Question about resin and blushing

Discussion in 'Boatbuilding' started by declan, Mar 30, 2013.

  1. declan
    Joined: Jun 2010
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    declan Junior Member

    Hi all!

    I'm now at the stage where I'm about to stitch my boat together so I can fiberglass it. I ended up ordering this resin kit. It seems fine so far, but it cost $125 and I used nearly half of it just getting the two hull sides together.

    Clearly, unless I'm doing something wrong in applying it, I'm going to need way more, and it'll get prohibitively expensive at this price.

    However, I also found this at home depot for WAYYY cheaper, and I've already used it to great success on a smaller part of the boat.

    My question is, could I use it for the whole boat? I know people keep saying you need to make sure your epoxy is nonblushing, but the "Epoxy Book" says:

    If this is the case, why do we care if epoxy is blushing? I don't mind wiping it down with a sponge after it dries. Is blushing really the only difference?

    I'm really excited to finish this boat, but I can't drop as much money as these other epoxies would make me have to. Can anyone shed some light on the issue?

    Thanks!
     
  2. michael pierzga
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    michael pierzga Senior Member

    Well....the limits of polyester resin are known. Dont use is.

    If budget is a problem its better to cancel work until you have saved up enough money to purchase epoxy

    As for epoxy blushing. Sure...you can wash blush off. When you do the outside skin, a wipedown to remove blush is simply an inconvenience.

    When you work on the inside of the boat...or on fairing or on details ...wiping off blush becomes a pain in the *** nightmare. Only use non blushing epoxy .

    Always endeavor to work wet on wet with any epoxy.

    Peel ply is the best defense against blush and contaminates for secondary bonds .

    quality ,non blush epoxy, is available for 100 dollars per gallon. Buy it.
     
  3. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Welcome to the forum.

    The AeroMarine epoxy is a non-blushing formulation, so no issues, unless you apply it in the rain.

    The 3M product is polyester resin and will not work on a taped seam (stitch and glue) build. Polyester resin is used for repairs on production ('glass) boats and part molding. It doesn't stick to wood very well and is quite weak compared to epoxy.

    At $125 for a 1.5 gallon kit, you're not using the most economical epoxy choice available. In the quantities you'll need, you should pay no more then $60 a gallon. Look into products from www.epoxyproducts.com and www.bateau.com. Both offer relatively inexpensive, blush free epoxies.

    I'm not sure which design you are building (did you decide to build Steve's little duck boat?), but a reasonable set of plans will include how much epoxy you'll need for the project. On a small powerboat, say 14', with a short foredeck and some seat boxes, you'll use in the 5 gallon range, if you sheath the outside with a light (4 - 6 ounce) cloth. It you have a cabin, plan on more sheathing, such as seat tops and cockpit soles, then you'll need more, but again the BOM should include this.

    Even with the BOM suggestions about how much epoxy you might need, it's very common for the novice to use a lot more than listed. If you apply epoxy with a roller or a brush, you'll use twice as much as necessary. The most economical way of applying resin is with a squeegee or plastic applicator. The first coat does down thin, real thin. In fact, I scrape the first coat, so there's absolutely no pooling epoxy on the surface, which mitigates outgassing. The next coat goes down with the same tools, but with an eye toward a nice, uniform thickness layer. At this point, it's ready for cloth or a final coat, prior to paint or clear coating. You can't apply epoxy in a uniform thickness with a brush, period. Yeah, this sucks, but it's true. Now there are some locations, you just don't have a choice, but most surfaces can be coated without a brush. Rollers can apply a uniform thickness, but the roller holds a lot of goo and this is just waste, which adds up.

    Download the free user's guides from westsystem.com and systemthree.com for techniques and tips. The EpoxyProducts site also has a lot of good information too.
     
  4. declan
    Joined: Jun 2010
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    declan Junior Member

    Hi, thanks for the reply!

    I am indeed building the "DuckSkiff". Right now I'm using a plastic scraper like this to apply the epoxy, which seems to work pretty well and scrape it thin enough that I'm not wasting a crazy amount.

    However, clearly I'm doing something very wrong, or the manual has a mistake or something... From the manual:

    I do want to totally seal the boat. But I've so far used about half of the 1.5gal Aeromarine, just for a single sheet (about 10" wide) down the middle of the hull, to just attach the two sides of the hull together. Clearly this 1.5 is not going to do for the rest of the hull, let alone the whole boat. So is his estimate just very off?

    I'll check out those sources, thanks!
     
  5. pauloman
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    pauloman Epoxy Vendor

    that epoxy is not a formulated marine epoxy like west, maas or progressive epoxy offer. Instead they buy the raw resin and raw curing agents in bulk from the handful of chemical companies that make the raw parts and decant off small units for resale. see how to compare marine epoxies at www.epoxyproducts.com/mepoxies.html
     
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  6. PAR
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    PAR Yacht Designer/Builder

    No kidding, Aero sells unrefined epoxy, well, learn something new everyday. Still got snow on the ground up there Paul - it's 83 today and I've had to drag out the lawn mower from it's short winter nap twice already.
     
  7. pauloman
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    pauloman Epoxy Vendor

    still snow on the ground - about 25% coverage, but its fading fast. mornings still below freezing - days in upper 30s, 40s or maybe 50s.
     
  8. tom kane
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    tom kane Senior Member

    If you do strike a blushing problem often if you wet the surface with solvent on a dry day that will repair the blushing.
     
  9. PAR
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    PAR Yacht Designer/Builder

    Solvent aren't the way to "fix" a blush - you'll just smear it around. Cleaning and abating are the only true ways of dealing with a blush. An epoxy blush is water soluble, so a quick scrub with a light soap and scouring pad will do. Do this before sanding for subsequent coatings, even if it's a non-blushing formulation, unless you have ideal environmental working conditions.
     
  10. solarflare
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    solarflare Junior Member

    When you "formulate" and "refine" a marine epoxy what exactly does that mean?
     
  11. PAR
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    PAR Yacht Designer/Builder

    Wow, that's a loaded question, but basically it boils down to all the resins used, by all the major players in the epoxy formulation industry, come as a raw resin from a few chemical companies. This "unrefined" product can be packaged and sold with a hardener, pretty much as it exists, meaning a much higher profit margin for the formulator, but less that desirable physical properties for marine industry use. The actual formulations can get fairly complex and unless you have a significant understanding of the chemistry involved, way more then you need to know (my assumption). If you look up epoxy formulations, you can get more information, but get ready for 12 and 15 character words, that are really tough to pronounce properly.
     
  12. tom kane
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    tom kane Senior Member

    Reading the specs on the container about ambient temperatures and application conditions and applying that information should save a lot of problems and adding retarders when appropriate should stop most problems. Blushing is moisture entraped on the surface under adverse conditions such as cold moist air and can be liberated re-wetting the surface with solvent under drier warmer conditions.
     
  13. PAR
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    PAR Yacht Designer/Builder

    Again, using solvent on a blush bloom, isn't the wise way to go. Being water soluble, it's very easy to remove, but using a solvent, you may just end up smearing it around, contaminating the surfaces further.

    Technically, blush isn't moisture trapped on or in the epoxy. It is in fact, amine groups on the surface, which combine at various levels with CO2 (carbon dioxide) and water (vapor), forming salts of amine carbonate, which grow (literally) on the surface. These are water soluble, but if the epoxy gets a good cure, even a good washing with mild soap can't get it all, so a wet sand is necessary. If you wash within 24 hours and use a scrubbing pad like ScotchBrite, then you'll be fine. If you wait more then a few days, before cleaning, the blush will dry to a much harder to remove powdery substance.
     
  14. michael pierzga
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    michael pierzga Senior Member

    I dont know anyone who uses solvent for cleaning epoxy or painted surfaces .

    Solvent dissolves any impurity on the surface or in you rag then deposits it back into the surface. Solvent is also an expensive, flammable , a health hazard that must be properly disposed of after use.

    Water, detergent and a soft brush or a 3m type scotchbright is best for removing surface contaminates.
    Scotchbright is particulary well suited because it abrades surfaces that are hard to attack with a sander...inside corners

    The beauty of water is that if a contaminate remains on the surface...water will bead, not flow. This area can then be re cleaned.
     

  15. pauloman
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    pauloman Epoxy Vendor

    PAR is right about the blushing being a CO2 and moisture thing. Epoxies range from easy to blush to very hard to blush - depending upon the blend - type of curing agents used. Some epoxies can be applied underwater. Formulated epoxies take the raw resins and raw curing agents and 'doctor' them for properties they want. Repackagers just sell the raw resins and curing agents purchased in bulk. My best advise to a good epoxy job is not to epoxy under conditions you would not paint under.
     
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