Quick draining vs self bailing

Discussion in 'Boat Design' started by Diego San, Apr 23, 2018.

  1. Diego San
    Joined: Jun 2014
    Posts: 21
    Likes: 0, Points: 1, Legacy Rep: 10
    Location: Medellín

    Diego San Junior Member

    Hi everyone,

    I would like to ask you, regarding the H-4 ABYC standard, which variables you would consider in order to design a boat either quick draining or self bailing.

    And just for the sake of curiosity, which is the most common drainage system category in your country?
     
  2. JSL
    Joined: Nov 2012
    Posts: 592
    Likes: 20, Points: 18, Legacy Rep: 41
    Location: Delta BC

    JSL Senior Member

    The self bailing is the absolute minimum and you can get away with 1" of freeboard. Not much of a margin.
    Quick draining is better (more freeboard)but even then might be borderline for some operations.
     
    Diego San likes this.
  3. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 467, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    If the swamped space can drain its contents in a minute or less, you've got enough drainage. If not, you need bigger drains. No set requirement, just experience with flooded cockpits that couldn't do this, in a building sea and a lot of wind trying to broach the now wallowing beast.
     
    Last edited: May 5, 2018
    Diego San likes this.
  4. JSL
    Joined: Nov 2012
    Posts: 592
    Likes: 20, Points: 18, Legacy Rep: 41
    Location: Delta BC

    JSL Senior Member

    agreed
    and other things: hatches etc. should be watertight, not weathertight
     
    Diego San likes this.
  5. Squidly-Diddly
    Joined: Sep 2007
    Posts: 1,244
    Likes: 30, Points: 48, Legacy Rep: 304
    Location: SF bay

    Squidly-Diddly Senior Member

    One minute sounds like a long time, given the problematic waves are going to be running on a much shorter cycle.

    I'm thinking there should be a ratio of:

    volume of cockpit VS
    size of boat (or in particular "moment of buoyancy" when weight added to cockpit) VS freeboard VS
    height of cockpit floor above waterline VS
    time to drain
     
    Diego San likes this.
  6. JSL
    Joined: Nov 2012
    Posts: 592
    Likes: 20, Points: 18, Legacy Rep: 41
    Location: Delta BC

    JSL Senior Member

    You are correct and classification (ABS, Lloyd's, etc)and safety organizations (USCG, etc) have some guidelines so you don't have to go into computational meltdown. I had a similar situation many years ago when designing a 55' alum sport fisher passenger vessel with a large cockpit. We did not want large freeing ports in the cockpit so fitted basic drain scuppers plus 2 large freeing ports (about 12" x 24") with flap valves (essentially a dump valve) in case she ever shipped a big load of water in heavy weather. In service for 30 years without any problems and now doing whale watching tours.
    (the attached is not quite applicable but it should give you an idea)
     

    Attached Files:

    Diego San likes this.
  7. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 467, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    My 1 minute fully drained suggestion is the maximum I would permit on an offshore craft, with much less being preferred. Yes, a minute is a long time, as you wait for the cockpit to drain and I've seen drains in production sailboat cockpits, that took a lot longer and managed to get certified by the regulators. Most powerboats would also struggle to drain off in less than a minute, without modification (more scuppers). I have a sailboat with a relatively small cockpit well of about 27 cubic feet, which is about 1,400 pounds of water when full. I've installed two additional drains and enlarged the others. About 30 seconds when I tested it several years ago, to drain the full cockpit well. This weight would make the boat handle very poorly at 1/3 the full up displacement if full, but likely enough to get her down hill and drain off, before getting swamped again.
     

  8. Diego San
    Joined: Jun 2014
    Posts: 21
    Likes: 0, Points: 1, Legacy Rep: 10
    Location: Medellín

    Diego San Junior Member

    thank you all for your replies!! I thought I was missing something because in the H-4 ABYC standard I couldn't find an explicit mention to whenever a boat shall have either drainage system.
     
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.