Cast Front-panel of case with Bondo?

[Xtrykr]

Hi, just wondering, can I cast a whole front-panel of a case with bondo? I was reading up a lot of stuff on these forums and some pple keep bringing up bondo for casting. But when I read the bondo uses, it says its only for dents and cracks. Will this stuff cure and become strong and hard for a big piece such as the front-panel? Suggestions much appreciated. The front-panel I'm thinking would be roughly 18"x16" or something like that.

[Skriger]

Are you talking about making a whole entire front panel out of bondo? if so, that is no recommended. As you have found out, it's mainly for small area cracks and fills. Using it in that amount would make it heavy and brittle. Majority of the people make would make something from acrylic or use a base from the original panel to customize their own. Bondo is mainly like a putty to hold and shape small areas.

[Bucko]

Bondo with nothing else wouldn't be the best idea. However, if you already have a case front and add bondo to that, by all means go for it!
The original front can be used as the actual strength and general shape of the case and the bondo then gets the look you want.

I made a complete new look to the front of this old Gateway (http://www.thebestcasescenario.com/forum/showthread.php?t=8956) using only Bondo and some odds and sods.

[Xtrykr]

Are you talking about making a whole entire front panel out of bondo? if so, that is no recommended. As you have found out, it's mainly for small area cracks and fills. Using it in that amount would make it heavy and brittle. Majority of the people make would make something from acrylic or use a base from the original panel to customize their own. Bondo is mainly like a putty to hold and shape small areas.

Great, thanks for the words of reassurance. Just wondering, can you elaborate on the acrylic part? I am interested in building a new front-panel for my case, but from ground up. Got any suggestions? Thanks a bunch!

P.S. And no, I won't be building it off of an pre-existing front-panel from a case because the shape is quite unique and doesn't quite match anything xD Actually, I will be molding the front-panel with Sculpey first then, will be making a mold out of it, and would like to know what I can use to cast it, thanks!

[Bucko]

The acrylic would need to be the actual front that goes on the case. Then all the Bondo applied to it.

Yo would need to cut out a sheet that matches the shape of the front of your case and then go from there. Also, rough up the acrylic with some coarse sandpaper so the Bondo has something to stick to.

[Xtrykr]

icic, how thick can the Bondo be before it becomes too brittle? Thankss bucko

[Bucko]

I'm not sure when it would become brittle, it has gone up to a couple of inches thick in some spots on that case I posted.
Really thin bondo layers snap easily, but the thicker stuff is fairly strong as long as it has some support (like the plexi backing)

Casting with it could be tricky because of how quickly it hardens. You have have to do it in sections in the cast, then a final layer on the top before attaching the plexi.

You will also need a LOT of it for the front of the case. That link I posted had over a kilo go into it.

[Xtrykr]

Yeah, I was looking up bondo in my local hardware stores, and they sell for like $20CAD for like 5kg, which is real cheap, it was either that or going for the Smooth-On Cast Urethane stuff, but that stuff is very expensive compared to the Bondo.

On a side note, if I were to cast Bondo, do I need a release agent? And is Bondo a two mix material (resin + catalyst?) Thanks again.

[Bucko]

yeah, Bondo is a two part mix. The Bondo and the Hardener.

You probably will need a releasing agent, because bondo sticks to most things very well.

[calumc]

what you could do is put a thin layer of bondo over your mould covering all the details and then put a backing of fibreglass on it

[Xtrykr]

That sounds like a pretty good idea. Just wondering though, lets just say i need to carve out a drive bay or something on the front-panel, if the fiberglass and the bondo are stuck together, and I start drilling through it, will the bondo shatter? I'm just worried about things like that when I start grinding and drilling it and stuff.

Also Bucko, do I sandwich the plexiglass? Or is it at the top layer?

One last thing, is the bondo porous when it hardens (like do I have to worry about air bubbles and stuff like that since its a resin?)

Thanks!

[calumc]

i dont think bondo is porus but somepne else might want to clarify that.
id say youd be alright drilling and cutting it just dont go bashing it with a hammer!
but generally youd be ok because they are kinda designed to work together for filling larger dents on cars (youd bulk it out the fibreglass and then finsh it with bondo)

[Bucko]

Bondo is fine to drill and grind. It won't shatter. Bondo is porous, but I wouldn't worry about that as I can't imagine you would be leaving it plain, you'll no doubt be painting it, which will seal it.
Air bubbles depends on how you mix it and how you apply it. It's not a big issue though.

For the plexi, I was more thinking as the backing for the front of the case.
If you are doing a mold, the bondo would be the first thing you pour in to make the front of the case, then once that's all done, the plexi would be the back of the front of the case, if you get what I mean.
So the backing to the front panel in a mold would be the last thing applied.

If I were you, I would go and buy a tub of Bondo and try it out. For a few bucks you'll see what it's like to work with how quick it dries and what it's like to sand/cut/grind etc.
Make any old thing and see how it goes.

[Xtrykr]

Okay, excellent, one last thing (i swear this is the last thing), is there a release agent for the bondo? Say I make a rubber/latex mold?

[Skriger]

Bondo sticks to pretty much anything. Think of it like a really thick glue than hardens quick. you can use rubber or resin I would say, but not certain, then carefully bend it away. I think if you use some grease or vaseline it might not stick.

If your thinking of making a cast, use fiberglass works way better and can come out quite nice.


My suggestion is first get your idea drawn then see what would be the most sufficient means to make your creation. Building from scratch always takes long but can be much more satisfying for the fact it's your creation and comes out how you want it. Also, once you have figured out a medium you want to use, play with it first so you have an understanding of how it works and what it does/doesn't like to do.

[Bucko]

I don't know of a release agent for bondo as it generally isn't used for casting.
Grease or vasoline would be a very bad idea though, as you'll never get it all off properly and paint won't stick to the finished product.

[Crimson Sky]

Just realize that Bondo or any other auto body filler shrinks about 5-8% when cured--you can not get close tolerances with one casting, you'll have to touch up with more Bondo afterwards. Also, Bondo gets very very hot when curing, and this might cause sticking in your mold and distortion of the parts.

The only mold material that Bondo does not stick to is rubber (or silicon)--this is why bodymen use rubber bowls and spatulas in the shop. You are better off perhaps making a frame out of Styrene and using Bondo to smooth curves and fill gaps.

[Xtrykr]

Woah, lolz, new materials everyday that I'm learning from you guys. Sounds like I will have to past on the bondo with the cast and go for a urethane resin, then use the bondo for touch up (since it has such a high shrinkage rate).

Crimson - What is Styrene? I wiki'd it and it appears to be a material with a melting point of -30C and a boiling point of 145C?

[Mysteriphys]

ya I was reading along and thought of fiberglass immediately, when it comes to getting a hard LIGHT back piece to work down fiberglass is your tool of choice, I've build subwoofer boxes, back window speaker panels, even an entire dashboard for an old sunbird out of fiberglass, it's heavy duty stuff for the thin layers you can use, just for the love of pete make sure you smooth out air bubbles or you might as well start from scratch, btw, fiberglass works the same as bondo the only diff is you should be using a close woven sheet of the fiber thread as your basis to apply the fiberglass resin/hardner mix, and when you cast, just use some wax paper or tin foil and fill in any inconsistancies (divots dents) with a little bondo, and then do all your final layer tweaking with bondo to get is smooth and purdy.

p.s. not sure if I made this clear so just clarifying, you'd put the tinfoil in that cast and smooth it out inside, thenplace the matting over the tinfoil, then apply resin to the matting, smoothing it out so you don't see any white bubbles underneath, (btw if you do it's really not the end of the work, you just need to shave the top layer off and re-resin that area, takes alot of sanding though.) and before you start bondo peel or sand the tin foil off, it's cheap, so it's not like it's a big loss.

[slaveofconvention]

If you need bondo to fill deeper sections, you can reinforce it on the fly by mixing in some fibreglass resin when mixing the bondo and hardener - just a little trick I picked up at work this week (I run the office for an auto-bodyshop) - it gives it extra strength too - it'll still crack if you bend it and flex it, but it helps some....