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Re: Composite deck layup

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  • Charles
    Thanks again for all the info- some good thoughts there Bob. I think I will build a table to mold this on. That will give me at least one good surface that
    Message 1 of 33 , Apr 1, 2008
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      Thanks again for all the info- some good thoughts there Bob. I think I
      will build a table to mold this on. That will give me at least one
      good surface that will take absolute minimum prep. Any thoughts on
      mold surface material? Someone said glass is best but 8x8 glass is a
      load. Charles
      > Charles,
      > Now that you've had made consideration of core type and resin
      choice. How do you plan to build this 8'x8' panel? Not a very large
      panel but large enough to plan very carefully so material is not
      wasted. There are very many mold surfaces to choose from. Hand lay-up
      or vacuum bag which I would very much recommend with corecell cores or
      RI. Edge treatment can save hours in the finishing process. If
      lighting is planned on the underside or other electrical equipment.
      Wiring can be installed in the core prior to glassing. The preparation
      list from large to small panel seems almost endless but when it comes
      time to actually build. You'll be very thankfull you took the time to
      think this out. Don't be afraid to Post any questions you have to the
      list. There are many that will help you out
      > Good Luck
      > Bob C.
      >
    • Phil Collins
      Bob, You are mistaken about epoxy. Either that or 90% of the rest of the world is mistaken... One-offs are almost always built in epoxy, for all the reasons
      Message 33 of 33 , Apr 7, 2008
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        Bob,
        You are mistaken about epoxy. Either that or 90% of the rest of the
        world is mistaken...

        One-offs are almost always built in epoxy, for all the reasons
        stated in the thread.
        Higher end boats, custom boats, and high performance boats (only
        talkin sailboats here, I don't care what powerboat companies do) are
        almost universally done in epoxy - spec'd by the designer
        generally. For all the reasons stated by Kurt.
        Production facilities almost always use polyester - for ONE reason -
        to save money.

        And I'd love to know where you can get poly resins that have
        anywhere NEAR the pot life of epoxies. The stuff gels in 10
        minutes, no matter what.

        --- In multihull_boatbuilder@yahoogroups.com, "Robert Crepeau"
        <nassaw@...> wrote:
        >
        > Well, I guess this thread is closed.
        > Kurt Hughes set the world straight on Poly vs. Epoxy. I'm not
        sure why you would use my mail to cross post. I merley stated a fact
        that mostly all builders here in northeast U.S. predominatley THE
        GREAT STATE OF MAINE use orthophalic as a boatbuilding choice of
        resin. So much, its sold like soda pop in a 5 gallon pail at the
        local hardware. I see all pros in your post but no Cons. I would
        consider that a biased one sided answer.This last post sounds like
        your trying to steer the small independent boatbuilding community in
        one direction .(Yours). You'll have to try to understand my theory
        on business. Economy heading toward the crapper. The boyzs that can
        afford those million $ boats will always have boats. The small
        building community will be the first affected with the crisis and
        pricing that will make building non affordable. Maybe you should
        move up with those Boyz. I haven't seen any real innovation from
        your camp. As a matter of fact. I thought I heard a whine about some
        loss of payment.
        > Pick on sombody your own size. Please leave us boatbuilders out of
        the equation or go build your own boat and don't forget to try and
        impress us. An I was being nice.
        > BOB CREPEAU
        > ----- Original Message -----
        > From: Kurt Hughes
        > To: multihull_boatbuilder@yahoogroups.com
        > Sent: Wednesday, April 02, 2008 5:31 PM
        > Subject: RE: [multihull_boatbuilder] Re: Composite deck layup
        >
        >
        > Ok, here it is,
        >
        > There are many good reasons to use epoxy instead of polyester.
        > First, stretch to failure. Glass fabric has about 6% stretch to
        failure. So
        > does most room-temperature epoxy, and many vinylesters.
        Polyester stretch
        > to failure is, everyone? About1%. So in tension, the glass is
        only loaded
        > to about 17% of its strength before the resin matrix starts to
        become a
        > necklace.
        >
        > Polyester will be bonding with water throughout its life, and it
        will gain
        > surprising weight from that water, while losing strength
        properties. If I
        > may quote from a D570 water weight gain test, "The orthophathlic
        casting had
        > more than a 2.5% weight gain after 4 days, then showed a weight
        loss on the
        > 7th and 14th days. That means the polymer is being broken down,
        solubilized,
        > leached out of the composite, and replaced with water."
        >
        > The biggest benefit of epoxy is that epoxy is more forgiving.
        Get the mix
        > ratio right and you are there. With polyester, or even
        vinylester, one has
        > to vary the MEKP level and vary the N,N-DMA level, oppositely,
        as a function
        > of temperature change. Or, also, vary the BPO level and again
        vary the
        > N,N-DMA level oppositely, as a function of temperature. The
        > catylist/promotors have to be done exactly right to get a good
        degree of
        > cure. The catylist/promoters will have amounts of down to
        fractions of a
        > percent. Those amounts must be very precise if good results are
        intended.
        > Also, if the part is stored at less than 10C it may never cure
        fully, even
        > with a later post cure. Using epoxy, you can improve the laminate
        > properties with a post cure, almost always.
        > Interplastic Corp. has some great papers on this.
        > I've never been able to afford a temperature controlled shop, so
        this
        > matters a great deal to me.
        > Until someone is using a Barcol hardness tool or even better, a
        D790
        > flexural strength test to prove it, I don't want to hear how a
        laminate is
        > acceptable with any or all the above conditions off, just
        because the layup
        > looks good.
        >
        > The point is if the temperature was too cold when you did an
        > epoxy laminate, you could bring it up to close to 100% cure
        later.
        > If you, for example, do a polyester laminate at 15C with 1% BPO
        and 0.3%
        > N,N-DMA, you will have only an 80% cure and it probably cannot
        be improved.
        > That same formulation however will give 96% cure at 25C.
        >
        > Most room temperature cure epoxies post-cure at around 65C to
        70C. Static
        > properties increase, but so does toughness against impacts.
        > One of the best reasons to post-cure is that you get to keep
        your paint job
        > smooth. Ideally every bit of composite structure and fairing bog
        should be
        > post-cured. Post-curing parts before the final fairing can be a
        problem
        > later on.
        > Heat will treat laminates, and fairing, kind of like a muffin in
        the oven.
        > Post cure gets the muffin to rise fully, as it were. Then, only
        after post
        > cure, you prime and paint, so it won't rise later if it gets
        heated. I
        > recall that the F40 trimaran Scissors was white most of its
        career. When it
        > was painted red for the advertisement filming in the tropics,
        the surface
        > then solar post cured and it looked like a big, red waffle. They
        apparently
        > used contour core and lots of bog in between the squares. It was
        literally
        > a red waffle.
        >
        > Blisters are also a huge issue. With polyester, especially with
        > orthophthalic resin, as Terry McCabe of Interplastic said, "Its
        not if it
        > will form blisters, but when." The useful paper is "A 15 Year
        Study of the
        > Effective Use of Permeation Barriers in Marine Composites to
        Prevent
        > Corrosion and Blistering". Again, Interplastic.
        >
        > Shelf life is another problem. The useful shelf life of epoxy
        resin is
        > years. Hardner has a shorter shelf life, it is still good for
        years. Both
        > vinylester and polyester components have a shelf live of just
        months.
        >
        > In conclusion, both epoxy and vinylester are much preferred to
        polyester.
        > Structurally epoxy and vinylester are close. Epoxy however is
        much easier
        > to work with, and is much more forgiving.
        >
        > Kurt Hughes
        >
        > -----Original Message-----
        > From: multihull_boatbuilder@yahoogroups.com
        > [mailto:multihull_boatbuilder@yahoogroups.com]On Behalf Of Robert
        > Crepeau
        > Sent: Wednesday, April 02, 2008 6:37 AM
        > To: multihull_boatbuilder@yahoogroups.com
        > Subject: Re: [multihull_boatbuilder] Re: Composite deck layup
        >
        > Charles, being from the northeast U.S. I've found the standard
        builder to
        > use poly. I've never had any problems with poly, Health or
        otherwise and
        > have been exposed to the raw product including styrene to water
        the eyes and
        > I probably have one of the dustiest shops in the state. As fact,
        The only
        > hazard I've found in boatbuilding after many many years is bad
        knees and a
        > thirst for A ice cold beer at the end of the day.
        > I don't know if you follow the KSS list but Derek just posted
        his stand on
        > poly. Hopefuly he'll post the thread to this list.
        >
        > Now I'm not trying to sway you to a resin choice. Its your
        pocket book.
        > The mixing of resin has pretty much been tabu. The standard rule
        is epoxy
        > will stick to poly but poly will not stick well to epoxy. I've
        never
        > understood this rule but since your building on a mold and in
        the reverse.
        > The gel would go down first and so the rule applies. Epoxy can
        follow.
        > I've found gelcoat is very difficult to spray. Rolling it out on
        the mold
        > table using a mill thickness guide and letting it partly cure
        before the
        > resin coat goes on.
        > Another coating system is Awlcraft 2000. This is my choice.
        Mixes easily
        > and sprays well. If you've never sprayed before its a little
        tricky on the
        > verticle but almost impossible to get a run on a horizontal
        surface. Add non
        > skid to the coating and it is impossible to get a run on a flat
        surface.
        > I posted this page on panel building on this list awhile back.
        You can
        > check it out. I will finish the text someday.
        > Hope this helps
        > Bob C.
        >
        > http://www.geocities.com/TheTropics/Shores/1748/index20PANEL.html
        >
        > ----- Original Message -----
        > From: Charles
        > To: multihull_boatbuilder@yahoogroups.com
        > Sent: Tuesday, April 01, 2008 11:05 PM
        > Subject: [multihull_boatbuilder] Re: Composite deck layup
        >
        > How about gel coat with an epoxy layup- did you spray the gel
        coat?
        > did you let it setup then make the panel? Is there a problem
        bonding
        > the epoxy panel to gelcoat- should I do it in poly- I have a lot
        more
        > faith in epoxy. Thanks
        >
        > [Non-text portions of this message have been removed]
        >
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