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Proper Bottom Design

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  • pateson@colton.com
    Bottom/Stern Design for low HP cruising boat. I am stilll in the Waiting to get well enough to build it stage of construction of my GP-16/18. (Non-Bolger,
    Message 1 of 7 , Oct 29, 2001
      Bottom/Stern Design for low HP cruising boat.

      I am stilll in the "Waiting to get well enough to build it"
      stage of construction of my GP-16/18. (Non-Bolger, although
      very Bolgeresque. 16' "Brick" ?)
      For many reasons, but mostly for the "Cool", Landing Craft
      Ramp, I chose it as my "Perfect Boat".
      It is to be the last boat I will have to build that will
      give me as few compromises as I can live with, and be
      comfortable for my Wife and me to spend some time "Cruising"
      some of the local water ways.

      Apparetly blinded by "All Things Good" about the boat,
      I missed the detail about a 50 HP outboard being the
      "Recomended" power.
      The cost of a "No Worries" (I want to be enjoying the "Scenery"
      of "Nature", and not that of the "Under Shroud" of some motor)
      50 HP motor is more than I had planned to spend to build the boat.
      Also, a "Relaxing time" for me, does not involve bouncing
      over crests at 30 MPH wondering what that was that just fell
      out of the Galley cabinet.
      I want to be on the water to enjoy the water, and am really
      in No Hurry to "Get" Anywhere, I'm already there.
      The boat is totally self contained, and drawing only a few
      inches of water, I could either drift, throw out an anchor,
      or find a sheltered shore, lower the ramp, and exlplore some
      place that few others have been.
      (For any of you near the Willamette Valey of Oregon, USA,
      there is a wonderful book "Willamette Landings" that chronicles
      nearly all of the, now forgotten, Willamette River steam boat
      landings. Nice read even if you are not near by.
      Forgotten communities.
      I would like to visit as many of those as I can, as well as
      the many miles, and forgotten places, of the Columbia.)
      (Elk City too, John)

      The question is.
      Is my "Perfect Boat" not so "Perfect" after all?
      I would like to power it with a low HP (25 HP max, less is better)
      Unfortunatly the design of the bottom is the worst example I
      have seen for a "Displacement Boat".
      Wateline is about 14 feet, and with the svelt, square, beam of
      7 feet, and perfectly flat run, it appears that, at speeds approaching
      "Hull Speed" of 5-6 knots, it will make a hole big enough to
      slide backward into and sink. (Don't you hate it when that happens?)

      See: http://groups.yahoo.com/group/Bolger2/files/GP-16%20%20%28Non-
      Bolger%29/GP16-Profile.jpg

      That is the picture I found next to "Worst Displacement Design"
      in my Nautical Dictionary.

      I haven't talked to Jim Betts, the designer, yet, about this
      minor problem. I still love the rest of the boat.
      Love Is Blind.

      I thought I might get some opinions first.
      It would be nice to go faster than 5.5 knots, but maybe
      that is to be.
      I can live with that, but I would like to do so without having
      the wake suck creatures off the bottom, and block my view aft.

      http://www.hotkey.net.au/~robruce/ is Bruce Robert's
      Nice GP-16 page. He is one of the first builders, and
      it appears he has made a Very Nice job of it.

      "Compromises, Compromisess, Always Compromises"
      "There Is No 'Perfect Boat'."


      Thanks
      Pat Patteson
      Molalla, Oregon
    • David Romasco
      Pat, have you thought about adding transom extensions a la Sneakeasy on either side of your outboard? That would extend the waterline and perhaps flatten the
      Message 2 of 7 , Oct 29, 2001
        Pat, have you thought about adding transom extensions a la Sneakeasy on
        either side of your outboard? That would extend the waterline and
        perhaps flatten the wake a bit. You could build them to have a lower
        section that floods freely, so your at-rest trim wouldn't be affected.
        Just a thought...

        David Romasco

        -----Original Message-----
        From: pateson@... [mailto:pateson@...]
        Sent: Monday, October 29, 2001 3:40 PM
        To: bolger@yahoogroups.com
        Subject: [bolger] Proper Bottom Design


        Bottom/Stern Design for low HP cruising boat.

        I am stilll in the "Waiting to get well enough to build it"
        stage of construction of my GP-16/18. (Non-Bolger, although
        very Bolgeresque. 16' "Brick" ?)
        For many reasons, but mostly for the "Cool", Landing Craft
        Ramp, I chose it as my "Perfect Boat".
        It is to be the last boat I will have to build that will
        give me as few compromises as I can live with, and be
        comfortable for my Wife and me to spend some time "Cruising"
        some of the local water ways.

        Apparetly blinded by "All Things Good" about the boat,
        I missed the detail about a 50 HP outboard being the
        "Recomended" power.
        The cost of a "No Worries" (I want to be enjoying the "Scenery"
        of "Nature", and not that of the "Under Shroud" of some motor)
        50 HP motor is more than I had planned to spend to build the boat.
        Also, a "Relaxing time" for me, does not involve bouncing
        over crests at 30 MPH wondering what that was that just fell
        out of the Galley cabinet.
        I want to be on the water to enjoy the water, and am really
        in No Hurry to "Get" Anywhere, I'm already there.
        The boat is totally self contained, and drawing only a few
        inches of water, I could either drift, throw out an anchor,
        or find a sheltered shore, lower the ramp, and exlplore some
        place that few others have been.
        (For any of you near the Willamette Valey of Oregon, USA,
        there is a wonderful book "Willamette Landings" that chronicles
        nearly all of the, now forgotten, Willamette River steam boat
        landings. Nice read even if you are not near by.
        Forgotten communities.
        I would like to visit as many of those as I can, as well as
        the many miles, and forgotten places, of the Columbia.)
        (Elk City too, John)

        The question is.
        Is my "Perfect Boat" not so "Perfect" after all?
        I would like to power it with a low HP (25 HP max, less is better)
        Unfortunatly the design of the bottom is the worst example I
        have seen for a "Displacement Boat".
        Wateline is about 14 feet, and with the svelt, square, beam of
        7 feet, and perfectly flat run, it appears that, at speeds approaching
        "Hull Speed" of 5-6 knots, it will make a hole big enough to
        slide backward into and sink. (Don't you hate it when that happens?)

        See: http://groups.yahoo.com/group/Bolger2/files/GP-16%20%20%28Non-
        Bolger%29/GP16-Profile.jpg

        That is the picture I found next to "Worst Displacement Design"
        in my Nautical Dictionary.

        I haven't talked to Jim Betts, the designer, yet, about this
        minor problem. I still love the rest of the boat.
        Love Is Blind.

        I thought I might get some opinions first.
        It would be nice to go faster than 5.5 knots, but maybe
        that is to be.
        I can live with that, but I would like to do so without having
        the wake suck creatures off the bottom, and block my view aft.

        http://www.hotkey.net.au/~robruce/ is Bruce Robert's
        Nice GP-16 page. He is one of the first builders, and
        it appears he has made a Very Nice job of it.

        "Compromises, Compromisess, Always Compromises"
        "There Is No 'Perfect Boat'."


        Thanks
        Pat Patteson
        Molalla, Oregon









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        [Non-text portions of this message have been removed]
      • John Bell
        One thing about your concerns. Unless you really load it down with a lot of stuff, GP-16 is a very shallow boat. I don t think you will be pulling a big wake,
        Message 3 of 7 , Oct 29, 2001
          One thing about your concerns. Unless you really load it down with a
          lot of stuff, GP-16 is a very shallow boat. I don't think you will be
          pulling a big wake, because the size of the wake is proportional to
          the size of the hole the boat makes in the water. GP-16 floats its
          displacement over a large shallow hole, instead of a small deep one.
          A shallow hole in the water will not make large waves like a deep one
          will. For instance compare the wakes made by a jon boat compared to a
          deep vee.

          Also unless deeply laden, I don't believe you'll be limited to
          displacement speeds with 25 hp either. My light shallow 18'er goes
          over 10 knots with just 7.5 HP. The best advice would be check with
          Betts on his thoughts, though.

          JB
        • Gerry
          According to the Bateau page, GP-16 is also available with a vee-bottom. While your draft would increase, it could improve your wake/hole in the water. Or it
          Message 4 of 7 , Oct 30, 2001
            According to the Bateau page, GP-16 is also available with a
            vee-bottom. While your draft would increase, it could improve your
            wake/hole in the water. Or it might make it worse, as per John Bell.
            I'm sure the designer will be able to straighten this question
            out. Please post what you find out, the GP-16 is "on my list" - along
            with too many others...:-)

            --- In bolger@y..., pateson@c... wrote:
            > Bottom/Stern Design for low HP cruising boat.
            >
            > I am stilll in the "Waiting to get well enough to build it"
            > stage of construction of my GP-16/18. (Non-Bolger, although
            > very Bolgeresque. 16' "Brick" ?)
            > For many reasons, but mostly for the "Cool", Landing Craft
            > Ramp, I chose it as my "Perfect Boat".
            > It is to be the last boat I will have to build that will
            > give me as few compromises as I can live with, and be
            > comfortable for my Wife and me to spend some time "Cruising"
            > some of the local water ways.
            >
            > Apparetly blinded by "All Things Good" about the boat,
            > I missed the detail about a 50 HP outboard being the
            > "Recomended" power.
            > The cost of a "No Worries" (I want to be enjoying the "Scenery"
            > of "Nature", and not that of the "Under Shroud" of some motor)
            > 50 HP motor is more than I had planned to spend to build the boat.
            > Also, a "Relaxing time" for me, does not involve bouncing
            > over crests at 30 MPH wondering what that was that just fell
            > out of the Galley cabinet.

            { ... }

            >
            > Thanks
            > Pat Patteson
            > Molalla, Oregon
          • pateson@colton.com
            My light shallow 18 er goes over 10 knots with just 7.5 HP. That s exactly what I want to hear. That performance would be Great for me. 10 miles every
            Message 5 of 7 , Oct 30, 2001
              "My light shallow 18'er goes over 10 knots with just 7.5 HP."

              That's exactly what I want to hear.
              That performance would be "Great" for me.
              10 miles every hour. That's a long ways.
              What exactly is the 18'er, and how does the bottom
              (especially the aft run) compare to the a GP-16?

              I Have an Old Johnson 15. Best thing about it is that
              it runs fine, and is paid for.
              That's what I want to use on it for some time.
              Maybe play with props to get best MPG.


              I "Plan" on keeping the displacement down, but then,
              we will be living on this thing for a while.
              Maybe anything "New" we want to take aboard, we have
              to exchange for something "Old", rather than just adding to.

              Thanks in advance.

              I will get hold of Jim Betts when I get some particurars
              to ask him.

              Anybody else that is familiar with GP-16 or similar types
              please chime in.

              Good help. thanks folks

              btw I have considered adding extensions, but I think I will
              just stretch the whole thing to 18 or maybe even 20 feet.
              I think most of the ones being built are opting for 18' oa.
              (Theoretically it can be make as long as one wants,
              but under 20' would be my choice.)

              Pat Patteson
              Molalla, Oregon



              --- In bolger@y..., "John Bell" <jmbell@m...> wrote:
              > One thing about your concerns. Unless you really load it down with
              a
              > lot of stuff, GP-16 is a very shallow boat. I don't think you will
              be
              > pulling a big wake, because the size of the wake is proportional to
              > the size of the hole the boat makes in the water. GP-16 floats its
              > displacement over a large shallow hole, instead of a small deep
              one.
              > A shallow hole in the water will not make large waves like a deep
              one
              > will. For instance compare the wakes made by a jon boat compared to
              a
              > deep vee.
              >
              > Also unless deeply laden, I don't believe you'll be limited to
              > displacement speeds with 25 hp either. My light shallow 18'er goes
              > over 10 knots with just 7.5 HP. The best advice would be check with
              > Betts on his thoughts, though.
              >
              > JB
            • John Bell
              Michalak AF4. She planes cleanly with the 7.5. JB ... From: To: Sent: Tuesday, October 30, 2001 11:44 AM Subject:
              Message 6 of 7 , Oct 30, 2001
                Michalak AF4. She planes cleanly with the 7.5.

                JB

                ----- Original Message -----
                From: <pateson@...>
                To: <bolger@yahoogroups.com>
                Sent: Tuesday, October 30, 2001 11:44 AM
                Subject: [bolger] Re: Proper Bottom Design


                | "My light shallow 18'er goes over 10 knots with just 7.5 HP."
                |
                | That's exactly what I want to hear.
                | That performance would be "Great" for me.
                | 10 miles every hour. That's a long ways.
                | What exactly is the 18'er, and how does the bottom
                | (especially the aft run) compare to the a GP-16?
                |
                | I Have an Old Johnson 15. Best thing about it is that
                | it runs fine, and is paid for.
                | That's what I want to use on it for some time.
                | Maybe play with props to get best MPG.
                |
                |
                | I "Plan" on keeping the displacement down, but then,
                | we will be living on this thing for a while.
                | Maybe anything "New" we want to take aboard, we have
                | to exchange for something "Old", rather than just adding to.
                |
                | Thanks in advance.
                |
                | I will get hold of Jim Betts when I get some particurars
                | to ask him.
                |
                | Anybody else that is familiar with GP-16 or similar types
                | please chime in.
                |
                | Good help. thanks folks
                |
                | btw I have considered adding extensions, but I think I will
                | just stretch the whole thing to 18 or maybe even 20 feet.
                | I think most of the ones being built are opting for 18' oa.
                | (Theoretically it can be make as long as one wants,
                | but under 20' would be my choice.)
                |
                | Pat Patteson
                | Molalla, Oregon
                |
                |
                |
                | --- In bolger@y..., "John Bell" <jmbell@m...> wrote:
                | > One thing about your concerns. Unless you really load it down with
                | a
                | > lot of stuff, GP-16 is a very shallow boat. I don't think you will
                | be
                | > pulling a big wake, because the size of the wake is proportional to
                | > the size of the hole the boat makes in the water. GP-16 floats its
                | > displacement over a large shallow hole, instead of a small deep
                | one.
                | > A shallow hole in the water will not make large waves like a deep
                | one
                | > will. For instance compare the wakes made by a jon boat compared to
                | a
                | > deep vee.
                | >
                | > Also unless deeply laden, I don't believe you'll be limited to
                | > displacement speeds with 25 hp either. My light shallow 18'er goes
                | > over 10 knots with just 7.5 HP. The best advice would be check with
                | > Betts on his thoughts, though.
                | >
                | > JB
                |
                |
                |
                | Bolger rules!!!
                | - no cursing, flaming, trolling, spamming, or flogging dead horses
                | - pls take "personals" off-list, stay on topic, and punctuate
                | - add your comments at the TOP and SIGN your posts, snip all you like
                | - To order plans: Mr. Philip C. Bolger, P.O. Box 1209, Gloucester, MA,
                01930, Fax: (978) 282-1349
                | - Unsubscribe: bolger-unsubscribe@yahoogroups.com
                |
                | Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
                |
                |
              • jhkohnen@boat-links.com
                Pat- Bring the bottom up to just above the waterline in a gentle curve and you should do fine at displacement speeds, not making much fuss unless you try to go
                Message 7 of 7 , Oct 31, 2001
                  Pat-

                  Bring the bottom up to just above the waterline in a gentle curve and you
                  should do fine at displacement speeds, not making much fuss unless you try
                  to go faster. For displacement speed you'd need much less than 25 hp.
                  "Semi-displacement" speeds appear to me (a total non-naval architect) quite
                  a bit harder to design for than either displacement or planing, I can't
                  offer any advice about that area. You're lengthening the GP-16 anyway, so
                  the displacement you lose by cutting away the bottom profile may be made up
                  in the extra length. Now you have an excuse to try out Gregg Carlson's free
                  Hulls program to help you get your boat to float on its lines:

                  http://www.carlsondesign.com/#Fun_Shareware

                  On Mon, 29 Oct 2001 20:39:46 -0000, Pat Pateson wrote:
                  > Bottom/Stern Design for low HP cruising boat.
                  >
                  > I am stilll in the "Waiting to get well enough to build it"
                  > stage of construction of my GP-16/18. (Non-Bolger, although
                  > very Bolgeresque. 16' "Brick" ?)
                  > ...
                  > I missed the detail about a 50 HP outboard being the
                  > "Recomended" power.
                  > ...
                  > The question is.
                  > Is my "Perfect Boat" not so "Perfect" after all?
                  > I would like to power it with a low HP (25 HP max, less is better)
                  > ...
                  > I thought I might get some opinions first.
                  > It would be nice to go faster than 5.5 knots, but maybe
                  > that is to be.
                  > I can live with that, but I would like to do so without having
                  > the wake suck creatures off the bottom, and block my view aft.
                  > ...

                  --
                  John <jkohnen@...>
                  http://www.boat-links.com/
                  Distrust any enterprise that requires new clothes.
                  <Henry David Thoreau>
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