Self bailing

Discussion in 'Boat Design' started by Albert Jr., Nov 18, 2013.

  1. Albert Jr.

    Albert Jr. Previous Member

    What qualifies as self bailing when talking boats and when is a boat really
    self bailing ? Not just a boat where the water goes in the bilge in a pump and
    out of the boat.
  2. lewisboats
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    lewisboats Obsessed Member

    Self bailing refers to the cockpit area usually and that means the sole is sealed and above the waterline, with drains to allow water to run out of the cockpit and back where it belongs. Hatches etc should be closed of course, if you are shipping enough water to require serious drainage.
  3. kapnD
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    kapnD Senior Member

    Although the term self bailing is intended to mean that water taken on board will drain off without pumping, I have learned that what it really means is that you need a working bilge alarm equipped with a loud bell, accompanied by a manual and an automatic bilge pump.
  4. TANSL
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    TANSL Senior Member

    I do not know if this can help but ISO 11812, for pleasure boats, defines the "quick draining" cockpits and features. The idea is that the cockpit is empty in a time small enough so that the water contained therein does not affect the stability.
    In my opinion a self draining cockpit should be emptied without the intervention of any pump.
  5. Saqa
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    Saqa Senior Member

    While shopping for boat bits recently, I came across a bung and housing combo that uses a traditional style screw in bung that also contains a ball system that lets water out but not in. I thought was very impressive simple design that's very functional and picked one up for my project. I am going to install a sole that will sit just above the water line with two people onboard and if boat motions moves the waterline up then cant see water getting in with the ball stopper
  6. PAR
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    PAR Yacht Designer/Builder

    TANSL, raises a good point and one often overlooked. Generally a cockpit sole will need to be at least 6" (152 mm) above the LWL to drain properly, though I've seen a few that could, that where slightly lower. Now picture a regular 25' sailboat cockpit, with deep foot well and seat risers. This can easily hold several hundred gallons of water. How fast can you scupper system get rid of the water. Having been in cockpits full to their bridge deck with water, I can tell you a minute under these conditions seems like an eternity. This is because if you have a sea state big enough to board and fill your cockpit, you're also being challenged in other areas, like big winds, difficult steering and more breaking seas coming aboard. A boat in this condition is wallowing, usually badly and everything is in jeopardy. I generally try to get cockpits to drain in 30 seconds or less.

    In a dayboat, things like Anderson scuppers or other "self bailers" can be employed, but boats like this are usually small enough that a capsize, though a pain in the butt, shouldn't be a big concern, because you can self right the boat. On slightly larger boats, you might have enough built in floatation to survive a knock down, but once your boat gets past say a ton or so in size, there's no floatation or self righting plan that can help you, so a real boarding water plan is necessary, with bilge pumps, keel sumps and self draining cockpits being required.
  7. gonzo
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    gonzo Senior Member

    I think the open transom cockpits are the only ones that drain fast enough. Also, the hoses usually installed to drain cockpits are always clogging
  8. michael pierzga
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    michael pierzga Senior Member

    Yah..i have 5 times 2 inch cocpit drains in the steering cockpit and it still floods when the boat gets washed by waves.

    The only defense is to fill the cockpit with bags of sails with fenders and bulk stuffed inside during heavy weather to displace all the water rushing in.

  9. TANSL
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    TANSL Senior Member

    An "open transom" is more than enough to maintain the cockpit without water. but for ships with full transom, as Michael says, is enough with 4 scuppers 2 "or 2.5" diameter. Depends, of course, on the volume of the cockpit.
  10. michael pierzga
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    michael pierzga Senior Member

    Drain Scuppers. alway clog in heavy weather...jellyfish, squid, flying fish,cheesburgers, wet packs of Camel lights.... .......

    Once the scupper swallows a squid the drain develops a digestion problem

    Putting grates on the drain reduces its diameter.

    Best to use twice as much drainage ... do not choose the minimum to satisfy a rule.

    And always protect the drains..

    All cockpit drains most not be thru the cockpit floor.

    Overfull drains , mounted higher up thru the cockpit sides , work just fine

    http://[​IMG] subirimagenes
  11. Mr Efficiency
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    Mr Efficiency Senior Member

    Round scuppers are less satisfactory than rectangular for quickly shedding water, fish blood and guts etc, in a flush and clean, the last half-inch depth escapes too slowly and the detritus stays aboard too often.
  12. frank smith
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    frank smith Senior Member

    I think you could make one with some pvc. It would have a pickup in the boat, then go up over the gunwale and exit below water. It should create a vacuum, if the boat is going fast enough, and once running it would act a a siphon. Of course it would have to be above the water line for the most part. Then there are those self bailing things they used to put in sunfishes. they had a little ball as a back flow preventer. I don't think any thing like that could be left unattended.
  13. michael pierzga
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    michael pierzga Senior Member

    Discharges below waterline are avoided. The drain ID picks up marine growth. Exit thru the boot top when possible. When done correctly...exit pipe angle down and angled aft , the boot top hole becomes disguised to the eye and looks invisible at distance

    You certainly could use rectangle shapes. They are hard to set into a cockpit sole and below deck they take up much space when transitioning from rectangle to round pipe,.

    The problem with all drainage systems it the below deck plumbing...keep it as straight as possible
  14. jimmy wise
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    jimmy wise Junior Member

    im thread robbing

    ok so on my 19.5 foot marlin i am putting new floors in. should i put drains in the deck in the rear or put a slight slope in the sole around the bildge opening for the engine?

  15. michael pierzga
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    michael pierzga Senior Member

    Hard to say...everyboat is different, every drain is different.

    Drains can be used to remove morning dew and rain sprinkles or they can be use to shed great walls of water
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