Standing/sleeping below waterline

Discussion in 'Boat Design' started by silentneko, Jul 11, 2021.

  1. silentneko
    Joined: Jan 2014
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    silentneko Junior Member

    This might seem pretty obvious to some, but is there any concern with having part of your interior cabin below the waterline? I recently posted up about a small houseboat or cabin cruiser. When talking to a friend I mentioned that some of the boats I've seen seem to have the interior sole below the waterline or a berth very close to it, and he thought that was unsafe.
    Obviously they do it all the time in large ships. On a smaller craft I'd think as long as your pumps and alarms are in good working order you should be ok. Thoughts?
     
  2. bajansailor
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    bajansailor Marine Surveyor

    If you are sleeping on the sole, and it is below the waterline, and you get a leak, you will be the ideal bilge alarm! :)

    More seriously, pretty much all yachts have at least part of their cabin sole below the waterline, both power and sailing boats.
    And when you are underway, the most comfortable berth is often a cushion on the cabin sole.
    Maybe you can ask your friend why he thinks it is 'unsafe' to have the interior sole below the waterline or a berth very close to it?
     
  3. fallguy
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    fallguy Senior Member

    A properly built craft would not sink. A boat designed with a flood box for the pumps would only flood to the waterline.

    The hull bunks in the Skoota are above the waterline, but a person woukd walk in water in a hull breach.

    The 'friend' is not understanding the dynamics of a properly built, modern boat. It can take on water, but ought not sink or capsize.

    The main threats to vessels are fire, engines drowning in rough seas, capsize, groundings. The threats to persons are small. Falling overboard in rough seas is real and must be mitigated.

    However, mitigating threats to persons must be high on a builder's list. Carbon monoxide and smoke detection are big. Multiple exits in case of a fire as well. In the Skoota build, fire is our greatest fear. Onboard, we will have a rapid discharge pump which could be used to put out a fire, but mainly all systems are designed to prevent fire. All wires are fused. All 3 sleeping areas have two exits. And, we will have a secondary vessel for emergencies like a massive fire.

    Sleeping on a boat under decks is never as nice as above. But, adding windows can improve it. Sleeping quarters in a houseboat are nice, my biggest problem on houseboats have been the hulls bouncing on hard bottoms which renders sleep difficult. (Spots where fishing was exceptional off the boat)
     
  4. TANSL
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    TANSL Senior Member

    That is true, the water level inside the boat can never exceed the water level outside the boat (pure physics), the problem is that the waterline goes up and up until it exceeds the deck of the boat.
     
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  5. comfisherman
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    comfisherman Senior Member

    About 60% of the commercial fishing boats in Alaska have a part of the cabin below the waterline. Usually give those bunks to the greenhorn. Not for safety reasons, just the water level being mid back makes for some noisy sleep.... so the new guy gets to listen to the waves more.

    Except on my little boat. Darn bottom bunk is the only one long enough for me to fit. Laying on my side my one shoulder is below water and the other above... and it blew 30 last night so the lovely sound of harbor chop hitting the bow all night. Downside of the design and an outside hull in a big harbor
     
  6. silentneko
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    silentneko Junior Member

    His reasoning was more along the lines of a catastrophic failure. I don't really see that as a possibility in most cases. A blown hose or crack in the hull will allow water in quick, but you'll get plenty of warning prior to drowning in your sleep. I don't anticipate anyone sleeping while underway, and the vessel would be a fair weather type vessel. Except for at anchor in a storm I think she will behave predictably. I don't see an issue with being below the waterlinepersonally, I was just wondering if i missed something.
     
  7. Squidly-Diddly
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    Squidly-Diddly Senior Member

    Houseboats had the more private (for the parents) sleeping quarters behind a low door towards the bow and sorta under the waterline. It was claustrophobic AF and word is particularly adults would refuse to sleep down there, so it sorta defeated the purpose.

    Buddy was spending first night after launching of a friends sloop and just by dumb luck and change of plan he is on an air mattress basically on the floor and an hour after going to sleep he starts to float because a P-Cock had been left open, so rest of crew is woken and boat is saved.
     
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  8. comfisherman
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    comfisherman Senior Member

    Catastrophic failures are a tough one to prep for. Obviously some practical bulkheads and bilge alarms.

    Truth be told nothing really preps you for catastrophic failure. My boat was one of 258 of the same mold. We lost 2x in my district last year. One a genuine accident the other due to drugs and stupidity. Ironically they get raised and reborn more often than destroyed.

    In on instance 3 years ago there was a dual fatality. But it was due to the door being blocked by gear and trapping them inside. The one last year had 0 fatalities. In the latter instance the boat had its original one piece wood door that was prone to stick replaced with a diamond sea glaze dutch door. The upper half was easy to open unencumbered and the crew escaped the stricken vessel... needless to say I'm happy to have the same door setup.

    In several recent sinking the difference in survival was which door or window each individual chose to attempt to escape from. One fairly well known recent ice caused rollover (about as fast as a boat can go down) 2 crew left the same stateroom one headed for door one headed for a wheel house window. The window was the better bet and he survived after a harrowing climb up a floor to the window.


    All that to say, best bet for survival is prevention. Its pretty easy to stay off rocks on Anchorage and traveling. Use good charts, maintain your running gear and do your partying at home. Then you can sleep above or below the waterline.
     
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  9. wet feet
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    wet feet Senior Member

    The small nineteenth century cruising yachts depicted by C P Kunhardt in his book Small Yachts had a lot of the accommodation below the waterline.

    from Kunhardt.jpg
     
  10. tlouth7
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    tlouth7 Senior Member

    There is nothing fundamentally different inside the boat between being above or below the waterline. If the boat floods you are likely to get wet either way. Once there is a significant amount of water inside the boat the original waterline will be considerably submerged anyway.
     
  11. fallguy
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    fallguy Senior Member

    This is an errant statement. Many boats are positive buoyant to the point they will flood without sinking much.

    When someone is trying to argue vessel safety, sinking is always the voodoo, but fire is the real enemy. If you have ever seen even a small bit of resin burn; the smoke is horrific.

    But the irony is most boating deaths are drownings, most of them involve the non-use of lifevests and many involve alcohol. And that isn't people falling asleep in a bunk. Most fatalities occur in small boats under 21' as well.

    Things like the duck boat tragedy lead people to believe all boats sink, which is fallacy.
     
  12. tlouth7
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    tlouth7 Senior Member

    I stand by my statement. No floating vessel can flood without the waterline moving. Especially for a vessel where the cabin sole is below the waterline (i.e. a ballasted vessel) this movement will be significant.

    The question of whether flooding or sinking is remotely likely is neither here nor there.
     
  13. TANSL
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    TANSL Senior Member

    The waterline does not move, what is moving is the boat and that movement is totally independent of the existence of a sole below the waterline. And I will add something else, it is independent of everything inside or outside the boat and regardless of the height at which those things are, it just depends on the total weight of the boat.
     
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  14. rxcomposite
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    rxcomposite Senior Member

    How do people sleep well in the submarine if they knew they are below waterline almost all the time?
     
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  15. fallguy
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    fallguy Senior Member

    People fear sinking. It isn't a question. Sinking is irrational for many vessels. The waterline is rising is like the sky is falling to that fear.
     
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