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kirkbauer

Well Known Member
I feel like this is an epoxy 101 question, but can anybody help me understand more about when to use each of these fillers? Here is what I have:
  • West Systems 406
  • Glass Bubbles
  • Flocked Cotton Fiber
  • Cabosil
Here is what I have figured out so far:
  • Glass Bubbles add volume without adding weight and are easy to sand
  • Flocked Cotton Fiber is similar but not as easy to sand (or doesn't sand as smooth)
  • Cabosil makes it thicker and prevents it from running (maybe also what 406 does?)
Early on I was only using the glass bubbles (aka "micro") but the material would always flow due to gravity while drying. These days I tend to put a mix of "micro" plus Cabosil so that the epoxy solution doesn't move once I have put it in place.

Am I doing this right? Any other tips around the use of these fillers?
 
kirkbauer said:
I feel like this is an epoxy 101 question, but can anybody help me understand more about when to use each of these fillers? Here is what I have:
  • West Systems 406
  • Glass Bubbles
  • Flocked Cotton Fiber
  • Cabosil
Here is what I have figured out so far:
  • Glass Bubbles add volume without adding weight and are easy to sand
  • Flocked Cotton Fiber is similar but not as easy to sand (or doesn't sand as smooth)
  • Cabosil makes it thicker and prevents it from running (maybe also what 406 does?)
Early on I was only using the glass bubbles (aka "micro") but the material would always flow due to gravity while drying. These days I tend to put a mix of "micro" plus Cabosil so that the epoxy solution doesn't move once I have put it in place.

Am I doing this right? Any other tips around the use of these fillers?
Click to expand...
it was my understanding that flox adds strength, micro reduces strength and cabo just makes it thick without affecting strength. i am sure someone will come along and confirm or reject. FG is not a major strength of mine. micro is for fairing, not structural applications, I believe.
 
If you're using epoxy to laminate something with glass cloth or carbon cloth, you should use the epoxy without any additives, FYI.

And if your micro sags, thicken it up with more micro, you'll get the right idea thinking of peanut butter.

Dave
 
David Paule said:
If you're using epoxy to laminate something with glass cloth or carbon cloth, you should use the epoxy without any additives, FYI.

And if your micro sags, thicken it up with more micro, you'll get the right idea thinking of peanut butter.

Dave
Click to expand...
I’ve found that everybody has their own idea of how thick peanut butter is.
I think it is better to suggest a visual test.
Keep adding micro to the mixing cup until you can turn the cup almost upside down and have the mix not move in the cup when held in that position for 10 seconds or so. This will give you a mix that’s still easily workable, but won’t sag or creep.
 
Everything commented here looks right to me.
I use a mix of micro, cabosil, and milled glass fiber for the peanut butter mix.
Vary the % mix if I want more or less structural function.

Sidebar question (sorry) . . . .
Difference between cotton flock and milled glass fiber (which I use) as a strengthener?
The milled glass fiber is heavy, but makes a solid peanut butter.
 
BruceW said:
Everything commented here looks right to me.
I use a mix of micro, cabosil, and milled glass fiber for the peanut butter mix.
Vary the % mix if I want more or less structural function.

Sidebar question (sorry) . . . .
Difference between cotton flock and milled glass fiber (which I use) as a strengthener?
The milled glass fiber is heavy, but makes a solid peanut butter.
Click to expand...
Pretty sure that glass fibers make a stronger composite than cotton. I have used various polyester and vynal ester repair fillers and they always use fiberglass strands. I believe the longer strands create a stronger repair than the shorter ones.
 
kirkbauer said:
I feel like this is an epoxy 101 question, but can anybody help me understand more about when to use each of these fillers? Here is what I have:
  • West Systems 406
  • Glass Bubbles
  • Flocked Cotton Fiber
  • Cabosil
Click to expand...
You'll be wanting to dig into some of those West Systems adhesive fillers, too, like the 403 and the ultimate 404 high-density adhesive. Those will come in very handy for such projects as the FWF induction snorkel and for bonding hardware to composites. You won't need to add anything to those two fillers because they not only make great peanut butter (not the runny Kirkland kind, either!), but they harden up into something like flint. You'll be having to work a lot harder at sanding, too, so be advised!
 
David Paule said:
If you're using epoxy to laminate something with glass cloth or carbon cloth, you should use the epoxy without any additives, FYI.

And if your micro sags, thicken it up with more micro, you'll get the right idea thinking of peanut butter.

Dave
Click to expand...
Micro reduces the epoxy strength. If you just need to thicken it, Cabo is the way to go.
 
Anybody been using SuperFil for a longer period of time? I just started dabbling in it and so far, seems to perform well. (Fairly thixotropic, low shrinkage, density fairly low, sandable) 12 hours to fully cured and sandable, ~ one hour pot life. It's a 2-part epoxy sold by ACS for aircraft applications. Long term how is it holding up? Adhesion and flexibility?
 
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