1. Skip to navigation
  2. Skip to content
  3. Skip to sidebar

Spar design versus flat raft platform design

Home Forums Archive Structure Designs Spar design versus flat raft platform design

This topic contains 39 replies, has 7 voices, and was last updated by Profile photo of elspru elspru 5 years, 4 months ago.

Viewing 15 posts - 1 through 15 (of 40 total)
  • Author
  • #1298

    I was surprised that spar (elevated platform) design seems to be on the table again due to the new engineering report.

    Was the spar design not dropped in favor of the much more economic “flat raft design” implemented in the Nkossa barge and similar.

    The discovery channel video (refloat New Orleans) gave the idea that “modular flat raft” is the path to follow…

    Video of New Orleans flat float concept: (The video only shows part of the longer discovery version that contains a interview with Patri)


    Does the design suggested at (seasteading.org/files/MIandT040_08_R1_Seastead_Exec_Sum.pdf) not just combine the “cost of a spar drilling platform” with the “cost of a tension cable bridge” to create a relative small expensive platform where we can only put lightweight buildings on.

    The oil/gas industry is going in a different direction. When living quaters and not drilling facilities, on the ocean, is the objective, a simple flat platform (LNG terminals and process installations) made from concrete shell is the newest direction. (nkossa barge)

    Any thoughts?



    European Submarine Structures AB

    Profile photo of Farmer

    I imagine two Stone Age architects arguing the relative merits of rock vs. wooden houses and how shocked they would both be that 10,000 years later the debate has not been entirely settled.
    As a member or Team Spar I will only argue that it is seasteading for people who don’t really like the ocean and yes, I understand how absurd that sounds.
    More importantly I think a diversity of designs; in fact a radically varied collection of totally unrelated strategies is the best way to go. That would allow different schools of thought to compete in the real world and all refine and improve their designs.
    For myself I would want something like your starfish platform that sits at least 5, 6 meters above the surface.
    Profile photo of OCEANOPOLIS

    Why would anybody want to dwell so high above the water, on a spar like design? Here are few reasons agains it:

    1. Start up and operation costs. Building spar seasteads will be far more expensive than ANY platform design. (see Clubstead construction estimate)
    2. Hauling cargo, people and fuel up and down will be a logistic nightmare.
    3. Docking alongside in heavy seas will be difficult.
    4. They will bob up and down.
    5. They are hardly modular and mobile.
    6. If not anchored on the seabed it will cost a fortune to DP them due to high windage.
    7. Whats the point of spending $ millions on a new design? Just rent an abandoned offshore oil rig, if YOUR TEAM is ready to share the faith of other “spar like” during a hurricane. http://www.msnbc.msn.com/id/9172765/ , http://www.smit.com/sitefactor/page.asp?pageid=846
    Profile photo of Jack

    I still dont think Spar or Raft is the way to go at all.

    you will be cheaper in the long term buying a quarry & shipping your foundations offshore as a charity, then building an island on a continental shelf up to 400m deep, its dry land & it aint going anywhere.

    I dont know about you guys but every time i think of offshore “platforms” i think about the horror of it tipping over.

    Concrete, Rock, & seabed thats what you want.

    Profile photo of Farmer

    The cost is not prohibitive. Some very inexpensive material would be needed to make it workable. Concrete, basalt, recycled polymers from the ocean gyres. There are options.
    Hauling up and down would require an elevator, true but most stuff by weight (fuel and any cargo) would not go up.
    About bobbing the crew of the Flip claims it has never moved more than a foot or two in the worst waves.
    BTW, the phrase “team spar” was a silly, self-effacing pop culture reference; suggesting that the debate itself is pointless.
    Never mind, wasn’t that funny anyway.
    Honestly, it’s all about avoiding salt water. Nasty stuff. Kills all normal plants and is not good for anything else.
    Profile photo of OCEANOPOLIS

    Just buy an island. http://www.privateislandsonline.com/inapupan-island.htm. Done deal.

    P.S. Actually this one looks like a good deal. http://www.privateislandsonline.com/green-ark-island-nicaragua.htm

    Profile photo of

    Any thoughts?

    Somebody on Discovery has been looking at Seasteading. I wonder what would happen with their floating New Orleans in a Katrina-type storm though. It doesn’t look like the interconnection system would be able to withstand any significant waves, and it certainly isn’t going to outrun a storm.

    I agree the flat raft/barge seems the best way to go, with one caveat: They must be hydrodynamically efficient, both as separate units and as an interconnected city. This will enable cheap and practical (compared to the alternatives) dynamic station-keeping.

    A spar might be the most hardened shape against heavy weather. But you shouldn’t place your seastead where the weather is often bad. You should place it where the weather is as good as possible most of the time, and when the rare big storm hits you can either try to outrun it (because a barge will be faster than a spar), or just endure the seasickness (and the risk of possibly capsizing) as the cost of actually getting something (reasonably priced) in the water.

    One thing on the Nkossa barge though: Doesn’t it use lots of mooring lines to enhance its stability in the water? What if it went with just propellers for station-keeping? I don’t believe mooring in deep water will be competitive or practical. And even if mooring would prove to be feasible, chances are you would be limited to just one line.

    FWIW: The Clubstead is not a spar buoy, I believe. I think it is more like a semi-submersible.

    Profile photo of OCEANOPOLIS

    And I’ve been saying that for a long time… The Modules, ” They must be hydrodynamically efficient, both as separate units and as an interconnected city.” to quote you, and also self propelled. When a storm comes, the whole structure can motor away, or, if it’s really bad, all modules should be disconnected, so they can ride the storm by themselves. The Modules will have a better chance of surviving a big storm (their max speed will be higher than the whole structure, when individually under power).

    What Will was trying to say is, why waste time with the spars, instead of moving forward with a raft/barge concrete platform design?

    I have adressed the hydrodynamical aspect of such modules by presenting the folowing design and some raft up configurations under Will’s thread “Apply Seasteadinh Concrete Shell Structures”.

    Profile photo of Jack

    Hmm I think you found a nice island their Oceanopolis, but again thats getting into political stuff, since its another country we would be trying to Annex. & these places would have narc forces watching the whole time.

    But yes the most logical course of action would be to procure an island or sand bank, its going to be the best choice for developers.

    However thats going against one of my 4 golden rules.(lol not that you have to agree)

    1. Any thing thats above water is already claimed.
    2. Any thing deeper than 350m is to exspensive.
    3. Nothing closer than 15nm to shore line.
    4. Nothing thats under environmental or historical protection (or you will look like a bad guy)

    Idealy we want somthing in an EEZ at about 100-200m deep about 15-16Nautical miles off the shore line, thats not got any cables, pipes, or well heads on the sea bed for about 3nm. It would also be good to get government aproval in writing, & an environmental department aproval/licence. for commercial & recreational use.

    After you get what you want, declare independence, & enoy the trip 😛


    Jack you might want to reconsider point 2 – European Submarine Structures AB is budgeting that kind of pressure resistant concrete shell structures at 331 Euro per ton of displacement (=cubic meter of living space) this is the equivalent to European and US city housing prices…

    Do not dismiss deep sea seasteading out of hand – deep sea mining and salvage is where some of the most magnificent open ocean business is located – if interested in chat about this follo to: seasteading.org/interact/forums/engineering/structure-designs/deep-sea-seasteading-vent-base-alpha


    Paper Number 3011-MS
    Authors Roy S. Highberg and Harvey H. Haynes, Civil Engineering Laboratory

    Offshore Technology Conference, 2-5 May , Houston, Texas
    Copyright 1977. Offshore Technology Conference
    Language English
    Preview ABSTRACT

    An ocean implosion test was conducted on a pressure-resistant concrete cylindrical structure to obtain the depth at implosion. The structure was a reinforced concrete cylinder with hemispherical end caps, twenty feet (6.1 m) in overall length, ten feet (3.05 m) in outside diameter, and 9.5 inches (241 mm) in wall thickness. The structure was near-neutrally buoyant having a positive buoyancy of 12,000 pounds (5.4 Mg) for a hull displacement of 85,000 pounds (38.5 Mg). The implosion depth of the cylinder was 4700 feet (1430 m). A predicted implosion depth, using an empirical design equation based upon past test results, was 16 percent less than the actual implosion depth.


    A pressure-resistant, reinforced concrete hull was constructed in 1971 as part of a Seafloor Construction Experiment, SEACON I. The structure was placed on the seafloor at a depth of 600 feet (180 m) for 10 months. Figure 1 shows the SEACON I hull prior to its ocean emplacement. Since its retrieval in 1972, it has been located in the open air about 150 ft. (50 m) from the ocean. In the summer of 1976, the structure was returned to the ocean for an ultimate load test, that is, the structure was lowered into the ocean until implosion.


    The cylindrical structure was assembled from three precast, reinforced concrete sections. The straight cylinder section, 10.1 feet (3080 mm) in outside diameter by 10 feet (3050 mm) in length by 9.5 inches (241 mm) in wall thickness, was fabricated by United Concrete Pipe Corporation. The concrete hemisphere end-closures, 10.1 feet (3080 mm) in outside diameter by 9.5 inches (241 mm) in wall thickness, were fabricated in-house. Tolerances on the sections conformed to concrete pipe standards of not to exceed to ±0.75 inch (19 mm) for the inside diameter or minus 0.5 inch (13 mm) for the wall thickness.

    Steel reinforcement in the amount of 0.70% by area was used in both the axial and hoop direction. Reinforcing bars of 0.6 inch (15 mm) diameter were employed throughout the structure. A double circular reinforcement cage was fabricated for each precast section; the concrete cover on the outside and inside reinforcing cage was 1 inch (25 mm). For the cylinder section, hoop rebars had a spacing of 27.25 inches (692 nm) and 31.25 inches (794 mm) for the inside and outside cages respectively.

    The hemispherical end-closures were bonded to the cylinder section with an epoxy adhesive, no other attachment besides the epoxy bond was employed (Figure 2). The gap between the mating surfaces of the hemisphere and the cylinder was less than 0.13 inch (3 mm) for 75% of the contact area. Prior to epoxy bonding, the concrete surfaces were prepared by sandblasting and washing with acetone.

    Source: http://www.onepetro.org/mslib/servlet/onepetropreview?id=OTC-3011-MS&soc=OTC

    Profile photo of wohl1917

    I was just struck by an odd coincidence: your modules have almost the same shape as the Floating Neutrinos ‘Son of Town Hall’!

    < http://ocr.wikia.com/wiki/Oceanic_Citizens_Republic_Wiki>

    Profile photo of OCEANOPOLIS

    Could be, If you say so….I haven’t heard of the Floating Neutrinos untill it was posted on this site. If so, its proof that is an exellent design, capable of ocean crossing.

    From what I know, they have “evolved” from the “kite” modules, an older project of mine. http://seasteading.org/interact/forums/engineering/structure-designs/waveland-modular-mobile-offshore-base.

    Profile photo of Jack

    Personally (on topic) I thought the engineering report was a bit weak, it lacked enough scientific data for me to get my teeth into. you got a link to that report ellmer?

    As for the 331 Euro per ton (metric?) & the cubic meter?? could you clear that up? what is that per Square meter cost?, thats the nromal measure when buying a house euro side. & per square foot would be nice for the yanks.

    However i’d like to know what you are charging per metric ton of concrete or marine concrete, i guess you wont tell me how much you buy it for 😛 ?

    Ive decided on going with a Man Made Island Project however if the cost is right, I would support any project leader who wants to procure concrete submarine vessels & buildings for mining or defense.

    But i like fresh air, grass & tree’s for living conditions, Yachts & the sea is a hobbie or job, not a way to live for me, i like dry private land & space to walk & play.

    as for unerwater dweling, uhm well i’ll answer taht on your other post.

    In conclusion I dont agree with floating islands to much shit can go wrong in the opan sea, & its not the best thing to defend.

    Profile photo of wohl1917

    I remember when you proposed your underwater kite design. Who knows how they came up with their shape but from reading it was probably dictated by the size and shape of the foam ‘logs’ they had to work with. In any case check out the link:

    < http://floatingneutrinos.com/Other%20Rafts/plans_of_the_son_of_town_hall_sa.htm> From a vertical perspective, the resemblance is a striking coincidence! Your modules are on a much larger scale (S. of T.H. seems to be about 50’LOA) but still it’s practically a ‘Proof of Concept’…

    < http://ocr.wikia.com/wiki/Oceanic_Citizens_Republic_Wiki>

    Profile photo of OCEANOPOLIS

    They do look alike! I am seriouslly taking this as a “Sign”.

    Originally, I designed the “kite module” (shown in blue) with modularity and mobility in mind. Later on, I was concern about stability and more space, and I added the midship section (shown in red), and increased the beam. Oops, just realized, that the freeboard should be @ least 2-3 times higher then shwon here,…

    The fact that the S. of a T. H. (basically the same design), did the Atlantic crossing, says a lot about this design, and personally I am very pleased and ecouraged by it. Another fact is that my design is twice as beamy as the S. of a T.H., in relation to the same LOA, making it very stable.

Viewing 15 posts - 1 through 15 (of 40 total)

The forum ‘Structure Designs’ is closed to new topics and replies.

Posted on at


Written by