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Plywood 12-1/2 - Keel Construction

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  • Mark & Marie-Claude
    I m building a model of Bolger s Plywood 12-1/2 (from BWAOM - a plywood interpretation of Herreshoff s 12-1/2 ) before deciding to build the full-size
    Message 1 of 10 , Dec 30, 2000
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      I'm building a model of Bolger's Plywood 12-1/2 (from BWAOM - a plywood interpretation of  Herreshoff's 12-1/2 ) before deciding to build the full-size version.  On paper I don't mind the chines, but since even Bolger admits the chined version isn't quite as pretty as the original, I want to take a look at a 3-D version before my final decision. 
       
      My question here though is regarding the keel/backbone construction used by Bolger for this design.  He's modified the construction details slightly from the sketches in BWAOM and now has a solid backbone/keel assembly made up from 6 layers of 1/2" plywood.  I'd be interested to hear any experiences (good or bad) that people have had with this style of keel nstruction. 
       
      My primary concern is all the plywood end-grain that is exposed on the leading edge of the keel.  My planned sailing area is fairly rocky and I'm concerned that any substantial knocks may damage the fiberglass/epoxy sheathing and allow the plywood to start 'wicking' in water - with the inevitable rot that follows.  Since it's going to be on a mooring, the keel will only get a close inspection once a year when the boat is pulled out for the winter.  Because of this I'm considering going with a traditional construction keel & backbone, but maybe I'm being too conservative.
       
      Additionally, just out of curiosity - is anyone aware of any completed Plywood 12-1/2's? 
       
      Thanks,
      Mark Oliver
    • Chuck Leinweber
      My primary concern is all the plywood end-grain that is exposed on the leading edge of the keel. My planned sailing area is fairly rocky and I m concerned
      Message 2 of 10 , Dec 30, 2000
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        My primary concern is all the plywood end-grain that is exposed on the leading edge of the keel.  My planned sailing area is fairly rocky and I'm concerned that any substantial knocks may damage the fiberglass/epoxy sheathing and allow the plywood to start 'wicking' in water - with the inevitable rot that follows. 
         
        Mark Oliver
         
        Mark:
         
        It seems to me that laminating the keel would tend to isolate smaller pieces of wood which would limit the progression of rot if it did take place.  A traditional type keel is subject to damage too, and rot travels much easier in a single piece of wood.
         
        Chuck Leinweber
      • StepHydro@aol.com
        In a message dated 12/30/2000 7: My primary concern is all the plywood end-grain that is
        Message 3 of 10 , Dec 30, 2000
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          In a message dated 12/30/2000 7:<BR34:<BR23 PM
          Eastern Standard , chuck@... writes:> My primary concern
          is all the plywood end-grain that is exposed on the
          > leading edge of the keel. My planned sailing area is fairly rocky and I'm
          > concerned that any substantial knocks may damage the fiberglass/epoxy
          > sheathing and allow the plywood to start 'wicking' in water - with the
          > inevitable rot that follows.

          An eighth inch of copper plate on that leading edge would go a long way
          toward easing my mind if I were in your situation.

          Cheers/Step
        • ellengaest@boatbuilding.com
          Hello Mark, Although I have never built the Bolger 12 1/2,I would share the same concerns about that plywood keel.The main reasoning for this is two fold;the
          Message 4 of 10 , Dec 30, 2000
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            Hello Mark,
            Although I have never built the Bolger 12 1/2,I would share the
            same concerns about that plywood keel.The main reasoning for this is
            two fold;the time and effort required to build your boat would be
            about the same regardless whether you stick with the dirt simple
            approach going all ply or attempt a more robust approach,and I
            believe
            that a more durable keel can be built without drastically modifying
            the design.
            To wit,I would be inclined to go pretty much with the same
            approach I used on my Micro.That is,laminate the keel out of some
            locally grown hard woods found in your
            area(teak,mahogany!?!?).Then install something of a sacrificial shoe
            to the bottom of the keel.That way,after a season or two,should you
            see signs of the shoe being chewed away,simply remove it and screw
            on another!Cheap,quick and simple without jeopardizing the integrity
            of your whole keel.Check out Chucks' wonderful Duckworks Magazine for
            my pictures of how I did the Micro keel....
            And speaking of pictures,go to the Bolger fil
            es,under"Lenihan",to
            see how YOUR pictures came out!!!THANKS!!
            Sincerely,
            Peter Lenihan,sorry to hear that you are having to address the many
            nuisances associated with swimming pools and perfectly willing to
            exchange places with you and take on such an awful burden so that you
            may luxuriate in true winter bliss,on the banks of the frozen
            St.Lawrence....


            --- In bolger@egroups.com, "Mark & Marie-Claude" <hobie@c...> wrote:
            > I'm building a model of Bolger's Plywood 12-1/2 (from BWAOM - a
            plywood interpretation of Herreshoff's 12-1/2 ) before deciding to
            build the full-size version. On paper I don't mind the chines, but
            since even Bolger admits the chined version isn't quite as pretty as
            the original, I want to take a look at a 3-D version before my final
            decision.
            >
            > My question here though is regarding the keel/backbone construction
            used by Bolger for this design. He's modified the construction
            details slightly from the sketches in BWAOM and now has a solid
            backbone/keel assembly made up from 6 layers of 1/2" plywood. I'd be
            interested to hear any experiences (good or bad) that people have had
            with this style of keel nstruction.
            >
            > My primary concern is all the plywood end-grain that is exposed on
            the leading edge of the keel. My planned sailing area is fairly
            rocky
            and I'm concerned that any substantial knocks may damage the
            fiberglass/epoxy sheathing and allow the plywood to start 'wicking'
            in
            water - with the inevitable rot that follows. Since it's going to be
            on a mooring, the keel will only get a close inspection once a year
            when the boat is pulled out for the winter. Because of this I'm
            considering going with a traditional construction keel & backbone,
            but
            maybe I'm being too conservative.
            >
            > Additionally, just out of curiosity - is anyone aware of any
            completed Plywood 12-1/2's?
            >
            > Thanks,
            > Mark Oliver
          • Orr, Jamie
            I have a Chebacco with a hollow keel, which has 1/2 plywood sides. I glassed the keel, then added a full width shoe of 1/4 inch oak set in epoxy. Didn t use
            Message 5 of 10 , Dec 30, 2000
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              I have a Chebacco with a hollow keel, which has 1/2 plywood sides.  I glassed the keel, then added a full width shoe of 1/4 inch oak set in epoxy.  Didn't use screws as I didn't want holes in the glass.  So far this has taken the wear of grounding, and of being winched up onto the trailer, without problem.
               
              Jamie Orr
              -----Original Message-----
              From: Mark & Marie-Claude [mailto:hobie@...]
              Sent: Saturday, December 30, 2000 12:00 PM
              To: bolger@egroups.com
              Subject: [bolger] Plywood 12-1/2 - Keel Construction

              I'm building a model of Bolger's Plywood 12-1/2 (from BWAOM - a plywood interpretation of  Herreshoff's 12-1/2 ) before deciding to build the full-size version.  On paper I don't mind the chines, but since even Bolger admits the chined version isn't quite as pretty as the original, I want to take a look at a 3-D version before my final decision. 
               
              My question here though is regarding the keel/backbone construction used by Bolger for this design.  He's modified the construction details slightly from the sketches in BWAOM and now has a solid backbone/keel assembly made up from 6 layers of 1/2" plywood.  I'd be interested to hear any experiences (good or bad) that people have had with this style of keel nstruction. 
               
              My primary concern is all the plywood end-grain that is exposed on the leading edge of the keel.  My planned sailing area is fairly rocky and I'm concerned that any substantial knocks may damage the fiberglass/epoxy sheathing and allow the plywood to start 'wicking' in water - with the inevitable rot that follows.  Since it's going to be on a mooring, the keel will only get a close inspection once a year when the boat is pulled out for the winter.  Because of this I'm considering going with a traditional construction keel & backbone, but maybe I'm being too conservative.
               
              Additionally, just out of curiosity - is anyone aware of any completed Plywood 12-1/2's? 
               
              Thanks,
              Mark Oliver


              Bolger rules!!!
              - no cursing, flaming, trolling, or spamming
              - no flogging dead horses
              - add something: take "thanks!" and "ditto!" posts off-list.
              - stay on topic and punctuate
              - add your comments at the TOP and SIGN your posts

            • Peter Vanderwaart
              ... the leading edge of the keel. I don t have any personal experience that is relevant, but I did notice that the stem of the Spartina dinghy is ply. PCB
              Message 6 of 10 , Dec 31, 2000
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                >> My primary concern is all the plywood end-grain that is exposed on
                the leading edge of the keel.

                I don't have any personal experience that is relevant, but I did
                notice that the stem of the Spartina dinghy is ply. PCB seems to
                think it should be ok, given epoxy glue on the surfaces.

                I would have to think that a keel laminated to suit as is shown for
                the Keel Whaler Sloop (30-Odd Boats, Chapter 31) would be better. In
                fact, I would think the structure of the Whaler would be a good
                paradigm for the entire backbone and hollow keel. Check with PCB of
                course.

                I'm sure the idea behind the plywood was to provide the simplest
                possible construction for a boat that is supposed to be a simple
                version of a very complex boat - the Herreshoff 12 1/2. I find it
                interesting that so many amateurs have build Joel White's Haven 12
                1/2. It almost makes the idea behind the Bolger 12 1/2 unnecessary.

                Peter

                Peter
              • Ann Romanczuk
                It wouldn t be hard to attach a solid piece of wood on the leading edge of the keel to cover and protect the plywood edges. Something rot-resistant and hard,
                Message 7 of 10 , Jan 2, 2001
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                  It wouldn't be hard to attach a solid piece of wood on the
                  leading edge of the keel to cover and protect the plywood edges.
                  Something rot-resistant and hard, preferably, which could take an
                  occasional bump without significant damage.

                  Does the plywood 12-1/2 still have the horizontal keelbolts as shown
                  in Boat Design Quarterly and BWAOM? If so, I'd be very
                  concerned - this is one of the few new ideas from Mr. Bolger that I
                  think is really mistaken and likely to fail. (I'm a mechanical
                  engineer, so I have at least some background in this sort of thing).
                  Under stress, the horizontal keelbolts are likely to tear out of the
                  edges of the plywood. Although I havent worked out the math in
                  detail, I'd sincerely recommend using conventional vertical
                  keelbolts. Remember, the keelbolts have to be strong enough
                  to keep the keel on when the boat is on her beam ends, with a safety
                  factor of 2 or 3 at least; this is not a place to take chances.

                  I don't know of any full size plywood 12-1/2s, but I did see a
                  model that Dymnamite Payson had made, and was really impressed. It
                  isn't as pretty as the origninal Herreshoff, few boats are, but I
                  was really surprised how handsome it looked.


                  --- In bolger@egroups.com, "Mark & Marie-Claude" <hobie@c...> wrote:
                  > I'm building a model of Bolger's Plywood 12-1/2 (from BWAOM - a
                  plywood interpretation of Herreshoff's 12-1/2 ) before deciding to
                  build the full-size version. On paper I don't mind the chines, but
                  since even Bolger admits the chined version isn't quite as pretty as
                  the original, I want to take a look at a 3-D version before my final
                  decision.
                  >
                  > My question here though is regarding the keel/backbone construction
                  used by Bolger for this design. He's modified the construction
                  details slightly from the sketches in BWAOM and now has a solid
                  backbone/keel assembly made up from 6 layers of 1/2" plywood. I'd be
                  interested to hear any experiences (good or bad) that people have had
                  with this style of keel nstruction.
                  >
                  > My primary concern is all the plywood end-grain that is exposed on
                  the leading edge of the keel. My planned sailing area is fairly
                  rocky and I'm concerned that any substantial knocks may damage the
                  fiberglass/epoxy sheathing and allow the plywood to start 'wicking'
                  in water - with the inevitable rot that follows. Since it's going to
                  be on a mooring, the keel will only get a close inspection once a
                  year when the boat is pulled out for the winter. Because of this I'm
                  considering going with a traditional construction keel & backbone,
                  but maybe I'm being too conservative.
                  >
                  > Additionally, just out of curiosity - is anyone aware of any
                  completed Plywood 12-1/2's?
                  >
                  > Thanks,
                  > Mark Oliver
                • Peter Vanderwaart
                  ... shown in Boat Design Quarterly and BWAOM? I m a little confused. My copy of BWAOM does not show any construction detail for the 12 1/2 at all. I am
                  Message 8 of 10 , Jan 2, 2001
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                    > Does the plywood 12-1/2 still have the horizontal keelbolts as
                    shown in Boat Design Quarterly and BWAOM?

                    I'm a little confused. My copy of BWAOM does not show any
                    construction detail for the 12 1/2 at all. I am beginning to get the
                    idea the PCB finally created a buildable plan which is shown in later
                    editions of BWAOM. True? False?

                    Peter
                  • Ann Romanczuk
                    Oops - I think the final plans were in Boat Design Quarterly. There was considerable detail, and that s where I saw the alarming keelbolts. I don t have
                    Message 9 of 10 , Jan 2, 2001
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                      Oops - I think the final plans were in Boat Design Quarterly. There
                      was considerable detail, and that's where I saw the alarming
                      keelbolts. I don't have BWAOM handy, but now that I think about it,
                      it doesn't show much.

                      -- In bolger@egroups.com, "Peter Vanderwaart" <pvanderw@o...> wrote:
                      > > Does the plywood 12-1/2 still have the horizontal keelbolts as
                      > shown in Boat Design Quarterly and BWAOM?
                      >
                      > I'm a little confused. My copy of BWAOM does not show any
                      > construction detail for the 12 1/2 at all. I am beginning to get
                      the
                      > idea the PCB finally created a buildable plan which is shown in
                      later
                      > editions of BWAOM. True? False?
                      >
                      > Peter
                    • Mark Oliver
                      Peter, I don t have my copy of BWAOM since I ve lent it to a friend, so I can t recall what detail was there. However, the plans have been completed for
                      Message 10 of 10 , Jan 2, 2001
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                        Peter,
                        I don't have my copy of BWAOM since I've lent it to a friend, so I
                        can't recall what detail was there. However, the plans have been
                        completed for 'experienced builders' (in PCB's words) and he has them
                        available for sale. I've got a copy and they have all the
                        information I think a builder would need. He has made some other
                        changes - the rig is now a Solent lug rig (the mainsail is about the
                        same shape as the jib-headed rig, but the top two-thirds fo the luff
                        hoists on a vertical yard)and the jib is a balanced-club type, self-
                        trimming in tacking and not hanked to a stay. Very pretty rig

                        Regarding the horizontal keelbolts - yes that is still in the plans.
                        The outer two layers of the keel/backbone assembly (6 layers of 1/2"
                        plywood total) overlap the lead by approximately 2 inches on the top
                        and back. The lead keel(750 lbs now) is attached by six 1/2"
                        horizontal keel bolts (3 on the top and 3 on the back)through the
                        outer two overlapping layers of plywood. Being a mechanical engineer
                        myself I was also a little suspect of this, but want to do some
                        calculations before I jump to conclusions. I was also considering
                        the vertical keelbolts, but looking at it, the vertical keelbolts
                        have the potential to start 'splitting' the plywood since some of the
                        forces will be 'cross-grain' between layers.

                        Whatever I do, you can be sure I'll have some more discussions on
                        this with PCB&F before proceeding with the full size boat. I've
                        almost completed the 1/6 scale model and am finding the shape quite
                        nice actually. Unfortunately, I've got to go back to work tomorrow
                        after a bit of time off and my schedule won't allow completion for a
                        couple of months. I'll put a picture of it in the files once it is
                        complete.

                        Additionally, regarding the earlier comment about the Haven 12-1/2.
                        I've looked at it and it is still quite a bit more complex even
                        though many amateurs have built it. While I do enjoy building - I
                        enjoy sailing even more. Additionally I prefer the fixed keel.

                        Regards,
                        Mark Oliver
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