Trouble with Edges

Discussion in 'Fiberglass and Composite Boat Building' started by dvt30490, Sep 24, 2009.

  1. dvt30490
    Joined: Aug 2009
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    dvt30490 dvt

    G'day everyone,
    have just started getting into the fun of glassing however my first project is not going to well. I've made some boxes out of structural ply (approx 10mm thick) and have started to glass them. I'm using 300gram chopped strand mat and polyester resin, and catalyst mix of approx 60drops per 100ml in about 21-23 celcius. Whilst the fibreglassing on the flat portions of the boxes are okay, the box edges do not hold and no matter how much I use the roller on them I cannot get the glass to adhere flat on the corners. I have now done this 3 times now and still the same result. I have also changed to a vinylester, but the same result. Can someone help me? I hope you can understand what I'm talking about.

    thanks in advance

    DVT
     
  2. apex1

    apex1 Guest

    Hmmm, yes. Polyester does not adhere properly to anything! Same is valid for vinylester. Use Epoxy instead!

    Richard
     
  3. daiquiri
    Joined: May 2004
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    daiquiri Engineering and Design

    Did you round-off the corners before glassing them?
     
  4. missinginaction
    Joined: Aug 2007
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    missinginaction Senior Member

    Absolutely round over the corners if you can. I'd suggest that you use a router and a roundover bit. You can bevel the edge too, see the photo I've attached but I think that rounding over the corners actually works a bit better. The radius that you need to get the cloth to easily settle down depends on the weight (heaviness) of the cloth. For instance 4 oz fiberglass cloth is very thin and light and will go around a fairly tight radius. Something thicker like stitchmat or roven woving needs a larger radius.

    Oh yes, byall means use epoxy. It works better and you don't want to be smelling that styrene all the time do you?

    Regards,

    MIA
     

    Attached Files:

  5. rwatson
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    rwatson Senior Member

    Epoxy or Vinyl - Fibreglass will not sit flat around sharp edges - its nothing to do with the goo - its the glass fibres not co-operating.

    You have to round edges that cloth is being placed over.

    If you have to have a sharp edge for something, you will need to build it up, over the rounded edge afterwards.
     
  6. Herman
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    Herman Senior Member

    If giving this guy advise, please keep it complete: If you are tempted to use epoxy resin, please forget about using the chopped strand mat. The binder will not dissolve, and the mat will stay stiff. Use fabric instead.

    Anyhow, the solution has been given many times now: Round off the corners, and this will solve your problem.
     
  7. Itchy&Scratchy
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    Itchy&Scratchy Senior Member

    Unless of course he uses powder bound chopped strand matt which the epoxy will saturate. I would personally recommend cloth with epoxy though.
    cheers
    J
     
  8. dvt30490
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    dvt30490 dvt

    thanks to everyone for replying, a little experience from you boys goes a long way for a novice like myself. I'm sure that I will have further questions over the next number of years.
     
  9. dvt30490
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    dvt30490 dvt

    thanks

    thanks Richard,
    I will probably use the Epoxy in the future.
     
  10. dvt30490
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    dvt30490 dvt



    MIA,
    thanks for this little tip. I was thinking for a while that a lighter mat might work however the beveled edge sounds so logical. thanks for that and thanks for the picture it makes a lot of sense. Will keep in touch.
     
  11. dvt30490
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    dvt30490 dvt

    Sir RWatson,
    thanks for this tip. I will get the grinder out first and clean it up and then rip the edges with the router and see what happens. Will keep in touch with the results.
     

  12. dvt30490
    Joined: Aug 2009
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    dvt30490 dvt

    Thanks Herman,
    I'm aware that using epoxy on chopped strand mat is a no no. Thanks for the tip and also the additional threads to look at.
    Greatly appreciated. You guys do a wonderful job for the novices.
     
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