Modifying window openings. Wrap glass around frame?

Discussion in 'Fiberglass and Composite Boat Building' started by mrybas, Apr 11, 2018.

  1. mrybas
    Joined: Jun 2017
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    Location: East Coast or Cruising

    mrybas Junior Member

    Im changing non opening glass for opening hatches. I had to add a piece of plywood to make the opening work for the new hatches.
    I plan on adding 3 layers of 1200 biax +\- 45 to the exterior and interior where the plywood was added extending 3” back to existing glass.
    My questions are:
    Should I try to wrap the perimeter (inside edge) of the opening in glass?
    It might be hard to wrap from the exterior to the interior with continuous pieces of glass because it is a right radius. Is it ok to use long 1.25” strips of glass (cabin top is 1”) and wrap/line the frame. Let it cure and sand the proud flush. Then I can add exterior/interior glass?
     

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  2. Blueknarr
    Joined: Aug 2017
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    Location: Colorado

    Blueknarr Senior Member

    Welcome
    Im changing non opening glass for opening hatches. I had to add a piece of plywood to make the opening work for the new hatches.
    I plan on adding 3 layers of 1200 biax +\- 45 to the exterior and interior where the plywood was added extending 3” back to existing glass.
    My questions are:
    Should I try to wrap the perimeter (inside edge) of the opening in glass?
    Yes
    It might be hard to wrap from the exterior to the interior with continuous pieces of glass because it is a right radius. Is it ok to use long 1.25” strips of glass (cabin top is 1”) and wrap/line the frame. Let it cure and sand the proud flush. Then I can add exterior/interior glass?
    I would use a wider strip of woven cloth. Weaves are easier to flex around a tight radius. Narrow strips with want to lift away from tight radius. Could radius be increased? Using Peel-ply will reduce eliminate sanding.
     
  3. Blueknarr
    Joined: Aug 2017
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    Location: Colorado

    Blueknarr Senior Member

    I almost forgot.

    Make a mockup section simular to window profile. Try different widths, weaves and weights of cloth unit you find what works well.
     
  4. Blueknarr
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    Blueknarr Senior Member

    A simple visual demonstration.
    The heavy bi-axe on the left has zero chance of mating. The wider knit on the left will lay down far easier than the narrow middle sample.
     

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  5. Rumars
    Joined: Mar 2013
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    Rumars Senior Member

    Lay the glass normally on both sides, trim flush then cut back the plywood and fill the resulting groove with thickend epoxy. Do this all around, that way water has no chance to penetrate the core. It might be easyer to cut the ply first and extend the glass over the edge when laminating then cutting a groove with a router.
     
  6. mrybas
    Joined: Jun 2017
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    mrybas Junior Member

    I did one of 4 window openings today. I wrapped continuous pieces of 1200 biax from exterior to interior. I let the epoxy get pretty tack before laying down the glass, which helped it stick. I also added some extra glass strips in the corners of 1200 (I should get some uni directional glass).
    It came out pretty good, with h not to many spots that have air behind them, but I had to babysit the lay up to keep working air out from behind the glass.
     

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  7. mrybas
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    mrybas Junior Member

    Thanks for the tip, but I thought biax +\-45 would bend around a radius easier because none of the strands have to make a 180 degree change like half of the fibers in a 0-90 woven cloth?
     
  8. mrybas
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    mrybas Junior Member

    Won’t the opening be weaker without glass in the opening?
     
  9. Rumars
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    Rumars Senior Member

    Yes it will be. But if you need a square corner... Maybe someone knows of a better way. If the corner can be rounded then wrapping glass is the better way. Looks good, keep going.
     
  10. Blueknarr
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    Blueknarr Senior Member

    As you just learned, all of the yarns in bi-axe are making the 90dry turn.
    Keys to folding FG:

    Fat radius
    Thin yarns
    Wide ear flaps
    Practice

    If sharp corners are nessicary, they can be built Bach up with fairing compounds after glasswork.

    Grab a scrap piece of ply. The mistakes can then easily thrown away, instead of needing to be ground out.
     
  11. mrybas
    Joined: Jun 2017
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    mrybas Junior Member

    How much weaker would the following method be vs continuous glass wrapped from interior to exterior?
    The opening has square corners (not radius):
    1. take uni glass slightly wider than opening thickness. Wrap entire frame interior with uni glass, let cure, sand proud glass flush.
    2. laminate exterior and interior glass.

    The fibers won't be continuous from interior to exterior, but it seems to me that unidrectional fibers would add the most stiffness to the frame?

    I have no clue, just throwing this idea out there to see if it makes sense?
     
  12. Blueknarr
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    Blueknarr Senior Member

    IMO most important is encapsulating ply with epoxy and firm attachment of ply to hull.
    Glass fibers on edge of ply are ineffective in adding stiffness to ply

    If glass connection from inside to out is important to you: round off, glass then rebuild squares.
    If ease of build: glass top and bottom separately, trim then square up

    Uni on edge of ply: pain in arse, but won't hurt
     
  13. mrybas
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    mrybas Junior Member

    I get your point that uni directional glass won’t make the ply stiffer in the middle of the frame. But wouldn’t adding unis to the corners make the frame as a whole stiffer?
    I’m not necessarily going this route for the next window, just asking for educational purposes.
     
  14. Blueknarr
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    Blueknarr Senior Member

    Yes connecting the corners would be stronger.
    How much does it add when compared to the total bond area?
     

  15. mrybas
    Joined: Jun 2017
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    Location: East Coast or Cruising

    mrybas Junior Member

    This is the window I dcan d yesterday. I used biax in a he corners, but I ordered some unis that I’ll try next time.
    They extend about 4” from the corners. 2 layers of 1200. Do you think this is doing much in terms of strengthening the frame?
     

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