What is CABOSIL ??

[Verne Koester]

MessageMike,
Gray's answer is coming from an expert, I'd listen to what he says. The point I was trying to make and didn't make so well is that epoxy mixed with cabosil has virtually no structural strength as compared to glass cloth impregnated with epoxy or epoxy mixed with milled fiber. As such, it would probably be prone to stress cracks if you relied on it in a high stress and/or high-flex area. 

I'd use microballoons for any filling task I intended to sand and paint. Cabosil does a much better job of thickening epoxy and turning it thixotropic (sp?) which means non-runny. It also tends to be a much lighter mix than microballoons but is very tuff to build. 

If I were installing a firewall that had some gaps here and there where the edges butt up to the glass fuse, I'd use cabosil, especially since it's all internal. If I wanted to make a stab filet on the outside of the fuse that was going to be sanded and painted, I'd go with microballoons. Hope this provides a little more clarity.

Verne


  ----- Original Message ----- 
  From: Baiano, Mike [HCS] 
  To: 'discussion at nsrca.org' 
  Sent: Friday, September 06, 2002 11:08 AM
  Subject: RE: What is CABOSIL ??


  HI Verne,

  So does micro-balloon expoxy mixtures have any structural strength? I have both micro-balloons and cabosil - and I'm never quite sure when I should use one as opposed to the other. I generally reserve the cabosil when I just want to thicken epoxy into a paste, and weight isn't a huge issue. How do you decide which one to use for a particular application?

  Thanks,
  Mike
    -----Original Message-----
    From: Verne Koester [mailto:verne at twmi.rr.com] 
    Sent: Thursday, September 05, 2002 11:41 PM
    To: discussion at nsrca.org
    Subject: Re: What is CABOSIL ??


    Cabosil is fumed silica sand. It's extremely light weight. When mixed with epoxy finishing resin, it creates a paste that won't run on vertical surfaces. It's also frequently mixed with epoxy in a thinner mix and brushed into a mold to create the external gel coat on a glass part which prevents pinholes from making it to the surface of a part. On a clear epoxy-cloth piece, the epoxy/cabosil mix can be seen in all the 90-degree corners to bridge the radius the cloth can't make. It'll show as an opaque white as opposed to the clear epoxy/cloth you see everywhere else. Down side is that it's much tougher to sand than micro-balloons and has virtually no structural strength. Good stuff to have around, though. I use it a lot.

    Verne


      ----- Original Message ----- 
      From: Van - E-Mail LIST 
      To: Pattern LIST 
      Sent: Thursday, September 05, 2002 8:32 PM
      Subject: What is CABOSIL ??


      Don't think I know what this is ?
      ________________________________________________

      Van Flowers
      AMA: 6216 IMAC: 2229 
      IMAA: 26019 NSRCA: 2778
      www.rc-aerobatics.com




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