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Bondo strength?

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MYX:

I can say that it will be a handle. So anything with fiber glass will probably cause an itch correct? I got the idea the other day and I am thinking stongly about trying it. I will avoid bondo. Figure the strength of a joystick handle (actually where I got the idea). But I do not know if my widget will get that kind of abuse or not. But I figured I would try.

Randy I have seen that. Is it fiberglass or will it become a plastic?

Derf00:

I think someone else mentioned this already but Alumilite is a cast resin that would work very well. Bondo works great as a filler but that's it. Fiber filled bondo works with bigger holes but again, not ideal for the job.

jace055:


--- Quote from: MYX on January 18, 2007, 04:26:52 pm ---I can say that it will be a handle. So anything with fiber glass will probably cause an itch correct?
--- End quote ---

The fiber in its raw state, like attic insulation, will itch before it is mixed with a resin.  Afterwards,  It can be sanded to shape with a dremel or sandpaper then use a light skim coat of bondo to even the surface.  Then paint or use the plasti-dip stuff for tool handles to put a rubber like coat on it. 

In my experience with auto repair and computer case modding,  fiberglass is great for this kind of thing.  Bondo cracks in thinkness over 1/8 inch or so with stress. 

RandyT:


--- Quote from: MYX on January 18, 2007, 04:26:52 pm ---I can say that it will be a handle. So anything with fiber glass will probably cause an itch correct? I got the idea the other day and I am thinking stongly about trying it. I will avoid bondo. Figure the strength of a joystick handle (actually where I got the idea). But I do not know if my widget will get that kind of abuse or not. But I figured I would try.

Randy I have seen that. Is it fiberglass or will it become a plastic?

--- End quote ---

The stuff I am talking about is technically a polyester resin.  So it gets very hard and becomes a plastic.  I made some balls from it once as an experiment and then threw one against a concrete floor as hard as I could.  After it bounced off of a 15' high ceiling I examined it and found that the impact with the floor marred the surface but it didn't crack or break.

For extra strength, like for boat or auto body repairs, you can use it with fiberglass cloth or loose fibers.  As long as you don't have very thin walls, you should be able to skip those and use the resin alone as an inexpensive casting material.  Other than the price, the availability can't be beat.  Just understand that very thick castings will generate a lot of heat and there will be some shrinkage (normal for a fair number of casting compounds.)  As long as you account for these in your molds, you should be fine.

Also, you can use the dispersed dyes from the craft store to tint it.  These are usually found by the crystal clear casting resins...which you should avoid due to the difficulties they present from the omission of a particular component in order to make them clear.  You won't get much of a color range, but if the translucent brown is too ugly, you can at least change it to a muddy green ;)

RandyT


MYX:

Yeah, Wow, that sounds great. I will look for some this weekend. Can it be dyed Black?
Which casting compounds shrink least?


--- Quote from: RandyT on January 19, 2007, 11:00:32 am ---So it gets very hard and becomes a plastic.  I made some balls from it once as an experiment
--- End quote ---

--- Quote from: RandyT on January 19, 2007, 11:00:32 am ---Just understand that very thick castings will generate a lot of heat and there will be some shrinkage (normal for a fair number of casting compounds.)

RandyT


--- End quote ---

So... Randy has plastic balls that when exposed to certain temperatures, may shrink? :-\

Sorry, it was there.

But thank you. I will try to put this together this weekend. How long does that stuff take to set? Is it thin enough to inject into a mold? Any ideas where to buy a syringe for injection? I have seen a number of folks mention air bubbles. How do I avoid them?
Are Air bubbles a bad thing if it is an opaque structure?

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