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Home Forums Research Engineering Pillarstead

This topic contains 11 replies, has 4 voices, and was last updated by Profile photo of Anenome Anenome 3 years ago.

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  • #21374
    Profile photo of elspru

    hey so after reviewing some seasteading designs,
    and realizing that a common feature is pillars,
    while issue being that people build ontop of pillars,
    and so the pillars themselves aren’t used for much.
    Thereby I decided to integrate the design,
    making ocean compatible pillar,
    that is also habitable:


    This is a minimally sized design, it is 3.48m across,
    and just over 5 and a half meters high, so is two floors.
    It’s technically enough space for 2 people to live comfortably,
    with a volume around 50m^3 can accommodate as many as 5 people,
    max recommended capacity for a party of about 16 people.

    Weighing 5.83 tons if done with ordinary ferro-cement,
    Materials to construct it are estimated to be $9,000 at a minimum.
    It can be constructed from bottom up, so first floor, should be $4,500.
    The deck is the construction site, plan is to have it floating on barrels,
    the ramp is motile so changes angle with deck height
    though should stay relatively the same.


    Anyways the materials cost for the whole thing,

    is equivalent to 4 months for shared accomodation at Blueseed,

    and considering it’s a whole house, it’s totally a better deal,

    though admitedly the complete price would be around $40,000

    if you’re including interior decoration, plumbing, solar panels and/or wind-generators.

    Profile photo of elspru

    here is the image, didn’t seem to work previous time

    Profile photo of elspru
    Profile photo of elspru

    <a href=”http://weyounet.info/blog/wp-content/uploads/2012/10/pillarstead-minimal.png”><img src=”http://weyounet.info/blog/wp-content/uploads/2012/10/pillarstead-minimal.png” alt=”” title=”pillarstead-minimal” width=”465″ height=”576″ /></a>

    The weight with all it’s utilities and ballast will be more, probably closer to 10 or 15,
    illustrated deck placement would be at weight of up to 20 tons.

    Profile photo of Theodore Schultz
    Theodore Schultz

    Some Fundamentals of Seastead Dynamics, (It’s not really the pillars. Sorry).

    Numerous semi-submersible seastead designs feature pillars. Here’s why:

    Elsewhere in the Seastead web site, you will find a good technical article on the oceans and wave mechanics, though it doesn’t really explain very much in terms of how waves are created. Waves are created primarily by wind. A fundamental property of differential mass motion is friction, whether the masses are solid, liquid or gas. At low relative fluid velocities, flow is smooth, predictable and differentiable, what we refer to as _laminar_flow_. As relative velocities increase, or material geometries become more obstructive, flow becomes _turbulent_. Various fluid properties such as velocity, viscosity and density can be used to calculate a value known as the _Reynold’s_Number_, which will predict this behavior to some degree, (bear with me, it’s been decades since I studied this). Drag a pole through water, or erect it in the wind, and in its wake it will often create a flow pattern known as _vortex_shedding_. This pattern is revealed when you see a flag waving in the breeze, and when you see waves traveling on a body of water. Initially, the wind motion may be perpendicular to the water surface, but pressure from a minor vortex produces changes in the water surface geometry, and that geometry reinforces vortex generation. The size of the waves may be limited by the water’s depth, by the wind’s speed, or by the distance over which the energy transfer can take place. If the depth is thousands of feet and the distance is thousands of miles, the waves can get quite large, and as the available depth decreases the energy present in this system doesn’t just go away. Energy and momentum are largely conserved, and water is pretty much incompressible. According to the report, waves on the open sea of eight meters are quite common, waves of sixteen meters occur one in a thousand, and there is no limit to how large occasional rogue waves may be. The motion of the water describes vertical circles, decreasing in size with depth. This energy can do a lot of damage, as clearly illustrated by the amount of sand created on the world’s beaches.


    A general approach to seasted design has been to try to dodge this energy through semi-submersible design, in essence submerging one or more floatation bodies below most of the wave action, (at least they don’t need to be habitable), and to suspend a habitable platform above the top of the waves. If this is done right it can be very stable, much to the satisfaction of those who commonly experience motion sickness at sea.


    What role do the pillars play? Let’s examine the behavior of a semisub design with minimal pillar displacement. Imagine two circular plates, maybe 400 ft. in diameter, one suspended a hundred feet above the other by a single, central “I” beam, the whole works stabilized by an octahedral network of cables connecting the perimeters of the two plates, specific Gravity of the resulting, gross assembly of about one-half that of seawater. The displacement of the cables and beam are really quite small, compared to the rest, so that while it might float half submerged, any substantial mass added near the perimeter will cause it to tilt, or cause the whole works to sink until the peaks of the waves sweep the bottom of the upper platform. Conversely, if the mass were slightly reduced, the whole works would float upward until the troughs of the waves swept the top of the lower platform. Tuning this thing to float in the middle looks about as hard as adjusting any other submerged body for neutral buoyancy and getting it to drift at a specific depth, (very difficult with any air-filled structure, as the rigid shell is more compressible than the water around it. There is an ongoing energy expense for vertical stationkeeping). The static stability of the platform system comes from increasing the volume of the pillars slightly, but the more cross-sectional area the pillars have at the water line, the more sensitivity the whole has to dynamic wave forces. The dynamic stability of the whole comes from the size and depth of the lower, submerged platform.


    So, there you have it. There’s no magic in the pillars, they are a byproduct of a semisub design, the stability of which comes from submerged section. Until a floating, basic capsule design approaches the dimensions of a cruise ship, it will tend to bob like a cork under wave action.

    Profile photo of elspru

    Hey, so I updated the design, to increase the amount of submerged section.

    A big disk as you mentioned, about 11m in diameter. can be used for buoys, or dock fittings.




    The bottom is green as it’s planned to allow bioaccumulation,  using it as a water garden of sorts.


    The green ballast section, which shall be around 40% iron as ballast.

    assuming interior stuff weighs at least a ton,  and up to 4 tons, can use less ballast if more weight, though unlikely.

    anyways so it has waterline at depth of between 40-60% of it’s height allowing boats with drafts of up to 2-3 meters respectively.


    Walls are 20cm thick.


    price of shell 11-thousandish.

    Profile photo of elspru

    So noted that common wave height is 8m,

    and previously read that a boat can be capsized by a wave 55% of it’s waterline length,

    I’m hoping it’s a significantly higher percentage for underwater length.


    anyways updated the design,  to use pure ferrocement bottom, extended to 18m diameter.



    Also it’s convenient as it means can have docks going outwards about 7m long.


    This means have about 250m^2 of seafloor, about 1/16th of acre or 1/40th of hectare,

    which seems like a fairly decent chunk for a 1 bedroom.

    In reality will probably have holes in the  ballast plate to allow for easier repairs, and light penetration.

    Potentially a slice could even be open for deep keeled boats. though they could come along side to a dock.


    It’ll probably act as somewhat of an artificial brakewater,

    am considering making it as a downwards facing cup to give it more geometric strength,

    while also making it more like a shore with an inclined beach of sorts.


    average waveheight in most of pacific in atlantic is under 3 meters,

    so it should be sufficient.  even if it does get flipped over (however unlikely) it’ll quickly return.

    Waves might wash over it, and some will definitely crash into it, but outside of storm season should be okay.

    can repair it during the calm seasons.


    The design is scalable, so should be able to get much bigger.

    though I think it’s essential that at least the first prototypes are accessible.

    Most difficult part of this would probably making that base plate,

    it weighs over 3 tons.    If made in hexagon, can interlink them as modules.



    Profile photo of elspru

    If scaled up to have 100m^2 per floor or ~1000square feet, 8 floors,

    then shell costs about half a million,  and has 1/4 hectare or 2/3 acre of seafloor ballast.


    though if it’s as is now, water depth will only be, 1.728m,

    likely will have to have a thinner section, perhaps several mini pillars,

    holding it up to achieve the 3m depth of most marinas.

    Alternatively can increase acreage…


    though I’m starting to think perhaps a c-shaped islet with a cup interior would be good.

    Especially considering how polluted much of the ocean is,

    can have locks to purify water surrounding incoming ships,

    so interior lagoon could have relatively pristine water.


    Also the interior cup would give the required submerged structure for stability.

    Profile photo of elspru

    Then again if incoming ships use anti-fouling,

    I guess it would defeat the purpose of having pristine interior waters…

    so could just have a simple-c with gate,  or else force anti-foulers to dock outside :-S.

    anyways that would be up to the individual c-colony ha-ha.


    oh ya, I guess depth would be greater than 1.728m considering people will bring many tons of stuff with them.

    the 52m width of the seafloor, should allow for it to be comfortable for all but a rogue wave.

    Profile photo of elspru

    oops. I had an extra 0 in my spreadsheet.  so actually the thickness of 6cm is more appropriate instead of 20.  and that would mean the large one has depth of 5.35m without any extra weight. also the cost is much higher,  $24k for the small one, and 1.5mil for the large one.

    In any case after designing island stead for a while… I’ve decided to switch over to boat stead as it’s a bit more useful.  Though likely we’ll simply buy a used boat to start living on the water.

    Profile photo of spark

    What kind of boat are you planning to buy?


    Profile photo of Anenome

    The problem with pillars is that they tend toward rocking and rolling motions and because of this are rather uncomfortable.
    You see them in oil rig designs because they are working vessels, not comfort vessels, and the guys that live on them more put up with them than enjoy their time there.


    For maximal comfort you want to laterally spread the floats, centralize the weight, creating almost an inverted pyramid shape or a T shape rather than an I shape.

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