Wiring and plumbing watertight compartments

Discussion in 'Boat Design' started by Annode, Aug 31, 2019.

  1. Annode
    Joined: Aug 2019
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    Annode Junior Member

    The threadvon Watertight compartmets was interesting but without sealing plumbing and elec ducts, the concept is flawed.
    How do you run these through the boat and seal the bulkheads so that more can be added later or servicing done?
     
  2. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    conduit

    sorry if I sound patronizing, but it is the only way to really do it right

    abs or pvc pipe work well and a 2" pipe handles almost any rigging requirement

    however, if only a few wires are expected an inch is just fine
     
  3. JSL
    Joined: Nov 2012
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    JSL Senior Member

    'google' sealing watertight bulkhead penetrations
     
  4. Ike
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    Ike Senior Member

    Is this a recreational boat or commercial? How large? Is is going to be certified to carry passengers for hire?

    For commercial vessels there are rules. In the UK consult the Maritime and Coast Guard Agency.
    For recreational boats, The Recreational Craft Directive may have some guidance. But as Fallguy said. Conduit. That is one way. If you are just running wire through the boat, it needs to be supported at least every 45 cm or so, (18 inches in the US) and holes in the bulkheads need some sort of grommet or a tube to protect the wire from chafing. A product called duct seal is often used (we had a ruder name for it in the Coast Guard) Essentially it is a type of putty that seals the hole but doesn't get hard.

    Also running a few extra wire pairs is a good practice. If the circuit you are using goes bad you can use the spares until you can troubleshoot and correct the problem.
     
  5. kapnD
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    kapnD Senior Member

    I prefer to use frp tubing for conduit, it’s strong, light, and best of all, is compatible with surrounding surfaces, so it’s easily glassed in place, insuring watertight integrity of sealed spaces.
     
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  6. Steve W
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    Steve W Senior Member

    I use G10 tube for smaller things but if I need longer lengths or have corners to go around, curves to follow, larger sizes etc i make up my own by using pvc as a form which I can join together to get any length and then use a heat gun to form to curves then sand it, wipe with acetone to clean it and soften the surface and then spiral wrap it with 2" fiberglass tape and epoxy overlapping 1" so I end up with a continuous 2 plies. When the epoxy has cured I sand it and can then bond it in with epoxy just like using G10 but more versatile and a whole lot cheaper. I have done this for drain tubes through buoyancy tanks, drain tubes for hatches and many other purposes.

    Steve.
     
  7. fallguy
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    fallguy Senior Member

    Couldn't you simply wrap the ends that will bond or simply bond the pvc itself to the BH or entries to the watertights?

    I don't understand the reason for wrapping in glass. Just adding weight.. Please forgive any tone, I just don't understand. Is it just for improved bonding glass to glass vs glass to pvc? PVC may not be the best bond to epoxy and glass, but it does bond somewhat..
     
  8. Squidly-Diddly
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    Squidly-Diddly Senior Member

    Not being a real boat builder, I'd say important thing would be make all the through-holes up high as possible, whether conduit or not.

    That Norwegian destroyer sank mostly because of hollow main propeller shafts. I don't think there was any reason why the shafts were hollow AND unobstructed. In addition to conduit I'd want things sealed as much as possible with dabs low-strength expanding foam. Nothing that will hinder refit too much, just enough to stop water flowing freely where its not supposed to.
     
  9. Eric ruttan
    Joined: Jul 2018
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    Eric ruttan Junior Member

    I also do not understand.
    I imagine a typical run will be going through bulkheads.
    Not need much more support? A typical 1 1/2" would be plenty stiff over most boat relavant spans.
    Perhaps a laminate piece glued into the corner to be a support, when holed, would be light and easy, if the span was considered too much?
     
  10. Steve W
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    Steve W Senior Member

    Pvc is great for many things in boat construction but it has a few deficiencies, even with proper prep it does not bond particularly well, ok , but not great, at least not well enough for me. The other problem is that some formulations tend to be quite brittle while others seem quite ductile. I have experienced two situations on boats I have owned that lead me to not want to trust it for anything that matters if it is not accessible such as maybe running through a buoyancy tank without wrapping it. I do use it for conduit in non critical areas.I once owned a Macgregor 36 catamaran that had inboard rudders where they had used pvc pipe for the rudder tubes that were glassed in to the hull and deck but otherwise unsupported for maybe 4 ft in between. I had a constant weep in the port hull in this area with zero access. This area had a small deck hatch and it was deep and filled with fitted blocks of Styrofoam for floatation. I could reach in through the hatch and actually turn the pvc so the tabbing was not bonded at all hence the leaking but there was no access to repair it. The pvc was fine and im sure the prep was not adequate and the tabbing was with polyester, not epoxy but still. I actually cut the transoms out for access and glassed the entire tube from the hull to deck and added knees. On my current Gemini cat it has one hull stringer on the outboard (Inside of course) side of each hull which is a 4" pvc pipe split in half lengthwise glassed over, the pvc is just used as a form ( makes for a great wiring chase) but there is a short section where they did not glass over it for whatever reason in the port hull and the pvc was shattered, I have no idea how this happened as it was like it when I bought the boat but the point is this particular piece was quite brittle, these are just a couple of reasons why I prefer to wrap it completely.

    Steve
     
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  11. Annode
    Joined: Aug 2019
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    Annode Junior Member

    The problem I am grappling with is running HVAC into watertight compartments. Do superyachts even bother with watertight compartments? They have all kinds of plumbing going everywhere
     
  12. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    If the designer specified watertights then there isn't much choice. Ducting through a watertight is not ideal and would probably require the duct be built of hull materials; then the ducting has a termination at each side of the watertight.

    But, honestly, this is outside my knowledge, so treat my reply as a new question.

    Also, any such built in duct/housing would need to meet the requirements of the system for temp ranges.

    And, by ducting through water tights; you may be adding an impairment to the buoyancy calculations and it should get checked by the designer.

    Also, stop mixing terms. Hvac is ducting, plumbing is piping...
     
  13. Eric ruttan
    Joined: Jul 2018
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    Eric ruttan Junior Member

    If, by HVAC, you mean air ducting, then there is no waytto keep it water tight. If by HVAC, you mean coolant tubes, then it's easy.
     
  14. fallguy
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    fallguy Senior Member

    Actually if built out of hull materials; air ducts can be made watertight (like a hull).

    This is why I got a little nitty.

    He has to be more specific than intertwining hvac and plumbing.
     

  15. Eric ruttan
    Joined: Jul 2018
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    Eric ruttan Junior Member

    I can understand a duct, it self, can be made water proof.
    I do not understand how a duct, that flows air, can not flow water.

    Is there some sort of fluid check valve that works in every orientation and case?
     
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