Quick & Easy epoxy question - How many layers can I do at once?

Discussion in 'Fiberglass and Composite Boat Building' started by Midday Gun, Nov 9, 2019 at 4:04 PM.

  1. Midday Gun
    Joined: Mar 2019
    Posts: 22
    Likes: 1, Points: 3
    Location: UK

    Midday Gun Junior Member

    I have a chain-plate relocation project ongoing.
    The laminating schedule I have from the designer specifies 7 layers of 600gm biax in epoxy for the patch on the inside of the hull.

    Patch will be 500x500mm wide and then each layer slightly smaller.

    Can I laminate all 7 layers at once, or do I need to break it up into two separate layups?
    Using West System, 205 hardener & working temp in the cabin will probably be around 15 degrees C.


    I was thinking if I can't do it in one go then to do the first 3 layers + peel ply. Followed by the last 4.
    Thoughts?

    Cheer
     
  2. KD8NPB
    Joined: Mar 2018
    Posts: 59
    Likes: 10, Points: 8
    Location: South Carolina

    KD8NPB Junior Member

    Based on the TDS, you'll have about 20-30 min before it gels off at that thickness. That only gives you about 3 minutes per layer to wet out, place, and roll out.

    You might want to break it up if you're not a pro.
     
  3. Midday Gun
    Joined: Mar 2019
    Posts: 22
    Likes: 1, Points: 3
    Location: UK

    Midday Gun Junior Member

    Thanks, I'm pretty confident I can wet it all out in that time, I was actually thinking more about the heat generated during the reaction causing issues, and is there a maximum thickness in one go before I have issues.
     
  4. KD8NPB
    Joined: Mar 2018
    Posts: 59
    Likes: 10, Points: 8
    Location: South Carolina

    KD8NPB Junior Member

    Should be about 7mm thick or so? That's pretty "industry average" for bulking lamination for production. Exotherm should be a non-issue, it may actually improve the properties of the laminate.
     
    Midday Gun likes this.
  5. leaky
    Joined: Sep 2008
    Posts: 161
    Likes: 5, Points: 18, Legacy Rep: 14
    Location: nh

    leaky Senior Member

    I don't think in mm, need to do a conversion, nor do I use west system, :).. but in short..

    All decent epoxy manufactures have some window where you do not need to prep, however where the resin still bonds perfectly. System III silvertip is 24 hours I believe for instance..

    In any layup, of course you do not want to have so much exothermic activity that the resin burns up, but also (and more commonly) you do not want to be disturbing the underlying layers when they begin to set by putting more layers on top. The only time I ever run into the problem where I'm worried about the thickness for the sake of the piece getting too hot is when doing seriously structural tabbing, ie surface area is small and potentially thick so you get lots of layers on quickly. Outside of that, it's about impossible to put too many layers on.

    Then additionally consider how your resin is working. Fast cure resin in 80 F (yes F :) ) is going to be a little on the wild side, especially if you load it on... Slow cure at 60 F and you have hours to work with.. Fast cure at 60 F and it will be a manageable pace..

    Typically with epoxy I work one layer at a time, I set one layer then allow it to cure until there is no way to disturb it with the next layer, basically because I do not need to work with mat and with one layer of a woven product only I can pull the excess resin out with a squeegee for a really good ratio. I'm not working "on the clock' but regardless usually I have enough things to do where I can come back to something 2X a day, putting a layer on each time, which is a fail proof window for the epoxies I've worked with (ie 6 hours between layers assures an undeniable chemical bond but also the layers underneath are cured to a point where there is no risk laying atop them) .

    Jon
     

  6. Midday Gun
    Joined: Mar 2019
    Posts: 22
    Likes: 1, Points: 3
    Location: UK

    Midday Gun Junior Member

    Cheers guys.
    Sounds like I'll be OK laying it out in one go, or two if I'm struggling to wet it all out.
    I'd actually worked the thickness out at about just over 5mm, but I was converting west systems website figures to metric from inches so could have ballsed it up.

    Hopefully I can wet out the layers on a staging area (with non stick plastic sheeting) that I've set up across the saloon settees, and then transfer them to the area they're going.

    Leaky, its time for you to make the switch to metric, you know it makes sense! :D
     
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