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OBCAT folding catamaran

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  • Olivier
    Hello all, I added 4 drawings in the file section, in the OBCAT folder. I want to share with you my progress on the folding cat design and read any comments! I
    Message 1 of 17 , Jan 25, 2010
      Hello all,
      I added 4 drawings in the file section, in the OBCAT folder. I want to share with you my progress on the folding cat design and read any comments!
      I am excited about this design, all the pieces seem to fit nicely together.
      The boat is now 25 feet long by 15 feet wide. The mast is 30 feet long. It is mostly foam-glass construction. The hull bottoms are vertical strip foam but everything else is flat panel, hard chine fashion. The boom is permanently attached to the mast post and will be roller furling. The bowsprit is also permanently rigged and doubles as a gin-pole. The two leeboards fit between the bridgedeck and the inboard hull sides. The cockpit seats open out. When folded, they increase the cabin length and provide a protected steering station. There will be a net between the to bows that will not need any tensionning during folding-unfolding.
      The folding-unfolding is done on the water. I am using the "targa post" aft of the cockpit to attach purchases to raise or lower the aft beam ends. The trailer is flat bed, very simple.
      Cheers!

      Olivier
    • Daniel
      Olivier, Looks interesting! Hard to tell using a scale but I m guessing the centre pod is approx 2.5m wide and the two hulls about 1.0m each? Does this mean
      Message 2 of 17 , Jan 26, 2010
        Olivier,
        Looks interesting!
        Hard to tell using a scale but I'm guessing the centre pod is approx 2.5m wide and the two hulls about 1.0m each?

        Does this mean the floats have usable space for "living'?

        Looks like the bow pole takes some serious loads - is it wired to the float bows when opened?
        Daniel


        --- In multihull_boatbuilder@yahoogroups.com, "Olivier" <le_skipper@...> wrote:
        >
        > Hello all,
        > I added 4 drawings in the file section, in the OBCAT folder. I want to share with you my progress on the folding cat design and read any comments!
        > I am excited about this design, all the pieces seem to fit nicely together.
        > The boat is now 25 feet long by 15 feet wide. The mast is 30 feet long. It is mostly foam-glass construction. The hull bottoms are vertical strip foam but everything else is flat panel, hard chine fashion. The boom is permanently attached to the mast post and will be roller furling. The bowsprit is also permanently rigged and doubles as a gin-pole. The two leeboards fit between the bridgedeck and the inboard hull sides. The cockpit seats open out. When folded, they increase the cabin length and provide a protected steering station. There will be a net between the to bows that will not need any tensionning during folding-unfolding.
        > The folding-unfolding is done on the water. I am using the "targa post" aft of the cockpit to attach purchases to raise or lower the aft beam ends. The trailer is flat bed, very simple.
        > Cheers!
        >
        > Olivier
        >
      • Olivier Blanc
        Daniel, I am designing the boat in imperial system, so the center pod is 8 feet wide and the hulls 3 feet. The hulls have the same headroom than the Woods
        Message 3 of 17 , Jan 26, 2010
          Daniel,
          I am designing the boat in imperial system, so the center pod is 8 feet wide and the hulls 3 feet. The hulls have the same headroom than the Woods Wizard (4 feet), just enough for a toilet and a bearth. With the sandwich construction, the hull volume will be very clean with no frames between the cross-beams bulkheads, and no centerboard trunk!
          The bow pole will be stayed to the bows, just like on a beach cat, using synthetic ropes. It will support a regular hank-on jib on a permanent forestay and a free flying genoa on a furler. The tip of the pole will support the asy-spinnaker tack. I can use a large genoa whitout fear of lee helm since I can pivot the 2 boards forward until the boat is balanced!
          Olivier

          --- On Tue, 1/26/10, Daniel <deepee58@...> wrote:


          From: Daniel <deepee58@...>
          Subject: [multihull_boatbuilder] Re: OBCAT folding catamaran
          To: multihull_boatbuilder@yahoogroups.com
          Date: Tuesday, January 26, 2010, 8:17 AM


           



          Olivier,
          Looks interesting!
          Hard to tell using a scale but I'm guessing the centre pod is approx 2.5m wide and the two hulls about 1.0m each?

          Does this mean the floats have usable space for "living'?

          Looks like the bow pole takes some serious loads - is it wired to the float bows when opened?
          Daniel

          --- In multihull_boatbuild er@yahoogroups. com, "Olivier" <le_skipper@ ...> wrote:
          >
          > Hello all,
          > I added 4 drawings in the file section, in the OBCAT folder. I want to share with you my progress on the folding cat design and read any comments!
          > I am excited about this design, all the pieces seem to fit nicely together.
          > The boat is now 25 feet long by 15 feet wide. The mast is 30 feet long. It is mostly foam-glass construction. The hull bottoms are vertical strip foam but everything else is flat panel, hard chine fashion. The boom is permanently attached to the mast post and will be roller furling. The bowsprit is also permanently rigged and doubles as a gin-pole. The two leeboards fit between the bridgedeck and the inboard hull sides. The cockpit seats open out. When folded, they increase the cabin length and provide a protected steering station. There will be a net between the to bows that will not need any tensionning during folding-unfolding.
          > The folding-unfolding is done on the water. I am using the "targa post" aft of the cockpit to attach purchases to raise or lower the aft beam ends. The trailer is flat bed, very simple.
          > Cheers!
          >
          > Olivier
          >











          [Non-text portions of this message have been removed]
        • dssaak
          Oliver, A couple of questions and then some comments if you don t mind .. The cockpit has a hard floor, yes? Why leeboards vs daggerboards? Have you
          Message 4 of 17 , Jan 26, 2010
            Oliver,

            A couple of questions and then some comments if you don't mind ..

            The cockpit has a 'hard' floor, yes? Why leeboards vs daggerboards? Have you settled on current dimensions as final? Can you give a more detail on the folding mechanism?

            I owned a TomCat 6.2 for several years. I am trying to think about your design using it as a reference. To me, 8 foot cockpit would be on the narrow side. Also, the space fore/aft in the cockpit from coaming back would be short and a bit cramped. Having crew sit on the back of the cockpit always made the stern drag.

            Although the TomCat wasn't the boat for me, your design gets much closer. Great ideas and look forward to seeing your progression.

            Dan

            --- In multihull_boatbuilder@yahoogroups.com, Olivier Blanc <le_skipper@...> wrote:
            >
            > Daniel,
            > I am designing the boat in imperial system, so the center pod is 8 feet wide and the hulls 3 feet. The hulls have the same headroom than the Woods Wizard (4 feet), just enough for a toilet and a bearth. With the sandwich construction, the hull volume will be very clean with no frames between the cross-beams bulkheads, and no centerboard trunk!
            > The bow pole will be stayed to the bows, just like on a beach cat, using synthetic ropes. It will support a regular hank-on jib on a permanent forestay and a free flying genoa on a furler. The tip of the pole will support the asy-spinnaker tack. I can use a large genoa whitout fear of lee helm since I can pivot the 2 boards forward until the boat is balanced!
            > Olivier
            >
            > --- On Tue, 1/26/10, Daniel <deepee58@...> wrote:
            >
            >
            > From: Daniel <deepee58@...>
            > Subject: [multihull_boatbuilder] Re: OBCAT folding catamaran
            > To: multihull_boatbuilder@yahoogroups.com
            > Date: Tuesday, January 26, 2010, 8:17 AM
            >
            >
            >  
            >
            >
            >
            > Olivier,
            > Looks interesting!
            > Hard to tell using a scale but I'm guessing the centre pod is approx 2.5m wide and the two hulls about 1.0m each?
            >
            > Does this mean the floats have usable space for "living'?
            >
            > Looks like the bow pole takes some serious loads - is it wired to the float bows when opened?
            > Daniel
            >
            > --- In multihull_boatbuild er@yahoogroups. com, "Olivier" <le_skipper@ ...> wrote:
            > >
            > > Hello all,
            > > I added 4 drawings in the file section, in the OBCAT folder. I want to share with you my progress on the folding cat design and read any comments!
            > > I am excited about this design, all the pieces seem to fit nicely together.
            > > The boat is now 25 feet long by 15 feet wide. The mast is 30 feet long. It is mostly foam-glass construction. The hull bottoms are vertical strip foam but everything else is flat panel, hard chine fashion. The boom is permanently attached to the mast post and will be roller furling. The bowsprit is also permanently rigged and doubles as a gin-pole. The two leeboards fit between the bridgedeck and the inboard hull sides. The cockpit seats open out. When folded, they increase the cabin length and provide a protected steering station. There will be a net between the to bows that will not need any tensionning during folding-unfolding.
            > > The folding-unfolding is done on the water. I am using the "targa post" aft of the cockpit to attach purchases to raise or lower the aft beam ends. The trailer is flat bed, very simple.
            > > Cheers!
            > >
            > > Olivier
            > >
            >
            >
            >
            >
            >
            >
            >
            >
            >
            >
            >
            > [Non-text portions of this message have been removed]
            >
          • Olivier Blanc
            Hello Dan, thanks for your input. Yes the cockpit has a hard floor, with a foot well about 2 feet wide and 8 inches deep.   I am using leeboards for several
            Message 5 of 17 , Jan 27, 2010
              Hello Dan, thanks for your input.
              Yes the cockpit has a hard floor, with a foot well about 2 feet wide and 8 inches deep.
               
              I am using leeboards for several reasons:
               get rid of the trunks
               get rid of the slot issues
               enable infinite helm trim adjustment
               enable towing (on the trailer) without removing daggerboards
               enable cleaning/repair/removing of the boards at any time, folded or not.
               enable board modifications without changing the trunks.
               
              Overall dimensions are 80% final. I still have to check the final weight and adjust the hull volumes.
               
              Folding mechanism: 4 large diameter stainless steel pins, that's it! I think it will be possible to fold and unfold on the water by hand, but I designed what I call the targa post on the rear to receive purchases (one per side) to help pull on the aft beam ends and control the folding motion: to unfold, you pull on the purchase until the beam is about at a 45° angle at which point it wants to uncontrolably fall down, but the purchase prevents that. Now you just ease the purchase to let the aft beam down onto its stop and insert a locking pin. Repeat for the other side. An image is worth 1000 words so I will make a drawing of this later.
               
              The cockpit floor is 8 feet wide by 34 inches long, plus the folding backrests add another 4 feet of width! I cannot make the cockpit longer and keep the ends light and the pod long enough. I will do the flotation calcs using 2 persons in the cockpit. Typical crew would be 2 adults and 2 children. Compromises...
               
              As free time permits I will continue the design and post it here!
              Olivier

              --- On Tue, 1/26/10, dssaak <dssaak@...> wrote:


              From: dssaak <dssaak@...>
              Subject: [multihull_boatbuilder] Re: OBCAT folding catamaran
              To: multihull_boatbuilder@yahoogroups.com
              Date: Tuesday, January 26, 2010, 11:45 PM


               





              Oliver,

              A couple of questions and then some comments if you don't mind ..

              The cockpit has a 'hard' floor, yes? Why leeboards vs daggerboards? Have you settled on current dimensions as final? Can you give a more detail on the folding mechanism?

              I owned a TomCat 6.2 for several years. I am trying to think about your design using it as a reference. To me, 8 foot cockpit would be on the narrow side. Also, the space fore/aft in the cockpit from coaming back would be short and a bit cramped. Having crew sit on the back of the cockpit always made the stern drag.

              Although the TomCat wasn't the boat for me, your design gets much closer. Great ideas and look forward to seeing your progression.

              Dan

              --- In multihull_boatbuild er@yahoogroups. com, Olivier Blanc <le_skipper@ ...> wrote:
              >
              > Daniel,
              > I am designing the boat in imperial system, so the center pod is 8 feet wide and the hulls 3 feet. The hulls have the same headroom than the Woods Wizard (4 feet), just enough for a toilet and a bearth. With the sandwich construction, the hull volume will be very clean with no frames between the cross-beams bulkheads, and no centerboard trunk!
              > The bow pole will be stayed to the bows, just like on a beach cat, using synthetic ropes. It will support a regular hank-on jib on a permanent forestay and a free flying genoa on a furler. The tip of the pole will support the asy-spinnaker tack. I can use a large genoa whitout fear of lee helm since I can pivot the 2 boards forward until the boat is balanced!
              > Olivier
              >
              > --- On Tue, 1/26/10, Daniel <deepee58@.. .> wrote:
              >
              >
              > From: Daniel <deepee58@.. .>
              > Subject: [multihull_boatbuil der] Re: OBCAT folding catamaran
              > To: multihull_boatbuild er@yahoogroups. com
              > Date: Tuesday, January 26, 2010, 8:17 AM
              >
              >
              >  
              >
              >
              >
              > Olivier,
              > Looks interesting!
              > Hard to tell using a scale but I'm guessing the centre pod is approx 2.5m wide and the two hulls about 1.0m each?
              >
              > Does this mean the floats have usable space for "living'?
              >
              > Looks like the bow pole takes some serious loads - is it wired to the float bows when opened?
              > Daniel
              >
              > --- In multihull_boatbuild er@yahoogroups. com, "Olivier" <le_skipper@ ...> wrote:
              > >
              > > Hello all,
              > > I added 4 drawings in the file section, in the OBCAT folder. I want to share with you my progress on the folding cat design and read any comments!
              > > I am excited about this design, all the pieces seem to fit nicely together.
              > > The boat is now 25 feet long by 15 feet wide. The mast is 30 feet long. It is mostly foam-glass construction. The hull bottoms are vertical strip foam but everything else is flat panel, hard chine fashion. The boom is permanently attached to the mast post and will be roller furling. The bowsprit is also permanently rigged and doubles as a gin-pole. The two leeboards fit between the bridgedeck and the inboard hull sides. The cockpit seats open out. When folded, they increase the cabin length and provide a protected steering station. There will be a net between the to bows that will not need any tensionning during folding-unfolding.
              > > The folding-unfolding is done on the water. I am using the "targa post" aft of the cockpit to attach purchases to raise or lower the aft beam ends. The trailer is flat bed, very simple.
              > > Cheers!
              > >
              > > Olivier
              > >
              >
              >
              >
              >
              >
              >
              >
              >
              >
              >
              >
              > [Non-text portions of this message have been removed]
              >











              [Non-text portions of this message have been removed]
            • Roger L.
              So if I understand right, that foot well is the longitudinal grey beam shown in your pics that also runs under the cabin? If so, that s a very cool way to use
              Message 6 of 17 , Jan 27, 2010
                So if I understand right, that foot well is the longitudinal grey beam shown
                in your pics that also runs under the cabin? If so, that's a very cool way
                to use beam theory as both a structure and for creating space.
                Hope you stay with the lee (dagger)boards concept. Nice to have a spare
                board and easy access too. Plus not giving away cabin space to a daggerboard
                box.
                Roger L.


                Cool...----- Original Message -----
                From: "Olivier Blanc" <le_skipper@...>
                To: <multihull_boatbuilder@yahoogroups.com>
                Sent: Wednesday, January 27, 2010 10:07 AM
                Subject: Re: [multihull_boatbuilder] Re: OBCAT folding catamaran


                Hello Dan, thanks for your input.
                Yes the cockpit has a hard floor, with a foot well about 2 feet wide and 8
                inches deep.

                I am using leeboards for several reasons:
                get rid of the trunks
                get rid of the slot issues
                enable infinite helm trim adjustment
                enable towing (on the trailer) without removing daggerboards
                enable cleaning/repair/removing of the boards at any time, folded or not.
                enable board modifications without changing the trunks.

                Overall dimensions are 80% final. I still have to check the final weight and
                adjust the hull volumes.

                Folding mechanism: 4 large diameter stainless steel pins, that's it! I think
                it will be possible to fold and unfold on the water by hand, but I designed
                what I call the targa post on the rear to receive purchases (one per side)
                to help pull on the aft beam ends and control the folding motion: to unfold,
                you pull on the purchase until the beam is about at a 45° angle at which
                point it wants to uncontrolably fall down, but the purchase prevents that.
                Now you just ease the purchase to let the aft beam down onto its stop and
                insert a locking pin. Repeat for the other side. An image is worth 1000
                words so I will make a drawing of this later.

                The cockpit floor is 8 feet wide by 34 inches long, plus the folding
                backrests add another 4 feet of width! I cannot make the cockpit longer and
                keep the ends light and the pod long enough. I will do the flotation calcs
                using 2 persons in the cockpit. Typical crew would be 2 adults and 2
                children. Compromises...

                As free time permits I will continue the design and post it here!
                Olivier

                --- On Tue, 1/26/10, dssaak <dssaak@...> wrote:


                From: dssaak <dssaak@...>
                Subject: [multihull_boatbuilder] Re: OBCAT folding catamaran
                To: multihull_boatbuilder@yahoogroups.com
                Date: Tuesday, January 26, 2010, 11:45 PM








                Oliver,

                A couple of questions and then some comments if you don't mind ..

                The cockpit has a 'hard' floor, yes? Why leeboards vs daggerboards? Have you
                settled on current dimensions as final? Can you give a more detail on the
                folding mechanism?

                I owned a TomCat 6.2 for several years. I am trying to think about your
                design using it as a reference. To me, 8 foot cockpit would be on the narrow
                side. Also, the space fore/aft in the cockpit from coaming back would be
                short and a bit cramped. Having crew sit on the back of the cockpit always
                made the stern drag.

                Although the TomCat wasn't the boat for me, your design gets much closer.
                Great ideas and look forward to seeing your progression.

                Dan

                --- In multihull_boatbuild er@yahoogroups. com, Olivier Blanc <le_skipper@
                ...> wrote:
                >
                > Daniel,
                > I am designing the boat in imperial system, so the center pod is 8 feet
                > wide and the hulls 3 feet. The hulls have the same headroom than the Woods
                > Wizard (4 feet), just enough for a toilet and a bearth. With the sandwich
                > construction, the hull volume will be very clean with no frames between
                > the cross-beams bulkheads, and no centerboard trunk!
                > The bow pole will be stayed to the bows, just like on a beach cat, using
                > synthetic ropes. It will support a regular hank-on jib on a permanent
                > forestay and a free flying genoa on a furler. The tip of the pole will
                > support the asy-spinnaker tack. I can use a large genoa whitout fear of
                > lee helm since I can pivot the 2 boards forward until the boat is
                > balanced!
                > Olivier
                >
                > --- On Tue, 1/26/10, Daniel <deepee58@.. .> wrote:
                >
                >
                > From: Daniel <deepee58@.. .>
                > Subject: [multihull_boatbuil der] Re: OBCAT folding catamaran
                > To: multihull_boatbuild er@yahoogroups. com
                > Date: Tuesday, January 26, 2010, 8:17 AM
                >
                >
                > Â
                >
                >
                >
                > Olivier,
                > Looks interesting!
                > Hard to tell using a scale but I'm guessing the centre pod is approx 2.5m
                > wide and the two hulls about 1.0m each?
                >
                > Does this mean the floats have usable space for "living'?
                >
                > Looks like the bow pole takes some serious loads - is it wired to the
                > float bows when opened?
                > Daniel
                >
                > --- In multihull_boatbuild er@yahoogroups. com, "Olivier" <le_skipper@
                > ...> wrote:
                > >
                > > Hello all,
                > > I added 4 drawings in the file section, in the OBCAT folder. I want to
                > > share with you my progress on the folding cat design and read any
                > > comments!
                > > I am excited about this design, all the pieces seem to fit nicely
                > > together.
                > > The boat is now 25 feet long by 15 feet wide. The mast is 30 feet long.
                > > It is mostly foam-glass construction. The hull bottoms are vertical
                > > strip foam but everything else is flat panel, hard chine fashion. The
                > > boom is permanently attached to the mast post and will be roller
                > > furling. The bowsprit is also permanently rigged and doubles as a
                > > gin-pole. The two leeboards fit between the bridgedeck and the inboard
                > > hull sides. The cockpit seats open out. When folded, they increase the
                > > cabin length and provide a protected steering station. There will be a
                > > net between the to bows that will not need any tensionning during
                > > folding-unfolding.
                > > The folding-unfolding is done on the water. I am using the "targa post"
                > > aft of the cockpit to attach purchases to raise or lower the aft beam
                > > ends. The trailer is flat bed, very simple.
                > > Cheers!
                > >
                > > Olivier
                > >
                >
                >
                >
                >
                >
                >
                >
                >
                >
                >
                >
                > [Non-text portions of this message have been removed]
                >











                [Non-text portions of this message have been removed]



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              • Olivier Blanc
                Exactly! I am using the foot well as a floor stiffener as well as a mast post support and an outboard motor support too. The foot well is not too deep to
                Message 7 of 17 , Jan 27, 2010
                  Exactly!
                  I am using the "foot well" as a floor stiffener as well as a mast post support and an outboard motor support too. The foot well is not too deep to keep the bridge deck clearance high.
                  I am trying to keep everything easy to build, so I am not using the "drop floor" that R. Woods uses on his wizard and I am not using a pop-top either. There is no room under the boom anyway. The OBCAT #1 will be a basic version that can be refined later.
                  Olivier

                  --- On Wed, 1/27/10, Roger L. <rogerlov@...> wrote:


                  From: Roger L. <rogerlov@...>
                  Subject: Re: [multihull_boatbuilder] Re: OBCAT folding catamaran
                  To: multihull_boatbuilder@yahoogroups.com
                  Date: Wednesday, January 27, 2010, 1:05 PM


                   



                  So if I understand right, that foot well is the longitudinal grey beam shown
                  in your pics that also runs under the cabin? If so, that's a very cool way
                  to use beam theory as both a structure and for creating space.
                  Hope you stay with the lee (dagger)boards concept. Nice to have a spare
                  board and easy access too. Plus not giving away cabin space to a daggerboard
                  box.
                  Roger L.

                  Cool...----- Original Message -----
                  From: "Olivier Blanc" <le_skipper@yahoo. com>
                  To: <multihull_boatbuild er@yahoogroups. com>
                  Sent: Wednesday, January 27, 2010 10:07 AM
                  Subject: Re: [multihull_boatbuil der] Re: OBCAT folding catamaran

                  Hello Dan, thanks for your input.
                  Yes the cockpit has a hard floor, with a foot well about 2 feet wide and 8
                  inches deep.

                  I am using leeboards for several reasons:
                  get rid of the trunks
                  get rid of the slot issues
                  enable infinite helm trim adjustment
                  enable towing (on the trailer) without removing daggerboards
                  enable cleaning/repair/ removing of the boards at any time, folded or not.
                  enable board modifications without changing the trunks.

                  Overall dimensions are 80% final. I still have to check the final weight and
                  adjust the hull volumes.

                  Folding mechanism: 4 large diameter stainless steel pins, that's it! I think
                  it will be possible to fold and unfold on the water by hand, but I designed
                  what I call the targa post on the rear to receive purchases (one per side)
                  to help pull on the aft beam ends and control the folding motion: to unfold,
                  you pull on the purchase until the beam is about at a 45° angle at which
                  point it wants to uncontrolably fall down, but the purchase prevents that.
                  Now you just ease the purchase to let the aft beam down onto its stop and
                  insert a locking pin. Repeat for the other side. An image is worth 1000
                  words so I will make a drawing of this later.

                  The cockpit floor is 8 feet wide by 34 inches long, plus the folding
                  backrests add another 4 feet of width! I cannot make the cockpit longer and
                  keep the ends light and the pod long enough. I will do the flotation calcs
                  using 2 persons in the cockpit. Typical crew would be 2 adults and 2
                  children. Compromises. ..

                  As free time permits I will continue the design and post it here!
                  Olivier

                  --- On Tue, 1/26/10, dssaak <dssaak@...> wrote:

                  From: dssaak <dssaak@...>
                  Subject: [multihull_boatbuil der] Re: OBCAT folding catamaran
                  To: multihull_boatbuild er@yahoogroups. com
                  Date: Tuesday, January 26, 2010, 11:45 PM

                  Oliver,

                  A couple of questions and then some comments if you don't mind ..

                  The cockpit has a 'hard' floor, yes? Why leeboards vs daggerboards? Have you
                  settled on current dimensions as final? Can you give a more detail on the
                  folding mechanism?

                  I owned a TomCat 6.2 for several years. I am trying to think about your
                  design using it as a reference. To me, 8 foot cockpit would be on the narrow
                  side. Also, the space fore/aft in the cockpit from coaming back would be
                  short and a bit cramped. Having crew sit on the back of the cockpit always
                  made the stern drag.

                  Although the TomCat wasn't the boat for me, your design gets much closer.
                  Great ideas and look forward to seeing your progression.

                  Dan

                  --- In multihull_boatbuild er@yahoogroups. com, Olivier Blanc <le_skipper@
                  ...> wrote:
                  >
                  > Daniel,
                  > I am designing the boat in imperial system, so the center pod is 8 feet
                  > wide and the hulls 3 feet. The hulls have the same headroom than the Woods
                  > Wizard (4 feet), just enough for a toilet and a bearth. With the sandwich
                  > construction, the hull volume will be very clean with no frames between
                  > the cross-beams bulkheads, and no centerboard trunk!
                  > The bow pole will be stayed to the bows, just like on a beach cat, using
                  > synthetic ropes. It will support a regular hank-on jib on a permanent
                  > forestay and a free flying genoa on a furler. The tip of the pole will
                  > support the asy-spinnaker tack. I can use a large genoa whitout fear of
                  > lee helm since I can pivot the 2 boards forward until the boat is
                  > balanced!
                  > Olivier
                  >
                  > --- On Tue, 1/26/10, Daniel <deepee58@.. .> wrote:
                  >
                  >
                  > From: Daniel <deepee58@.. .>
                  > Subject: [multihull_boatbuil der] Re: OBCAT folding catamaran
                  > To: multihull_boatbuild er@yahoogroups. com
                  > Date: Tuesday, January 26, 2010, 8:17 AM
                  >
                  >
                  > Â
                  >
                  >
                  >
                  > Olivier,
                  > Looks interesting!
                  > Hard to tell using a scale but I'm guessing the centre pod is approx 2.5m
                  > wide and the two hulls about 1.0m each?
                  >
                  > Does this mean the floats have usable space for "living'?
                  >
                  > Looks like the bow pole takes some serious loads - is it wired to the
                  > float bows when opened?
                  > Daniel
                  >
                  > --- In multihull_boatbuild er@yahoogroups. com, "Olivier" <le_skipper@
                  > ...> wrote:
                  > >
                  > > Hello all,
                  > > I added 4 drawings in the file section, in the OBCAT folder. I want to
                  > > share with you my progress on the folding cat design and read any
                  > > comments!
                  > > I am excited about this design, all the pieces seem to fit nicely
                  > > together.
                  > > The boat is now 25 feet long by 15 feet wide. The mast is 30 feet long.
                  > > It is mostly foam-glass construction. The hull bottoms are vertical
                  > > strip foam but everything else is flat panel, hard chine fashion. The
                  > > boom is permanently attached to the mast post and will be roller
                  > > furling. The bowsprit is also permanently rigged and doubles as a
                  > > gin-pole. The two leeboards fit between the bridgedeck and the inboard
                  > > hull sides. The cockpit seats open out. When folded, they increase the
                  > > cabin length and provide a protected steering station. There will be a
                  > > net between the to bows that will not need any tensionning during
                  > > folding-unfolding.
                  > > The folding-unfolding is done on the water. I am using the "targa post"
                  > > aft of the cockpit to attach purchases to raise or lower the aft beam
                  > > ends. The trailer is flat bed, very simple.
                  > > Cheers!
                  > >
                  > > Olivier
                  > >
                  >
                  >
                  >
                  >
                  >
                  >
                  >
                  >
                  >
                  >
                  >
                  > [Non-text portions of this message have been removed]
                  >

                  [Non-text portions of this message have been removed]

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                  [Non-text portions of this message have been removed]
                • stunnedmullet@rocketmail.com
                  Hi Olivier, Cool looking cat - just a couple of questions - The design appears you have assymetical hulls. Is this correct? If so why the need for
                  Message 8 of 17 , Jan 31, 2010
                    Hi Olivier,
                    Cool looking cat - just a couple of questions - The design appears you have assymetical hulls. Is this correct? If so why the need for Centreboards?
                    Stunnedmullet

                    --- In multihull_boatbuilder@yahoogroups.com, "Olivier" <le_skipper@...> wrote:
                    >
                    > Hello all,
                    > I added 4 drawings in the file section, in the OBCAT folder. I want to share with you my progress on the folding cat design and read any comments!
                    > I am excited about this design, all the pieces seem to fit nicely together.
                    > The boat is now 25 feet long by 15 feet wide. The mast is 30 feet long. It is mostly foam-glass construction. The hull bottoms are vertical strip foam but everything else is flat panel, hard chine fashion. The boom is permanently attached to the mast post and will be roller furling. The bowsprit is also permanently rigged and doubles as a gin-pole. The two leeboards fit between the bridgedeck and the inboard hull sides. The cockpit seats open out. When folded, they increase the cabin length and provide a protected steering station. There will be a net between the to bows that will not need any tensionning during folding-unfolding.
                    > The folding-unfolding is done on the water. I am using the "targa post" aft of the cockpit to attach purchases to raise or lower the aft beam ends. The trailer is flat bed, very simple.
                    > Cheers!
                    >
                    > Olivier
                    >
                  • Olivier Blanc
                    Hello Stunned,   The hulls below the waterline are symmetrical, which make it easy to make in vertical foam sandwich, without the need to flip the templates
                    Message 9 of 17 , Jan 31, 2010
                      Hello Stunned,
                       
                      The hulls below the waterline are symmetrical, which make it easy to make in vertical foam sandwich, without the need to flip the templates to make the other hull. It is also the best for speed with a low drag and almost circular cross-sections. Above the water line, they become asymetrical to give internal cabin space and create a flat hull side to support the leeboards as far away from the part of the hull that is in the water. I hope this will eliminate the wave interaction between the hull and the boards. It also pushes the hull center of flottation as far outboard as possible to maximize the boat stability.
                      Also, I want this boat to be a real performer, and asymetrical hulls are not fast: large wetted area, low load capacity, large leeway angle going upwind, low pitch damping ability, slow tacking. You might say: if you really want speed, use daggerboards! Well, I am not sure that large leeboards are slower: I am saving the deadweight of 2 trunks with anti-grounding slot reinforcing, the drag of the slots themselves, and I have infinite helm adjustment enabling larger masthead headsails whitout lee-helm in light winds or sailing with full main only in heavy wind without weather-helm.
                       
                      Olivier

                      --- On Sun, 1/31/10, stunnedmullet@... <stunnedmullet@...> wrote:


                      From: stunnedmullet@... <stunnedmullet@...>
                      Subject: [multihull_boatbuilder] Re: OBCAT folding catamaran
                      To: multihull_boatbuilder@yahoogroups.com
                      Date: Sunday, January 31, 2010, 6:35 AM


                       



                      Hi Olivier,
                      Cool looking cat - just a couple of questions - The design appears you have assymetical hulls. Is this correct? If so why the need for Centreboards?
                      Stunnedmullet

                      --- In multihull_boatbuild er@yahoogroups. com, "Olivier" <le_skipper@ ...> wrote:
                      >
                      > Hello all,
                      > I added 4 drawings in the file section, in the OBCAT folder. I want to share with you my progress on the folding cat design and read any comments!
                      > I am excited about this design, all the pieces seem to fit nicely together.
                      > The boat is now 25 feet long by 15 feet wide. The mast is 30 feet long. It is mostly foam-glass construction. The hull bottoms are vertical strip foam but everything else is flat panel, hard chine fashion. The boom is permanently attached to the mast post and will be roller furling. The bowsprit is also permanently rigged and doubles as a gin-pole. The two leeboards fit between the bridgedeck and the inboard hull sides. The cockpit seats open out. When folded, they increase the cabin length and provide a protected steering station. There will be a net between the to bows that will not need any tensionning during folding-unfolding.
                      > The folding-unfolding is done on the water. I am using the "targa post" aft of the cockpit to attach purchases to raise or lower the aft beam ends. The trailer is flat bed, very simple.
                      > Cheers!
                      >
                      > Olivier
                      >











                      [Non-text portions of this message have been removed]
                    • rfilsell
                      Hi all, my first post here (I think). Congratulations on a very smart and well thought out design. My only doubts are the leeboards, having them out of the
                      Message 10 of 17 , Feb 1, 2010
                        Hi all,
                        my first post here (I think). Congratulations on a very smart and well thought out design.
                        My only doubts are the leeboards, having them out of the hulls is great but being so far inboard one has to ask why not just have one centrally mounted. A V shaped central pod starting aft at the outboard and running forward to include the pivoting centreboard a floor for the pod and running forward to become the mast step and finally the bowsprit would simplify at least the sailing aspect, I also believe it would simplify the operation and maintenance of the leeboard(s). I have my doubts about the longevity of the pivot in the current position only being supported on one side. I would envisage a gullwing type support in way of the centreboard in the centre mounted position. The other benefit is of course spreading the loads further between both main beams.

                        Cheers,

                        Reuben
                      • Olivier Blanc
                        Hello reuben, My leeboards are well supported. At the top, the are wedged between the hull and the pod, where significant backup structure is present and
                        Message 11 of 17 , Feb 2, 2010
                          Hello reuben,
                          My leeboards are well supported. At the top, the are wedged between the hull and the pod, where significant backup structure is present and access to low friction strips is good. At the pin, there is a hull chine with another backup structure that is very easy to engineer. On one tack, the pin is not loaded, on the other tack, it is loaded in tension, just like a chainplate for example, no problems. Of course, the pin will be very strong.
                          There is simply no room to use a centerline board. To get good board support, I would have to build a heavy trunk that would cut through the pod floor and would be difficult to engineer. Right now, the pod floor is very lightweight with a foot well that doubles as a longitudinal beam for mast support. Also the board would be much larger and heavier to get similar lateral plane area, and impossible to remove without going for a swim. With the boat folded, it would also be innacessible and would probably interfere with the hull bottoms.
                          Lastly, on the subject of ventilation, I think 2 foils are better than one: they are less likely to ventilate exactly together. Probably the windward foil will ventilate first, in waves.
                          Cheers!
                           
                          Olivier
                           


                          --- On Mon, 2/1/10, rfilsell <filsell@...> wrote:


                          From: rfilsell <filsell@...>
                          Subject: [multihull_boatbuilder] Re: OBCAT folding catamaran
                          To: multihull_boatbuilder@yahoogroups.com
                          Date: Monday, February 1, 2010, 8:02 AM


                           





                          Hi all,
                          my first post here (I think). Congratulations on a very smart and well thought out design.
                          My only doubts are the leeboards, having them out of the hulls is great but being so far inboard one has to ask why not just have one centrally mounted. A V shaped central pod starting aft at the outboard and running forward to include the pivoting centreboard a floor for the pod and running forward to become the mast step and finally the bowsprit would simplify at least the sailing aspect, I also believe it would simplify the operation and maintenance of the leeboard(s). I have my doubts about the longevity of the pivot in the current position only being supported on one side. I would envisage a gullwing type support in way of the centreboard in the centre mounted position. The other benefit is of course spreading the loads further between both main beams.

                          Cheers,

                          Reuben











                          [Non-text portions of this message have been removed]
                        • dssaak
                          I can second Oliver s comments about the single center board. On my TomCat, the center board trunk was massive in the cockpit and certainly cut into the
                          Message 12 of 17 , Feb 2, 2010
                            I can second Oliver's comments about the single center board. On my TomCat, the center board trunk was massive in the cockpit and certainly cut into the 'accomodations'.

                            dk


                            --- In multihull_boatbuilder@yahoogroups.com, Olivier Blanc <le_skipper@...> wrote:
                            >
                            > Hello reuben,
                            > My leeboards are well supported. At the top, the are wedged between the hull and the pod, where significant backup structure is present and access to low friction strips is good. At the pin, there is a hull chine with another backup structure that is very easy to engineer. On one tack, the pin is not loaded, on the other tack, it is loaded in tension, just like a chainplate for example, no problems. Of course, the pin will be very strong.
                            > There is simply no room to use a centerline board. To get good board support, I would have to build a heavy trunk that would cut through the pod floor and would be difficult to engineer. Right now, the pod floor is very lightweight with a foot well that doubles as a longitudinal beam for mast support. Also the board would be much larger and heavier to get similar lateral plane area, and impossible to remove without going for a swim. With the boat folded, it would also be innacessible and would probably interfere with the hull bottoms.
                            > Lastly, on the subject of ventilation, I think 2 foils are better than one: they are less likely to ventilate exactly together. Probably the windward foil will ventilate first, in waves.
                            > Cheers!
                            >  
                            > Olivier
                            >  
                            >
                            >
                            > --- On Mon, 2/1/10, rfilsell <filsell@...> wrote:
                            >
                            >
                            > From: rfilsell <filsell@...>
                            > Subject: [multihull_boatbuilder] Re: OBCAT folding catamaran
                            > To: multihull_boatbuilder@yahoogroups.com
                            > Date: Monday, February 1, 2010, 8:02 AM
                            >
                            >
                            >  
                            >
                            >
                            >
                            >
                            >
                            > Hi all,
                            > my first post here (I think). Congratulations on a very smart and well thought out design.
                            > My only doubts are the leeboards, having them out of the hulls is great but being so far inboard one has to ask why not just have one centrally mounted. A V shaped central pod starting aft at the outboard and running forward to include the pivoting centreboard a floor for the pod and running forward to become the mast step and finally the bowsprit would simplify at least the sailing aspect, I also believe it would simplify the operation and maintenance of the leeboard(s). I have my doubts about the longevity of the pivot in the current position only being supported on one side. I would envisage a gullwing type support in way of the centreboard in the centre mounted position. The other benefit is of course spreading the loads further between both main beams.
                            >
                            > Cheers,
                            >
                            > Reuben
                            >
                            >
                            >
                            >
                            >
                            >
                            >
                            >
                            >
                            >
                            >
                            > [Non-text portions of this message have been removed]
                            >
                          • Michael Katz
                            I ll add a humble opinion to the leeboard vs central board debate.  A few years ago I crewed aboard a Stiletto 27.  It had a centrally - located board just
                            Message 13 of 17 , Feb 2, 2010
                              I'll add a humble opinion to the leeboard vs central board debate.  A few years ago I crewed aboard a Stiletto 27.  It had a centrally - located board just aft of the mast.  It was easy to operate but it had a major flaw at that location.  When winds were light -- as in 5 knots or so -- we were forced to sail no higher than a close reach.  Apparently, without a hull form atop the daggerboard to constrict water flow and the low boat speed, leeway was just too great to sail close hauled.  Tacking was more challenging too.
                               
                              Conversely, on my amateur designed and built catamaran, the in-hull daggerboards remain effective in light air.  I can sail close hauled and tack with ease.  And my boat is nowhere as well designed as a Stiletto 27.
                               
                              My thoughts about leeboards for the Obcat are positive.  While they may not end up providing all the lift or anti-leeway effect of in-hull boards they will certainly be better than a centrally-located one.  Construction and maintenance will be easier than what I have.  Interior hull access will be better too.  A fair compromise, IMHO.
                               
                              --- On Tue, 2/2/10, dssaak <dssaak@...> wrote:












                              [Non-text portions of this message have been removed]
                            • rfilsell
                              Thanks to all, I wondered what the pitfalls to a single board were and now I know ! I assumed you would sail with the windward board up, so I can see how a
                              Message 14 of 17 , Feb 3, 2010
                                Thanks to all,

                                I wondered what the pitfalls to a single board were and now I know !
                                I assumed you would sail with the windward board up, so I can see how a single (large) board would be impractical, it looks so "neat" on the Kelsall's.
                                Cheers,
                                Reuben.
                              • dstgean
                                A single board can be fine. The problem with some of the ineffective results are the central location of a board. These surface piercing boards lose
                                Message 15 of 17 , Feb 3, 2010
                                  A single board can be fine. The problem with some of the ineffective results are the central location of a board. These surface piercing boards lose effectiveness at both low and high speeds. At low speed you can get results like the Stiletto catamaran not being able to make good windward progress--but cats automatically are at a disadvantage there with the large wetted surface compared to tris for example. At high speeds these same foils tend to ventilate without a good fence--which are hard to use on a tilting foil as they'd be a brake tilted back.

                                  And that is why daggers are king for racing...

                                  But after breaking off two sacrificial tips on daggers, I'm all about kick up foils and rudders.

                                  .02

                                  Dan

                                  --- In multihull_boatbuilder@yahoogroups.com, "rfilsell" <filsell@...> wrote:
                                  >
                                  >
                                  >
                                  > Thanks to all,
                                  >
                                  > I wondered what the pitfalls to a single board were and now I know !
                                  > I assumed you would sail with the windward board up, so I can see how a single (large) board would be impractical, it looks so "neat" on the Kelsall's.
                                  > Cheers,
                                  > Reuben.
                                  >
                                • Don Nicholson
                                  Actually in many situations it is better to sail with only the weather board down - this way if you lift a hull you also lift the board & hopefully allow the
                                  Message 16 of 17 , Feb 3, 2010
                                    Actually in many situations it is better to sail with only the weather board down - this way if you lift a hull you also lift the board & hopefully allow the boat to slide sideways rather than flip.

                                    Don
                                    ----- Original Message -----
                                    From: rfilsell
                                    To: multihull_boatbuilder@yahoogroups.com
                                    Sent: Wednesday, February 03, 2010 11:20 PM
                                    Subject: [multihull_boatbuilder] Re: OBCAT folding catamaran





                                    Thanks to all,

                                    I wondered what the pitfalls to a single board were and now I know !
                                    I assumed you would sail with the windward board up, so I can see how a single (large) board would be impractical, it looks so "neat" on the Kelsall's.
                                    Cheers,
                                    Reuben.





                                    [Non-text portions of this message have been removed]
                                  • rhaldridge
                                    ... It can also be superior to dual boards, according to John Shuttleworth, who says this: This design, like all my cruising designs uses only one retractable
                                    Message 17 of 17 , Feb 3, 2010
                                      --- In multihull_boatbuilder@yahoogroups.com, "dstgean" <dstgean@...> wrote:
                                      >
                                      > A single board can be fine.


                                      It can also be superior to dual boards, according to John Shuttleworth, who says this:

                                      "This design, like all my cruising designs uses only one retractable daggerboard in one hull. Some years ago I conducted a tank test to find out the validity of this idea, and the test showed that one board in one hull had less drag that one in each hull. The only difference was a loss in tacking angle of 1.5 degrees when the board was upwind. I believe this loss is mostly compensated for by the saving in weight of a board and case."

                                      This makes perfect sense, if you think about why the very fastest boats generally use a sloop rig rather than ketch or yawl. The big single mainsail is more efficient than two smaller sails.

                                      I'm not a fan of leeboards for fast multis. I think they can work fine for slower boats, but I would expect them to lose a lot of efficiency from ventilation at high speed. To elaborate on the Stiletto story above, some later Stilettos were built (or converted) to in-hull daggerboards and they were consistently faster than the older boats with centrally-mounted board.

                                      Ray

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