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MDO plywood for the hull?

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  • dkb715
    Does anyone have any long term experience with using MDO (medium density overlay) plywood for sheathing a hull? This is the stuff that is commonly used for
    Message 1 of 16 , Dec 30, 2003
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      Does anyone have any long term experience with using MDO
      (medium density overlay) plywood for sheathing a hull? This is the
      stuff that is commonly used for signs, concrete forms, etc. and it's
      finished with a resin impregnated paper product. I'm told it works
      very well for lockers and other interior functions, and 1 person in
      another group said he had used it successfully in building his
      transom.
      It seems to be the perfect alternative to marine fir ply since
      it wouldn't check like fir is prone to do. I would still glass the
      exterior, but I think the inside would only need to be epoxy
      covered. I'm concerned however, how it will hold up over time.
    • John Bell
      I built my AF4 two years ago out of two sided MDO. It s very good stuff and is holding up well. I will use it again the next time I build a hull that requires
      Message 2 of 16 , Dec 31, 2003
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        I built my AF4 two years ago out of two sided MDO. It's very good stuff and
        is holding up well. I will use it again the next time I build a hull that
        requires 3/8" minimum thickness. The only problem with MDO is that 3/8" is
        the thinnest material in the market. 1/2" and 3/4" is much more common.

        ----- Original Message -----
        From: "dkb715" <lburright@...>
        To: <bolger@yahoogroups.com>
        Sent: Wednesday, December 31, 2003 12:32 AM
        Subject: [bolger] MDO plywood for the hull?


        | Does anyone have any long term experience with using MDO
        | (medium density overlay) plywood for sheathing a hull?
      • David Romasco
        dkb715, I ve used MDO in a dinghy bottom with good results so far. It s sheathed in xynole and epoxy externally, but the interior is simply primed and painted
        Message 3 of 16 , Dec 31, 2003
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          dkb715,

          I've used MDO in a dinghy bottom with good results so far. It's sheathed in
          xynole and epoxy externally, but the interior is simply primed and painted
          with oil-based enamel paint. Looks great so far. My only concern with MDO,
          as with any plywood, is to seal the end grain with epoxy. Other than that,
          take a good look at all the exterior signs surrounding you every day, and
          you'll get a good idea of how weather-resistant MDO really is. IMHO, it's
          good stuff when you can find it, most particularly the type that has the
          overlay on both sides. Caveat: there is a single-sided product sold for
          concrete form work; examine each sheet carefully! The wood quality in the
          single-sided stuff varies.

          David Romasco



          _____

          From: dkb715 [mailto:lburright@...]
          Sent: Wednesday, December 31, 2003 12:32 AM
          To: bolger@yahoogroups.com
          Subject: [bolger] MDO plywood for the hull?


          Does anyone have any long term experience with using MDO
          (medium density overlay) plywood for sheathing a hull? This is the
          stuff that is commonly used for signs, concrete forms, etc. and it's
          finished with a resin impregnated paper product. I'm told it works
          very well for lockers and other interior functions, and 1 person in
          another group said he had used it successfully in building his
          transom.
          It seems to be the perfect alternative to marine fir ply since
          it wouldn't check like fir is prone to do. I would still glass the
          exterior, but I think the inside would only need to be epoxy
          covered. I'm concerned however, how it will hold up over time.



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        • Nels
          ... it s ... Information about MDO is available here: Check out the sign making link for Crezon which is what Peter the Pirate it using for Windermere. It is
          Message 4 of 16 , Dec 31, 2003
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            --- In bolger@yahoogroups.com, "dkb715" <lburright@c...> wrote:
            > Does anyone have any long term experience with using MDO
            > (medium density overlay) plywood for sheathing a hull? This is the
            > stuff that is commonly used for signs, concrete forms, etc. and
            it's
            > finished with a resin impregnated paper product.

            Information about MDO is available here:

            Check out the sign making link for Crezon which is what Peter the
            Pirate it using for Windermere. It is good looking stuff. I have
            looked at some down at my local yard, and could find no sign of voids
            along the edges. Unfortunately it was already made into signs!

            http://www.olypanel.com/

            (This company recently bought out Simpson.)

            Nels
          • Peter Lenihan
            ... This is an excellent alternative to the more costly marine plys.Make sure you get yourself some of the better quality MDO like those available through
            Message 5 of 16 , Dec 31, 2003
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              --- In bolger@yahoogroups.com, "dkb715" <lburright@c...> wrote:
              > Does anyone have any long term experience with using MDO
              > (medium density overlay) plywood for sheathing a hull?


              This is an excellent alternative to the more costly marine plys.Make
              sure you get yourself some of the better quality MDO like those
              available through OLYMPIC PANELS(ex-Simpson Ply)like their CREZON
              line of panels.
              Indeed,as has been mentioned,you must ensure proper sealing of the
              edge grain.
              For larger lay-ups, where you intend on using two layers of ply,I
              would suggest using only the good one side panels to gain maximun
              benefit from the two wood faces and epoxy.
              When glassing over MDO,don't forget to give the surface a light
              sanding to remove any oils on the surface and to give some "tooth" to
              the surface for a better bond.
              Properly done and maintained,there is no reason why your boat should
              not last as long as you like if built with MDO panels.
              Remember also to read and follow the respective manufacturers
              instructions for the application of any epoxy or paint product you
              intend on using with your MDO panels.
              So.......whatcha planin' on buildin' with MDO?

              Sincerely,

              Peter Lenihan,who works exclusively with MDO for his Bolger Boxes :-)
              from along the shores of the mighty polluted St.Lawrence.........
            • Nels
              ... plys.Make ... Regarding this company - I phoned the 1-800 number of the sales rep. who covers my area. (Western Canada) and they seem very co-operative and
              Message 6 of 16 , Dec 31, 2003
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                --- In bolger@yahoogroups.com, "Peter Lenihan" <lestat@b...> wrote:
                > --- In bolger@yahoogroups.com, "dkb715" <lburright@c...> wrote:
                > > Does anyone have any long term experience with using MDO
                > > (medium density overlay) plywood for sheathing a hull?
                >
                >
                > This is an excellent alternative to the more costly marine
                plys.Make
                > sure you get yourself some of the better quality MDO like those
                > available through OLYMPIC PANELS(ex-Simpson Ply)like their CREZON
                > line of panels.

                Regarding this company - I phoned the 1-800 number of the sales rep.
                who covers my area. (Western Canada) and they seem very co-operative
                and helpful. They only sell to dealerships, and he gave me the name,
                number and contact person of the nearest locations to me.

                Of course their biggest sales are to concrete form builders, but they
                are quite familiar with the interests of boat builders and recommend
                the Crezon as being the most versatile. If you order ahead of time
                the dealer will likely combine your order with a bigger one to make
                the freight costs lower.

                They also do custom scarfing of huge panels, which of course, makes
                is pretty darn expensive to ship anywhere.

                Their offices are right at the mill by the sounds of it:-)

                Happy New Year!

                Nels
              • Roger Derby
                Scarfing MDO is as easy as scarfing any plywood, except that the resin layer doesn t feather. Figure on filling the indentation and applying a painted finish.
                Message 7 of 16 , Dec 31, 2003
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                  Scarfing MDO is as easy as scarfing any plywood, except that the resin layer
                  doesn't feather. Figure on filling the indentation and applying a painted
                  finish. Plywood is easy to scarf since the laminates provide guide lines
                  that tell you when the surface is not a plane.

                  re: http://derbyrm.mystarband.net/daDori.html (scroll down for scarfed
                  bulkheads).

                  Roger
                  derbyrm@...
                  http://derbyrm.mystarband.net

                  ----- Original Message -----
                  From: "Nels" <arvent@...>


                  > --- In bolger@yahoogroups.com, "Peter Lenihan" <lestat@b...> wrote:
                  > > --- In bolger@yahoogroups.com, "dkb715" <lburright@c...> wrote:
                  > > > Does anyone have any long term experience with using MDO
                  > > > (medium density overlay) plywood for sheathing a hull?
                  > >
                  > >
                  > > This is an excellent alternative to the more costly
                  > > marine plys. Make sure you get yourself some of the
                  > > better quality MDO like those available through
                  > > OLYMPIC PANELS(ex-Simpson Ply)like their
                  > > CREZON line of panels.
                  >
                  > Regarding this company - I phoned the 1-800 number of the sales rep.
                  > who covers my area. (Western Canada) and they seem very co-operative
                  > and helpful. They only sell to dealerships, and he gave me the name,
                  > number and contact person of the nearest locations to me.
                  >
                  > Of course their biggest sales are to concrete form builders, but they
                  > are quite familiar with the interests of boat builders and recommend
                  > the Crezon as being the most versatile. If you order ahead of time
                  > the dealer will likely combine your order with a bigger one to make
                  > the freight costs lower.
                  >
                  > They also do custom scarfing of huge panels, which of course, makes
                  > is pretty darn expensive to ship anywhere.
                • Nels
                  ... resin layer ... Hi Roger, Have you seen in WB#175 (Dec2003) where they show a jig to create what they call nibbed scarfs ? This is what some of the kit
                  Message 8 of 16 , Dec 31, 2003
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                    --- In bolger@yahoogroups.com, "Roger Derby" <derbyrm@s...> wrote:
                    > Scarfing MDO is as easy as scarfing any plywood, except that the
                    resin layer
                    > doesn't feather.

                    Hi Roger,

                    Have you seen in WB#175 (Dec2003) where they show a jig to create
                    what they call "nibbed scarfs"? This is what some of the kit
                    companies are doing. A nibbed scarf is described as follows:

                    "The final result is a nibbed scarf, meaning that each panel has a
                    slight shoulder at each side. These interlock perfectely, so it's
                    easy to find the right alignment, achieve a tight fit, and end up
                    with a perfectly fair panel."

                    It is very simple to perform on this jig as you have the saw blade
                    only cutting so the teeth dont't quite clear the thickness of the
                    plywood and the scarf ends in a small ridge or shoulder about half
                    the width of the saw kerf. (No feathering.)

                    Only trouble is the damn jig looks more complicated to build than a
                    Bolger boat:-)

                    But I bet it would really work well on MDO.

                    Nels

                    " In theory, there is no difference between theory and practice. In
                    practice there is. Yogi Berra "
                  • Frank Bales
                    Nels, is there a Web site that shows this jig? Thanks! --FrankB ... From: Nels [mailto:arvent@hotmail.com] Have you seen in WB#175 (Dec2003) where they show
                    Message 9 of 16 , Dec 31, 2003
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                      Nels, is there a Web site that shows this jig? Thanks! --FrankB

                      -----Original Message-----
                      From: Nels [mailto:arvent@...]

                      Have you seen in WB#175 (Dec2003) where they show a jig to create
                      what they call "nibbed scarfs"? This is what some of the kit
                      companies are doing. A nibbed scarf is described as follows:

                      "The final result is a nibbed scarf, meaning that each panel has a
                      slight shoulder at each side. These interlock perfectely, so it's
                      easy to find the right alignment, achieve a tight fit, and end up
                      with a perfectly fair panel."

                      It is very simple to perform on this jig as you have the saw blade
                      only cutting so the teeth dont't quite clear the thickness of the
                      plywood and the scarf ends in a small ridge or shoulder about half
                      the width of the saw kerf. (No feathering.)

                      Only trouble is the damn jig looks more complicated to build than a
                      Bolger boat:-)

                      But I bet it would really work well on MDO.
                    • Peter Lenihan
                      ... Frank, Don t know about a web site for jig shown in Woodenboat(which appears limited to 4 widths) but check out this:
                      Message 10 of 16 , Dec 31, 2003
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                        --- In bolger@yahoogroups.com, "Frank Bales" <fbales@l...> wrote:
                        > Nels, is there a Web site that shows this jig? Thanks! --FrankB
                        >

                        Frank,
                        Don't know about a web site for jig shown in Woodenboat(which
                        appears limited to 4' widths) but check out this:

                        http://groups.yahoo.com/group/bolger/files/Dakota/

                        and scroll down to the bottom for a nice clear illustration of a very
                        easy set-up for scarfing plywood.
                        Thanks to Vince,of Dakota fame, for this presentation:-)

                        Sincerely,

                        Peter Lenihan
                      • Frank Bales
                        The recent discussions that mentioned scarfing plywood has been interesting. I ve been reading over the four articles in MAIB that Bolger wrote about Tahiti,
                        Message 11 of 16 , Dec 31, 2003
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                          The recent discussions that mentioned scarfing plywood has been interesting.
                          I've been reading over the four articles in MAIB that Bolger wrote about
                          Tahiti, and was wondering if anyone knows how he joins the five (4X8) panels
                          on the bottom? Here's how he describes it in the article:

                          "We base this hull on a straightforward 5 ply sheet hull length (5 X 8'
                          nominal) resulting in a structure around 39' in length."

                          It would appear that he isn't using scarf joints here since if so with an
                          8:1 ratio that would make the boat about 36' long. Since this bottom is
                          made up of 4 layers of 1/2" plywood (2" total thickness) is each layer
                          acting as a kind of butt joint for the one below it?

                          I've not made a final decision yet, but Tahiti is at the top of my list of
                          large power boats that I would like to start building in probably a year or
                          so. There are some others of interest (Buehler's Pilgrim for one), and I've
                          been talking with another NA about a similar design, which I'm expecting
                          some preliminary ideas from in a month or so. Not having study plans for
                          Tahiti is a real drawback. I've written PCB a couple of times, and he's
                          written back quickly with the answers to my questions, but study plans would
                          be so nice. The $950 for the plans is a great price, in my opinion, but
                          since I can't contact the builder of the first Tahiti (he hasn't given
                          Bolger permission, but it is on the water), and he hasn't published any
                          information on his building of Tahiti, it's hard for me to plunk down the
                          money for the plans based on four (very good) MAIB articles.

                          Frank (who's fighting a bad cold this New Year's eve, and not partying.
                          Have a Happy New Year All, and have one for me!)
                        • Peter Lenihan
                          ... is each layer ... Hi Frank, Don t have the plans either but,based solely on how Windermeres double laminate bottom is done, I think it safe to say that
                          Message 12 of 16 , Dec 31, 2003
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                            --- In bolger@yahoogroups.com, "Frank Bales" <fbales@l...> wrote:
                            is each layer
                            > acting as a kind of butt joint for the one below it?

                            Hi Frank,
                            Don't have the plans either but,based solely on how Windermeres
                            double laminate bottom is done, I think it safe to say that Bolger
                            does indeed simply call for straight forward butt joints with the
                            subsequent layer staggered 50%.That is,if one is laying the 4X8
                            panels athwarthship(butts every 4 feet),then the second layer is set
                            such that it over-laps the butt by 2 feet(50% of panel width).
                            As similar scheme may be what is called for on Tahiti.
                            Hope this helps and that you recover quickly from your cold. How
                            about a few stiff glass of vodka/gin/rum taken with several nice big
                            cloves of garlic,then quickly under the covers to sweat it out?

                            Sincerely,

                            Peter Lenihan
                          • Nels
                            ... Hi Frank, Here is the closest I could find. http://www.oneoceankayaks.com/stitchglue/plyshophtm/scarfjig2.htm The one on WB has a fancier clamping system
                            Message 13 of 16 , Dec 31, 2003
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                              --- In bolger@yahoogroups.com, "Frank Bales" <fbales@l...> wrote:
                              > Nels, is there a Web site that shows this jig? Thanks! --FrankB

                              Hi Frank,

                              Here is the closest I could find.

                              http://www.oneoceankayaks.com/stitchglue/plyshophtm/scarfjig2.htm

                              The one on WB has a fancier clamping system as the guy was doing it
                              comercially and needed a quicker set-up.

                              You will notice here that he is scarfing two sheets at the same time -
                              in which case you can't nib them. It shows the saw blade going well
                              past the edge of the top scarf. To get a nib you have to have the
                              blade adjusted much shallower so that it will leave a bit of an edge.

                              Of course on thin plywood - like here - it would not work well. But
                              on 3/8 to 1/2" it would be great.

                              You hold the saw verticaly to the table end and run it along a guide
                              that is below the saw while pressing against the jig face with the
                              saw base. Seems to me the higher the table the better - up to chest
                              height. The jig is not constructed at a 90 degree angle but something
                              like 82 1/2 depending on the scarf ratio you want.

                              BTW the best contact I got for MDO was in Edmonton Alberta.

                              Also for Derek Waters - they list Campion Marine in Kelowna. Does
                              that sound reasonable Derek?

                              Cheers, Nels
                            • Frank Bales
                              Thanks, Peter, that is what I was thinking too. As far as the glass of spirits with some garlic, I think I ll pass. Love it in food, but, uh, don t think my
                              Message 14 of 16 , Dec 31, 2003
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                                Thanks, Peter, that is what I was thinking too. As far as the glass of
                                spirits with some garlic, I think I'll pass. Love it in food, but, uh,
                                don't think my tequila would go well with it. I think I'd prefer a shot or
                                two with lime. :) --Frank

                                -----Original Message-----
                                From: Peter Lenihan [mailto:lestat@...]

                                > acting as a kind of butt joint for the one below it?

                                Hi Frank,
                                Don't have the plans either but,based solely on how Windermeres
                                double laminate bottom is done, I think it safe to say that Bolger
                                does indeed simply call for straight forward butt joints with the
                                subsequent layer staggered 50%.That is,if one is laying the 4X8
                                panels athwarthship(butts every 4 feet),then the second layer is set
                                such that it over-laps the butt by 2 feet(50% of panel width).
                                As similar scheme may be what is called for on Tahiti.
                                Hope this helps and that you recover quickly from your cold. How
                                about a few stiff glass of vodka/gin/rum taken with several nice big
                                cloves of garlic,then quickly under the covers to sweat it out?
                              • dkb715
                                I m doing all my research in preparation of building a 26 Bartender (popular double ender inboard on the west coast - primarily Oregon and Washington).
                                Message 15 of 16 , Dec 31, 2003
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                                  I'm doing all my research in preparation of building a 26' Bartender
                                  (popular double ender inboard on the west coast - primarily Oregon
                                  and Washington). Realistically it will be about a year before I can
                                  start cutting wood since I have to add on to my shop in order to
                                  have a space to build it. Won't be able to pour concrete until
                                  spring. My exisiting shop is full with the 19' jet sled I finished
                                  about 2 1/2 years ago, and I'm very ready for another "mental
                                  health" project.

                                  I greatly appreciate all your help!

                                  Dave B


                                  --- In bolger@yahoogroups.com, "Peter Lenihan" <lestat@b...> wrote:
                                  > --- In bolger@yahoogroups.com, "dkb715" <lburright@c...> wrote:
                                  > > Does anyone have any long term experience with using MDO
                                  > > (medium density overlay) plywood for sheathing a hull?
                                  >
                                  >
                                  > This is an excellent alternative to the more costly marine
                                  plys.Make
                                  > sure you get yourself some of the better quality MDO like those
                                  > available through OLYMPIC PANELS(ex-Simpson Ply)like their CREZON
                                  > line of panels.
                                  > Indeed,as has been mentioned,you must ensure proper sealing of the
                                  > edge grain.
                                  > For larger lay-ups, where you intend on using two layers of ply,I
                                  > would suggest using only the good one side panels to gain maximun
                                  > benefit from the two wood faces and epoxy.
                                  > When glassing over MDO,don't forget to give the surface a light
                                  > sanding to remove any oils on the surface and to give some "tooth"
                                  to
                                  > the surface for a better bond.
                                  > Properly done and maintained,there is no reason why your boat
                                  should
                                  > not last as long as you like if built with MDO panels.
                                  > Remember also to read and follow the respective manufacturers
                                  > instructions for the application of any epoxy or paint product you
                                  > intend on using with your MDO panels.
                                  > So.......whatcha planin' on buildin' with MDO?
                                  >
                                  > Sincerely,
                                  >
                                  > Peter Lenihan,who works exclusively with MDO for his Bolger
                                  Boxes :-)
                                  > from along the shores of the mighty polluted St.Lawrence.........
                                • Frank Bales
                                  Thanks Nels. I thought there might be some photos of the one in WB somewhere on the net. I had found the one you mentioned here, but it s one of the better
                                  Message 16 of 16 , Dec 31, 2003
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                                    Thanks Nels. I thought there might be some photos of the one in WB
                                    somewhere on the net. I had found the one you mentioned here, but it's one
                                    of the better links, I think. --Frank

                                    -----Original Message-----
                                    From: Nels [mailto:arvent@...]

                                    Here is the closest I could find.

                                    http://www.oneoceankayaks.com/stitchglue/plyshophtm/scarfjig2.htm
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