I would like some critique on a boat I'm designing

Discussion in 'Boat Design' started by Mely, Jul 22, 2018.

  1. misanthropicexplore
    Joined: Apr 2018
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    Location: Upper middle Missouri River

    misanthropicexplore Junior Member

    Use a 8' diameter, 2' deep stock tank. :) 8' length, >5000 lbs displacement before it floods, seats 5 no problem.
     
  2. Mely
    Joined: Jul 2018
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    Location: Canada, Alberta

    Mely Junior Member

    Alright, here is my second draft. A pram boat 20" high and 4' wide. 4 people could sit on the top edge on top of the hatch doors and maybe a fifth person in the middle. Meant to sail with one or two people.
    tfs2.jpg open2.jpg side2.jpg
     
  3. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    The profile and plan/section views don't seem to correlate. On the plan/section views you show a pram bow, while in the profile there is a curve on the bow, which would generate a curve at the sides to bow edge. The keel should have some rocker. Also, the deadrise it has will make the dinghy quite tender.
     
  4. Raffaele Frontera
    Joined: Feb 2018
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    Location: Amsterdam, The Netherlands

    Raffaele Frontera Naval Architect

    I don't have any idea to be honest @BlueBell I thought that the problem was more to keep a certain value of the freeboard that I founded more interesting but apparently it was not the issue in this discussion. Like the formula in attachment could be fun to use it. :);)

    Regards

    Raffaele
     

    Attached Files:

    Last edited: Jul 23, 2018
  5. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    And, what do you do with that formula, what do you use it for?. Thanks in advance for your kind, I do not doubt, answer.
     
  6. Raffaele Frontera
    Joined: Feb 2018
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    Location: Amsterdam, The Netherlands

    Raffaele Frontera Naval Architect

    @TANSL what do you think of my approach as a "deadweight"? :)

    Did you see the formula?
     
  7. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    I do not know what formula BlueBell is talking about, that's why my question.
    As for your formula, I do not know it or know for what kind of boats it is applicable. I miss many things that do not depend on the dimensions of the boat, or the hull material, ... I do not think it's good for any type of floating object but, I tell you, I have not studied it thoroughly, I lack data. It is very strange that the dead weight depends on the density of the salt water, in fact, it is clear that I do not understand it.
     
  8. Mely
    Joined: Jul 2018
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    Location: Canada, Alberta

    Mely Junior Member

    Should the deadrise be deeper?
     
  9. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    The more deadrise, the more tender it will be.
     
  10. LP
    Joined: Jul 2005
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    LP Flying Boatman

    Here is a link that should help you determine a safe capacity limit for your dingy. The applicable information starts on page 35.

    https://www.uscgboating.org/regulations/assets/builders-handbook/SAFELOADING.pdf


    You latest update is a vast improvement over your first. I concur with Gonzo on all counts. I little deadrise, in your case has its benefits, but too much will be destabilizing. Adding rocker to the keel is going to improve performance.

    I would probably add move width to your bow knowing that you are trying to get so much out of such a short waterline. Personally, I wouldn't be trying to put so many people in such a small boat. I've build a 18'6" x 5' powered runabout and I typically limit that one to 5 adults.

    Best of luck.
     
  11. Mely
    Joined: Jul 2018
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    Location: Canada, Alberta

    Mely Junior Member

    Thanks JSL for the plans. After thinking them over these last few days I got a better understanding and crafted my third draft.
    tc-.jpg open-.jpg side-.jpg
    The walls would be made with 4mm plywood but the top needs to be thicker to be used as a seat. So the railing would extend a half inch below the top edge of the wall and the top seat section would also be 1/2 inch and sit flush on top of the rail. There may be additional support on hatch lids and sitting edges(additional 1/2" strip or section on underside). The rail strip would be about 9-10mm thick on both sides with the 4mm wall to make it an inch thick in total or the rail would be 1/2" thick.

    My goal is to make it match this style and have this color scheme when finished.
    [​IMG]

    The limit at this point seems to be 2-3 people, likely 2 because of the storage weight.
     

  12. kapnD
    Joined: Jan 2003
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    Location: hawaii, usa

    kapnD Senior Member

    9A64FCD3-62DD-449A-B025-64FB00D2CA61.jpeg
    I think this was about seven feet, and it was pretty dicey with three men, all fairly slim!
     
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