Loading ...
Sorry, an error occurred while loading the content.
 

Model in relation to ballast

Expand Messages
  • Timtone
    Can anyone tell me if when you build a scale model of a proposed design, does the ballast of that model relate in scale to the full scale version? In other
    Message 1 of 13 , Apr 30, 2005
      Can anyone tell me if when you build a scale model of a proposed design, does the ballast of that model relate in scale to the full scale version?

      In other words, if you did a 1/4 scale model of a 20 foot boat, and found 100 pounds worked well as ballast. Would this mean that 400 lbs. is going to work for the 20 footer?

      Thanks, Tim.

      [Non-text portions of this message have been removed]
    • donschultz8275
      ... design, does the ballast of that model relate in scale to the full scale version? ... I don t think it would scale in that direct linear fasion because the
      Message 2 of 13 , May 1, 2005
        --- In Michalak@yahoogroups.com, "Timtone" <tim@t...> wrote:
        > Can anyone tell me if when you build a scale model of a proposed
        design, does the ballast of that model relate in scale to the full
        scale version?
        >


        I don't think it would scale in that direct linear fasion because the
        capacity of the boat is increasing by a square factor. Michalak
        himself would be a better source, though Payson, who is a big
        proponent of model building may also have the answer.

        Michalak is the trained engineer, and Payson the "seat of the pants"
        guy.
      • Timtone
        ... I don t think it would scale in that direct linear fasion because the capacity of the boat is increasing by a square factor. Michalak himself would be a
        Message 3 of 13 , May 1, 2005
          >Thanks very much donshultz.

          I don't think it would scale in that direct linear fasion because the
          capacity of the boat is increasing by a square factor. Michalak
          himself would be a better source, though Payson, who is a big
          proponent of model building may also have the answer.

          Michalak is the trained engineer, and Payson the "seat of the pants"
          guy.





          ------------------------------------------------------------------------------
          Yahoo! Groups Links

          a.. To visit your group on the web, go to:
          http://groups.yahoo.com/group/Michalak/

          b.. To unsubscribe from this group, send an email to:
          Michalak-unsubscribe@yahoogroups.com

          c.. Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.



          [Non-text portions of this message have been removed]
        • Stefan Probst
          ... In theory (means I have no experience): The real boat would be 4 times as long, 4 times as broad, and 4 times as high, i.e. at the same WL it would
          Message 4 of 13 , May 1, 2005
            --- "Timtone" <tim@t...> wrote:
            > Can anyone tell me if when you build a scale model
            > of a proposed design, does the ballast of that model relate
            > in scale to the full scale version?
            >
            > In other words, if you did a 1/4 scale model of a 20 foot boat,
            > and found 100 pounds worked well as ballast.
            > Would this mean that 400 lbs. is going to work for the 20 footer?

            In theory (means I have no experience):
            The real boat would be 4 times as long, 4 times as broad, and 4 times
            as high, i.e. at the same WL it would displace 64 times as much water.

            Question is, whether your other weights (hull) are also to 1/4 scale:
            did you use ply that is 1/4 of the designed thickness?....

            So, in reality that 64 will not be exactly. And of course, waves don't
            scale up 1/4, but that is a totally different issue.

            Cheers,
            Stefan
          • Timtone
            Right. OK. I get you. Makes sense. It might be a little tricky scaling a 1/4 ply hull thickness down to 1/4 size. ~:0) But there may be some kind of factor
            Message 5 of 13 , May 1, 2005
              Right. OK. I get you. Makes sense.
              It might be a little tricky scaling a 1/4" ply hull thickness down to 1/4 size. ~:0)
              But there may be some kind of factor that would compensate for the 'natural' ballast of the boat...humans, gear batteries etc.
              I took donshultz's advice and went to the source for advice. I will share the result.

              Cheers, TT

              BTW.....Jim's newsletter essay on drawing and designing a hull is outstanding. I just came a cross it a few days ago. Finally, finding this info at a level my wee brain can comprehend. Eureka.

              ----- Original Message -----
              From: Stefan Probst
              To: Michalak@yahoogroups.com
              Sent: Sunday, May 01, 2005 07:56
              Subject: [Michalak] Re: Model in relation to ballast


              --- "Timtone" <tim@t...> wrote:
              > Can anyone tell me if when you build a scale model
              > of a proposed design, does the ballast of that model relate
              > in scale to the full scale version?
              >
              > In other words, if you did a 1/4 scale model of a 20 foot boat,
              > and found 100 pounds worked well as ballast.
              > Would this mean that 400 lbs. is going to work for the 20 footer?

              In theory (means I have no experience):
              The real boat would be 4 times as long, 4 times as broad, and 4 times
              as high, i.e. at the same WL it would displace 64 times as much water.

              Question is, whether your other weights (hull) are also to 1/4 scale:
              did you use ply that is 1/4 of the designed thickness?....

              So, in reality that 64 will not be exactly. And of course, waves don't
              scale up 1/4, but that is a totally different issue.

              Cheers,
              Stefan






              ------------------------------------------------------------------------------
              Yahoo! Groups Links

              a.. To visit your group on the web, go to:
              http://groups.yahoo.com/group/Michalak/

              b.. To unsubscribe from this group, send an email to:
              Michalak-unsubscribe@yahoogroups.com

              c.. Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.



              [Non-text portions of this message have been removed]
            • Ronald Fossum
              1/4 x 1/4 = 1/16 and plywood down to 1/64 thickness is available in most hobby stores that cater to the model airplane crowd. If you give the entire boat a
              Message 6 of 13 , May 1, 2005
                1/4" x 1/4" = 1/16" and plywood down to 1/64" thickness is available in most hobby stores that cater to the model airplane crowd.

                If you give the entire boat a couple of coats of varnish (to seal it for floating purposes) and then a coat of paint, you'll approximate the weight of fiberglass, resin. and boat paint.

                Ron Fossum
                ----- Original Message -----
                From: Timtone
                To: Michalak@yahoogroups.com
                Sent: Sunday, May 01, 2005 8:05 AM
                Subject: Re: [Michalak] Re: Model in relation to ballast


                Right. OK. I get you. Makes sense.
                It might be a little tricky scaling a 1/4" ply hull thickness down to 1/4 size. ~:0)
                But there may be some kind of factor that would compensate for the 'natural' ballast of the boat...humans, gear batteries etc.
                I took donshultz's advice and went to the source for advice. I will share the result.

                Cheers, TT

                BTW.....Jim's newsletter essay on drawing and designing a hull is outstanding. I just came a cross it a few days ago. Finally, finding this info at a level my wee brain can comprehend. Eureka.



                [Non-text portions of this message have been removed]
              • David Davis
                ... design, does the ballast of that model relate in scale to the full scale version? ... and found 100 pounds worked well as ballast. Would this mean that 400
                Message 7 of 13 , May 1, 2005
                  --- In Michalak@yahoogroups.com, "Timtone" <tim@t...> wrote:
                  > Can anyone tell me if when you build a scale model of a proposed
                  design, does the ballast of that model relate in scale to the full
                  scale version?
                  >
                  > In other words, if you did a 1/4 scale model of a 20 foot boat,
                  and
                  found 100 pounds worked well as ballast. Would this mean that 400
                  lbs.
                  is going to work for the 20 footer?
                  >
                  > Thanks, Tim.

                  Hi Tim,

                  One might need to use the models design water line and compute the
                  designed displacement of the model. Then uses the same percentage
                  ballast on the model as was called for in the full size plans. If
                  25%
                  of the model's fully loaded displacement weight is ballast and will
                  allow the model to recover from a 90 degree knockdown then the same
                  may be true of the full size design. Likely the test results will
                  depend on how well the design was modeled. Lead shot glued into the
                  same spot as the planed ballast in the full size boat might work.

                  Figure the models displacement at designned water line, add the
                  percentage of designed model ballast, weigh the model, the
                  difference
                  between the model weight with ballast installed and the computed
                  waterline displacement weight is usable model load carrying
                  ability.
                  to get a true "recovery from a knockdown" test you might want to add
                  model crew weight where ever you think they might be seated.

                  I am interested in water ballast, should be able to model that as
                  well
                  without great difficulty.

                  Models in the 2 inches = one foot size might be able to be built
                  using
                  1/4 inch plywood without changing the waterline very much,
                  especially
                  with boats 15 foot and longer. No reason a model needs to be 1 inch
                  =
                  one foot -- the larger models might be easier to build with regular
                  shop tools than the very small models. 1/4 scale or 3 inches = 1
                  foot
                  might be a little large to get into a car for the ride to the lake
                  (depending on boat size - still thinking Cormorant size!) or pond
                  and
                  of course would cost a little more to build.

                  David Davis
                  >
                • Howard Stephenson
                  If you try to take all the factors into account, this subject soon becomes very complicated. FOr example, it s not easy to scale down the thickness and weight
                  Message 8 of 13 , May 1, 2005
                    If you try to take all the factors into account, this subject soon
                    becomes very complicated. FOr example, it's not easy to scale down
                    the thickness and weight per unit area of the paint or varnish needed
                    to protect the surface of the hull. And to make it worse, although
                    the displacement and weight of a 1/4 scale model is 1/64 of the
                    original, its surface area is 1/4 x 1/4 = just 1/16 of the original.
                    That's why racing model yachts often have unpainted carbon-fibre
                    hulls.

                    There are also considerations of stability and wind strength: you
                    can't scale down wind speed in proportion, yet the force exerted by
                    the wind is proportioanl to the square of its speed.

                    So it all depends on why you are building a model: is it to put on
                    the mantelpiece, to fool arond with in the swimming pool, or to sail
                    in real water with a real wind? There will have to be compromises
                    somewhere.

                    Howard

                    --- In Michalak@yahoogroups.com, "Ronald Fossum" <artemis@p...> wrote:
                    > 1/4" x 1/4" = 1/16" and plywood down to 1/64" thickness is
                    available in most hobby stores that cater to the model airplane crowd.
                    >
                    > If you give the entire boat a couple of coats of varnish (to seal
                    it for floating purposes) and then a coat of paint, you'll
                    approximate the weight of fiberglass, resin. and boat paint.
                    >
                    > Ron Fossum
                  • John B. Trussell
                    Given the uncertainties of material weight, as well as gear and crew, I would take a pragmatic approach. Build the model, mark the waterline, put the model
                    Message 9 of 13 , May 1, 2005
                      Given the uncertainties of material weight, as well as gear and crew, I would take a pragmatic approach. Build the model, mark the waterline, put the model in the water, and add ballast until the model floats on her lines!

                      John T
                      ----- Original Message -----
                      From: Ronald Fossum
                      To: Michalak@yahoogroups.com
                      Sent: Sunday, May 01, 2005 3:36 PM
                      Subject: Re: [Michalak] Re: Model in relation to ballast


                      1/4" x 1/4" = 1/16" and plywood down to 1/64" thickness is available in most hobby stores that cater to the model airplane crowd.

                      If you give the entire boat a couple of coats of varnish (to seal it for floating purposes) and then a coat of paint, you'll approximate the weight of fiberglass, resin. and boat paint.

                      Ron Fossum
                      ----- Original Message -----
                      From: Timtone
                      To: Michalak@yahoogroups.com
                      Sent: Sunday, May 01, 2005 8:05 AM
                      Subject: Re: [Michalak] Re: Model in relation to ballast


                      Right. OK. I get you. Makes sense.
                      It might be a little tricky scaling a 1/4" ply hull thickness down to 1/4 size. ~:0)
                      But there may be some kind of factor that would compensate for the 'natural' ballast of the boat...humans, gear batteries etc.
                      I took donshultz's advice and went to the source for advice. I will share the result.

                      Cheers, TT

                      BTW.....Jim's newsletter essay on drawing and designing a hull is outstanding. I just came a cross it a few days ago. Finally, finding this info at a level my wee brain can comprehend. Eureka.



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



                      ------------------------------------------------------------------------------
                      Yahoo! Groups Links

                      a.. To visit your group on the web, go to:
                      http://groups.yahoo.com/group/Michalak/

                      b.. To unsubscribe from this group, send an email to:
                      Michalak-unsubscribe@yahoogroups.com

                      c.. Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.




                      ------------------------------------------------------------------------------


                      No virus found in this incoming message.
                      Checked by AVG Anti-Virus.
                      Version: 7.0.308 / Virus Database: 266.11.0 - Release Date: 4/29/2005


                      [Non-text portions of this message have been removed]
                    • Timtone
                      Ronald, David and Howard. Too cool. Thanks very much for the input. My head hurts.... and there is a little smoke....but I will recover. I don t think in my
                      Message 10 of 13 , May 1, 2005
                        Ronald, David and Howard. Too cool. Thanks very much for the input.
                        My head hurts.... and there is a little smoke....but I will recover.

                        I don't think in my case, this is going to be too critcal.
                        I am just at the very beginnings of thinking about coming up with the design I want for myself. The waterline/model/ballast issue was just one of my first 'stumped' details. Many to come I am sure.
                        Just to see how it turns out, just a wee distraction. I have yet to find a design that quite fits my criterium.
                        If it turns out as planned at the model stage, then it might become a reality....but not soon.
                        I have put too much work into the boat I am currently sailing to move right into another any time soon.

                        I have been stimulated by the recent discovery of Jims Design essay. So I, went ahead and started to compile all of my details in one place. Soon to start coming up with some critical dimensions so I can eventually begin layout. Should be fun.

                        Cheer and thanks, Tim.

                        [Non-text portions of this message have been removed]
                      • Timtone
                        ... Thanks John T. That was the direction I was thinking. In my case, I figure a person could get pretty dang close just referring to historical data. Similar
                        Message 11 of 13 , May 1, 2005
                          >>Given the uncertainties of material weight, as well as gear and crew, I would take a pragmatic approach. Build the model, mark the waterline, put the model in the water, and add ballast until the model floats on her lines!

                          Thanks John T. That was the direction I was thinking. In my case, I figure a person could get pretty dang close just referring to historical data. Similar boat/ what ballast. Any discrepancies could be sorted with internal additions....or a Sawzall.

                          On this topic, I posted the same question to Jim. (as I mentioned before)
                          His reply was interesting and I thought you all might like to read it as well.

                          "I'm not sure you can learn anything from a boat model besides what it
                          looks like. Some folks disagree and Kilburn Adams told me he worked the
                          bugs out of his Skiff America design with a large powered RC model. As
                          for ballast calcs, they are related to stability. A lot easier to do now
                          that we have programs like Hullform. It the past it usually was not
                          calculated, only based on experience. I wrote an essay about the topic
                          based mostly on how to figure how much sail your boat can carry."

                          Does anyone know the title of that essay?

                          Cheers, Tim.

                          [Non-text portions of this message have been removed]
                        • Timtone
                          Excellent resource Chuck, thanks so much. [Non-text portions of this message have been removed]
                          Message 12 of 13 , May 1, 2005
                            Excellent resource Chuck, thanks so much.


                            [Non-text portions of this message have been removed]
                          • Chuck Leinweber
                            Tim: Jim wrote a lot of essays about sails. Check the index: HYPERLINK http://marina.fortunecity.com/breakwater/274/michalak/alphabetical.htm http ... Chuck
                            Message 13 of 13 , May 1, 2005
                              Tim:



                              Jim wrote a lot of essays about sails. Check the index:



                              HYPERLINK
                              "http://marina.fortunecity.com/breakwater/274/michalak/alphabetical.htm"http
                              ://marina.fortunecity.com/breakwater/274/michalak/alphabetical.htm



                              Chuck



                              _____

                              From: Michalak@yahoogroups.com [mailto:Michalak@yahoogroups.com] On Behalf
                              Of Timtone
                              Sent: Sunday, May 01, 2005 5:47 PM
                              To: Michalak@yahoogroups.com
                              Subject: [Michalak] Model in relation to ballast



                              >>Given the uncertainties of material weight, as well as gear and crew, I
                              would take a pragmatic approach. Build the model, mark the waterline, put
                              the model in the water, and add ballast until the model floats on her lines!

                              Thanks John T. That was the direction I was thinking. In my case, I figure
                              a person could get pretty dang close just referring to historical data.
                              Similar boat/ what ballast. Any discrepancies could be sorted with internal
                              additions....or a Sawzall.

                              On this topic, I posted the same question to Jim. (as I mentioned before)
                              His reply was interesting and I thought you all might like to read it as
                              well.

                              "I'm not sure you can learn anything from a boat model besides what it
                              looks like. Some folks disagree and Kilburn Adams told me he worked the
                              bugs out of his Skiff America design with a large powered RC model. As
                              for ballast calcs, they are related to stability. A lot easier to do now
                              that we have programs like Hullform. It the past it usually was not
                              calculated, only based on experience. I wrote an essay about the topic
                              based mostly on how to figure how much sail your boat can carry."

                              Does anyone know the title of that essay?

                              Cheers, Tim.

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




                              _____

                              Yahoo! Groups Links

                              * To visit your group on the web, go to:
                              HYPERLINK
                              "http://groups.yahoo.com/group/Michalak/"http://groups.yahoo.com/group/Micha
                              lak/

                              * To unsubscribe from this group, send an email to:
                              HYPERLINK
                              "mailto:Michalak-unsubscribe@yahoogroups.com?subject=Unsubscribe"Michalak-un
                              subscribe@yahoogroups.com

                              * Your use of Yahoo! Groups is subject to the HYPERLINK
                              "http://docs.yahoo.com/info/terms/"Yahoo! Terms of Service.


                              --
                              No virus found in this incoming message.
                              Checked by AVG Anti-Virus.
                              Version: 7.0.308 / Virus Database: 266.11.0 - Release Date: 4/29/2005



                              --
                              No virus found in this outgoing message.
                              Checked by AVG Anti-Virus.
                              Version: 7.0.308 / Virus Database: 266.11.0 - Release Date: 4/29/2005



                              [Non-text portions of this message have been removed]
                            Your message has been successfully submitted and would be delivered to recipients shortly.