglass, either mat or cloth. If you try to fix it with regular fiberglass resin, it will not stick.
Grind at least 1"-2" around the hole, clean the bottom of the car around the hole well enough for some tape to stick. Stretch this tight and reinforce it with some cardboard. Now lay the glass from the inside.
Hope this helps.
Dan
03-12-2007, 04:17 PM
#15
Le Mans Master
I just reworked a bondo fix in my kids '76 floor panel. Bubba just filled that crack and hole with a quart of bondo! I ground it all out, dished the hole and used epoxy resin and mat from both sides. It's strong as a rock now. Then we shot the firewall, bottom of the floor panels and trans tunnel with a ceramic bead based thermo barrier spray using a rocker schutz gun. I shot the inside of the floor panels and firewall to add some more heat protection from the headers and exhaust too.
