Jet boat moored in ice

Discussion in 'Jet Drives' started by cwzsu, Aug 3, 2013.

  1. cwzsu
    Joined: Aug 2013
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    Location: China

    cwzsu New Member

    I am a new comer from China, we have the idea to build a boat with water jet propulsion, the boat hull is steel, and body of the water jet is aluminium, the impeller and shaft of water jet is stainless steel.

    My question is:

    Since the boat will be running in a extreme cold area, there are alomost half of year, the river is frozen, we do not like to move the boat out of the river, so the boat will be frozen in the ice about 5-6 six months, I think the steel hull should be no problem of being frozen in the ice, How about the water jet? Because the structure of jet body is aluminium.

    Thank you very much for giving me the comments and suggestions.

    If you can put some pictures of the jet boat moored in ice, I will be much appreciated.

    Thanks & Best Regards,

    Steve Chen
     
  2. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    Steve

    Aluminium exhibits extremely good notch toughness in low temperatures. It is significantly better than steel. When you also consider that LNG's are made with aluminium, ie operating at circa -150c, frozen ice won't cause any problems.

    Your main issue will be that of corrosion. Mixing too many dissimilar metals and then how to ensure a suitable steel-aluminium joint for the waterjet foundations.
     
  3. cwzsu
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    cwzsu New Member

    Thanks Ad Hoc.

    I understand aluminium is no problem in low temperatures because of extremely good notch toughness. But there is an intake block on the bottom of the steel hull, the block is aluminium, it likes a tunnel, when the water becomes frozen, I am afraid the block may be broken because of the water forms ice.

    Thanks,
     
  4. speedboats
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    speedboats Senior Member

    I would fear that as the water inside the tunnel and body freezes that it would expand and crack or break the pump, much like when you put a bottle of beer the freezer for to long...
     
  5. cwzsu
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    cwzsu New Member

    Yes, you are correct, if we put a bottle of beer into the freezer, it will expand and crack because of the water expands when it is frozen. But there is a little different from the beer, the beer is in a sealed container, the jet is not a sealed tunnel, and the water is not frozen to the ice immediatley, it gradually becomes into the ice, so I think the expansion or break of the jet boday may not happened.

    If any body has the information for similar experience, much appreciated you will give me the comments.
     
  6. speedboats
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    speedboats Senior Member

    Yes the bottle is a sealed vessel. The same too could be said if the intake and nozzle freeze first, then what is left inside the pump is essentially in a sealed vessel. This is feasable as the section inside the hull would remain slightly warmer than other emmersed sections of the pump, probably only a decimal of a degree, but enough to cause said effect
     
  7. Petros
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    Petros Senior Member

    can you raise the boat out of the water on floats for the winter? I see that often around here. also reduces the amount of growth on the bottom.
     

  8. cwzsu
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    cwzsu New Member

    Thanks Petros,

    Normally the boats need to be moved out of the water on floats for the winter, we have many small boats with water jets did like this, but the coming boats is steel and very heavy, so we would not like to raise the boat out of the water. The boats will be running in the river not in the sea, the growth is not the issues.

    Regards,
     
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