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Thread: Fiberglass material questions: bondo vs jelly vs short vs long strands etc

  1. #1
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    Fiberglass material questions: bondo vs jelly vs short vs long strands etc

    I am learning this stuff as I go. Was wondering if you guys could give a quick leason based on your own experience what are the best applications to use bondo, fiberglass jelly, bondo short strand, bondo long strand etc.

    I am about to start filling in the gap from my quarter panel stretch. Up to this point I have only used bondo filler or fiberglass jelly on my build. I think for such a large area I should use short or long strand and use something alot smoother for the final layer.

    I quick class from the forum Yodas on what to use ans when would be very helpful.

    Comments welcome.

    michael
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    Building a F40 replica, 4.9 caddy, 5 speed.

  2. #2
    Senior Member murcilambo's Avatar
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    Re: Fiberglass material questions: bondo vs jelly vs short vs long strands etc

    I would stick with fiberglass, bondo is basically just a filler. Fiberglass also will actually stick to some plastics that would be found in cars like header panels where as bondo wont. Also the fibers in the fiberglass cloth will add to the strength. Also most bondo style fillers cure too fast. fiberglass will cure more slowly and allow you to smooth it out more and fix any little areas that you may decide to work on.

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    Re: Fiberglass material questions: bondo vs jelly vs short vs long strands etc

    Quote Originally Posted by murcilambo
    I would stick with fiberglass, bondo is basically just a filler. Fiberglass also will actually stick to some plastics that would be found in cars like header panels where as bondo wont. Also the fibers in the fiberglass cloth will add to the strength. Also most bondo style fillers cure too fast. fiberglass will cure more slowly and allow you to smooth it out more and fix any little areas that you may decide to work on.
    Thanks murcilambo,

    So is the short and long fiber stuff basically jelly with fibers mixed in the compond? Or is it a thick liquid like fiberglass resin?

    michael

    Building a F40 replica, 4.9 caddy, 5 speed.

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    Re: Fiberglass material questions: bondo vs jelly vs short vs long strands etc

    mike,
    I use short strand when I eed to bond two surfaces together, such as the fiberglass door to the fiero steel and also when I needed to make my door longer. I would back up the gap with HVAC tape and then fill in the gap with the short strand filler. Once that has dried, remove the tape and then put 2 layers of fiberglass over the filled in area overlapping the fiberglass panel.

  5. #5

    Re: Fiberglass material questions: bondo vs jelly vs short vs long strands etc

    Quote Originally Posted by mikebrnch
    I am learning this stuff as I go. Was wondering if you guys could give a quick leason based on your own experience what are the best applications to use bondo, fiberglass jelly, bondo short strand, bondo long strand etc.

    I am about to start filling in the gap from my quarter panel stretch. Up to this point I have only used bondo filler or fiberglass jelly on my build. I think for such a large area I should use short or long strand and use something alot smoother for the final layer.

    I quick class from the forum Yodas on what to use ans when would be very helpful.

    Comments welcome.

    michael

    First of all, congrats on stretching the F40....stock fiero is WAY to short . Doesn't even come close to doing justice to such a beautifull car.

    I would suggest grinding back the gelcoat at least 2 inches on either side of the patch and building up as many layers of mat and resin as it takes to bring it up to the original level. Putty and long strand fillers contain too much resin and therefore offer very little strength. Carefull to work out bubles so they don't come back to haunt you later. Then, a skim coat of quality bondo and high build primer.

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    Re: Fiberglass material questions: bondo vs jelly vs short vs long strands etc

    Quote Originally Posted by NSX
    Quote Originally Posted by mikebrnch
    I am learning this stuff as I go. Was wondering if you guys could give a quick leason based on your own experience what are the best applications to use bondo, fiberglass jelly, bondo short strand, bondo long strand etc.

    I am about to start filling in the gap from my quarter panel stretch. Up to this point I have only used bondo filler or fiberglass jelly on my build. I think for such a large area I should use short or long strand and use something alot smoother for the final layer.

    I quick class from the forum Yodas on what to use ans when would be very helpful.

    Comments welcome.

    michael

    First of all, congrats on stretching the F40....stock fiero is WAY to short . Doesn't even come close to doing justice to such a beautifull car.

    I would suggest grinding back the gelcoat at least 2 inches on either side of the patch and building up as many layers of mat and resin as it takes to bring it up to the original level. Putty and long strand fillers contain too much resin and therefore offer very little strength. Carefull to work out bubles so they don't come back to haunt you later. Then, a skim coat of quality bondo and high build primer.
    Thanks for the congrats and advice. I have no doubts I will have a couple of moments that I will want to bang my head against a wall but I know it will be worth it.

    michael
    Building a F40 replica, 4.9 caddy, 5 speed.

  7. #7

    Re: Fiberglass material questions: bondo vs jelly vs short vs long strands etc

    first you will need to grind the sides of the repair area feathered out about 4 inches on both inside and out. add fiberglass matt or cloth until you have about 1/8 inch at LEAST. each piece wider than the next to build out along the feathered edge. once that is cured sand smooth. use short hair filler next to fill the low spots. sand smooth. next use regular body filler to skim coat it. it this point your repair area will be rather wide and smooth

    bondo is a brand name like bandaid. the drying time for either fiberglass or filler will depend on outside temps and hardener ratio. you can make either cure fast or slow depending on how much hardener you use. faster hardened fiberglass tends to be more brittle than slow cured.

  8. #8

    Re: Fiberglass material questions: bondo vs jelly vs short vs long strands etc

    Quote Originally Posted by Ferrari Berlinetta
    mike,
    I use short strand when I eed to bond two surfaces together, such as the fiberglass door to the fiero steel and also when I needed to make my door longer. I would back up the gap with HVAC tape and then fill in the gap with the short strand filler. Once that has dried, remove the tape and then put 2 layers of fiberglass over the filled in area overlapping the fiberglass panel.
    Hi
    what is that HVAC tape? what is that used for?

    thanks.

  9. #9
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    Re: Fiberglass material questions: bondo vs jelly vs short vs long strands etc

    Quote Originally Posted by jelpspeed
    Quote Originally Posted by Ferrari Berlinetta
    mike,
    I use short strand when I eed to bond two surfaces together, such as the fiberglass door to the fiero steel and also when I needed to make my door longer. I would back up the gap with HVAC tape and then fill in the gap with the short strand filler. Once that has dried, remove the tape and then put 2 layers of fiberglass over the filled in area overlapping the fiberglass panel.
    Hi
    what is that HVAC tape? what is that used for?

    thanks.
    Alum foil tape. Works good, some think it's kind of pricey. I have used it but have also used blue painters tape and even packing tape in a pinch.
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    Building a F40 replica, 4.9 caddy, 5 speed.

  10. #10
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    Re: Fiberglass material questions: bondo vs jelly vs short vs long strands etc

    I use it as a backer when I need to fill a gap and do not want the short strand to ooz onto the backside. It is also great for covering a part before you fiberglass as the fiberglass doesnt stick to it. You can get it at lowes or home depot.

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