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Low Cost Seastead

Home Forums Archive Structure Designs Low Cost Seastead

This topic contains 32 replies, has 5 voices, and was last updated by Avatar of Carl-Pålsson Carl-Pålsson 5 years, 11 months ago.

Viewing 15 posts - 16 through 30 (of 33 total)
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  • #3618
    Avatar of Eelco
    Eelco
    Participant

    Hey dont go overboard with the enthusiasm :)

    I made a simple model, ill see if i can add it to the wiki (never tried that before)

    Ok, i just added two pictures and a paragraph to the wiki. Feel free to merge it into the rest if you see fit.

    #3619
    Avatar of Thorizan
    Thorizan
    Participant

    Nice.

    #3621
    Avatar of Eelco
    Eelco
    Participant

    I corrected a mistake i made:: given the dimensions as they are now, each floor would have 92, not 46 square meters of floor area. Quite a difference.

    #3627
    Avatar of Carl-Pålsson
    Carl-Pålsson
    Participant

    This “heave plate” thing could put very large stresses on the truss and bottom of the cylinder. It will effectively be anchored in the water, by means of large water drag. Any waves lifting the cylinder will have to fight against this anchor. Without heave plate the waves will just be accelerating the counterweight which shouldn´t be that much of an increase in stress compared to the whole structure being at rest.

    I am not saying it will not work as advertised. It certainly will decrease heaving. But the increase in truss dimensions required to take the increased stresses might be too costly to make it worthwhile.

    It seems to me like a heave plate is sort of fighting the ocean, while a truss and counterweight that just floats with the waves is a more “go with the flow” approach, and as such, more efficient.

    I could be wrong though, just throwing these thoughts out there.

    You could of course also put vertical plates to deal with lateral/rotational movements. Which may or may not suffer from the above mentioned problems.

    #3628
    Avatar of Eelco
    Eelco
    Participant

    You are right, a heave plate could potentially cause quite big dynamic loads on the truss. However big, i think they should basically be on the same order of magnitude as the static loads.

    The dynamic loads are due to a fluctuation in flotation. The static loads are pretty much proportional to flotation, since the ballast should be on the same order of magnitude as the weight of the structure itself to have any effect.

    Its something to keep in mind, but not a dealbreaker.

    What i am worried about is horizontal motion. Waves create quite some horizontal displacement, and i do not see an easy way to counteract that effect.

    Then again, horizontal movement of water merely has a drag effect, not a flotation effect. drag << flotation. Probably the structure is simply too heavy to be affected much by fluctuating horizontal forces.

    #3660
    Avatar of Wayne-Gramlich
    Wayne-Gramlich
    Participant

    Your cable stabilization is simpler that what I propose.

    It is probably better to keep the windows above sea level.

    #3663
    Avatar of Wayne-Gramlich
    Wayne-Gramlich
    Participant

    We need some marine engineering here. We are pretty much at the limit of what I can figure out.

    Heave plates are used in the offshore industry, so the real issue is how big and what are the trade-offs. Other than asking a marine engineer or building a model, I do not know how to answer the question.

    #3669
    Avatar of Eelco
    Eelco
    Participant

    Have you ever been to a zoo where they have these underwater tunnels? Its essentially the same situation. Plexiglass is tough stuff, appearently its deemed safe in such applications.

    If you do not know what i am talking about: the first result of googling ‘underwater tunnel’
    http://www.planetware.com/i/photo/valencia-e1272.jpg

    #3681
    Avatar of Wayne-Gramlich
    Wayne-Gramlich
    Participant

    Most boats do not put windows below the waterline unless they have a good reason to do so. The exception is “glass bottom” boats.

    Risk of putting a window below the water line is that it will spring a leak. There is not much to see underwater in the middle of the ocean. It is clearly technologically possible, but Is the risk/cost with the benefit?

    I still like your basic picture, it is better than mine.

    #3684
    Avatar of Carl-Pålsson
    Carl-Pålsson
    Participant

    Another potential drawback with a heave plate on a buoy like this is that it might increase sideways movements when the cylinder rides up on a wave slope. And it could possibly push the cylinder entirely out of the water if things go really bad.

    At least when considering small seasteads. These are small enough to disappear completely below a decent wave and will probably always have a wild ride in a storm. The goal here is survival, not necessarily comfort.

    But it´s clear we need to model this in a tank to find out for sure.

    #3685
    Avatar of Eelco
    Eelco
    Participant

    Well, there might not be much to see, but i think you can still get a fair amount of light at that depth. A window a few meters above the waterlevel will need to hold up to the same standards, because its going to be effectively under water quite a lot of the time. That line of argument quickly leads to no windows at all, and although personally i dont really care, no natural light is generally frowned upon.

    As for leaks: if you mean catastrophic leaks, i think the plexiglass can be made such that the concrete would fail before the glass would. Minor leaks would not be a big problem, and should be very preventable.

    #3688
    Avatar of Carl-Pålsson
    Carl-Pålsson
    Participant

    Here is some related reading.

    http://en.wikipedia.org/wiki/Porthole

    http://en.wikipedia.org/wiki/Saale_disaster

    I hade the idea earlier to have the windows unable to open to decrease risks with flooding. Perhaps not a good idea after all.

    #3689
    Avatar of Eelco
    Eelco
    Participant

    I was thinking of steel frames cast into the concrete, with a thick slab of plexiglass clamped and bolted to these steel frames. Thats not going to leak short of a torpedo.

    As a result of this disaster it was legislated that portholes had to be big enough for a person of reasonable size to escape.

    There are many effective ways to lessen the risk of fire. This doesnt seem like one of them. Either way, a closed window isnt any harder to climb through than no window at all.

    #3690
    Avatar of Carl-Pålsson
    Carl-Pålsson
    Participant

    Well, I´m not going to set foot on any seasteads that have no emergency exits. Fire prevention is all well and good, but you should expect there to be fires anyway, and try to reduce the potential damages with that in mind (within reason). I am quite sure the people who built the Saale thought they had eliminated any chances of a fire.

    Besides, if there are laws about the openability and size of portholes we might have to comply with that anyway to stay out of trouble with the law. For the first few seasteads anyway.

    #3691
    Avatar of Eelco
    Eelco
    Participant

    I disagree with that for two reasons.

    First of all, if you expect seasteading to be a walk in the park, i think you will end up desillusioned. Things like this seem like the smaller of the risks that you will have to take as a pioneer.

    Secondly, its simply not rational. A well-built seastead, with modern techniques and materials is probably orders of magnitude safer than your average wooden construction, which many mostly older houses have. Extra fire escapes or not.

Viewing 15 posts - 16 through 30 (of 33 total)

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