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Re: MDO

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  • Vince and Mary Ann Chew
    Yes, I used 10oz. cloth with a total of five coats of epoxy on the bottom. I mixed WEST copper powder in the final coat. It gives a very hard glass-smooth
    Message 1 of 122 , Dec 28, 2000
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      Yes, I used 10oz. cloth with a total of five coats of epoxy on the
      bottom. I mixed WEST copper powder in the final coat. It gives a very
      hard glass-smooth surface which they claim is more water resistant. I
      will paint over it before I launch. I used 6oz.cloth and five coats of
      epoxy on the side panels. I will coat the inside as well later.

      This boat will spend months at a time in the water. If it were a smaller
      trailerable boat, I would still glass the bottom and tape the chines for
      abrasion resistance, but maybe just epoxy on the topsides.

      I have a Tortoise dinghy which I used for three years coated with just
      epoxy and paint over marine fir ply. The bottom got pretty scuffed from
      dragging it up over a steel bulkhead at the marina. Last summer, I
      glassed the bottom and taped the chines. The paint still scuffs off, but
      the wood is protected now.

      No, I don't think the MDO soaks up significantly more epoxy than
      plywood. I haven't actually done any real accurate comparisons, but it
      seems like a batch of resin covers about the same area on the paper side
      as it does on the plain side. I have, however, tested resistance to
      delaminating. I applied a strip of 10 oz.cloth to a test scrap of MDO
      leaving enough cloth to grab with both hands and pull while standing on
      the piece. After curing several days, it pulled a layer of ply off
      rather than the cloth or paper.

      Vince Chew

      (In northern Michigan where the temperatures are currently running
      single digits Fahrenheit and the Dakota project languishes in an
      unheated steel building with a 3 foot drift in front of the door.)
    • prairiedog2332
      I would just like to add that OPP is one very good company. When you call their toll-free number you get a real person on the other end who will answer your
      Message 122 of 122 , Aug 22, 2010
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        I would just like to add that OPP is one very good company. When you
        call their toll-free number you get a real person on the other end who
        will answer your questions. They will give you the name of the nearest
        retailer in your area and also which ones place the most orders with
        them, so you can "piggy-back" a special order through them and not have
        to wait too long.

        My 3/8" order was placed through Windsor Plywood here in Canada and
        arrived in three days.

        http://www.olypanel.com/company/contact_us.php

        There are however "cheap imitators" out there that stock off-shore MDO
        and it is not necessarily made to the same quality standards. The good
        stuff has either Made in USA or Made in Canada stamped on each panel.

        Nels


        --- In bolger@yahoogroups.com, "Jon n Wanda" <windyjon@...> wrote:
        >
        > Just trying to help. The 1/4" is not a comon run but a specal order
        that is sometimes run for arcitecual orders. In reality they will make
        anything you want for a price if order is big enough. Only a few grades
        are made in 5/16ths with 3/8ths being the thinnest in all grades. Price
        wise it is all about how it is sorced. In Portland Or. the wholesailers
        care a good stock that can be gotten through most lumber yards in a day
        but shop for price when looking for it.
        >
        > Jon
        >
        > --- In bolger@yahoogroups.com, "prairiedog2332" arvent@ wrote:
        > >
        > > Hi Jon,
        > >
        > > Once again I stand corrected!
        > >
        > > You are correct that the manufacturers do not claim the overlay is
        > > waterproof, but DO claim the glue joints are. Therefor sealing with
        > > epoxy seems more useful than I inferred even though they do not
        mention
        > > that - just proper sealers and paint.
        > >
        > > I was not aware 1/4" MDO was available. I "estimate" the overlay as
        > > being 1/16" roughly - basically "paper thin".
        > >
        > > Just a side-light in my experience the 3/8" cost me more per sheet
        than
        > > the 5/8" which was "on sale" at the time. I suspect it is far more
        > > widely used were weight is not that great a consideration, like in
        > > cabinetry for example so is more readily available in stock. I had
        to
        > > place a special order and if I ordered a 10 sheet minimum there was
        no
        > > added freight. They just threw it in on top of a bulk order.
        > >
        > > Nels
        > >
        > >
        > >
        > > --- In bolger@yahoogroups.com, "Jon n Wanda" <windyjon@> wrote:
        > > >
        > > > I have used a lot of it on a 32X8' hull and it is no differant
        then
        > > working with regular plywood other then no checking. The overlay is
        not
        > > waterproof and the overlay thickness is not added to the ply
        thickness.
        > > 1/4" is 1/4" and 5/16th is 5/16th. The ply has more glue in the glue
        > > lines then even most marine ply so even unpainted it holds up well
        20
        > > years in the road sign case in the elaments. This is differant then
        in
        > > the water for a weekend or more so don't confuse the issue. My take
        is
        > > it is cheaper then marine with more glue but should be treated like
        any
        > > other plywood. When coldmolding I used laminating epoxy rather then
        > > glueing epoxy for soak in applyed with a 1/4' foam roller to alow
        for
        > > soak in. Sanding is your friend and what makes a glassed wood boat
        look
        > > like a plastic boat. How much better a complament could you get.
        With
        > > cild molding I turned layers 90 degrees to each other and on single
        > > layer used butblocks of the same plywood 8x thickness each side of
        > > joint. You can not find the joints even when you look on the inside
        to
        > > see where they are.
        > > >
        > > > Jon
        > > >
        > > > --- In bolger@yahoogroups.com, "prairiedog2332" arvent@ wrote:
        > > > >
        > > > > From my understanding MDO (medium Density Overlaid) plywoods
        main
        > > > > advantage is that it prevents checking and grain print-through
        from
        > > the
        > > > > underlying plies of either fir or hemlock. The overlay is
        cellulose-
        > > > > based and and the medium density means it is the same density as
        the
        > > > > underlying plies.
        > > > >
        > > > > It is applied with a phenolic resin using both heat and pressure
        to
        > > > > create a molecular bond that is stronger than the underlying
        wood.
        > > The
        > > > > surface then becomes weatherproof and immediately paintable with
        no
        > > need
        > > > > to fiberglas over - unless added wear resistance is required
        e.g.
        > > below
        > > > > the waterline for instance.
        > > > >
        > > > > Also from what I understand epoxy bonds with the overlay with
        no
        > > more
        > > > > difficulty than any other standard exterior grade plywood,
        although
        > > some
        > > > > builders rough up the joint area with a bit of sanding.
        > > > >
        > > > > http://www.canply.org/english/products/overlaidplywood.htm
        > > > >
        > > > > It is available both in Canada and the USA. Olympic Panel Crezon
        is
        > > > > often considered a good choice for boat building. Complete specs
        > > here
        > > > > including finishing and painting recommendations.
        > > > >
        > > > >
        > >
        http://www.olypanel.com/common/pdf/Crezon%20-%202%20Step%20Prod%20LIt%20\
        \
        > > \
        > > > > -%2011-07.pdf
        > > > >
        > > > > Note the recommended paints. Also it is available overlaid on
        one
        > > side
        > > > > onl., and in 10' sheets.
        > > > >
        > > > > Also the available thicknesses seem a bit odd but they include
        the
        > > > > overlay. So a 5/16" sheet is actually a 1/4" with the overlay
        > > added.
        > > > > Also with the open grain of the fir/hemlock it doesn't slice as
        > > thinly
        > > > > that easily as tropical brands. So the plies will be a bit
        thicker
        > > and
        > > > > the panels somewhat heavier. So for light weight, multi-ply
        thin
        > > panels
        > > > > - forget it. Go with the marine-grade hardwoods. (My 5/8" MDO
        has 5
        > > > > plies and 2 overlays.)
        > > > >
        > > > > All of this info is subject to clarification and correction!
        > > > >
        > > > > Nels
        > > > >
        > > >
        > >
        >
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