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Nkossa Barge

Home Forums Archive Structure Designs Nkossa Barge

This topic contains 48 replies, has 10 voices, and was last updated by Profile photo of ellmer - http://yook3.com ellmer – http://yook3.com 3 years, 9 months ago.

Viewing 15 posts - 31 through 45 (of 49 total)
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    ocean, i agree that a “sea state dependent connection” is a universal principle that we should adopt. I also agree that Eelcos Math may be completly correct – but the universal conclusion- connecting impossible- is not correct.

    I see you are a strong advocate for “not permanent” and it is problably because you have practical experience at sea – i give you that – nothing in life and at sea is really permanent that is philosophical and technical. If you check the nkossa connections you see that it is a “break away connection” if things would come really bad, the truss will break the tube be valved off, a tanker docking at nkossa would destroy the fender, and the asociated truss with no major damage to both structures.

    If that happens, you send out a couple of welders after the climate calms down and fix it within days and you are back in business. There is no difference to land based building – some extreme climate happening once in 100 years will do some limited damage to the infrastructure. The point is LIMITED and this must be constructed into the connection from the beginning.

    Happens that the nkossa connection had no need to break up for about a decade – so it is kind of permanent (in the above mentioned limits).

    If you check a modern oil tanker even the connection between bow and stern is not 100% permanent – we have seen occacionally a “forced break up” between the two parts in extreme conditions – in a good built ship the 2 resulting parts would be chambered and still float after the break up.

    This is why i advocate for “chambered rafted structures” instead of elevated platforms they can break up – every group of chambers on its own (as you suggest) but they will still not sink. It is much like a foam block – you can break it but not sink it. Seasteads should be built that way.

    I agree with Eelco that the sea can create almost arbitrary conditions that can even convert an oil tanker into a submarine (check this awsome video: tanker in storm ). The question if we should break up voluntarily, let the sea break some connections designed to break, (once in 10 years) or be ultimatly be prepared to break our structures in half with no fatal consequence is not a either or, it is probalby a “all of it”.

    There is a good reason why no surface swimming animal exists in the high seas – all animals are submarine – or flying. Maybe the surface is just not a good place to be sometimes – maybe we should investigate submerged, or semisubmerged, solutions.

    As you see in the video above at some point in some climate we need to be prepared for almost everything.

    Nkossa shows us that connections are possible in the high seas – and can last quite long – but there is always this perfect storm…


    Profile photo of OCEANOPOLIS

    They’re called collision bulkheads. They can closed watertight and depending on the size of the ship can have from 3 (fore, midship, aft) to quite a few.If @ any point one or two or even several of this chambers gets flooded due to collision, or being hit by a freak wave, etc. the whole ship will still float, until repairs are done. Nkossa HAS to be built the same way, no doubt about it.

    Let me clarify one thing. When I said semi-permanently I didn’t mean being able to break appart Nkossa’s hull into 5 pieces, for example. What I meant was that when we are rafting up 5 Nkossa like structures to just be able to disconnect when needed. (the sea state shown in your video would be the perfect disconnection point in time – actualy, way before the sea state builds up to that). So I would say that the breaking up should be voluntarily.

    I based the whole concept on 2 major fundamental principals that I personaly belive in: 1) Always better safe then sorry. 2) Financially wise incremental modular seasteading. The first one need no explanation. The second one it’s like craving chocolates NOW, but you are waiting and dreaming of buying a box of premium Belgian ones that costs 20 bucks when all you got is only 3 bucks in your pocket. Just go and buy a Milky Way bar for 3 bucks and enjoy it NOW.

    Design modular capable seasteads based on your actual budget that can build 1 module. Build it, start operating it and be happy. (you got your Milky Way). When you have more money build 2,3,…5 and raft them up….Here comes your box.

    And of course that “…the universal conclusion- connecting impossible- is not correct.”

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    The Nkossa also uses flexible connections. This avoids one structure from having to support the other and allows the use of a much lighter srength connecting member. The connecting members envisioned by Eelco can swing like gates, so are flexible on the horizontal plane parallel to the ocean surface, but were rigid against heave in the direction perpendicular to the ocean surface. Actual connections currently in use are typically opposite, double or multiple hinged to allow vertical travel for heave and roll while rigid against pitch and yaw. An exception is the ferry loading gate at the bow and/or stern which is still hinged for heave but rigid against roll instead of pitch while rigid against yaw.

    Flexible, non-permanent connections among independent Seasteads are a given, to preserve the dynamic geography functionality, to relieve stress from relative motion between seasteads, and to allow disconnection in extreme conditions beyond the design limitations of the connections. The asthetics are better as well, allowing sunlight and open water throughout the colony instead of creating a huge patch of dark ocean underneath a solid swath of structure.

    The rigid concrete cell system like Nkossa makes sense for a floating ring breakwater. Allowing for modular expansion of cells means it can start small and grow. The enclosed protected area, and hence, value, increases with the square of the diameter while the cost only increases linearly with the circumference.

    Freedom Ship is designed as a rigid cell structure, with the superstructure contributing to the overall strength. It was originally designed as a rectangular barge, which was fine for water drag at the planned 10 knot speed, but too much drag from wind. Thus, the design was changed to the pointed bow. The entire ship is designed to be supported at each end with no support in between. Concrete was considered as an alternate material.

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    I am not familiar with Eelco’s flexible connection design. Is there a drawing of it somewhere around?

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    He presented it in his talk at Seastead Conference 2009. The video is at http://seasteading.org/blogs/main/2009/12/28/eelco-hoogendoorn-seastead-engineering-overview

    Profile photo of OCEANOPOLIS

    I see what he’s proposing, which is not an actual raft up. It also seems that he is applying it to spar like seasteads, and I’m not sure if it can work for the raft like ones. Definately food for thought.


    miguel, it says Checking engineering Bureau Veritas – so that means they had some “bystanders from veritas on the set” not a full scale classing for the build. It still makes sense to let the electric cables check by RINA (as cruiseships do) the industrial pressure applications by ASME, like the land based industry does, machinery by TUV or whatever etc. etc. but that is not building to class approval.

    The idea that we should make a seastead to class approval is “buerocratic suizide” they will never be satisfied and free of concerns until your structure is so similar to other structures they already approved as one egg to another – this is what they do – their very nature of existance.

    If seastead.org management is going for “classed seasteads” the movement is dead – a mortal management failure. It is like a intent to “establish paypal within the existing banking supervising sistem”. New things can never fit into old sistems (legal, technical, insurance) new things naturally break the borders of those sistems – it is THEIR very nature. Napster does not work with record companies, paypal not with banking, internet not with press laws, seasteads not with classification – thats it .

    Some of the above mentioned offshore concrete structures are now 50 years at sea – some barge type structures built 1914 still float – so i am not surpirsed that SOME classification societies start to mention this possibility today in a 3.3 subchapter – as brand new engineering development they may develop codes for it someday – this is the time horizont – if you build it 1914 and float it out you get building codes 2014 – if we build seasteads today we will get building codes around 2110…

    But that is for the mainstream of classification societies, maybe one of over 50 classification societies worldwide is willing to make an exception…but we should go for “non class status” as general strategy – or we will repeat the ephemerisle experience ….


    I have to agree with ( i_is_j_smith ) So we can have our freedom after we…, get our ideas approved by some bureaucratic society, … Wow, I feel more free already…



    European Submarine Structures


    As a general course of action i would suggest not to try to reinvent the wheel with overcomplicated engineering solutions developed from cero at the computer. Connecting heavy things that pump around is a problem that you can see solved in any harbor and marina on small and large scale.

    The problem is basicly a mental block – it was postulated (directly or indirectly) by leading TSI voices that NON of those solutions would ever be possible in the open ocean. Happens that we can see now that Nkossa and similar structures apply the good old standard marine fender in (impressive large) but still simple form in the high seas. So we need to UNPOSTULATE that the standard marine fender can not work in the open ocean.

    What Nkossa does is use the standard fender plus a “damageable truss zone” behind it – voila the standard marine fender works and is safe for all seasteads that you can expect in a decade – a hundred year storm might do some damage to the truss – but that would not do any harm to anybody.

    The other candidates for connections we should look at is the movement control of cable bridges with shock absorbers, which have a eqal situation of permanent movement during decades, and the joints between saddle trucks and trailers, cars and trailers, floating restaurants and land, articulated buses, trains, etc.etc…. i would assume that a connection between moving parts that works should be invented already and in wide use as we speak.

    It is important to realize that the problem is a common one and easy to solve with little need for high tech engineering – just as the Nkossa team has demonstrated. We are up to 1 million load cycles per year (wave movements) which is a manageable order of magnitude very similar to many existing applications.



    European Submarine Structures AB

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    While researching that ridiculous Botanical City Concept in the blogs I came across the Yee Precast Design Group and this project:


    325ft x 325ft floating platform, built in four months for US$75 million in 1984 and able to handle arctic conditions and ice pressures at 130000 lbs/ft^2.

    Don’t know if that cost includes the entire oil exploration equipment and support facilities or not. Also I’m sure this thing was overdesigned to handle the arctic conditions. It could probably be scaled down quite a bit if the floating platform was located in calmer locations.

    These Very Large Floating Structures predate Nkossa by more than a decade, The simplest solutions are often the best…

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    To clarify my position here. When I said “raft up” I was reffering to applying it to same shape, modular, raft like seasteads. Also, when I said “raft up” I really meant that, as in


    Definition from Wiktionary, the free dictionary

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    [edit] English

    [edit] Noun

    raftup (plural raft-ups)

    1. (nautical) The roping together of a number of small vessels to form a raft-like structure

    Marine fenders are a bit expensive for my budget :). I would go with “the old fashioned solution”: used tires bought for 5 bucks a piece from the local junkyard, and dock lines on cleat. Few bow/stern breast lines and few fore/aft spring lines. Thats it.

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    Link to a PDF about a LNG processing barge built out of prestressed precast concrete:


    Check the hull section image on page 2 of the PDF. That one structure alone would make an excellent seastead. Plenty of room on deck for housing. Tons of room below for aeroponics and other systems.

    It’s probably way over designed…I doubt a seastead would need 10ft thick walls. But even at the current design specs you are looking at only 86000 cu yd of concrete, and at about US$120 per cu yd you are looking at US$10M for your seastead materials.

    No fancy technology…just standard building materials and standard concrete labor practices.


    i_is_j_smith, thanks for your find of the pictures of the Glomar Beaufort 1 project. I like the engineering term honeycomb structure better than the ship builder term collision bulkheads, i find also the the yellow truss for the land connection during building interesting, very similar to the nkossa mooring, as this project preceeded nkossa a decade it looks that the experience was a good one.

    There are more than 50 floating concrete structures similar to this in the water at the moment. So we really should consider the basic engineering as solved. I agree completly – the simpler the better – as you said…don´t overengineer it should be a basic seasteading principle too.



    European Submarine Structures AB


    Adriatic LNG (more here) features not only a floating platform 375 meters long by 115 meters wide – it also features connections (docking) of lage structures in open ocean.



    European Submarine Structures AB

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    They appear to be using huge fenders, to prevent the motion from doing damage and it’s not a great really-long-term connection, as the friction wears the fenders and the tied-up craft…



    Never be afraid to try something new…

    Remember, amateurs built the ark, professionals built the Titanic.


    For a general idea how connections should look like the kind of connection that exist between the floatel and the production platform in the oil / gas industry is a good example

    See Laurizen floating crew quaters (website here)

    What we see is : a beafed up gangway (longer flexibe telescope ) can do the job and is doing so as we speak.


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