How to decrease the inclining oscillation and increase the stability on the boat

Discussion in 'Stability' started by Nickname123, May 30, 2017.

  1. Ad Hoc
    Joined: Oct 2008
    Posts: 6,227
    Likes: 417, Points: 83, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    For the very hard of reading....SEE ABOVE!!!
     
    Nickname123 likes this.
  2. Mr Efficiency
    Joined: Oct 2010
    Posts: 8,033
    Likes: 360, Points: 83, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    As TANSL says, the OP already understands he has a serious problem, what he needs is explication of what the "serious changes required" actually might be. Other than running it over with a bulldozer.
     
    Nickname123 likes this.
  3. Ad Hoc
    Joined: Oct 2008
    Posts: 6,227
    Likes: 417, Points: 83, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    So...what you're saying is...you like to give quick throw away comments to sound impressive and knowledgeable. The squeaky wheel gets the oil....

    Yet when an analysis of the facts such as GZ curve and loading data which very clearly indicate the problem and thus way forward, by using numbers, you're lost, and yet complain at those than can understand, because you can't!

    Gesssss....
     
    Nickname123 likes this.
  4. Mr Efficiency
    Joined: Oct 2010
    Posts: 8,033
    Likes: 360, Points: 83, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    Still waiting to hear what practical changes might be made. We hear the GZ curve is no good, but no mention how it might be remediated.
     
    Nickname123 and TANSL like this.
  5. TANSL
    Joined: Sep 2011
    Posts: 5,864
    Likes: 220, Points: 73, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    He does not know, or does not want to say, what the solution is but he does know that you do not know anything. Try to get up from your arm chair to see if that increases your knowledge.
    What does the OP need, at this moment, the curve of the GZ if just by getting on the boat he already knows he has a serious problem ?. To give a solution, quantified, non a generic one, indeed it will be necessary to draw the GZ curve but also many other things. Only with the GZ curve we do nothing.
     
    Last edited: Jun 7, 2017
    Nickname123 likes this.
  6. Mr Efficiency
    Joined: Oct 2010
    Posts: 8,033
    Likes: 360, Points: 83, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    I know "nussink" ?

    upload_2017-6-7_19-6-2.png
     

    Attached Files:

    Nickname123 likes this.
  7. Mr Efficiency
    Joined: Oct 2010
    Posts: 8,033
    Likes: 360, Points: 83, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    Turning it into a tri-hull is likely the best hope, imo. Again, easier said than done, but one boat might be salvaged. The existing moulds can't be adapted easily.
    cross section.png
     
    Nickname123 likes this.
  8. gonzo
    Joined: Aug 2002
    Posts: 13,786
    Likes: 436, Points: 93, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    The first question is whether it is worth investing time and money into a bad design. I think it should be considered good data for an experiment that shows the shape, size and method of construction generates a bad result. If the OP really needs to reuse the mold, it could be cut in the center and made wider. However, that is not a guarantee that the boat will perform properly, only that the stability will increase.
     
    Nickname123 likes this.
  9. TANSL
    Joined: Sep 2011
    Posts: 5,864
    Likes: 220, Points: 73, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    Think a little, please, in what you say and how to carry it out in the reality because that, as it is, it is not possible to do.
     
    Nickname123 likes this.
  10. gonzo
    Joined: Aug 2002
    Posts: 13,786
    Likes: 436, Points: 93, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    Widening and lengthening molds is very common.
     
    Nickname123 likes this.
  11. TANSL
    Joined: Sep 2011
    Posts: 5,864
    Likes: 220, Points: 73, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    Widening molds is not so common, but it can be done. In any case it is by no means a simple operation as you seem to suggest. It is a complicated operation and very expensive and not always, with any mold, it is possible. Unless you have a solution, which I would like to know, and I guess the OP.
    It does not make sense to talk about generalities. It is about giving solutions to the current problem, the current ship and the current mold. Have you seen the shapes of the bow ?. Are you still thinking of widening the mold, without anything else? How much could be enlarged without having to do very strange things in the bow?. How would change the position of the center of buoyancy ?. Would you change the trim of the ship?. Would it reduce the draft and, therefore, increase the area exposed to the wind, which is so damaging for this boat ?. Would the increase in inertia of the flotation offset the decrease in draft?. ...
    Have you seen the solution proposed by Mr.Efficiency ?. Is not it more logical to do something similar? ....
    Thank you, Gonzo, in advance for your explanations.
     
    Last edited: Jun 9, 2017
    Nickname123 likes this.
  12. Mr Efficiency
    Joined: Oct 2010
    Posts: 8,033
    Likes: 360, Points: 83, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    Possibilities exist that could be economically feasible, but the people to talk to would be the makers.
    upload_2017-6-8_20-26-6.png
     
    Nickname123 likes this.
  13. Nickname123
    Joined: Aug 2014
    Posts: 25
    Likes: 0, Points: 1, Legacy Rep: 10
    Location: Viet Nam

    Nickname123 Junior Member

    Hello all,

    Thank you for your all comments, your comments were helped me very much.

    I were working with my designer and discuss how to resolve this problem.

    We make a decision that we will put 2 bilge keels along the hull side and decrease the height of cabin 500mm.

    How do you think about my solutions?
     
  14. Mr Efficiency
    Joined: Oct 2010
    Posts: 8,033
    Likes: 360, Points: 83, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    Bilge keels do not belong on a hull like this, and one would wonder how the cabin roof can be lowered 500mm and still have headroom.
     
    Nickname123 likes this.

  15. Ad Hoc
    Joined: Oct 2008
    Posts: 6,227
    Likes: 417, Points: 83, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    Did you understand my post above...perhaps not!?

    The GZ curve clearly indicates, that you need to make a minimum 0.6tm change in the KG. So moving 1 tonne 0.6m or 2.0 tonne down 0.3m etc....and given the limitations of your boat, in terms of sole level and what is under it etc....not feasible. Thus unless you coat the hull bottom with lead, you're wasting time. Not to mention adding such ballast low down does what...increase the full load displacement, which does what....increases drag which does what....lowers your speed, possibly even limiting it to pre-hump speeds!

    Design is all about compromise and greater than the sum of its individual parts!

    You need a more suitable hull form.
     
    Nickname123 likes this.
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.