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Re: [bolger] Re: Water Ballasted Chebacco

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  • Christopher C. Wetherill
    Denny, Here s what I did: 1 reply to e-mail - opens editable copy of message 2 delete line feed in link 3 copy and paste link to address line of either Firefox
    Message 1 of 26 , Jan 8, 2009
      Denny,

      Here's what I did:

      1 reply to e-mail - opens editable copy of message
      2 delete line feed in link
      3 copy and paste link to address line of either Firefox or Internet Exploder

      In Firefox the links do not appear, only the captions. In IE, they show
      up as closed images. I tried again while writing this and found I could
      open them by right click selecting properties for each closed image and
      pasting the urls in seperate tabs. Strange. Could be the result of my
      firewall settings.

      V/R
      Chris

      mcdennyw wrote:
      > Chris, You need both lines of the link - the yahoo text editor cut
      > it in two. Alternatively look in the "designs and plans" section of
      > the WoodenBoat Forum for the "Water Ballast Chebacco topic"
      >
      >


      [Non-text portions of this message have been removed]
    • mcdennyw
      Thanks, Ed. I went to Chebacco.com and looked at your pictures - very nice job! I was at MASCF in 2007 with my electric launch. What a great time. Another
      Message 2 of 26 , Jan 8, 2009
        Thanks, Ed.

        I went to Chebacco.com and looked at your pictures - very nice job!

        I was at MASCF in 2007 with my electric launch. What a great time.

        Another question: Have you ever weighed your boat?

        Denny

        --- In bolger@yahoogroups.com, eheins@... wrote:
        >
        > Denny,
        > I have a very stock sheet ply version. No ballast. The CB is
        > only weighted to the basic spec to facilitate lowering and staying
      • Chris Feller
        It sounds like you have many good ideas. I would not change the hull shape. That would make it a different boat than the designer had in mind. One benefit
        Message 3 of 26 , Jan 8, 2009
          It sounds like you have many good ideas. I would not change the hull
          shape. That would make it a different boat than the designer had in
          mind. One benefit you would be loosing is the ability to beach the
          boat on the flat bottom as well. Also on construction the flat bottom
          with lapstrake sides is a traditional style. In John Gardner's Dory
          Book he describes this construction on the Semi-Dory. Below is a link
          to an article on one.

          http://www.duckworksmagazine.com/03/r/articles/affair/index.htm

          On ballast I believe water ballast is an effective way of adding
          ballast. I know there is much controversy over it but it has been
          used effectively on many boats. Although I don't know that I would
          use it on this boat since it was designed for no ballast. For the
          answer to this question I would look to those who have used a
          Chebacco. Perhaps someone has done some testing with ballast.

          Chris Feller
          --- In bolger@yahoogroups.com, "mcdennyw" <dwolfe@...> wrote:
          >
          > In casting about for a sail boat that two (geezerish) people could
          > weekend on and I could tow comfortable behind my RAV4 (like to stay
          > below 2000# incl trailer, lighter is better) I first spent a lot of
          > Freeship time massaging Garden's "Eel" to make it bigger but finally
          > decided I ought to find a larger, simpler (no boomkin or bowsprit)
          > boat. Most designs are ballasted, making them too heavy for me to
          > trailer. Irens' Romilly is a beauty but has an 1150# lead shoe
          >
          > Bolger's Chebacco fits my parameters pretty well and comes in 19.5'
          > and 25' glued lapstrake versions. No ballast so the weight on the
          > trailer for the 19'er is about 1100#, about 1350# for the 25. (all
          > according to Freeship). There is a nice Chebacco website with lots of
          > good pics to keep me surfing the net instead of shoveling snow.
          >
          > Since I can't leave well enough alone, I'd like to improve two things-
          > 1) Get rid of the flat bottom. It must be a carry over from the
          > sheet ply version. Building lapstrake, it wouldn't be much extra work
          > to carry the strakes down to the keel. This would improve the looks
          > IMHO and avoid the chance for ripples to slap against the bottom at
          > anchor. 2) Add some ballast to stiffen the boat (geezerish, remember -
          > no hiking straps).
          >
          > Hey - how about filling the extra volume created by the round instead
          > of flat bottom with water? Now the boat will float on its designed
          > waterline, no extra weight on trailer and considerably stiffer. Turns
          > out there is room for 500# of water under the sole. Wetted surface
          > only goes up 2%
          >
          > Using water ballast adds weight and righting moment without making
          > the boat more "sinkable" or more difficult to trailer. It does add 3
          > inches to board up draft but I can live with that. Righting moment at
          > 20 degree heel increases from 1040 to 1440 ft-lbs, at 40 degrees from
          > 1270 to 2520 ft-lbs. To put these numbers in perspective, at 20
          > degrees I create a righting moment of 390 ft-lbs sitting on the
          > windward seat; 320 ft-lbs at 40 degrees. So the water ballast is like
          > having 4 extra people sitting to windward when it's getting hairy.
          >
          > Negatives: the exra 500# will reduce the speed by about 10% unless
          > sail area is increased and there is some added construction
          > complexity.
          >
          >
          > What do you think? This seems like such an obviously good idea I must
          > be missing something. I'd be especially interested in hearing from
          > actual Chebacco owners
          >
          > This notion is also posted on the WoodenBoat Forum at
          > http://www.woodenboat.com/forum/showthread.php?
          > p=2060781&posted=1#post2060781
          >
          >
          > There you can see Freeship renderings of the two hulls and the
          > righting moment curves.
          >
        • Jack&Lois
          You are obviously well informed and educated re.righting moment, hull speed, and other mystical aspects of boat design. I only want to say that I spent a
          Message 4 of 26 , Jan 8, 2009
            You are obviously well informed and educated re.righting moment, hull speed,
            and other mystical aspects of boat design. I only want to say that I spent a
            delightful afternoon last summer with Harold Payson on his back porch last
            summer discussing Bolger designs. One comment from Payson stays with me.
            "Bolger has an uncanny understanding of what the underwater shape of a boat
            should be." That remark alone is enough to prevent me mucking about with
            anything below the waterline on any Bolger design. I have taken some
            liberties with the top sides of several of his designs. None have proved
            disastrous. But have I really improved anything? Who knows? Just thought I
            should mention this. Good luck.



            jeb, suspecting global warming is a very silly conspiracy theory, on the
            frozen shores of the Bay of Fundy.



            [Non-text portions of this message have been removed]
          • Christopher C. Wetherill
            Chris, There is a keel. V/R Chris
            Message 5 of 26 , Jan 8, 2009
              Chris,

              There is a keel.

              V/R
              Chris

              Chris Feller wrote:
              > One benefit you would be loosing is the ability to beach the
              > boat on the flat bottom as well.
              >
            • Christopher C. Wetherill
              Denny, I have had a chance to check Boats with an Open Mind. Drawing on page226 shows design displacement for plywood 19.5 Chebacco is 1740 lbs. Drawing on
              Message 6 of 26 , Jan 8, 2009
                Denny,
                I have had a chance to check Boats with an Open Mind. Drawing on
                page226 shows design displacement for plywood 19.5' Chebacco is 1740
                lbs. Drawing on page 232 shows 25' at 2300 lbs.

                V/R
                Chris

                mcdennyw wrote:
                > In casting about for a sail boat that two (geezerish) people could
                > weekend on and I could tow comfortable behind my RAV4 (like to stay
                > below 2000# incl trailer, lighter is better) I first spent a lot of
                > Freeship time massaging Garden's "Eel" to make it bigger but finally
                > decided I ought to find a larger, simpler (no boomkin or bowsprit)
                > boat. Most designs are ballasted, making them too heavy for me to
                > trailer. Irens' Romilly is a beauty but has an 1150# lead shoe
                >
                > Bolger's Chebacco fits my parameters pretty well and comes in 19.5'
                > and 25' glued lapstrake versions. No ballast so the weight on the
                > trailer for the 19'er is about 1100#, about 1350# for the 25. (all
                > according to Freeship). There is a nice Chebacco website with lots of
                > good pics to keep me surfing the net instead of shoveling snow.
                >
                > Since I can't leave well enough alone, I'd like to improve two things-
                > 1) Get rid of the flat bottom. It must be a carry over from the
                > sheet ply version. Building lapstrake, it wouldn't be much extra work
                > to carry the strakes down to the keel. This would improve the looks
                > IMHO and avoid the chance for ripples to slap against the bottom at
                > anchor. 2) Add some ballast to stiffen the boat (geezerish, remember -
                > no hiking straps).
                >
                > Hey - how about filling the extra volume created by the round instead
                > of flat bottom with water? Now the boat will float on its designed
                > waterline, no extra weight on trailer and considerably stiffer. Turns
                > out there is room for 500# of water under the sole. Wetted surface
                > only goes up 2%
                >
                > Using water ballast adds weight and righting moment without making
                > the boat more "sinkable" or more difficult to trailer. It does add 3
                > inches to board up draft but I can live with that. Righting moment at
                > 20 degree heel increases from 1040 to 1440 ft-lbs, at 40 degrees from
                > 1270 to 2520 ft-lbs. To put these numbers in perspective, at 20
                > degrees I create a righting moment of 390 ft-lbs sitting on the
                > windward seat; 320 ft-lbs at 40 degrees. So the water ballast is like
                > having 4 extra people sitting to windward when it's getting hairy.
                >
                > Negatives: the exra 500# will reduce the speed by about 10% unless
                > sail area is increased and there is some added construction
                > complexity.
                >
                >
                > What do you think? This seems like such an obviously good idea I must
                > be missing something. I'd be especially interested in hearing from
                > actual Chebacco owners
                >
                > This notion is also posted on the WoodenBoat Forum at
                > http://www.woodenboat.com/forum/showthread.php?
                > p=2060781&posted=1#post2060781
                >
                >
                > There you can see Freeship renderings of the two hulls and the
                > righting moment curves.
                >
                >
                > ------------------------------------
                >
                > Bolger rules!!!
                > - NO "GO AWAY SPAMMER!" posts!!! Please!
                > - no cursing, flaming, trolling, spamming, respamming, or flogging dead horses
                > - stay on topic, stay on thread, punctuate, no 'Ed, thanks, Fred' posts
                > - Pls add your comments at the TOP, SIGN your posts, and snip away
                > - Plans: Mr. Philip C. Bolger, P.O. Box 1209, Gloucester, MA, 01930, Fax: (978) 282-1349
                > - Unsubscribe: bolger-unsubscribe@yahoogroups.com
                > - Open discussion: bolger_coffee_lounge-subscribe@yahoogroups.com Yahoo! Groups Links
                >
                >
                >
                >
                >


                [Non-text portions of this message have been removed]
              • Christopher C. Wetherill
                Denny, Please excuse the terse nature of my last post. I claim the lateness of the hour. I have since spent a little more time with BwaOM. Loaded
                Message 7 of 26 , Jan 9, 2009
                  Denny,

                  Please excuse the terse nature of my last post. I claim the lateness of
                  the hour. I have since spent a little more time with BwaOM. Loaded
                  displacements below are per Mr Bolger's drawings. There is a further
                  section in the book for a trailerable sharpie, based on Black Skimmer,
                  called Martha Jane. Per drawings on page 248 and 249, this boat is
                  designed for water ballast of 500 lbs seawater and loaded displacement
                  of 2350 lbs. In the text he states the dry weight at 1300 lbs. Since
                  he is talking about trailer sailing, I would presume he includes the
                  weight of the rig. This implies the weight of crew and gear is around
                  550 lbs. If this is a consistent value in his designs, one could infer
                  that the 19.5' Chebacco would weigh less than 1200 lbs and the 25' one
                  about 1750 lbs.

                  If you want a boat that will dry out standing up, I would look at MJ.
                  It's designed for water ballast and I doubt you will get more in 23.5'
                  at under 1500 lbs on the trailer.

                  V/R
                  Chris

                  Christopher C. Wetherill wrote:
                  > Denny,
                  > I have had a chance to check Boats with an Open Mind. Drawing on
                  > page226 shows design displacement for plywood 19.5' Chebacco is 1740
                  > lbs. Drawing on page 232 shows 25' at 2300 lbs.
                  >
                  > V/R
                  > Chris
                  >
                • mcdennyw
                  Chris, the displacement figures refer to how much weight is required to sink the boat down to its designed waterline. This includes the weight of the boat
                  Message 8 of 26 , Jan 9, 2009
                    Chris, the displacement figures refer to how much weight is required to
                    sink the boat down to its designed waterline. This includes the weight
                    of the boat itself plus the weight of people and gear.

                    On pg 229 Bolger says, referring to the 25'er, " The extra length adds
                    several hundred pounds to the half ton weight of the 20'er". Here he
                    is talking about the boat's weight, not displacement.

                    My Freeship model indicates the weight of the empty 20' boat is 1100
                    pounds and the 25 is a bit over 1400 lbs. 1100# is close enough to
                    a "half ton" to suggest the model is reasonably accurate.

                    I've towed a 1700# boat on a 600# trailer to Florida and back with the
                    RAV4 (2007, V6 engine). It drove OK but the gas mileage really sucked -
                    from its usual 24 down to 14 mpg.

                    Denny

                    --- In bolger@yahoogroups.com, "Christopher C. Wetherill"
                    <wetherillc@...> wrote:
                    >
                    > Denny,
                    > I have had a chance to check Boats with an Open Mind. Drawing on
                    > page226 shows design displacement for plywood 19.5' Chebacco is 1740
                    > lbs. Drawing on page 232 shows 25' at 2300 lbs.
                    >
                    > V/R
                    > Chris
                    >
                  • Christopher C. Wetherill
                    Denny, You will see in my second post, that after spending a little more time thinking than spouting I came into agreement with your numbers. One question
                    Message 9 of 26 , Jan 9, 2009
                      Denny,

                      You will see in my second post, that after spending a little more time
                      thinking than spouting I came into agreement with your numbers. One
                      question though. Since the modification you propose changes the
                      displacement, did you run an evaluation on the effect of simply fitting
                      the water in the unmodified volume?

                      V/R
                      Chris


                      mcdennyw wrote:
                      > Chris, the displacement figures refer to how much weight is required to
                      > sink the boat down to its designed waterline. This includes the weight
                      > of the boat itself plus the weight of people and gear.
                      >
                      > On pg 229 Bolger says, referring to the 25'er, " The extra length adds
                      > several hundred pounds to the half ton weight of the 20'er". Here he
                      > is talking about the boat's weight, not displacement.
                      >
                      > My Freeship model indicates the weight of the empty 20' boat is 1100
                      > pounds and the 25 is a bit over 1400 lbs. 1100# is close enough to
                      > a "half ton" to suggest the model is reasonably accurate.
                      >
                      > I've towed a 1700# boat on a 600# trailer to Florida and back with the
                      > RAV4 (2007, V6 engine). It drove OK but the gas mileage really sucked -
                      > from its usual 24 down to 14 mpg.
                      >
                      > Denny
                      >
                      >
                      >
                    • Chris Feller
                      Good point. I guess I should have looked at the plans before writing. Never mind about the beaching thing. Chris Feller
                      Message 10 of 26 , Jan 9, 2009
                        Good point. I guess I should have looked at the plans before writing.
                        Never mind about the beaching thing.

                        Chris Feller
                        --- In bolger@yahoogroups.com, "Christopher C. Wetherill"
                        <wetherillc@...> wrote:
                        >
                        > Chris,
                        >
                        > There is a keel.
                        >
                        > V/R
                        > Chris
                        >
                        > Chris Feller wrote:
                        > > One benefit you would be loosing is the ability to beach the
                        > > boat on the flat bottom as well.
                        > >
                        >
                      • Mark Albanese
                        ... Thanks to all who commented on this. I tried refaxing my inquiry. Good news! A reply came not 48 hours later, signed by Phil. The not so good news is that
                        Message 11 of 26 , Jan 9, 2009
                          >>

                          Thanks to all who commented on this.

                          I tried refaxing my inquiry. Good news! A reply came not 48 hours
                          later, signed by Phil.
                          The not so good news is that Diamond Kayak plans, #615, are now $75.

                          Mark
                        • Jamie Orr
                          Hi, Somone in this thread asked if anyone had ballasted a Chebacco. If you check the earliest Chebacco Newsletters, which are archived at www.chebacco.com,
                          Message 12 of 26 , Jan 9, 2009
                            Hi,

                            Somone in this thread asked if anyone had ballasted a Chebacco. If
                            you check the earliest Chebacco Newsletters, which are archived at
                            www.chebacco.com, you'll see there was a boat owned by Sister Krista
                            with 300# of ballast. When sold the boat the new owner didn't waste
                            much time before removing the ballast.

                            I have an unballasted Chebacco and have never felt the need for
                            ballast. My feeling is that PCB got it right, why screw it up?

                            Jamie Orr
                            S/V Wayward Lass

                            --- In bolger@yahoogroups.com, "mcdennyw" <dwolfe@...> wrote:
                            >
                            > In casting about for a sail boat that two (geezerish) people could
                            > weekend on and I could tow comfortable behind my RAV4 (like to stay
                            > below 2000# incl trailer, lighter is better) I first spent a lot of
                            > Freeship time massaging Garden's "Eel" to make it bigger but
                            finally
                            > decided I ought to find a larger, simpler (no boomkin or bowsprit)
                            > boat. Most designs are ballasted, making them too heavy for me to
                            > trailer. Irens' Romilly is a beauty but has an 1150# lead shoe
                            >
                            > Bolger's Chebacco fits my parameters pretty well and comes in 19.5'
                            > and 25' glued lapstrake versions. No ballast so the weight on the
                            > trailer for the 19'er is about 1100#, about 1350# for the 25. (all
                            > according to Freeship). There is a nice Chebacco website with lots
                            of
                            > good pics to keep me surfing the net instead of shoveling snow.
                            >
                            > Since I can't leave well enough alone, I'd like to improve two
                            things-
                            > 1) Get rid of the flat bottom. It must be a carry over from the
                            > sheet ply version. Building lapstrake, it wouldn't be much extra
                            work
                            > to carry the strakes down to the keel. This would improve the looks
                            > IMHO and avoid the chance for ripples to slap against the bottom at
                            > anchor. 2) Add some ballast to stiffen the boat (geezerish,
                            remember -
                            > no hiking straps).
                            >
                            > Hey - how about filling the extra volume created by the round
                            instead
                            > of flat bottom with water? Now the boat will float on its designed
                            > waterline, no extra weight on trailer and considerably stiffer.
                            Turns
                            > out there is room for 500# of water under the sole. Wetted surface
                            > only goes up 2%
                            >
                            > Using water ballast adds weight and righting moment without making
                            > the boat more "sinkable" or more difficult to trailer. It does add
                            3
                            > inches to board up draft but I can live with that. Righting moment
                            at
                            > 20 degree heel increases from 1040 to 1440 ft-lbs, at 40 degrees
                            from
                            > 1270 to 2520 ft-lbs. To put these numbers in perspective, at 20
                            > degrees I create a righting moment of 390 ft-lbs sitting on the
                            > windward seat; 320 ft-lbs at 40 degrees. So the water ballast is
                            like
                            > having 4 extra people sitting to windward when it's getting hairy.
                            >
                            > Negatives: the exra 500# will reduce the speed by about 10% unless
                            > sail area is increased and there is some added construction
                            > complexity.
                            >
                            >
                            > What do you think? This seems like such an obviously good idea I
                            must
                            > be missing something. I'd be especially interested in hearing from
                            > actual Chebacco owners
                            >
                            > This notion is also posted on the WoodenBoat Forum at
                            > http://www.woodenboat.com/forum/showthread.php?
                            > p=2060781&posted=1#post2060781
                            >
                            >
                            > There you can see Freeship renderings of the two hulls and the
                            > righting moment curves.
                            >
                          • mcdennyw
                            Someone suggested that I try the water balast calculation with the boat as-designed, that is without rounding off the bottom. After finding this post from a
                            Message 13 of 26 , Jan 11, 2009
                              Someone suggested that I try the water balast calculation with the
                              boat as-designed, that is without rounding off the bottom. After
                              finding this post from a respected NA, Tad Roberts, on the Woodenboat
                              forum:
                              -------------------------------------
                              Water ballast is useful and does work, but only in very specific
                              circumstances. In the typical lead mine sailboat (and your physics
                              experiments above) that Bob is referring to, it would be useless.

                              Mr. Bolger, Hunter, and I believe Macgregor all use water ballast to
                              good effect. These are all hulls that are shallow, wide bottomed (in
                              Bolger's case rectangular), and lightweight. The water ballast is
                              contained in tanks that are the full width of the boat, but not very
                              high vertically. The rectangular or almost rectangular midsection
                              means these boats rely on form stability at low heel angles. As the
                              boat heels, the water ballast rises above the waterline very quickly,
                              and becomes working ballast. The barge hull form runs out of form
                              stability quickly, and this is were the ballast becomes effective.
                              But only at fairly high heel angles, probably 20 degrees or more.
                              Most of us aren't used to sailing at those high angles any more.

                              It enables a hull of very light trailering weight to also be self
                              righting (if she has either floation or a watertight cabin) from a
                              complete knockdown. Water ballast will also smooth out motion and
                              give a very light hull some momentum. In the case of the Macgregor it
                              enables a useable (and reasonably safe) sailboat, to dump her ballast
                              and plane off under outboard power. Another excellent feature is that
                              if your water ballasted boat is knocked down and fills, she will not
                              sink. Coupled with extremely shallow draft on launching, which can be
                              very handy, it makes sense.

                              As always, horse's for course's.

                              All the best, Tad.
                              -------------------------
                              The Chebacco, as designed, is just the form Tad suggests would
                              benefit from water ballast. I revised my Freeship model to put 500#
                              of water ballast in the 19' flat bottom boat and...

                              ta daa - it is much stiffer than my round bottom idea. At a 20
                              degree angle of heel (sailing to windward in a fresh breeze, the flat
                              bottom water ballasted boat has a righting moment of 1880 ft-lbs, 30%
                              better than the round bottom boat and 80% more than the unballasted
                              boat. Evan at 5 and 10 degrees the water ballasted boat has almost
                              double the moment of the stock boat. The extra 500# causes the boat
                              to sink down just 1.5" deeper.

                              The ballast tank is essentially a false bottom parallel to the
                              waterline and 5" deeep at its deepest point in the middle of the
                              boat. Sounds like an even better idea than the original post.

                              Denny Wolfe
                            • Doug Pollard
                              ... While your at it put a fifty gallon inflatable holding bladder inside the water ballast tank that will expand when waste is pumped in and collaps when it
                              Message 14 of 26 , Jan 11, 2009
                                mcdennyw wrote:
                                >
                                > Someone suggested that I try the water balast calculation with the
                                > boat as-designed, that is without rounding off the bottom. After
                                > finding this post from a respected NA, Tad Roberts, on the Woodenboat
                                > forum:
                                > -------------------------------------
                                > Water ballast is useful and does work, but only in very specific
                                > circumstances. In the typical lead mine sailboat (and your physics
                                > experiments above) that Bob is referring to, it would be useless.
                                >
                                > Mr. Bolger, Hunter, and I believe Macgregor all use water ballast to
                                > good effect. These are all hulls that are shallow, wide bottomed (in
                                > Bolger's case rectangular), and lightweight. The water ballast is
                                > contained in tanks that are the full width of the boat, but not very
                                > high vertically. The rectangular or almost rectangular midsection
                                > means these boats rely on form stability at low heel angles. As the
                                > boat heels, the water ballast rises above the waterline very quickly,
                                > and becomes working ballast. The barge hull form runs out of form
                                > stability quickly, and this is were the ballast becomes effective.
                                > But only at fairly high heel angles, probably 20 degrees or more.
                                > Most of us aren't used to sailing at those high angles any more.
                                >
                                > It enables a hull of very light trailering weight to also be self
                                > righting (if she has either floation or a watertight cabin) from a
                                > complete knockdown. Water ballast will also smooth out motion and
                                > give a very light hull some momentum. In the case of the Macgregor it
                                > enables a useable (and reasonably safe) sailboat, to dump her ballast
                                > and plane off under outboard power. Another excellent feature is that
                                > if your water ballasted boat is knocked down and fills, she will not
                                > sink. Coupled with extremely shallow draft on launching, which can be
                                > very handy, it makes sense.
                                >
                                > As always, horse's for course's.
                                >
                                > All the best, Tad.
                                > -------------------------
                                > The Chebacco, as designed, is just the form Tad suggests would
                                > benefit from water ballast. I revised my Freeship model to put 500#
                                > of water ballast in the 19' flat bottom boat and...
                                >
                                > ta daa - it is much stiffer than my round bottom idea. At a 20
                                > degree angle of heel (sailing to windward in a fresh breeze, the flat
                                > bottom water ballasted boat has a righting moment of 1880 ft-lbs, 30%
                                > better than the round bottom boat and 80% more than the unballasted
                                > boat. Evan at 5 and 10 degrees the water ballasted boat has almost
                                > double the moment of the stock boat. The extra 500# causes the boat
                                > to sink down just 1.5" deeper.
                                >
                                > The ballast tank is essentially a false bottom parallel to the
                                > waterline and 5" deeep at its deepest point in the middle of the
                                > boat. Sounds like an even better idea than the original post.
                                >
                                > Denny Wolfe
                                >
                                >
                                While your at it put a fifty gallon inflatable holding bladder inside
                                the water ballast tank
                                that will expand when waste is pumped in and collaps when it is pumped
                                out and you will have provided a conciderable amount of cruising time
                                before pumping out with out any change of boat weight while in the
                                water. Seems like a good idea to me???

                                Doug
                              • graeme19121984
                                ... Wost case (Water ballast caught Bolger out once or twice): At what angle does the RM curve go negative - masts and all? Is there any bouyant volume of a
                                Message 15 of 26 , Jan 12, 2009
                                  --- In bolger@yahoogroups.com, "mcdennyw" <dwolfe@...> wrote:
                                  > At a 20 degree angle of heel (sailing to windward in a fresh
                                  > breeze, the flat bottom water ballasted boat has a righting moment
                                  > of 1880 ftlbs, 30% better than the round bottom boat and 80% more
                                  > than the unballasted boat. Evan at 5 and 10 degrees the water
                                  > ballasted boat has almost double the moment of the stock boat. The
                                  > extra 500# causes the boat to sink down just 1.5" deeper.

                                  Wost case (Water ballast caught Bolger out once or twice): At what
                                  angle does the RM curve go negative - masts and all? Is there any
                                  bouyant volume of a size that may concern at or near the same height
                                  as the water ballast -- eg under cockpit seats? Consider on beam ends
                                  wave rocking too.

                                  I'm just cautious that the ballast for extra RM for improved sailing
                                  in exhilarating conditions doesn't cause a boat that might otherwise
                                  rest on her side when knocked down to go... right over.

                                  Red Zinger, Beachcat, Chebaccos (mostly), etc, are the
                                  daysailing/cruising alternatives for those who want no messing with
                                  lead pouring... Well, certainly Beachcat has been described as such
                                  by PB&F. The OSTAR RACER #459 has a deep pivoting centreboard with
                                  distal, auto-trimming, winged ballast.

                                  Graeme
                                  (PS Talking of ostar and sharpie keels, and RM. gee, I can't believe
                                  #543 isn't in the database. sure it were once. will take a look later
                                  off-line)
                                • mcdennyw
                                  Graeme, According to my Freeship model, the unballasted Chebacco (this is the lapstrake 19 offsets) righting moment goes negative at 93 degrees of heel.
                                  Message 16 of 26 , Jan 12, 2009
                                    Graeme,

                                    According to my Freeship model, the unballasted Chebacco (this is the
                                    lapstrake 19' offsets) righting moment goes negative at 93 degrees of
                                    heel. Water ballasted as above has a RM of 950 ft-lbs at 93 degrees,
                                    does not go negative until 107 degrees. This ignores any flotational
                                    aspects of rig and assumes cockpit seats are water tight.

                                    Max RM of unballasted boat is 1200 ft-lbs from 30 to 60 degrees.
                                    Ballasted boat has RM of 2300 at 30, max of 2600 between 45 and 60
                                    degrees.

                                    If the boat were at 180 degrees, exactly turtle, I don't know it it
                                    would come back upright or not. I'm pretty sure most all unballasted
                                    boats are stable at 180 degrees.

                                    For sure the ballasted boat would be a lot less likely to get upside
                                    down in the first place.

                                    Denny


                                    >
                                    > Wost case (Water ballast caught Bolger out once or twice): At what
                                    > angle does the RM curve go negative - masts and all? Is there any
                                    > bouyant volume of a size that may concern at or near the same
                                    height
                                    > as the water ballast -- eg under cockpit seats? Consider on beam
                                    ends
                                    > wave rocking too.
                                    >
                                    > I'm just cautious that the ballast for extra RM for improved
                                    sailing
                                    > in exhilarating conditions doesn't cause a boat that might
                                    otherwise
                                    > rest on her side when knocked down to go... right over.
                                    >
                                    > Red Zinger, Beachcat, Chebaccos (mostly), etc, are the
                                    > daysailing/cruising alternatives for those who want no messing with
                                    > lead pouring... Well, certainly Beachcat has been described as such
                                    > by PB&F. The OSTAR RACER #459 has a deep pivoting centreboard with
                                    > distal, auto-trimming, winged ballast.
                                    >
                                    > Graeme
                                    > (PS Talking of ostar and sharpie keels, and RM. gee, I can't
                                    believe
                                    > #543 isn't in the database. sure it were once. will take a look
                                    later
                                    > off-line)
                                    >
                                  • graeme19121984
                                    Denny, that sounds all to be good. Great. I wonder how much different are the figures for the lead ballasted keel version. They d cost a little extra in the
                                    Message 17 of 26 , Jan 13, 2009
                                      Denny,

                                      that sounds all to be good. Great.

                                      I wonder how much different are the figures for the lead ballasted
                                      keel version. They'd cost a little extra in the 246lbs to trailer,
                                      and another 6 inches of draft. I wonder if that lead ballast keel
                                      might add a bit more than the 500lbs internal water ballast to
                                      initial stability, but then not to final stability?

                                      Graeme

                                      --- In bolger@yahoogroups.com, "mcdennyw" <dwolfe@...> wrote:
                                      >
                                      > Graeme,
                                      >
                                      > According to my Freeship model, the unballasted Chebacco (this is
                                      the
                                      > lapstrake 19' offsets) righting moment goes negative at 93 degrees
                                      of
                                      > heel. Water ballasted as above has a RM of 950 ft-lbs at 93
                                      degrees,
                                      > does not go negative until 107 degrees. This ignores any
                                      flotational
                                      > aspects of rig and assumes cockpit seats are water tight.
                                      >
                                      > Max RM of unballasted boat is 1200 ft-lbs from 30 to 60 degrees.
                                      > Ballasted boat has RM of 2300 at 30, max of 2600 between 45 and 60
                                      > degrees.
                                      >
                                      > If the boat were at 180 degrees, exactly turtle, I don't know it it
                                      > would come back upright or not. I'm pretty sure most all
                                      unballasted
                                      > boats are stable at 180 degrees.
                                      >
                                      > For sure the ballasted boat would be a lot less likely to get
                                      upside
                                      > down in the first place.
                                      >
                                      > Denny
                                    • mcdennyw
                                      Graeme, I modelled the full keel 246# lead ballast design (Bolger s Cruiser version) and the RM is right in between the no ballast and water ballast designs.
                                      Message 18 of 26 , Jan 13, 2009
                                        Graeme,

                                        I modelled the full keel 246# lead ballast design (Bolger's 'Cruiser'
                                        version) and the RM is right in between the no ballast and water
                                        ballast designs. At 20 degrees the 246# lead gives RM of 1393 ft-
                                        lbs. No ballast RM is 1041, water ballast RM is 1883.

                                        The vertical CG of the water ballasted boat is 2.5" lower than the
                                        one with lead ballast. The lead is lower but only half the weight.:
                                        >
                                        > Denny,
                                        >
                                        > that sounds all to be good. Great.
                                        >
                                        > I wonder how much different are the figures for the lead ballasted
                                        > keel version. They'd cost a little extra in the 246lbs to trailer,
                                        > and another 6 inches of draft. I wonder if that lead ballast keel
                                        > might add a bit more than the 500lbs internal water ballast to
                                        > initial stability, but then not to final stability?
                                        >
                                        > Graeme
                                        >
                                      • graeme19121984
                                        I missed that. Charles posted there was info about Big Tortoise in Instant Boatbuilding with Dynamite Payson . I browsed on to Catfish, a Chebacco spin-off,
                                        Message 19 of 26 , Feb 6, 2009
                                          I missed that.

                                          Charles' posted there was info about Big Tortoise in "Instant
                                          Boatbuilding with Dynamite Payson". I browsed on to Catfish, a
                                          Chebacco spin-off, and, blow me down, in the first short paragraph
                                          Payson describes the self-righting and light trailering gained from
                                          the free flooding keel under this design. I mean - it's the first
                                          thing he jumps in at to describe!

                                          PB&F have described aspects of the high and wide decks of Beachcat
                                          that make for ease of mind in potential knock-down sailing
                                          conditions. They mention the good ability of the salient keel in
                                          thinner water than the centreboard of the upgrade plans can handle.
                                          PCB seems to prefer the salient keel on Beachcat for himself, but to
                                          my knowledge they have never elaborated on the benefits of the keel
                                          being free flooding. Never published on this design aspect - I
                                          thought it solid. This free-flooding/slow-draining is what adds so
                                          much to Micro, supplemental to the lead ballast, in self-righting
                                          immediately following a knockdown all the way to a beam ends attitude
                                          where the keel is lifted above the water and before the internal
                                          water has had time to drain out. The cross section of Beachcat
                                          probably means that the flooded keel begins to lift above the water
                                          and have a righting effect at more intermediate angles of heel than
                                          on Micro, and keeps righting moment fairly positive as heeling
                                          progresses for some arc beyond 90deg.

                                          In a certain published vignette, that although un-named could only
                                          have featured cruising aboard an original Catfish, a prominent Aussie
                                          designer/builder didn't mention the designed benefits of freely
                                          flooding the Catfish keel. Has Mr Payson got his wires crossed?

                                          Graeme



                                          --- In bolger@yahoogroups.com, "mcdennyw" <dwolfe@...> wrote:
                                          >
                                          > Graeme,
                                          >
                                          > I modelled the full keel 246# lead ballast design
                                          (Bolger's 'Cruiser'
                                          > version) and the RM is right in between the no ballast and water
                                          > ballast designs. At 20 degrees the 246# lead gives RM of 1393 ft-
                                          > lbs. No ballast RM is 1041, water ballast RM is 1883.
                                          >
                                          > The vertical CG of the water ballasted boat is 2.5" lower than the
                                          > one with lead ballast. The lead is lower but only half the weight.:
                                          > >
                                          > > Denny,
                                          > >
                                          > > that sounds all to be good. Great.
                                          > >
                                          > > I wonder how much different are the figures for the lead
                                          ballasted
                                          > > keel version. They'd cost a little extra in the 246lbs to
                                          trailer,
                                          > > and another 6 inches of draft. I wonder if that lead ballast keel
                                          > > might add a bit more than the 500lbs internal water ballast to
                                          > > initial stability, but then not to final stability?
                                          > >
                                          > > Graeme
                                          > >
                                          >
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