about to fiberglass my first boat build

Discussion in 'Boatbuilding' started by kjprag01, Apr 25, 2016.

  1. kjprag01
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    kjprag01 New Member

    Hello everybody, Im building my first boat and just finished the plywood hull today. Ive sanded the entire boat to 180 grit and will get it dust and contaminant free later on in the week. My plan is to use 6oz fiberglass cloth and system three epoxy with a slow cure activator, utilizing the wet on wet method. Im not a professional fiberglasser, so i am not expecting a yacht quality finish, just enough to proudly stand over the vessel in moderate accomplishment. But i would like a few nudges in the right direction. should i lay the glass and epoxy down first then fair it out or should i fair out the hull first then lay the glass? My initial thought is to lay the glass and system three epoxy first, then use a more cost effective(cough cheap cough) polyester resin to fair it out on top of the good stuff. keep in mind this being my first she will not be used on the ocean, or in a bay, maybe and its a big maybe on the ohio river. Thanks for any help, satire, and and sarcastic remarks in advance.

    p.s. historically i like to skip occams razor and jump right into murphys law:)
     
  2. Tungsten
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    Tungsten Senior Member

    Look through other posts on any subject,go to one of Pars posts and on the bottom he has a tips page.scroll through that a few times.It has all the basic answers
     
  3. gonzo
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    gonzo Senior Member

    A plywood hull should be pretty fair by the time you are ready to fiberglass over it. It won't be a huge difference in price between using epoxy and polyester for fairing. Polyester won't give you the adhesion or water resistance that epoxy has.
     
  4. Mr Efficiency
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    Mr Efficiency Senior Member

    That is almost a crime, plastering PE bog over epoxy. It wouldn't surprise me if someone hasn't already called the epoxy police ! Scratch that idea !
     
  5. PAR
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    PAR Yacht Designer/Builder

    Don't mix resin systems. If you apply polyester over epoxy, it's not going to stick well. The costs you're concerned about are a result of using a name brand epoxy. There are many much cheaper formulations available. Check epoxyproducts.com, bateau.com and raka.com for goo's that are at least 1/2 the cost of the System Three and West System.

    As a rule the hull should be pretty fair, before you sheath it, simply because it's a lot easier to modify the surface (fairing) without cloth in the way. Once you've got the surface fair, then sheath it, but I'd recommend the dry method, where you place the cloth on the surface, trimming as necessary. Once fitted, trimmed and smoothed out, pour neat epoxy into the center and move it around with a plastic applicator, brush or whatever you're comfortable with. This assumes the surface is ready to accept the sheathing and has at least a sealing coat of goo applied previously. After the sheathing is down, you'll need to fair again (yeah, it sucks), partly to fill the fabric weave, partly to nail down all the humps and hollows, so you can smooth the surface in preparation for paint. 180 grit under cloth is way too fine, you only need 100 or 120, before the cloth goes on.
     
  6. SukiSolo
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    SukiSolo Senior Member

    Note this sentence. A lot of people forget to seal the surface with one or maybe (om a porous surface) two coats of epoxy to seal it properly. Without this sealing coat you will not get the best adhesion and strength you are looking for.

    80 grit or 120 WITH the grain is plenty fine enough for this stage, on the bare ply and timber. Only exception is if you want a clear perfect gloss through the glass, when you might want to remove any grit scratches for cosmetic reasons.
     
  7. upchurchmr
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    upchurchmr Senior Member

    Cloth on a sanded surface (no initial epoxy coat), then pour on the epoxy works fine.

    In spite of the "its better with a first coat" no one can give you any numbers on how much the adhesion is less.

    When doing a "dry" cloth coating it is certainly true the first coat will require more epoxy, but no more than doing an initial coat before putting down the glass.

    No matter how you do it, if you have exposed end grain, you need to make sure that gets plenty of resin. It will suck it like a sponge, you could get poorly attached cloth in that place, and that is a real bad spot.

    So many personal preferences and most of them can work with some care.

    No polyester - I agree with everyone on that.
     
  8. PAR
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    PAR Yacht Designer/Builder

    Certain species do suck out resin at an alarming rate, if using the dry method and these aren't always seen, which is the reason of my recommendation to a novice laminator. Douglas fir is well known, though plenty of others as well. I do dry applications all the time with no worries, but I have a few rodeos under my belt.
     
  9. kjprag01
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    kjprag01 New Member

    Im glad i didn't jump right into it. Thank you everybody, alot of good information. Im going to return the system three and research more epoxy systems, and this dry method. And please ignore the polyester sin, I am super new to boat building. . . Thank you all again. And i think novice is well above my current rank.
     
  10. PAR
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    PAR Yacht Designer/Builder

    Download the free "Epoxy Book" from the System Three site, the "User's Guides" and the "Gougeon Brothers on Boat Construction" book from the West System site. They're cover many of the techniques and the other sites I listed previously for a discount goo.
     
  11. SukiSolo
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    SukiSolo Senior Member

    They certainly are 'seen' - later, when needing repair where water has seeped in....;) and the 'dry' core has become saturated too!.

    Agreed on a dense species you could get away with it but for WR Cedar, Spruce, Doug Fir etc, I prefer to coat first. It also depends on the cloth type and how well that wets out....;)
     

  12. PAR
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    PAR Yacht Designer/Builder

    Yeah, there's a number of variables when making these decisions, most based on what you've screwed up previously, unfortunately.
     
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