what % of broken ice is shoved under the shelf by Icebreaker ships?

Discussion in 'Boat Design' started by Squidly-Diddly, Jan 19, 2023.

  1. Squidly-Diddly
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    Squidly-Diddly Senior Member

    and what % of broken ice is almost immediately floating on surface in the channel to begin to re-freeze?

    I was thinking about inventing a rig to cut'N'stuff blocks of ice under the shelf of a channel cut in the ice, the idea being to create a channel that will remain open order of magnitude longer time frame, as well as cut unlimited ice thickness without a huge ship, but looking at Icebreaker bows I'm wondering if they aren't already doing much of that. But it still sorta looks like a lot of non-moving slush is left in the channel.

    Any vids or animations of Icebreaker in action from fish-eye view underwater? I guess its harder to find frogmen willing to take those pics.
     
  2. skaraborgcraft
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    skaraborgcraft Senior Member

    Ice is buoyant, pushing it under the existing ice edge will more likely break that up, but would have an effect of making a wider channel of broken ice. There is also the current effect under ice that would/could push the ice back out into free water space.

    Having ridden a few ships in the Baltic ice, it does not take long for wind or current to repack broken ice.
     
  3. Squidly-Diddly
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    Squidly-Diddly Senior Member

    Thats why I'm thinking of breaking it off in as big of blocks as possible. Less energy to cut a steak than to turn that steak into ground beef.
    Also I'd like to send the ice to the down current side of the channel.
    In theory, I think you could balance the force required to shove ice blocks under the shelf with the force required to lift 1/10th of the blocks up onto the shelf.
    In current Icebreakers, what I'm guessing is going on is 80% of the ice is shoved under the shelf as loose slush but as soon as the ship passes and prop suction, etc, most of the ice oozes back out into the channel as slush tries to rise and that which does rise creates suction for the rest. Also thinking the jagged course slush will present greater surface area to cold air and freeze up harder than the surrounding ice after a couple days.
     
  4. Andrew Kirk
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    Andrew Kirk Pedal boater.

    Since ice floats it would surely require a lot of energy to fight the natural buoyancy to push it under an ice shelf. Throwing it on top would need a bigger energy input but it may have a better chance of staying there.
     
  5. skaraborgcraft
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    skaraborgcraft Senior Member

    Well,they have been breaking ice for a long time. Must be a reason they are still crushing it under and to the sides.

    The point you may be missing, even if it was piled on top of the ice or under each edge, how long do you think a nice ice free river stays open? Wind and current often push pack ice back together in a short time, back to square one.......
     
  6. Squidly-Diddly
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    Squidly-Diddly Senior Member

    Good point, this would only work where ice sheets are fairly stable. Even if they WERE stable maybe if a channel is cut through them it would relieve pressures and otherwise stable or very slow moving sheets would tend to fill that "vacuum" fairly fast, even if that means breaking off and forming fissures elsewhere.
    Mostly I'm trying to come up with a way to cut unlimited ice thickness with standard off the shelf type heavy construction equip working off a barge VS an entire huge dedicated single purpose ship. I'd like an Icebreaker that can be delivered in pieces via big trucks or RR cars to a launch point, using mostly equip that is already available VS ship building schedule.
     
  7. Squidly-Diddly
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    Squidly-Diddly Senior Member

    I'm trying to figure out if the same physics concept that allows an heavy elevator car to go up and down with little input due to counter weight could also work pushing most ice under water but some ice up on the shelf.
     
  8. skaraborgcraft
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    skaraborgcraft Senior Member

    Certainly a cut channel does relieve hull pressure from ice. "construction type equipment" is only going to be large enough for small craft. Ice breakers usually use their hull form to mount the ice and break it with their hull weight, as you probably know. What you propose may be suitable for thin ice.
     

  9. Squidly-Diddly
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    Squidly-Diddly Senior Member

    I'm thinking my proposal would be best for super thick ice, where sheets would be more static so the channel would be less likely to close in from drifting sheets.
    Also, the entire concept is sorta like how a chainsaw is perfectly happy to cut a 1ft log as a 1" branch, and even seems more at home cutting through thicker material that wont bounce around.
    In contrast the Russians are building bigger and more expensive nuclear powered Icebreakers because so far that is the only way to get through thicker ice. I'm thinking of something like a measly 500-1000hp diesel spinning a 20ft diameter circular saw to cut through ice up to 9ft thick, which no Icebreaker can do without going to ramming and backing mode.
    I don't think cutting the ice with a big saw, with a tiny fraction of energy and equipment costs of a huge Icebreaker, will be an issue, just got to figure out a way to also get the cut ice under the shelf (or some on the shelf) with a nice reliable elegant fairly low energy method. That might become a bit more complex that the simple Big Saw, but should be OK because the material being handled will be at least clean and pure and mostly constant dimensions. Like how a Harvester "Combine" is a very complex piece of equipment but it works reliably because the fields its used on are very uniform. Generally the idea would be to do the least possible cutting and shove the largest possible blocks at the slowest speeds possible to keep up with the rest of the operation (the saws). I'm thinking an underwater upside-down "push chute" where the items are typically pushed up a chute by the items being pushed behind them, so the power is only the beginning of the chute. Robot rollers would only grab and push ice blocks down the underwater chute at the beginning and the next block would push the last one. The chute would be angled and end somewhere well under the ice shelf where the blocks would be expelled and float up under the shelf and hopefully self glue to the underside of the shelf.
     
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