Bondo Filler vs Microballoons

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bguffer

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Anyone have any opinions when it comes to Bondo filler vs microballoons, for smoothing fin fillets? I'm not sure why to pick one over the other.
 

mkadams001

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I would base my choice on how much filling I am doing and which one weighs the least. The micro balloons should be lighter when mixed with epoxy. The bondo might be easier to sand. The end result will be the same.:)

I use red lacquer spot putty to fill any imperfections and pinholes. No mixing, dries fast, and sands easy.:cheers:
 

MarkII

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What is Bondo's working time? Can you mix small batches of it that will stay usable long enough to enable you to apply it around all of your fins? If the pot life is too brief, then can you just mix up small batches of it so that you can do one or two fillets without having a large amount go to waste? And is it possible to use both? That is, mix microballoons into the Bondo to lower its density and make it lighter in weight?

MarkII
 

Trident

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I think mkadams001's reference to the red lacquer spot putty is the same stuff as what I am using -- Bondo Glazing Putty. Squirt it out of the tube like toothpaste. Spreads like toothpaste (OK, spreads like I think toothpaste would, if I were using it instead ...). I use a nitrile glove, and use my finger to spread it, much like you would with a white glue fillet.

No mixing, dries fast, sands beautifully. I'll use this, sand, then prime, and then if I find another imperfection -- fill it, sand, prime, and repeat this as often as needed. I tend to let the putty dry overnight, so I am not sure how quickly I could do the cycles, but thin coats might be ready in a few hours.

I used to buy the Squadron Putty from hobby stores, but it WAY more expensive than the Bondo brand. You can find this in Walmart or Kmart automotive departments, or any automotive store.
 

mkadams001

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What is Bondo's working time? Can you mix small batches of it that will stay usable long enough to enable you to apply it around all of your fins? If the pot life is too brief, then can you just mix up small batches of it so that you can do one or two fillets without having a large amount go to waste? And is it possible to use both? That is, mix microballoons into the Bondo to lower its density and make it lighter in weight?

MarkII
Mixed properly Bondo's working time is maybe 10 minutes or so. I think that you would have more than enough time to apply the bondo around the fins. Most people use too much of the hardener and it goes off much faster.

Interesting idea about adding microballoons to bondo....
 

Multi-Stage

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I use microballon's and epoxy on the last pass with a piece of pvc or derlin rod's instead of my finger. It make's a much more uniform fillet. The pvc or derlin rod depend's on the size of the fin. After it's dry I use the same piece of pvc or derlin wrapped with 400 grit sandpaper and sand the fillet's smooth. This technique has worked great for me. I read about this on somebodies HPR website.
 
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stantonjtroy

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My experience is that your material should suit the need. Bondo uses polyester resin as a suspender which may attack some plastics. As well it has a fixed density. Microballoons come in different bases ( glass, phenolic, ect.) and can be mixed with most any glue suspender. Additionally the density can be adjusted from soup to fluff just by altering the mix.

FWIW
Troy
 

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