Ballast in a catamaran

Discussion in 'Multihulls' started by ADAM87, Oct 17, 2011.

  1. ADAM87
    Joined: Oct 2011
    Posts: 13
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: NC

    ADAM87 Junior Member

    Speaking in terms of a catamaran vessel. If a non-compressed ballast chamber was added in the bottom of the each hull. For example, I create a 24" tall section, and flood the bottom 6". I expect the waterline to then be equal to that of a 18" tall section (plus the additional weight of the structure bellow the 18" mark). The extra 6" of structure would still have some affect on the actions of the vessel, Right? How would this affect the boat in a stationary position? Specifically in terms of stability and sea keeping? FYI, the initial design concept is that this would only be used for stationary use at sea, never under power.
  2. sabahcat
    Joined: Dec 2008
    Posts: 792
    Likes: 28, Points: 0, Legacy Rep: 273
    Location: australia

    sabahcat Senior Member

    Why would it need it?
    How much more stability do you need when stationary?
  3. waikikin
    Joined: Jan 2006
    Posts: 2,439
    Likes: 176, Points: 73, Legacy Rep: 871
    Location: Australia

    waikikin Senior Member

    To increase the resistance to rolling via higher moment of inertia?
  4. ADAM87
    Joined: Oct 2011
    Posts: 13
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: NC

    ADAM87 Junior Member

    sabahcat, It is for a small craft design that would be used for a specific purpose in a niche market. It doesn't fall under what I would consider typical multi-hull design.

    That was my thought and part of the intent, along with lowering the waterline to the desired level when stationary. Yet allowing extra freeboard under power for the seakeeping side of things.

  5. Wavewacker
    Joined: Aug 2010
    Posts: 709
    Likes: 25, Points: 28, Legacy Rep: 226
    Location: Springfield, Mo.

    Wavewacker Senior Member

    I had inquired several times about a landing craft being a cat and I thought of the same thing basically, water balast to stabilize the stern while loading and off loading. I just thought that a 24/27 foot cat would be rather light (which is the usual goal) and it would certainly see action from wakes on a lake for example. I simply based this seeing boats that were full of water, half sunk, as they don't move much.

    I have moved on as I thought such a build would add difficulty that would yield a small return, it's probably easier to anchor and tie it off than filling and draining a lower compartment.....:(
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.