New here, thinking about boat

Discussion in 'Boat Design' started by Jaro, Jun 30, 2014.

  1. Jaro
    Joined: Jun 2014
    Posts: 11
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Bohemia

    Jaro Junior Member

    Hello, years ago I was a machine engineer on a ship. I m now thinking about building a boat to live on and travel.
    I can have steelwork really really cheap, so I m sort of trying to fit the hull into something easy developable. She is rather narrow, 36´ long or around, wont be very spacey inside, but life is a compromise. Also flat sides and lots of flat panels for easy build.
    This will never be very fast, but very efficient - I think it should need only about 12-14 hp to go at 6.5 knts continuously. So with 35 hp engine for emergencies it should take only about 2 l of diesel/hour. This will give it huge range - at expense of speed off course.

    This is hull only, I shall draw the upper structure in autocad later, neverthelless its gonna be something like "dieselducks".

    [​IMG]

    Could you possibly comment, or point me to similar ship. I cannot make her any faster that short cannt I?

    Thanks Jaro
     
  2. TANSL
    Joined: Sep 2011
    Posts: 5,548
    Likes: 160, Points: 73, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    The bottom between frame 0 and frame 2600 does not seem right, and between frame 9600 and bow is not developable. You should work it a little more.
     
  3. Jaro
    Joined: Jun 2014
    Posts: 11
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Bohemia

    Jaro Junior Member

    I know about bow, I thought that will be only dificulty, though there is a steelyard near which can bend most any plate shape.

    What do you mean about botom "does not seem right"?

    This is by no means fisnihed, its a starters, model in works.


    Jaro
     
  4. TANSL
    Joined: Sep 2011
    Posts: 5,548
    Likes: 160, Points: 73, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    Water lines # 3 and # 4, starting from the baseline, should not have straight runs, in my opinion.
     
  5. Jaro
    Joined: Jun 2014
    Posts: 11
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Bohemia

    Jaro Junior Member

    O.K. I shall look into it, many thanks.
    Jaro
     
  6. tdem
    Joined: Oct 2013
    Posts: 130
    Likes: 5, Points: 18, Legacy Rep: 41
    Location: NZ

    tdem Senior Member

  7. Jaro
    Joined: Jun 2014
    Posts: 11
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Bohemia

    Jaro Junior Member

    Many thanks, that is lots of reading. :) I have dropped the transom area since and the resistance figures go down.
     
  8. Sleipnir
    Joined: Jun 2014
    Posts: 28
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Central Europe

    Sleipnir Junior Member

    If you want propulsive efficiency with a displacement boat then you should maximize waterline length. That means vertical bow and vertical transom. Very little overhang.

    I have no experience with steel constructions, but intuitively I would say that vertical bow and transom should make things easier.

    If you have access to real cheap steel construction and is not limited by a certain length of mooring then go for a longer hull. As long as you can afford. You can always leave part of the interior empty for a few years if your budget can't cover everything now.

    In a few years you will probably wish your boat was 42'-45'..... not 36' And the extra waterline length give you more speed potential, even if you don't intend to use it initially.
     
  9. TANSL
    Joined: Sep 2011
    Posts: 5,548
    Likes: 160, Points: 73, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    Jaro, I checked the water lines aft and, contrary to what I said in the post # 2 and # 4, they may be correct. My apologies.
     
  10. Jaro
    Joined: Jun 2014
    Posts: 11
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Bohemia

    Jaro Junior Member

    Well I m playing with it more, I might try to make transom vertical and see how it looks.
     
  11. Jaro
    Joined: Jun 2014
    Posts: 11
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Bohemia

    Jaro Junior Member

    [​IMG]

    Resistance curve now looks like this. Am I doing something wrong or is this absurdly low?

    http://hawkwind.sweb.cz/Resistance curve 4182382484331.jpg

    When I did my school, that was more than 20 years ago, tools like this werent availble and I was ment to be engine specialist. We skimmed hydrodynamics, not that I remember anything much anymore. .)

    Jaro
     
  12. Jaro
    Joined: Jun 2014
    Posts: 11
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Bohemia

    Jaro Junior Member

    [​IMG]

    Now transom vertical and the chine too more so.
     
  13. Jaro
    Joined: Jun 2014
    Posts: 11
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Bohemia

    Jaro Junior Member

    Shows this now:

    [​IMG]

    Jaro
     
  14. TANSL
    Joined: Sep 2011
    Posts: 5,548
    Likes: 160, Points: 73, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    I can not say that some shapes are better or worse than others because it depends mainly on what you want to do with your boat, but you could try something similar to FIG. Thus, the outflow of water from the stern be much smoother. Although other aspects, such as the wet surface increases. But it is to play and compare results.
     

    Attached Files:


  15. Jaro
    Joined: Jun 2014
    Posts: 11
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Bohemia

    Jaro Junior Member

    I see what you mean.

    Jaro
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.