Weight Distribution. What do you think?

Discussion in 'Boatbuilding' started by snowbirder, Mar 20, 2015.

  1. snowbirder

    snowbirder Previous Member

    So I heeded the advice to run an individual line of propane for each device.... one regulator though. One of those for each is madness.

    Also, I minimized my wiring distances by locating the batteries over by the galley. Terrible weight distribution.


    I want to put 100 gallons of gasoline below deck directly opposite the galley and batteries, as well as 100 gallons of water in a different bilge more forward.



    Does this sound reasonable given tanks will be empty sometimes?

    What is the permeability of bladder tanks these days? The main gasoline tank would be in a stateroom to get it forward. Under a berth.

    Will a bladder tank stink like gasoline in a few years making that room uninhabitable?

  2. waikikin
    Joined: Jan 2006
    Posts: 2,390
    Likes: 153, Points: 73, Legacy Rep: 871
    Location: Australia

    waikikin Senior Member

    I might be a little unimaginative but like to mirror tankage port to stb. With petrol/gasoline have tanks where the space/locker arrangement drains through the underwing. I have limited experience with bladder tanks except for an outboard petrol tank for a small inflatable & plastimo water tanks...... kinda biased me towards using existing structure/boundaries for water.... with that & having lived with limited tankage I'm all for lots of water storage, when you don't need it don't carry it, my boat under planning/build has 6 tanks, 4 x @500l & 2 @300l & mirrored p to stb.

  3. TANSL
    Joined: Sep 2011
    Posts: 6,807
    Likes: 499, Points: 93, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    Actual permeabilities depend on the total volume and the interior structure of the tank. In relation to the official studies can take 97%.
    Some tips about tanks:
    - Placing tanks to be symmetrical and make possible consumption so as not occur undesired heeling.
    - Next placing the centers of gravity of the flotation tanks so that neither large trims occur as you are emptying / filling the tanks.
    - Once the tanks located, prepare a plan of consumption to avoid as far as possible these effects.
    It is likely that prohibited placing a gas tank under the bed, in the same stateroom. In any case, I think it will always be a source of problems.
  4. snowbirder

    snowbirder Previous Member


    Am I just being too much of a fanatic about trim?

    I am very particular about my boats' trim. I move things around inside already built catamarans to even it out, putting weight low and outboard as possible while also as close as possible to amidships in a fore and aft sense.

    So what will balance the galley out?

    I have a true kitchen galley with full size refrigerator, wall oven, cooktop, double sink, plus forward of that is a small crew cabin. The crew cabin is amidships. Also, think of the hundreds of pounds of provisions associated with the galley.

    Essentially, the majority of the boat's systems are located starboard aft, including the batteries now as well, while the rest of the boat is just empty rooms for guests. The propane is located port though, at bridgedeck level.

    I have a tool room opposite the crew cabin amidships on the port side. that's heavy.

    But how to make up for the starboard galley on the port side??

    There is nothing in the port hull at all except tools.

    My gut sense of trim suggests tankage.

    Any ideas?

    Regarding the fuel tanks... I do have a watertight bulkhead aft of the galley which makes up the main aft structural beam. Aft of the watertight bulkhead on both hulls is an engine room, or an abbreviated engine room because an outboard well has been made out of some of the engine room.

    I could put 50 or 75 gallons on each side, in those engine rooms, which is always preferable to having any smelly stuff in the main cabin area. (taking Tansl's advice), but I'm concerned to have an outboard, 50-75 gallons of fuel on each side, and reduced buoyancy from the outboard well cutout all affecting my sterns, whic are always prone to squat in cats anyway. (because all the weight always ends up in cat sterns)

    Am I stuck?
  5. TANSL
    Joined: Sep 2011
    Posts: 6,807
    Likes: 499, Points: 93, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    You have given many explanations, but at least for me, are not enough. A General Arrangemet drawing would be great to know your boat and give you some valid advice. Nor should we forget that some regulations may force to put things in special locations.
  6. snowbirder

    snowbirder Previous Member

    Advanced Graphic Design

    I used some rendering software to mock up a nice 3d model. :p

    Last edited: Jun 27, 2015
  7. snowbirder

    snowbirder Previous Member

    One thing missing. Directly forward of the "small engine rooms" are watertight bulkheads.

    Glitch in my 3d modeling algorithm. ;)

  8. whitepointer23

    whitepointer23 Previous Member

    Excellent 3d program. Similar to mine.:D
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.